четверг, 19 ноября 2020 г.
Астероид Рюгу поможет ученым разгадать главные "головоломки" Вселенной
Ученые называют астероиды строительными блоками, которые остались в космосе после образования Солнечной системы. Это делает их очень важными для науки, так как исследования космических тел помогут разгадать многие «головоломки» Вселенной. На данный момент астрофизики всего мира с нетерпением ждут прибытия образцов почвы с астероида Рюгу – относительно небольшого (диаметром около километра) околоземного астероида из группы Аполлонов, открытого в 1999 году. Астероид вращается вокруг Солнца каждые 16 месяцев на расстоянии до 131 млн миль. Образцы грунта, которые могут ответить на самые важные вопросы о Солнечной системе и нашей планете, доставит на Землю космический аппарат «Хаябуса-2». Если все пойдет по плану, капсула благополучно приземлится с парашютом на полигон Вумера в Австралии 6 декабря, сообщает Sputnik News. Ученые возьмут часть почвы астероида и обработают его внешнюю поверхность с помощью лазера. Другими словами, специалисты взорвут атомы один за другим, чтобы определить конкретный изотоп элемента. Не исключено, что это приблизит человечество к разгадке причин появления воды на Земле. Согласно одной из гипотез, вода была принесена на нашу планету ледяными астероидами и кометами, которые долгое время обрушивались на Землю. Это подтвердили исследования кометы Чурюмова-Герасименко. Тогда удалось выяснить, что на небесном теле действительно была вода, но она отличалась от той, что есть на нашей планете.
Ученые ожидают, что образцы Рюгу решат и другие загадки. Например, это поможет понять, что происходит с космическими камнями, когда они постоянно бомбардируются солнечным ветром. Ведь в отличие от нашей планеты, астероиды и другие небесные тела не обладают магнитным полем и атмосферой.
вторник, 3 ноября 2020 г.
Hubble показал астероид, стоимость которого превышает всю мировую экономику
Космический телескоп Hubble получил более четкое изображение редкого металлического астероида 16 Психея. Названный в честь древнегреческой богини, космический камень был обнаружен в 1852 году учеными из Неаполя, но до сих пор остается загадкой для астрономов. Диаметр астероида составляет 225 километров, что делает его одним из самых массивных объектов в главном поясе астероидов, вращающимся между Марсом и Юпитером. Астроном Линди Элкинс-Тантон, одна из членов миссии NASA «Психея», подсчитала, что если бы все металлы, входящие в состав этого редкого небесного тела, можно было доставить на Землю, их общая стоимость составила бы около $10000 квадрлн. Для сравнения: по данным Forbes, в прошлом году мировая экономика оценивалась примерно в $142 трлн. Пока об этом астероиде мало что известно. Единственное, что ученые знают – его состав очень похож на ядро Земли. Считается, что небесное тело может быть остатком ядра такой же планеты, как наша, которая по неизвестной причине не смогла сформироваться. «Мы видели метеориты, которые в основном состоят из металла, но астероид Психея является уникальным в том смысле, что он состоит из железа и никеля», – пояснила Трейси Беккер из Американского Юго-Западного исследовательского института (Сан-Антонио, Техас).
Металлические астероиды относительно редки в Солнечной системе, поэтому Беккер надеется, что более тщательное изучение Психеи может дать уникальную возможность узнать больше о недрах планеты.
воскресенье, 1 ноября 2020 г.
OSIRIS-REx упаковал пробу астероидного грунта
Межпланетная станция OSIRIS-REx успешно установила головную часть пробоотборника, содержащего вещество астероида Бенну, в возвращаемую на Землю капсулу. Ожидается, что в сентябре 2023 года около 400 грамм грунта этого небесного тела окажутся в земных лабораториях, сообщается в твиттере миссии. 20 октября 2020 года автоматическая станция OSIRIS-REx смогла успешно взять пробу грунта из области «Соловей» в северном полушарии небольшого околоземного астероида Бенну, став третьим по счету космическим аппаратом, которому это удалось сделать. Ожидается, что она сбросит капсулу с грунтом в атмосферу Земли в сентябре 2023 года, после чего та приземлится на полигоне в штате Юта. Дальнейшее исследование грунта в земных лабораториях поможет разобраться в процессе образования Солнечной системы и роли астероидов в доставке на молодую Землю воды и органических соединений. Снимки, которые станция прислала через пару дней после операции, не только смогли рассказать команде миссии о том, как аппарат проводил забор пробы грунта, но и выяснить, что он собрал около 400 граммов вещества Бенну, что намного больше установленного минимального предела. Более крупные фрагменты реголита привели к заклиниванию майларовой крышки пробоотборника, из-за чего тот стал постепенно терять мелкие частицы грунта.
Сложившаяся ситуация привела к отмене двух запланированных маневров и ускорению процедуры укладки пробы. 27 октября станция начала медленно перемещать манипулятор пробоотборника к возвращаемой капсуле, а уже 28 октября инженеры получили снимки камеры StowCam, продемонстрировавшие, что головная часть пробоотборника встала в нужное положение в капсуле. Это также подтверждают телеметрические данные. Теперь станции предстоит отделить от пробоотборника манипулятор и трубки от азотных баллонов, после чего капсула будет загерметизирована.
четверг, 29 октября 2020 г.
Переполненный грунтом Бенну космический зонд Osiris-Rex не смог закрыться
Космический зонд NASA OSIRIS-REx собрал столько пород астероида, что не смог закрыться. Теперь драгоценные частицы улетают в космос. Об этом ученые рассказали через три дня после того, как аппарат взял образцы грунта с Бенну. Ведущий ученый миссии Данте Лауретта признался, что 21 октября удалось собрать гораздо больше материала, чем ожидалось, – несколько сотен грамм. Контейнер для сбора образцов на конце манипулятора проник так глубоко в астероид, что несколько камешков оказались втянуты внутрь и застряли у края крышки, сообщает Phys.org. Специалисты на Земле изо всех сил пытались втянуть контейнер с грунтом обратно, но частицы образцов продолжают улетать в космос. Ученые пытаются минимизировать потери. «Мы почти стали жертвой собственного успеха», – сказал Лауретта на пресс-конференции. По его словам, единственное, что сейчас могут сделать операторы, чтобы устранить препятствие и предотвратить дальнейшие потери, – как можно скорее доставить образцы в капсулу. Как отметил Лауретта, ситуация более-менее стабилизировалась, когда рука робота перестала двигаться и зафиксировалась на месте.
Orisis-Rex приземлился на астероид 20 октября. Он должен доставить на Землю минимум 2 унции (60 граммов) образцов с Бенну. Богатый углеродом материал содержит «строительные блоки» нашей Солнечной системы, что поможет ученым лучше понять, как образовались планеты и зародилась жизнь на Земле. Планируется, что домой комический аппарат вернется в 2023 году.
воскресенье, 11 октября 2020 г.
На опасном астероиде сделали неожиданное открытие
Астероид 101955 Бенну – один из самых опасных космических соседей Земли. Астрономы оценивают вероятность его столкновения с Землей в ближайшие два века как 1 к 2700. Зато благодаря близости к Земле Бенну – удобный объект для изучения космическими аппаратами. Миссия НАСА Osiris-REx, которая 20 октября должна взять на Бенну пробы грунта, обнаружила на астероиде необычные для полукилометрового небесного тела геологические образования. Как сообщает журнал Sky & Telescope, на фотографиях Бенну астрономы нашли следы древних потоков воды. Ученые считают, что вода из гидротермальных источников текла по астероиду тогда, когда он был частью более крупного небесного тела – так называемого планетезималя. В начальный период образования Солнечной системы этот объект распался на отдельные обломки. «Мы думаем, что вода текла очень рано, через несколько миллионов лет после образования Солнечной системы», – объяснила сотрудник Центра космических полетов имени Годдарда Ханна Каплан. По оценке ученых, объект, от которого откололся Бенну, имел диаметр около 100 км. Раньше считалось, что на таких маленьких небесных телах гидротермальной активности не бывает. Эд Янг из Калифорнийского университета в Лос-Анжелесе предположил такую возможность еще в 1999 году, и только сейчас гипотеза начала подтверждаться.
Ранее сообщалось, что на Бенну обнаружили необычные камни, которые не могли сами образоваться на маленьком астероиде. Возможно, что они происходят с крупного астероида Веста.
вторник, 22 сентября 2020 г.
OSIRIS-REx finds possible pieces of Vesta on Bennu
In an interplanetary faux pas, it appears some pieces of asteroid Vesta ended up on asteroid Bennu, according to observations from NASA's OSIRIS-REx spacecraft. The new result sheds light on the intricate orbital dance of asteroids and on the violent origin of Bennu, which is a "rubble pile" asteroid that coalesced from the fragments of a massive collision. "We found six boulders ranging in size from 5 to 14 feet (about 1.5 to 4.3 meters) scattered across Bennu's southern hemisphere and near the equator," said Daniella DellaGiustina of the Lunar and Planetary Laboratory, University of Arizona, Tucson. "These boulders are much brighter than the rest of Bennu and match material from Vesta." "Our leading hypothesis is that Bennu inherited this material from its parent asteroid after a vestoid (a fragment from Vesta) struck the parent," said Hannah Kaplan of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Then, when the parent asteroid was catastrophically disrupted, a portion of its debris accumulated under its own gravity into Bennu, including some of the pyroxene from Vesta."The unusual boulders on Bennu first caught the team's eye in images from the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) Camera Suite (OCAMS). They appeared extremely bright, with some almost ten times brighter than their surroundings. They analyzed the light from the boulders using the OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) instrument to get clues to their composition.
A spectrometer separates light into its component colors. Since elements and compounds have distinct, signature patterns of bright and dark across a range of colors, they can be identified using a spectrometer. The signature from the boulders was characteristic of the mineral pyroxene, similar to what is seen on Vesta and the vestoids, smaller asteroids that are fragments blasted from Vesta when it sustained significant asteroid impacts.
Of course it's possible that the boulders actually formed on Bennu's parent asteroid, but the team thinks this is unlikely based on how pyroxene typically forms. The mineral typically forms when rocky material melts at high-temperature. However, most of Bennu is composed of rocks containing water-bearing minerals, so it (and its parent) couldn't have experienced very high temperatures.
Next, the team considered localized heating, perhaps from an impact. An impact needed to melt enough material to create large pyroxene boulders would be so significant that it would have destroyed Bennu's parent-body. So, the team ruled out these scenarios, and instead considered other pyroxene-rich asteroids that might have implanted this material to Bennu or its parent.
Observations reveal it's not unusual for an asteroid to have material from another asteroid splashed across its surface. Examples include dark material on crater walls seen by the Dawn spacecraft at Vesta, a black boulder seen by the Hayabusa spacecraft on Itokawa, and very recently, material from S-type asteroids observed by Hayabusa2 at Ryugu. This indicates many asteroids are participating in a complex orbital dance that sometimes results in cosmic mashups.
As asteroids move through the solar system, their orbits can be altered in many ways, including the pull of gravity from planets and other objects, meteoroid impacts, and even the slight pressure from sunlight. The new result helps pin down the complex journey Bennu and other asteroids have traced through the solar system.
Based on its orbit, several studies indicate Bennu was delivered from the inner region of the Main Asteroid Belt via a well-known gravitational pathway that can take objects from the inner Main Belt to near-Earth orbits.
There are two inner Main Belt asteroid families (Polana and Eulalia) that look like Bennu: dark and rich in carbon, making them likely candidates for Bennu's parent. Likewise, the formation of the vestoids is tied to the formation of the Veneneia and Rheasilvia impact basins on Vesta, at roughly about two billion years ago and approximately one billion years ago, respectively.
"Future studies of asteroid families, as well as the origin of Bennu, must reconcile the presence of Vesta-like material as well as the apparent lack of other asteroid types. We look forward to the returned sample, which hopefully contains pieces of these intriguing rock types," said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona in Tucson. "This constraint is even more compelling given the finding of S-type material on asteroid Ryugu. This difference shows the value in studying multiple asteroids across the solar system."
The spacecraft is going to make its first attempt to sample Bennu in October and return it to Earth in 2023 for detailed analysis. The mission team closely examined four potential sample sites on Bennu to determine their safety and science value before making a final selection in December 2019. DellaGiustina and Kaplan's team thinks they might find smaller pieces of Vesta in images from these close-up studies.
DellaGiustina and Kaplan are primary authors of a paper on this research appearing in Nature Astronomy September 21.
Of course it's possible that the boulders actually formed on Bennu's parent asteroid, but the team thinks this is unlikely based on how pyroxene typically forms. The mineral typically forms when rocky material melts at high-temperature. However, most of Bennu is composed of rocks containing water-bearing minerals, so it (and its parent) couldn't have experienced very high temperatures.
Next, the team considered localized heating, perhaps from an impact. An impact needed to melt enough material to create large pyroxene boulders would be so significant that it would have destroyed Bennu's parent-body. So, the team ruled out these scenarios, and instead considered other pyroxene-rich asteroids that might have implanted this material to Bennu or its parent.
Observations reveal it's not unusual for an asteroid to have material from another asteroid splashed across its surface. Examples include dark material on crater walls seen by the Dawn spacecraft at Vesta, a black boulder seen by the Hayabusa spacecraft on Itokawa, and very recently, material from S-type asteroids observed by Hayabusa2 at Ryugu. This indicates many asteroids are participating in a complex orbital dance that sometimes results in cosmic mashups.
As asteroids move through the solar system, their orbits can be altered in many ways, including the pull of gravity from planets and other objects, meteoroid impacts, and even the slight pressure from sunlight. The new result helps pin down the complex journey Bennu and other asteroids have traced through the solar system.
Based on its orbit, several studies indicate Bennu was delivered from the inner region of the Main Asteroid Belt via a well-known gravitational pathway that can take objects from the inner Main Belt to near-Earth orbits.
There are two inner Main Belt asteroid families (Polana and Eulalia) that look like Bennu: dark and rich in carbon, making them likely candidates for Bennu's parent. Likewise, the formation of the vestoids is tied to the formation of the Veneneia and Rheasilvia impact basins on Vesta, at roughly about two billion years ago and approximately one billion years ago, respectively.
"Future studies of asteroid families, as well as the origin of Bennu, must reconcile the presence of Vesta-like material as well as the apparent lack of other asteroid types. We look forward to the returned sample, which hopefully contains pieces of these intriguing rock types," said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona in Tucson. "This constraint is even more compelling given the finding of S-type material on asteroid Ryugu. This difference shows the value in studying multiple asteroids across the solar system."
The spacecraft is going to make its first attempt to sample Bennu in October and return it to Earth in 2023 for detailed analysis. The mission team closely examined four potential sample sites on Bennu to determine their safety and science value before making a final selection in December 2019. DellaGiustina and Kaplan's team thinks they might find smaller pieces of Vesta in images from these close-up studies.
DellaGiustina and Kaplan are primary authors of a paper on this research appearing in Nature Astronomy September 21.
воскресенье, 13 сентября 2020 г.
New small satellite mission to rendezvous with binary asteroids
The University of Colorado Boulder and Lockheed Martin will soon lead a new space mission to capture the first-ever closeup look at a mysterious class of solar system objects: binary asteroids. These bodies are pairs of asteroids that orbit around each other in space, much like the Earth and Moon. In a project review on Sept. 3, NASA gave the official go-ahead to the Janus mission, named after the two-faced Roman god. The mission will study these asteroid couplets in never-before-seen detail. Known as Key Decision Point-C (KDP-C), this review and approval from NASA allows for the project to begin implementation, and baselines +the project's official schedule and budget. It will be a moment for twos: In 2022, the Janus team will launch two identical spacecraft that will travel millions of miles to individually fly close to two pairs of binary asteroids. Their observations could open up a new window into how these diverse bodies evolve and even burst apart over time, said Daniel Scheeres, the principle investigator for Janus. "Binary asteroids are one class of objects for which we don't have high-resolution scientific data," said Scheeres, distinguished professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences at CU Boulder. "Everything we have on them is based on ground observations, which don't give you as much detail as being up close." The mission, which will cost less than $55 million under NASA's SIMPLEx program, may also help to usher in a new era of space exploration, said Lockheed Martin's Janus Project Manager Josh Wood. He explained that Janus' twin spacecraft are designed to be small and nimble, each one about the size of a carry-on suitcase.
"We see an advantage to be able to shrink our spacecraft," said Wood. "With technology advancements, we can now explore our solar system and address important science questions with smaller spacecraft."
Janus is led by the University of Colorado Boulder, where Scheeres is based, which will also undertake the scientific analysis of images and data for the mission. Lockheed Martin will manage, build and operate the spacecraft.
The mission will rendezvous with two binary pairs-named 1996 FG3 and 1991 VH-each showcasing a different kind of orbital pattern. The pair called 1991 VH, for example, has a "moon" that whips around a much bigger "primary" asteroid following a hard-to-predict pattern.
The team will use a suite of cameras to track the dynamical motion in unprecedented detail. Among other goals, Scheeres and his colleagues hope to learn more about how binary asteroids move-both around each other and through space.
"Once we see them up close up, there will be a lot of questions we can answer, but these will raise new questions as well," Scheeres said. "We think Janus will motivate additional missions to binary asteroids."
Wood added that the mission's twin spacecraft, each of which weigh just about 80 pounds, will travel farther than any small satellite to date.
After blasting off in 2022, they'll first complete an orbit around the sun, before heading back toward Earth and sling-shotting their way far into space and beyond the orbit of Mars.
"I think it's a great test for what is achievable from the aerospace community," Wood said. "And the Colorado-centric development for this mission, combining the space talent of both CU Boulder and Lockheed Martin, is a testament to the skills available in the state."
"We see an advantage to be able to shrink our spacecraft," said Wood. "With technology advancements, we can now explore our solar system and address important science questions with smaller spacecraft."
Janus is led by the University of Colorado Boulder, where Scheeres is based, which will also undertake the scientific analysis of images and data for the mission. Lockheed Martin will manage, build and operate the spacecraft.
The mission will rendezvous with two binary pairs-named 1996 FG3 and 1991 VH-each showcasing a different kind of orbital pattern. The pair called 1991 VH, for example, has a "moon" that whips around a much bigger "primary" asteroid following a hard-to-predict pattern.
The team will use a suite of cameras to track the dynamical motion in unprecedented detail. Among other goals, Scheeres and his colleagues hope to learn more about how binary asteroids move-both around each other and through space.
"Once we see them up close up, there will be a lot of questions we can answer, but these will raise new questions as well," Scheeres said. "We think Janus will motivate additional missions to binary asteroids."
Wood added that the mission's twin spacecraft, each of which weigh just about 80 pounds, will travel farther than any small satellite to date.
After blasting off in 2022, they'll first complete an orbit around the sun, before heading back toward Earth and sling-shotting their way far into space and beyond the orbit of Mars.
"I think it's a great test for what is achievable from the aerospace community," Wood said. "And the Colorado-centric development for this mission, combining the space talent of both CU Boulder and Lockheed Martin, is a testament to the skills available in the state."
пятница, 28 августа 2020 г.
Meteorite strikes may create unexpected form of silica
When a meteorite hurtles through the atmosphere and crashes to Earth, how does its violent impact alter the minerals found at the landing site? What can the short-lived chemical phases created by these extreme impacts teach scientists about the minerals existing at the high-temperature and pressure conditions found deep inside the planet? New work led by Carnegie's Sally June Tracy examined the crystal structure of the silica mineral quartz under shock compression and is challenging longstanding assumptions about how this ubiquitous material behaves under such intense conditions. The results are published in Science Advances. "Quartz is one of the most abundant minerals in Earth's crust, found in a multitude of different rock types," Tracy explained. "In the lab, we can mimic a meteorite impact and see what happens." Tracy and her colleagues - Washington State University's (WSU) Stefan Turneaure and Princeton University's Thomas Duffy, a former Carnegie Fellow - used a specialized cannon-like gas gun to accelerate projectiles into quartz samples at extremely high speeds - several times faster than a bullet fired from a rifle. Special X-ray instruments were used to discern the crystal structure of the material that forms less than one-millionth of a second after impact. Experiments were carried out at the Dynamic Compression Sector (DCS), which is operated by WSU and located at the Advanced Photon Source, Argonne National Laboratory.
Quartz is made up of one silicon atom and two oxygen atoms arranged in a tetrahedral lattice structure. Because these elements are also common in the silicate-rich mantle of the Earth, discovering the changes quartz undergoes at high-pressure and -temperature conditions, like those found in the Earth's interior, could also reveal details about the planet's geologic history.
When a material is subjected to extreme pressures and temperatures, its internal atomic structure can be re-shaped, causing its properties to shift. For example, both graphite and diamond are made from carbon.
But graphite, which forms at low pressure, is soft and opaque, and diamond, which forms at high pressure, is super-hard and transparent. The different arrangements of carbon atoms determine their structures and their properties, and that in turn affects how we engage with and use them.
Despite decades of research, there has been a long-standing debate in the scientific community about what form silica would take during an impact event, or under dynamic compression conditions such as those deployed by Tracy and her collaborators. Under shock loading, silica is often assumed to transform to a dense crystalline form known as stishovite - a structure believed to exist in the deep Earth. Others have argued that because of the fast timescale of the shock the material will instead adopt a dense, glassy structure.
Tracy and her team were able to demonstrate that counter to expectations, when subjected to a dynamic shock of greater than 300,000 times normal atmospheric pressure, quartz undergoes a transition to a novel disordered crystalline phase, whose structure is intermediate between fully crystalline stishovite and a fully disordered glass. However, the new structure cannot last once the burst of intense pressure has subsided.
"Dynamic compression experiments allowed us to put this longstanding debate to bed," Tracy concluded. "What's more, impact events are an important part of understanding planetary formation and evolution and continued investigations can reveal new information about these processes."
Quartz is made up of one silicon atom and two oxygen atoms arranged in a tetrahedral lattice structure. Because these elements are also common in the silicate-rich mantle of the Earth, discovering the changes quartz undergoes at high-pressure and -temperature conditions, like those found in the Earth's interior, could also reveal details about the planet's geologic history.
When a material is subjected to extreme pressures and temperatures, its internal atomic structure can be re-shaped, causing its properties to shift. For example, both graphite and diamond are made from carbon.
But graphite, which forms at low pressure, is soft and opaque, and diamond, which forms at high pressure, is super-hard and transparent. The different arrangements of carbon atoms determine their structures and their properties, and that in turn affects how we engage with and use them.
Despite decades of research, there has been a long-standing debate in the scientific community about what form silica would take during an impact event, or under dynamic compression conditions such as those deployed by Tracy and her collaborators. Under shock loading, silica is often assumed to transform to a dense crystalline form known as stishovite - a structure believed to exist in the deep Earth. Others have argued that because of the fast timescale of the shock the material will instead adopt a dense, glassy structure.
Tracy and her team were able to demonstrate that counter to expectations, when subjected to a dynamic shock of greater than 300,000 times normal atmospheric pressure, quartz undergoes a transition to a novel disordered crystalline phase, whose structure is intermediate between fully crystalline stishovite and a fully disordered glass. However, the new structure cannot last once the burst of intense pressure has subsided.
"Dynamic compression experiments allowed us to put this longstanding debate to bed," Tracy concluded. "What's more, impact events are an important part of understanding planetary formation and evolution and continued investigations can reveal new information about these processes."
четверг, 13 августа 2020 г.
На Землю нацелился 30-метровый астероид
Астероид 2011 ES4 летит к Земле со скоростью 8,2 км в секунду (29,5 тысячи км в час) и вплотную приблизится к ней 1 сентября 2020 года. Причем, расстояние, на которое он подлетит к нашей планете опасно мало, по космическим масштабам — ничтожно: всего 0,3 лунной дистанции (расстояние от Земли до Луны). По данным NASA, диаметр астероида составляет около 30 метров, что примерно соответствует по высоте 9-этажному дому. Впервые астероид 2011 ES4 был замечен 2 марта 2011 года. Он относится к группе Аполлона и один оборот вокруг Солнца он совершает за 416 земных дней или 1,14 земных года. По данным in-space.ru, максимально с Землей астероид сблизится 1 сентября. В 19:12 по московскому времени он окажется на расстоянии всего около 121 тысячи километров. Учитывая его скорость, это расстояние до Земли он бы смог преодолеть за 4 часа.
среда, 10 июня 2020 г.
OSIRIS-REx finds heat, cold fracturing rocks on Asteroid Bennu
Close-up observations of asteroid Bennu by NASA's OSIRIS-REx spacecraft contain the first evidence of thermal fracturing of rocks on an airless body, a Nature Communications paper by Planetary Science Institute Research Scientist Jamie Molaro says. Thermal fracturing or thermal stress weathering occurs as rocks heat and cool each day, and mechanical stresses build up that can cause cracks to develop and grow. Over time the cracks grow larger and cause the rock to disaggregate or split into multiple pieces. For example, daytime highs on Bennu can reach about 400 degrees Kelvin (260 degrees Fahrenheit), and nighttime lows plummet to 200 degrees Kelvin (-100 degrees Fahrenheit). "This is the first time evidence for thermal fracturing has been definitively observed on an object without an atmosphere," said Molaro, lead author of the paper "In Situ Evidence of Thermally Induced Rock Breakdown Widespread on Bennu's Surface" published June 9, 2020. "It is one piece of a puzzle that tells us what the surface used to be like, and what it will be like millions of years from now." "This thermally induced breakdown has long been known on Earth. The OSIRIS-REx Camera Suite (OCAMS) orbiting as close as 0.6 km (0.4 mi) has obtained images of the surface of Bennu at pixel scales down to about 1 centimeter per pixel, providing an opportunity to search over a wide range of scales for evidence of thermal breakdown occurring in situ," Molaro said.
"On Earth there are chemical weathering processes that help make thermal fracturing more efficient. The presence of air and moisture within cracks makes them easier to grow, and so on Earth this effect really cannot be decoupled from the effect of the thermal stresses themselves.
"We've observed evidence of thermal fracturing on Earth and on Mars, both environments where chemical weathering may play a role. Therefore, while it was theoretically possible for thermal fracturing on an airless body to occur alone, it was not clear whether or not the stresses would be strong enough to cause crack growth in absence of the chemical effects," Molaro said.
"Like any weathering process, thermal fracturing can cause the evolution of boulders and planetary surfaces over time; from changing the shape and size of individual boulders, to producing pebbles or fine-grained regolith, to breaking down crater walls," Molaro said. "How quickly this occurs relative to other weathering processes tells us how quickly the surface has changed.
It is one piece of a puzzle that tells us what the planetary surface used to be like, and what it will be like millions of years from now. We don't have good constraints yet on breakdown rates from thermal fracturing, but we can get them now that we can actually observe evidence for it for the first time in-situ.
"We show observations of boulder morphologies and fractures on Bennu that are consistent with models of thermally induced rock breakdown, and not easily explained by other weathering mechanisms. Boulders on Bennu exhibit many possible signs of thermal fracturing, but the clearest is images showing exfoliation, where thin layers of material flake off boulder surfaces," Molaro said.
"These findings provide substantive and compelling evidence that thermal fracturing plays an important role on airless body surfaces, which has major implications for understanding the evolution of asteroid surfaces, orbits, and populations."
"We've observed evidence of thermal fracturing on Earth and on Mars, both environments where chemical weathering may play a role. Therefore, while it was theoretically possible for thermal fracturing on an airless body to occur alone, it was not clear whether or not the stresses would be strong enough to cause crack growth in absence of the chemical effects," Molaro said.
"Like any weathering process, thermal fracturing can cause the evolution of boulders and planetary surfaces over time; from changing the shape and size of individual boulders, to producing pebbles or fine-grained regolith, to breaking down crater walls," Molaro said. "How quickly this occurs relative to other weathering processes tells us how quickly the surface has changed.
It is one piece of a puzzle that tells us what the planetary surface used to be like, and what it will be like millions of years from now. We don't have good constraints yet on breakdown rates from thermal fracturing, but we can get them now that we can actually observe evidence for it for the first time in-situ.
"We show observations of boulder morphologies and fractures on Bennu that are consistent with models of thermally induced rock breakdown, and not easily explained by other weathering mechanisms. Boulders on Bennu exhibit many possible signs of thermal fracturing, but the clearest is images showing exfoliation, where thin layers of material flake off boulder surfaces," Molaro said.
"These findings provide substantive and compelling evidence that thermal fracturing plays an important role on airless body surfaces, which has major implications for understanding the evolution of asteroid surfaces, orbits, and populations."
понедельник, 8 июня 2020 г.
STEREO watches Comet ATLAS as Solar Orbiter crosses its tail
NASA's Solar Terrestrial Relations Observatory, or STEREO-A spacecraft, captured these images of comet ATLAS as it swooped by the Sun from May 25 - June 1. During the observations and outside STEREO's field of view, ESA/NASA's Solar Orbiter spacecraft crossed one of the comet's two tails. In the animated image, ATLAS emerges from the top of the frame and approaches the Sun - off camera to left - against gusts of solar wind. Its dust tail, which reflects sunlight, appears white. Mercury is also visible as a bright dot emerging from the left against the stationary starfield. The vertical streaks in the image are artifacts created by saturation from bright background stars. While STEREO recorded this footage, Solar Orbiter crossed one of comet ATLAS's tails. Launched in February 2020, the spacecraft wasn't scheduled to enter full science operations until June 15, but engineers adjusted Solar Orbiter's testing schedule and turned on its four most relevant instruments for the encounter. It's the first time a comet tail crossing by a spacecraft not designed to chase them was predicted in advance. As material sheds from a comet's nucleus, it leaves behind two tails: a thin ion tail, made of charged particles, and a more diffuse dust tail that reflects visible light. The ion tail always points away from the Sun regardless of the comet's trajectory; the dust tail more closely follows the comet's path. Solar Orbiter crossed the ion tail on May 31, some 27 million miles downstream and outside STEREO's field of view. The team is still awaiting those results. It will fly through the remnants of the dust tail on June 6.
Comet ATLAS was discovered on Dec. 28, 2019 in images captured by the Asteroid Terrestrial-impact Last Alert System, or ATLAS robotic astronomical survey system in Hawaii. Comets are traditionally named after the instruments or person that discovered them.
The comet follows an orbit that takes it past the Sun approximately every 6,000 years, though observations suggest the comet is currently disintegrating and is unlikely to return. It likely originated in the Oort cloud, a spherical cloud of ice and rocks surrounding our solar system. The Oort cloud begins about 185 billion miles away, some 67 times farther than Neptune.
The comet follows an orbit that takes it past the Sun approximately every 6,000 years, though observations suggest the comet is currently disintegrating and is unlikely to return. It likely originated in the Oort cloud, a spherical cloud of ice and rocks surrounding our solar system. The Oort cloud begins about 185 billion miles away, some 67 times farther than Neptune.
четверг, 4 июня 2020 г.
OSIRIS-REx swoops over sample site Osprey
This view of sample site Osprey on asteroid Bennu is a mosaic of images collected by NASA's OSIRIS-REx spacecraft on May 26. A total of 347 PolyCam images were stitched together and corrected to produce the mosaic, which shows the site at 0.2 inches (5 mm) per pixel at full size. The spacecraft took these images during an 820-foot (250-meter) reconnaissance pass over the site, which is the closest Osprey has been imaged. The pass was designed to provide high-resolution imagery to identify the best areas within the site to collect a sample. The sample site is located in the crater at the bottom of the image, just above the dark patch at the crater's center. The long, light-colored boulder to the left of the dark patch, named Strix Saxum, is 17 ft (5.2 m) in length. The mosaic is rotated so that Bennu's east is at the top of the image. Osprey is the backup sample collection site for the OSIRIS-REx mission. OSIRIS-REx is scheduled to make its first sample collection attempt at primary site Nightingale on Oct. 20.
понедельник, 1 июня 2020 г.
Миссия DART по отклонению движений астероида идет по плану
Согласно новой оценке Управления по подотчетности правительства (GAO), оборонная планетарная миссия НАСА, направленная на отклонение небольшого астероида, продолжает двигаться по своему пути к запуску в феврале 2022 года, сохраняя при этом бюджет в $313,9 миллионов. Тест миссии на перенаправление двойного астероида (DART) будет проведен на двойном астероиде Didymos. Аппарат будет воздействовать на меньшее из двух тел, чтобы оценить методы отклонения опасных астероидов с курса от столкновения с Землей. Первоначально НАСА планировало отправить миссию DART в полет на раета-носителе с другой полезной нагрузкой. Впоследствии агентство выбрало Falcon 9 от SpaceX в качестве новой ракеты-носителя. «По словам официальных лиц, наличие специальной ракеты-носителя позволяет создать новую траекторию, которая снижает количество необходимого топлива», - говорится в оценке GAO. «В результате проект больше не опирается на демонстрацию технологии эволюционного ксенонового двигателя (NEXT-C) НАСА Evolutionary, которая испытывает задержки в своей разработке». Миссия НАСА DART является частью международной миссии по оценке воздействия и отклонения астероида, сотрудничества с Европейским космическим агентством (ESA) и Итальянским космическим агентством (ASI).
ASI предоставит легкий итальянский CubeSat для получения изображений астероида (LICIACube), который будет документировать влияние DART на астероид Didymos.
«В ноябре 2019 года Европейское космическое агентство (ESA) утвердило миссию HERA, возможную миссию, которая должна быть запущена в 2024 году. Она предоставит дополнительный последующий анализ воздействия аппарата DART. НАСА и ЕКА еще не достигли официального соглашения по этой миссии», - говорится в сообщении.
«В ноябре 2019 года Европейское космическое агентство (ESA) утвердило миссию HERA, возможную миссию, которая должна быть запущена в 2024 году. Она предоставит дополнительный последующий анализ воздействия аппарата DART. НАСА и ЕКА еще не достигли официального соглашения по этой миссии», - говорится в сообщении.
суббота, 30 мая 2020 г.
The asteroids Ryugu and Bennu were formed by the destruction of a large asteroid
What is the origin of the asteroids Bennu and Ryugu, and of their spinning-top shape? An international research team led by Patrick Michel, a CNRS researcher at the Laboratoire Lagrange and Ronald-Louis Ballouz from the University of Arizona, proposes an answer to this question in an article published in Nature Communications on May 27, 2020. Numerical simulations of large asteroid disruptions, such as those that take place in the asteroid belt between Mars and Jupiter, show that during such events, fragments are ejected and then reaccumulate forming aggregates, some of which have a spinning-top shape. The simulations also show that Bennu and Ryugu may have formed from the disruption of the same parent asteroid even though their levels of hydration are different. The scientists conclude that the overall properties of these asteroids could directly result from the disruption of their parent body. The analysis of return samples from Ryugu and Bennu by the Hayabusa2 (JAXA) and OSIRIS-REx (NASA) spacecraft will allow us to verify this by measuring precisely their composition and by determining their formation age.
воскресенье, 24 мая 2020 г.
Миссия «Психея» задерживается из-за проблем с приобретением электронных компонентов
Первая миссия НАСА по исследованию металлического астероида столкнулась с задержками в получении ключевых инструментов и передовых электронных компонентов, согласно новой оценке Управления по подотчетности правительства США (GAO). Миссия «Психея» стоимостью $996,4 миллионов нацелена на изучение металлического астероида 16 Психея. Запуск космического корабля запланирован на август 2022 года. «Главный технический риск для проекта заключается в том, что доставка магнитометров, используемых для обнаружения и измерения магнитного поля астероида Психея, вероятно, будет отложена на срок до 4 месяцев из-за потери опытного персонала и рабочих на заводах его подрядчика», - говорится в оценке. Чиновники программы также сообщают, что приобретение передовых электронных компонентов стоит дороже и занимает больше времени, чем предполагалось. «Официальные лица заявили, что эти длительные сроки подготовки привели к задержкам в поставках деталей, что в свою очередь задержало испытание конструкции прибора для гамма-лучевого и нейтронного спектрометра (GRNS), который будет использоваться для определения элементного состава Психеи - примерно через 3 месяца», - говорится в сообщении.
Миссия пытается уменьшить эти риски, нанимая больше персонала, ища альтернативных поставщиков и повышая приоритет на покупку запчастей, изготовление которых требует длительного времени.
пятница, 22 мая 2020 г.
NASA's Webb will study the 'building blocks' of our solar system
Millions of asteroids roam our solar system. Many are clustered between Mars and Jupiter in the main asteroid belt while another group, known as Trojans, both lead and follow Jupiter. What can these chunks of rock, which zip around the solar system like race cars, tell us about the formation of the solar system? Upcoming research with NASA's James Webb Space Telescope, led by Andrew S. Rivkin of the Johns Hopkins University Applied Physics Laboratory, will yield new data that will help astronomers begin to unravel these mysteries. "What's great about asteroids is that there are so many of them," said Rivkin. "It means there is always something bright enough and in the right place for Webb to observe." Rivkin is collaborating with Cristina A. Thomas of Northern Arizona University; Stefanie N. Milam of NASA's Goddard Space Flight Center; and Heidi Hammel, a planetary astronomer and vice president for science of the Association of Universities for Research in Astronomy (AURA) in Washington, D.C., to observe these asteroids in near- and mid-infrared light. This team's program will add many new observations to the growing body of research about asteroids, and will help them learn more about the origins and makeup of asteroids, providing clues to the history of how planets moved around in the early solar system.
The Dawn of the Solar System
Imagine our solar system as it formed 4.6 billion years ago: around our young Sun, a disk of gas and dust swirled, slowly condensing and creating small objects. As larger bodies like Jupiter and Saturn began forming, they collected gobs of gas, growing bigger and bigger. Soon, the gravitational influence of these larger bodies started to sculpt the disk, creating gaps.
Over millions of years, it's theorized that Jupiter, Saturn, Uranus and Neptune began moving from where they initially formed to their current locations, continuing to shape the inner solar system and eventually locking leftover rocks between Mars and Jupiter in regular orbits. As Jupiter moved inward, it kept these small objects stirred up, which meant that they could not as easily merge with one another to eventually form larger bodies like planets.
These messy, rocky leftovers are asteroids. Scientists now know that asteroids were the "building blocks" of the rocky, inner planets. Some formed closer to the Sun and others formed farther away, which means their compositions vary a lot. Perhaps the most intriguing detail researchers have already learned is that many asteroids may not have formed where they currently orbit.
The Rock Stars
This research team plans to study five known asteroids, three in the main asteroid belt and two Trojans, in near- and mid-infrared wavelengths to complement and extend other NASA missions' observations, and test new techniques with Webb.
They will observe these asteroids in part by using Webb's Near-Infrared Spectrograph (NIRSpec), an instrument that breaks light into its component colors to create a spectrum that the researchers will analyze to learn about each object's composition.
One key target in the main asteroid belt is a dwarf planet known as Ceres, which was visited by NASA's Dawn spacecraft from 2015 to 2018. Ceres has minerals containing ammonia on its surface, leading researchers to wonder whether it formed farther out in the solar system or if the dwarf planet incorporated material from farther afield. By obtaining Webb measurements at longer wavelengths than those obtained by Dawn, the team will be able to use the unique and complementary data set to verify if previous conclusions about its surface composition are correct.
At the same time, the observations will help establish a technique to observe targets that may be slightly too bright to observe in these wavelengths with Webb. "By doing the best science we can do with this bright object, we may open doors to new science opportunities with Webb for other researchers," Milam said.
Pallas, the second-largest asteroid in the main belt and a dwarf planet candidate, is another important target. Because of its orbit, Pallas would be very difficult for a spacecraft to visit. By observing it with Webb, this team will gather data about its surface and composition that is otherwise difficult to obtain. The team will also compare measurements of Pallas and another dwarf planet candidate, Hygeia, to data about Ceres, helping them identify the similarities and differences of their targets. These comparisons may offer clues about the formation histories of these building blocks of the inner planets.
The Trojan targets, Patroclus and Hektor, are very different from Webb's other asteroid targets-not only due to their location near Jupiter, but because they also have moons. Hektor is a binary and its moon orbits closely. In contrast, Patroclus and its moon have more space between them. "Webb will allow us to investigate each asteroid and moon separately," explained Rivkin. "By studying their moons, we'll also be able to examine how each of these binaries formed and compare these two systems." The data will also help astronomers refine models of how the Trojan asteroids were captured in their current orbits.
Data for the Entire Planetary Science Community
The team selected the program's targets carefully, ensuring that their data enhance those from existing and future missions and observatories. "Patroclus, for example, is a target of NASA's upcoming Lucy mission," Thomas said. "We can also compare the Webb data to previous data from ground-based observatories. There will be a lot of complementary data to examine."
By unraveling the histories of these particular asteroids, the research team hopes to learn more about our solar system's past. They emphasize that Webb provides a unique opportunity, not only due to its specialization in infrared light, but also because some of these targets are so difficult to observe with other facilities. "Webb lets us 'visit' a lot more asteroids with really high-quality observations we can't get with telescopes on the ground," Rivkin said.
The observatory also offers new scientific opportunities. "Webb will open a frontier for all scientists," explained Milam. "Our data will lead to new questions and provoke a lot of new science ideas for astronomers who are considering using Webb in the future."
This research is being conducted as part of a Webb Guaranteed Time Observations (GTO) program
of the solar system led by Heidi Hammel, a Webb interdisciplinary scientist. Dedicated GTO time was provided to the scientists who have worked with NASA to craft the science capabilities of Webb throughout its development.
"The purpose of these investigations is to ensure we're not only doing the best science we can do, but also setting the stage for the science that will come with Webb in the future," Hammel said.
Imagine our solar system as it formed 4.6 billion years ago: around our young Sun, a disk of gas and dust swirled, slowly condensing and creating small objects. As larger bodies like Jupiter and Saturn began forming, they collected gobs of gas, growing bigger and bigger. Soon, the gravitational influence of these larger bodies started to sculpt the disk, creating gaps.
Over millions of years, it's theorized that Jupiter, Saturn, Uranus and Neptune began moving from where they initially formed to their current locations, continuing to shape the inner solar system and eventually locking leftover rocks between Mars and Jupiter in regular orbits. As Jupiter moved inward, it kept these small objects stirred up, which meant that they could not as easily merge with one another to eventually form larger bodies like planets.
These messy, rocky leftovers are asteroids. Scientists now know that asteroids were the "building blocks" of the rocky, inner planets. Some formed closer to the Sun and others formed farther away, which means their compositions vary a lot. Perhaps the most intriguing detail researchers have already learned is that many asteroids may not have formed where they currently orbit.
The Rock Stars
This research team plans to study five known asteroids, three in the main asteroid belt and two Trojans, in near- and mid-infrared wavelengths to complement and extend other NASA missions' observations, and test new techniques with Webb.
They will observe these asteroids in part by using Webb's Near-Infrared Spectrograph (NIRSpec), an instrument that breaks light into its component colors to create a spectrum that the researchers will analyze to learn about each object's composition.
One key target in the main asteroid belt is a dwarf planet known as Ceres, which was visited by NASA's Dawn spacecraft from 2015 to 2018. Ceres has minerals containing ammonia on its surface, leading researchers to wonder whether it formed farther out in the solar system or if the dwarf planet incorporated material from farther afield. By obtaining Webb measurements at longer wavelengths than those obtained by Dawn, the team will be able to use the unique and complementary data set to verify if previous conclusions about its surface composition are correct.
At the same time, the observations will help establish a technique to observe targets that may be slightly too bright to observe in these wavelengths with Webb. "By doing the best science we can do with this bright object, we may open doors to new science opportunities with Webb for other researchers," Milam said.
Pallas, the second-largest asteroid in the main belt and a dwarf planet candidate, is another important target. Because of its orbit, Pallas would be very difficult for a spacecraft to visit. By observing it with Webb, this team will gather data about its surface and composition that is otherwise difficult to obtain. The team will also compare measurements of Pallas and another dwarf planet candidate, Hygeia, to data about Ceres, helping them identify the similarities and differences of their targets. These comparisons may offer clues about the formation histories of these building blocks of the inner planets.
The Trojan targets, Patroclus and Hektor, are very different from Webb's other asteroid targets-not only due to their location near Jupiter, but because they also have moons. Hektor is a binary and its moon orbits closely. In contrast, Patroclus and its moon have more space between them. "Webb will allow us to investigate each asteroid and moon separately," explained Rivkin. "By studying their moons, we'll also be able to examine how each of these binaries formed and compare these two systems." The data will also help astronomers refine models of how the Trojan asteroids were captured in their current orbits.
Data for the Entire Planetary Science Community
The team selected the program's targets carefully, ensuring that their data enhance those from existing and future missions and observatories. "Patroclus, for example, is a target of NASA's upcoming Lucy mission," Thomas said. "We can also compare the Webb data to previous data from ground-based observatories. There will be a lot of complementary data to examine."
By unraveling the histories of these particular asteroids, the research team hopes to learn more about our solar system's past. They emphasize that Webb provides a unique opportunity, not only due to its specialization in infrared light, but also because some of these targets are so difficult to observe with other facilities. "Webb lets us 'visit' a lot more asteroids with really high-quality observations we can't get with telescopes on the ground," Rivkin said.
The observatory also offers new scientific opportunities. "Webb will open a frontier for all scientists," explained Milam. "Our data will lead to new questions and provoke a lot of new science ideas for astronomers who are considering using Webb in the future."
This research is being conducted as part of a Webb Guaranteed Time Observations (GTO) program
of the solar system led by Heidi Hammel, a Webb interdisciplinary scientist. Dedicated GTO time was provided to the scientists who have worked with NASA to craft the science capabilities of Webb throughout its development.
"The purpose of these investigations is to ensure we're not only doing the best science we can do, but also setting the stage for the science that will come with Webb in the future," Hammel said.
четверг, 21 мая 2020 г.
OSIRIS-REx ready for touchdown on Asteroid Bennu for sample collection
NASA's first asteroid sample return mission is officially prepared for its long-awaited touchdown on asteroid Bennu's surface. The Origins, Spectral Interpretation, Resource Identification and Security - Regolith Explorer (OSIRIS-REx) mission has targeted Oct. 20 for its first sample collection attempt. "The OSIRIS-REx mission has been demonstrating the very essence of exploration by persevering through unexpected challenges," said Thomas Zurbuchen, NASA's associate administrator for science. "That spirit has led them to the cusp of the prize we all are waiting for - securing a sample of an asteroid to bring home to Earth, and I'm very excited to follow them through the home stretch." From discovering Bennu's surprisingly rugged and active surface, to entering the closest-ever orbit around a planetary body, OSIRIS-REx has overcome several challenges since arriving at the asteroid in December 2018. Last month, the mission brought the spacecraft 213 ft (65 m) from the asteroid's surface during its first sample collection rehearsal - successfully completing a practice run of the activities leading up to the sampling event. Now that the mission is ready to collect a sample, the team is facing a different kind of challenge here on Earth. In response to COVID-19 constraints and after the intense preparation for the first rehearsal, the OSIRIS-REx mission has decided to provide its team with additional preparation time for both the final rehearsal and the sample collection event.
Spacecraft activities require significant lead time for the development and testing of operations, and given the current requirements that limit in-person participation at the mission support area, the mission would benefit from giving the team additional time to complete these preparations in the new environment. As a result, both the second rehearsal and first sample collection attempt will have two extra months for planning.
"In planning the mission, we included robust schedule margin while at Bennu to provide the flexibility to address unexpected challenges," said Rich Burns, OSIRIS-REx project manager at NASA's Goddard Space Flight Center. "This flexibility has allowed us to adapt to the surprises that Bennu has thrown at us. It's now time to prioritize the health and safety of both team members and the spacecraft."
The mission had originally planned to perform the first Touch-and-Go (TAG) sample collection event on Aug. 25 after completing a second rehearsal in June. This rehearsal, now scheduled for Aug. 11, will bring the spacecraft through the first three maneuvers of the sample collection sequence to an approximate altitude of 131 ft (40 m) over the surface of Bennu. The first sample collection attempt is now scheduled for Oct. 20, during which the spacecraft will descend to Bennu's surface and collect material from sample site Nightingale.
"This mission's incredible performance so far is a testament to the extraordinary skill and dedication of the OSIRIS-REx team," said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson. "I am confident that even in the face of the current challenge, this team will be successful in collecting our sample from Bennu."
During the TAG event, OSIRIS-REx's sampling mechanism will touch Bennu's surface for approximately five seconds, fire a charge of pressurized nitrogen to disturb the surface, and collect a sample before the spacecraft backs away.
The mission has resources onboard for three sample collection opportunities. If the spacecraft successfully collects a sufficient sample on Oct. 20, no additional sampling attempts will be made. The spacecraft is scheduled to depart Bennu in mid-2021, and will return the sample to Earth on Sept. 24, 2023.
"In planning the mission, we included robust schedule margin while at Bennu to provide the flexibility to address unexpected challenges," said Rich Burns, OSIRIS-REx project manager at NASA's Goddard Space Flight Center. "This flexibility has allowed us to adapt to the surprises that Bennu has thrown at us. It's now time to prioritize the health and safety of both team members and the spacecraft."
The mission had originally planned to perform the first Touch-and-Go (TAG) sample collection event on Aug. 25 after completing a second rehearsal in June. This rehearsal, now scheduled for Aug. 11, will bring the spacecraft through the first three maneuvers of the sample collection sequence to an approximate altitude of 131 ft (40 m) over the surface of Bennu. The first sample collection attempt is now scheduled for Oct. 20, during which the spacecraft will descend to Bennu's surface and collect material from sample site Nightingale.
"This mission's incredible performance so far is a testament to the extraordinary skill and dedication of the OSIRIS-REx team," said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson. "I am confident that even in the face of the current challenge, this team will be successful in collecting our sample from Bennu."
During the TAG event, OSIRIS-REx's sampling mechanism will touch Bennu's surface for approximately five seconds, fire a charge of pressurized nitrogen to disturb the surface, and collect a sample before the spacecraft backs away.
The mission has resources onboard for three sample collection opportunities. If the spacecraft successfully collects a sufficient sample on Oct. 20, no additional sampling attempts will be made. The spacecraft is scheduled to depart Bennu in mid-2021, and will return the sample to Earth on Sept. 24, 2023.
понедельник, 11 мая 2020 г.
Hayabusa 2 помог определить, что астероид Рюгу «обгорел» на Солнце, приблизившись к нему
Японский зонд Hayabusa 2 продолжает свой путь на Землю после успешно выполненной миссии у астероида Рюгу. Ожидается, что аппарат доставит на нашу планету образцы астероида в декабре этого года. Но уже собранных Hayabusa 2 данных достаточно для проведения ряда исследований, о некоторых из них, раскрывающих химическую и физическую природу Рюгу, мы уже рассказывали. Теперь выяснились новые подробности из жизни космического камня, который хранит следы древней Солнечной системы. Hayabusa 2 несколько раз сближался с астероидом, посылал на его поверхность посадочные аппараты, дважды совершил заборы проб грунта. В ходе работ он снимал поверхность Рюгу с помощью своей камеры и спектрометра. Изучая снимки, физики Токийского университета обнаружили, что на поверхности присутствуют два разных типа материала, отличающихся цветами: материал ближе к синей части спектра распределен на экваториальном гребне и в полярных областях, а красноватый материал сосредоточен в средних широтах. В качестве места для отбора проб 21 февраля 2019 года был выбран участок со смешанными цветами. Однако когда поверхностный слой был поврежден воздействием пробоотборного механизма, под ним обнажился красноватый материал. Также астрономы выяснили, что более крупные валуны чаще имеют синеватый цвет, а более мелкий материал вокруг них – красноватый. Было обнаружено, что кратеры, заполненные более синим материалом, оказывались моложе, чем красноватые. Как будто удар пробил красный верхний слой и обнажил синюю поверхность под ним. Все это предполагало, что основная часть астероида была первоначально синеватой и покраснела под воздействием некоторых процессов. Причем временные и химические ограничения накладывает тот факт, что более крупные валуны не покраснели в отличие от мелких частиц.
Астрономам известны два механизма, которые могут приводить к такому результату. Это космическое выветривание и солнечная радиация. Но выветривание обычно «красит» только очень тонкий поверхностный слой, буквально нанометры его, тогда как солнечная радиация проникает глубже. Расчеты же показывают, что красноватый слой Рюгу составлял несколько десятков сантиметров.
Исследователи считают, что Рюгу мог «покраснеть», сблизившись с Солнцем в какой-то фазе своей жизни, оказавшейся менее спокойной, чем можно было предположить. Последние изменения его структуры произошли всего 8,7 миллиона лет назад, то есть астероид очень молодой. Он начал свою жизнь в поясе астероидов на орбите между Марсом и Юпитером, где столкновения с другими телами происходят гораздо чаще, чем на нынешней орбите Рюгу относительно недалеко от земной. Основываясь на цветах и количестве крупных кратеров на поверхности, ученые и рассчитали время, когда Рюгу мог покинуть главный пояс астероидов и «обгореть».
Учитывая эти химические отпечатки путешествия Рюгу по Солнечной системе, ученые с еще большим нетерпением ждут доставки образцов Hayabusa 2, поскольку в пробоотборник должны были попасть образцы и синеватые, и красноватые.
Учитывая эти химические отпечатки путешествия Рюгу по Солнечной системе, ученые с еще большим нетерпением ждут доставки образцов Hayabusa 2, поскольку в пробоотборник должны были попасть образцы и синеватые, и красноватые.
четверг, 30 апреля 2020 г.
Космический телескоп NASA показал уникальные снимки гибели кометы
Комета ATLAS (формально известная как C/2019 Y4) распалась и два новых изображения с космического телескопа Hubble показывают, что комета раскололась на 25 частей. После того, как 29 декабря 2019 года комета была обнаружена роботизированной съемочной системой ATLAS, она начала быстро осветляться. Однако в середине марта комета начала резко тускнеть, и, как позже подтвердил ATLAS, ее ледяное ядро начало распадаться и разрушаться на расстоянии 146 миллионов километров от Земли. Невероятно, но Hubble смог запечатлеть гибель этой кометы. 20 апреля космический телескоп наблюдал 30 фрагментов кометы, и всего несколько дней спустя, 23 апреля, он обнаружил только 25 фрагментов. "Это действительно захватывающе - и потому, что на такие события очень круто смотреть, и потому, что они происходят не очень часто. Большинство комет с такими фрагментами слишком тусклы, чтобы их видеть. События такого масштаба происходят только один или два раза в десятилетие", - сказала в своем заявлении Цюаньчжи Йе из Университета Мэриленда и руководитель группы наблюдателей Hubble .
Ранее в этом месяце, 24 апреля, Hubble отметил 30-летие пребывания в космосе. За эти 30 лет космический телескоп сделал более 1,4 миллиона снимков, обнаружив и отобразив более 47 000 объектов в космосе. Это привело к множеству невероятных открытий, включая открытие темной энергии. Изображения, сделанные Hubble, открыли человечеству глаза на то, насколько прекрасна наша вселенная на самом деле.
пятница, 24 апреля 2020 г.
Interstellar comet Borisov reveals its chemistry and possible origins
On Aug. 30, 2019, when amateur astronomer Gennady Borisov gazed upward with his homemade telescope, he spotted an object moving in an unusual direction. Now called 2I/Borisov, this runaway point of light turned out to be the first confirmed comet to enter our solar system from some unknown place beyond our Sun's influence. Astronomers everywhere rushed to take a look with some of the most powerful instruments in the world, hoping to learn as much as they could about the mysterious visitor. Now, thanks to observations with NASA's Hubble Space Telescope and the National Radio Astronomy Observatory's Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have figured out that 2I/Borisov has an unusual composition. Specifically, it has a higher concentration of carbon monoxide than any comet seen at a similar distance; that is, within about 200 million miles (300 million kilometers) of the Sun. This suggests to scientists that the comet could have formed around a red dwarf - a smaller, fainter type of star than the Sun - though other kinds of stars are possible. Another idea is that 2I/Borisov could be a carbon monoxide-rich fragment of a small planet.
What is an interstellar comet?
Comets are snowballs of ice, dust and frozen gas. When totally frozen (or "inactive"), they're approximately the diameter of a small town, but when heated by the Sun their tails can extend for millions of miles. 2I/Borisov is about the length of nine football fields, or 0.61 miles (0.98 kilometers), making it relatively small. The new results on the comet's composition are published in the journal Nature Astronomy.
All comets form in the primordial disk of material that encircles a young star, preserving remnants of a planetary system's ancient past. Comets from our own solar neighborhood reveal the history of materials, including water, that made Earth the planet we know today, as well as our other planetary neighbors. An interstellar comet, on the other hand, is a chemical ambassador from an entirely different star system - containing a treasure trove of clues to worlds too far to reach with modern technology.
"With an interstellar comet passing through our own solar system, it's like we get a sample of a planet orbiting another star showing up in our own backyard," said John Noonan of the Lunar and Planetary Laboratory at the University of Arizona, Tucson, and a member of the Hubble research team led by Dennis Bodewits of Auburn University in Alabama.
What scientists found
Bodewits and colleagues used Hubble to look at 2I/Borisov from Dec. 11, 2019 to Jan. 13, 2020. Separately, a team of international scientists led by Martin Cordiner and Stefanie Milam at NASA's Goddard Space Flight Center in Greenbelt, Maryland, studied the comet on December 15 and 16, 2019, with ALMA, an array of radio telescopes at an altitude of 16,570 feet (5,050 meters) in northern Chile. Radio telescopes are especially useful for looking at cold, low-energy gas in objects like comets.
Results from both Hubble and ALMA estimate that 2I/Borisov's carbon monoxide concentration is higher than that of the average solar system comet.
Where did it come from?
A high carbon-monoxide-to-water ratio suggests that the comet has traveled from a very cold place - as cold as the area where Pluto is in relation to our Sun, called the Kuiper Belt. The group using Hubble additionally theorizes 2I/Borisov may have originated around the most common type of star in the Milky Way: a red dwarf. Red dwarfs are much smaller and dimmer than the Sun, so the planet-forming material around them would be colder than the building blocks of our solar system.
"These stars have exactly the low temperatures and luminosities where a comet could form with the type of composition found in comet 2I/Borisov," said Noonan.
Scientists using ALMA say it's possible that 2I/Borisov could be a fragment of a dwarf planet that had a lot of carbon monoxide near its surface, regardless of which type of star it came from. "If that object collided with another, then the carbon monoxide-rich fragments could be released into space," said Cordiner.
But 2I/Borisov may have simply formed as a comet with a high concentration of carbon monoxide, the ALMA team points out. Alternatively, it may have an unusually thick outer layer that insulates frozen gases like hydrogen cyanide and water.
As the more volatile carbon monoxide evaporates or "outgasses," it may appear more abundant than other cometary gases. 2I/Borisov's unusual properties may also suggest a wider diversity of carbon monoxide in comets in our own solar system than previously thought.
"Whatever the answer is, 2I/Borisov opens up a whole new can of worms for cometary science," says Milam, one of the scientists using ALMA.
In our own solar system, there are two places where most comets reside: The Kuiper Belt, an area that includes Pluto; and the Oort Cloud, which is much farther away. All of these comets likely formed closer to the Sun, but may have been booted outward by the erratic movements of Jupiter and Saturn billions of years ago. These giant planets, because of their immense gravity, could have even sent comets flying toward other stars, escaping the influence of the Sun's gravity altogether.
Given this history, scientists using Hubble theorize that a massive planet in a red dwarf system, in an environment with frozen carbon monoxide, may have punted 2I/Borisov our way.
"If a Jupiter-sized planet migrates inward, it could kick out a lot of these comets," Bodewits said.
The team using ALMA agrees that a young moving planet likely sent the comet on its way. "Then, after a cold, lonely voyage, 2I/Borisov made its close encounter with our solar system and started outgassing and showing us what it's got inside," Cordiner says.
More to come
2I/Borisov is only the second object astronomers have detected that definitely came from a different star system. The first was 'Oumuamua, discovered in October 2017, that whizzed by too quickly for scientists to pin down its chemistry. Whether it too is a comet, an asteroid, or something else - we may never know.
2I/Borisov is continuing on its path through the solar system, and will eventually head out. As more advanced telescopes and other instruments turn on and gaze out in the coming years, astronomers expect to find more interstellar objects, though they will still be rare.
"Our solar system is so tiny compared to the distances between star systems," Cordiner says. "For an interstellar comet to come in and hit the bullseye like Borisov did is incredible."
Comets are snowballs of ice, dust and frozen gas. When totally frozen (or "inactive"), they're approximately the diameter of a small town, but when heated by the Sun their tails can extend for millions of miles. 2I/Borisov is about the length of nine football fields, or 0.61 miles (0.98 kilometers), making it relatively small. The new results on the comet's composition are published in the journal Nature Astronomy.
All comets form in the primordial disk of material that encircles a young star, preserving remnants of a planetary system's ancient past. Comets from our own solar neighborhood reveal the history of materials, including water, that made Earth the planet we know today, as well as our other planetary neighbors. An interstellar comet, on the other hand, is a chemical ambassador from an entirely different star system - containing a treasure trove of clues to worlds too far to reach with modern technology.
"With an interstellar comet passing through our own solar system, it's like we get a sample of a planet orbiting another star showing up in our own backyard," said John Noonan of the Lunar and Planetary Laboratory at the University of Arizona, Tucson, and a member of the Hubble research team led by Dennis Bodewits of Auburn University in Alabama.
What scientists found
Bodewits and colleagues used Hubble to look at 2I/Borisov from Dec. 11, 2019 to Jan. 13, 2020. Separately, a team of international scientists led by Martin Cordiner and Stefanie Milam at NASA's Goddard Space Flight Center in Greenbelt, Maryland, studied the comet on December 15 and 16, 2019, with ALMA, an array of radio telescopes at an altitude of 16,570 feet (5,050 meters) in northern Chile. Radio telescopes are especially useful for looking at cold, low-energy gas in objects like comets.
Results from both Hubble and ALMA estimate that 2I/Borisov's carbon monoxide concentration is higher than that of the average solar system comet.
Where did it come from?
A high carbon-monoxide-to-water ratio suggests that the comet has traveled from a very cold place - as cold as the area where Pluto is in relation to our Sun, called the Kuiper Belt. The group using Hubble additionally theorizes 2I/Borisov may have originated around the most common type of star in the Milky Way: a red dwarf. Red dwarfs are much smaller and dimmer than the Sun, so the planet-forming material around them would be colder than the building blocks of our solar system.
"These stars have exactly the low temperatures and luminosities where a comet could form with the type of composition found in comet 2I/Borisov," said Noonan.
Scientists using ALMA say it's possible that 2I/Borisov could be a fragment of a dwarf planet that had a lot of carbon monoxide near its surface, regardless of which type of star it came from. "If that object collided with another, then the carbon monoxide-rich fragments could be released into space," said Cordiner.
But 2I/Borisov may have simply formed as a comet with a high concentration of carbon monoxide, the ALMA team points out. Alternatively, it may have an unusually thick outer layer that insulates frozen gases like hydrogen cyanide and water.
As the more volatile carbon monoxide evaporates or "outgasses," it may appear more abundant than other cometary gases. 2I/Borisov's unusual properties may also suggest a wider diversity of carbon monoxide in comets in our own solar system than previously thought.
"Whatever the answer is, 2I/Borisov opens up a whole new can of worms for cometary science," says Milam, one of the scientists using ALMA.
In our own solar system, there are two places where most comets reside: The Kuiper Belt, an area that includes Pluto; and the Oort Cloud, which is much farther away. All of these comets likely formed closer to the Sun, but may have been booted outward by the erratic movements of Jupiter and Saturn billions of years ago. These giant planets, because of their immense gravity, could have even sent comets flying toward other stars, escaping the influence of the Sun's gravity altogether.
Given this history, scientists using Hubble theorize that a massive planet in a red dwarf system, in an environment with frozen carbon monoxide, may have punted 2I/Borisov our way.
"If a Jupiter-sized planet migrates inward, it could kick out a lot of these comets," Bodewits said.
The team using ALMA agrees that a young moving planet likely sent the comet on its way. "Then, after a cold, lonely voyage, 2I/Borisov made its close encounter with our solar system and started outgassing and showing us what it's got inside," Cordiner says.
More to come
2I/Borisov is only the second object astronomers have detected that definitely came from a different star system. The first was 'Oumuamua, discovered in October 2017, that whizzed by too quickly for scientists to pin down its chemistry. Whether it too is a comet, an asteroid, or something else - we may never know.
2I/Borisov is continuing on its path through the solar system, and will eventually head out. As more advanced telescopes and other instruments turn on and gaze out in the coming years, astronomers expect to find more interstellar objects, though they will still be rare.
"Our solar system is so tiny compared to the distances between star systems," Cordiner says. "For an interstellar comet to come in and hit the bullseye like Borisov did is incredible."
воскресенье, 19 апреля 2020 г.
Новая комета появится возле Земли
Недавно открытая комета Swan (C/2020 F8) летит к Земле и уже отлично видна в небольшие телескопы, а в следующем месяце ее можно будет наблюдать невооруженным глазом. Джеральд Риман на днях опубликовал снимок космической гостьи, сделанный в Намибии. «Хвост кометы — почти полный градус. Это была легкая цель для моего 12-дюймового телескопа», — сказал фотограф. По оценкам ученых, комета впервые направляется к Солнцу, и солнечная гравитация, вероятно, отправит ее обратно в глубокий космос. Комета Swan может быть гиперболической, то есть ее орбита имеет эксцентриситет больше 1. Такие кометы происходят из Облака Оорта или даже могут быть межзвездными. Гиперболические кометы отличаются высокой скоростью и следуют по незамкнутой траектории. Они могут посетить Солнечную систему только один раз, а затем навсегда исчезают в межзвездном пространстве.
пятница, 17 апреля 2020 г.
Метеорный поток Лириды: в чем его особенность и кто сможет наблюдать
16 апреля начинается один из важнейших и самых красивых звездопадов 2020 года - Лириды. Он считается одним из самых сильных метеорных потоков вместе с августовскими Персеидами и декабрьскими Геминидами, в редких случаях может бомбардировать небо с интенсивностью почти 100 м в час. Каждый год поток Лириды начинается 16 апреля, а заканчивается 25 апреля. Пиковые значения падающих звезд придутся на 21 и 23 число и составят примерно 30 метеоров в час. 22 апреля это значение может достигать 40 штук в час. Это довольно скромный показатель относительно других потоков, однако этого вполне достаточно, чтобы увидеть невооруженным взглядом, как обломки кометы Тэтчера бомбардируют атмосферу Земли. Что касается видимости метеоров, то они влетают в атмосферу с большими вспышками, но не оставляют следов. Из-за этого порой кажется, что это зарница на горизонте, хотя на самом деле это падающие звезды. Тем не менее около 20 % метеоров этого потока оставляют четкие следы. Такое разнообразие приходится по вкусу наблюдателям и астрономам. Наблюдать поток лучше всего в северном полушарии и после полуночи. Разумеется, стоит надеяться на ясную погоду, потому что за облаками видимость будет практически нулевой.
Что такое звездопад Лириды:
Это один из самых древних потоков: он известен человечеству около 2500 лет. Древние астрологи и астрономы установили, что поток имеет радиант в созвездии Лиры. Это звездное скопление на ночном небе символизирует творческий потенциал человека.
Где и когда наблюдать звездопад Лириды:
Где и когда наблюдать звездопад Лириды:
Звездопад Лириды можно наблюдать из любой точки земного шара, но более яркое и красочное зрелище увидят жители северного полушария. Звездопад астрономы-любители смогут наблюдать невооруженным взглядом - для этого достаточно находиться вдали от любого источника света и поднять голову к созвездию Лиры. Правда, жители многих стран, где из-за пандемии коронавируса действует чрезвычайное положение и комендантский час, смогут наблюдать это красивейшее явление природы только из окон своего дома.
среда, 15 апреля 2020 г.
Сегодня рядом с Землей пролетит крупный астероид
Сегодня, 15 апреля, рядом с Землей пролетит крупный астероид. Его орбита находится внутри орбиты Луны. Астрономы обнаружили астероид 2020 GH2 11 апреля, а его размер составляет от 13 до 70 м. Это соизмеримо с размерами большого дома. Космический пришелец пронесется от Земли на расстоянии 359 тыс. км. По космическим меркам данное расстояние считается очень маленьким. Напомним, что расстояние до Луны составляет 385 тыс. км. Астрономы определили траекторию полета астероида и утверждают, что он не представляет опасности для Земли. По мнению ученых, 2020 GH2 по сравнению с астероидом, который 65 млн лет назад уничтожил динозавров, как песчинка соли.
вторник, 14 апреля 2020 г.
«Не совсем безобидны»: куда направляются новые космические «убийцы»
В начале января ученые открыли первый астероид из группы ватир, движущихся полностью внутри орбиты Венеры. Считается, что таких объектов много. Их траектории нестабильны, и они могут столкнуться с Землей. Астрономы постоянно прочесывают небо в поисках опасных — их еще называют околоземными — астероидов. Маршруты некоторых лежат внутри земной орбиты, то есть они ближе к Солнцу, чем наша планета. Долгое время они оставались гипотетическими. "В подобных открытиях существуют объективные сложности: эти астероиды, в отличие от других, нельзя наблюдать в противосолнечной области, они всегда расположены на относительно небольших элонгациях — угловых расстояниях от Солнца. Это значит, что искать космические тела надо в сумеречном и околосумеречном сегменте. Наблюдения в этих зонах затруднены, поэтому первое достоверное открытие сделали лишь в 2003 году — после развертывания системы автоматизированных обзоров по поиску околоземных астероидов", — пояснил Артем Новичонок, заведующий учебной астрономической лабораторией Петрозаводского государственного университета. Первенец получил имя Атиры (давшее название всему классу подобных тел) в честь богини индейского племени пауни из штата Оклахома. Астероид открыли в американском обзоре LINEAR. У 163693 Atira максимально возможная элонгация — порядка 75 градусов, но достигает он ее далеко не каждый год, уточняет исследователь.
Трудноуловимые попутчики Венеры
Ученые предсказывали существование еще более близких к Солнцу астероидов, движущихся полностью внутри орбиты Венеры. Их пока неофициально назвали ватирами — венерианскими атирами. Ватиры начали искать в 2013 году с помощью канадского спутника NEOSSat, предназначенного для слежения за опасными объектами. Вскоре наземный проект Паломарской обсерватории Zwicky Transient Facility (ZTF) в Калифорнии, наблюдающий за удаленными транзиентами, в основном сверхновыми, вошел в игру.
В 2019-м ZTF открыл два атира — 2019 AQ3 и 2019 LF6 — с самыми короткими периодами обращения из известных. Это означало, что их венерианские аналоги существуют и, вероятно, многочисленны, поскольку есть механизм перехода на более близкую к Солнцу орбиту.
Первый ватир ZTF открыл 4 января 2020 года.
"У это комплекса уникальная огромная матрица, снимающая сразу большие области неба, и хорошее ПО. Впервые предприняты масштабные поиски на малых солнечных элонгациях, где другие обзоры почти или вообще не работали из-за технических сложностей и малых перспектив обнаружить околоземные астероиды. Тут максимально возможная элонгация уже ниже 45-50 градусов, а классические обзоры обычно ограничиваются примерно 60 градусами, что резко осложняет задачу. Но поскольку в наблюдаемом спектре оказались довольно крупные астероиды, их увидели, как только начали искать. Очевидно, можно ждать и следующие подобные открытия от ZTF", — рассказывает Новичонок.
Ватир 2020 AV2 сразу стали наблюдать многие астрономы по всему миру. В циркуляре Центра малых планет от 8 января 2020 года приведен внушительный список, где есть и данные российского исследователя-любителя Филиппа Романова.
Сход с орбиты
Согласно расчетам братьев де ла Фуэнте Маркос из Мадридского университета Комплутенсе, 2020 AV2 изначально был атирой, но примерно сто тысяч лет назад сблизился с Меркурием, сменил орбиту и перешел в разряд ватир. Еще через двести тысяч лет он может уйти и из-под влияния Меркурия.
Причина тому — механизм Лидова — Козаи, вызывающий колебания (осцилляции) орбиты малого тела под действием сил притяжения планет. Траектория становится все более эллиптической, наклоняясь все сильнее к плоскости орбиты ближайшей планеты, пока ее не разрывают приливные силы.
"Атиры и ватиры не совсем безобидны. Многие относятся к подклассу потенциально опасных околоземных астероидов. Из-за гравитационного взаимодействия с Землей, Венерой и Меркурием они могут изменять орбиты и в итоге попадать на траектории столкновения с Землей. За исключением двух популяций, которые могут быть стабильны, но еще не открыты, их орбиты нестабильны, и в долгосрочной перспективе, на масштабах десятков тысяч лет, они могут стать угрозой землянам", — объясняет Артем Новичонок.
К примеру, диаметр 163693 Atira — 4,8 километра, а 2020 AV2 — приблизительно два километра. Для сравнения: астероид, породивший челябинский метеорит, при входе в атмосферу был размером примерно 17 метров в продольной оси, а разрушения произвел довольно заметные.
"Самое интересное для меня в популяции атир — и в большей степени ватир — исследовательские перспективы, некая научная неизвестность. Из-за сложностей наблюдений внутри орбиты Венеры мы почти ничего не знаем о скоплении существующих там малых тел, разве что там нет объектов более пятидесяти километров в поперечнике, как следует из наблюдений на коронографе космического телескопа SOHO. И конечно, еще больше интригуют потенциальные вулканоиды — группа (население) астероидов внутри орбиты Меркурия. Ни один из них пока не открыт", — подчеркивает астроном.
воскресенье, 12 апреля 2020 г.
Rehearsal Time for NASA's Asteroid Sampling Spacecraft
In August, a robotic spacecraft will make NASA's first-ever attempt to descend to the surface of an asteroid, collect a sample, and ultimately bring it safely back to Earth. In order to achieve this challenging feat, the OSIRIS-REx mission team devised new techniques to operate in asteroid Bennu's microgravity environment - but they still need experience flying the spacecraft in close proximity to the asteroid in order to test them. So, before touching down at sample site Nightingale this summer, OSIRIS-REx will first rehearse the activities leading up to the event. On Apr. 14, the mission will pursue its first practice run - officially known as "Checkpoint" rehearsal - which will also place the spacecraft the closest it's ever been to Bennu. This rehearsal is a chance for the OSIRIS-REx team and spacecraft to test the first steps of the robotic sample collection event. During the full touchdown sequence, the spacecraft uses three separate thruster firings to make its way to the asteroid's surface. After an orbit departure burn, the spacecraft executes the Checkpoint maneuver at 410 ft (125 m) above Bennu, which adjusts the spacecraft's position and speed down toward the point of the third burn. This third maneuver, called "Matchpoint," occurs at approximately 164 ft (50 m) from the asteroid's surface and places the spacecraft on a trajectory that matches the rotation of Bennu as it further descends toward the targeted touchdown spot.
The Checkpoint rehearsal allows the team to practice navigating the spacecraft through both the orbit departure and Checkpoint maneuvers, and ensures that the spacecraft's imaging, navigation and ranging systems operate as expected during the first part of the descent sequence. Checkpoint rehearsal also gives the team a chance to confirm that OSIRIS-REx's Natural Feature Tracking (NFT) guidance system accurately updates the spacecraft's position and velocity relative to Bennu as it descends towards the surface.
Checkpoint rehearsal, a four-hour event, begins with the spacecraft leaving its safe-home orbit, 0.6 miles (1 km) above the asteroid. The spacecraft then extends its robotic sampling arm - the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) - from its folded, parked position out to the sample collection configuration. Immediately following, the spacecraft slews, or rotates, into position to begin collecting navigation images for NFT guidance. NFT allows the spacecraft to autonomously guide itself to Bennu's surface by comparing an onboard image catalog with the real-time navigation images taken during descent. As the spacecraft descends to the surface, the NFT system updates the spacecraft's predicted point of contact depending on OSIRIS-REx's position in relation to Bennu's landmarks.
Before reaching the 410-ft (125-m) Checkpoint altitude, the spacecraft's solar arrays move into a "Y-wing" configuration that safely positions them away from the asteroid's surface. This configuration also places the spacecraft's center of gravity directly over the TAGSAM collector head, which is the only part of the spacecraft that will contact Bennu's surface during the sample collection event.
In the midst of these activities, the spacecraft continues capturing images of Bennu's surface for the NFT navigation system. The spacecraft will then perform the Checkpoint burn and descend toward Bennu's surface for another nine minutes, placing the spacecraft around 243 ft (75 m) from the asteroid - the closest it has ever been.
Upon reaching this targeted point, the spacecraft will execute a back-away burn, then return its solar arrays to their original position and reconfigure the TAGSAM arm back to the parked position. Once the mission team determines that the spacecraft successfully completed the entire rehearsal sequence, they will command the spacecraft to return to its safe-home orbit around Bennu.
Following the Checkpoint rehearsal, the team will verify the flight system's performance during the descent, and that the Checkpoint burn accurately adjusted the descent trajectory for the subsequent Matchpoint burn.
The mission team has maximized remote work over the last month of preparations for the checkpoint rehearsal, as part of the COVID-19 response. On the day of rehearsal, a limited number of personnel will command the spacecraft from Lockheed Martin Space's facility, taking appropriate safety precautions, while the rest of the team performs their roles remotely.
The mission is scheduled to perform a second rehearsal on Jun. 23, taking the spacecraft through the Matchpoint burn and down to an approximate altitude of 82 ft (25 m). OSIRIS-REx's first sample collection attempt is scheduled for Aug. 25.
Checkpoint rehearsal, a four-hour event, begins with the spacecraft leaving its safe-home orbit, 0.6 miles (1 km) above the asteroid. The spacecraft then extends its robotic sampling arm - the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) - from its folded, parked position out to the sample collection configuration. Immediately following, the spacecraft slews, or rotates, into position to begin collecting navigation images for NFT guidance. NFT allows the spacecraft to autonomously guide itself to Bennu's surface by comparing an onboard image catalog with the real-time navigation images taken during descent. As the spacecraft descends to the surface, the NFT system updates the spacecraft's predicted point of contact depending on OSIRIS-REx's position in relation to Bennu's landmarks.
Before reaching the 410-ft (125-m) Checkpoint altitude, the spacecraft's solar arrays move into a "Y-wing" configuration that safely positions them away from the asteroid's surface. This configuration also places the spacecraft's center of gravity directly over the TAGSAM collector head, which is the only part of the spacecraft that will contact Bennu's surface during the sample collection event.
In the midst of these activities, the spacecraft continues capturing images of Bennu's surface for the NFT navigation system. The spacecraft will then perform the Checkpoint burn and descend toward Bennu's surface for another nine minutes, placing the spacecraft around 243 ft (75 m) from the asteroid - the closest it has ever been.
Upon reaching this targeted point, the spacecraft will execute a back-away burn, then return its solar arrays to their original position and reconfigure the TAGSAM arm back to the parked position. Once the mission team determines that the spacecraft successfully completed the entire rehearsal sequence, they will command the spacecraft to return to its safe-home orbit around Bennu.
Following the Checkpoint rehearsal, the team will verify the flight system's performance during the descent, and that the Checkpoint burn accurately adjusted the descent trajectory for the subsequent Matchpoint burn.
The mission team has maximized remote work over the last month of preparations for the checkpoint rehearsal, as part of the COVID-19 response. On the day of rehearsal, a limited number of personnel will command the spacecraft from Lockheed Martin Space's facility, taking appropriate safety precautions, while the rest of the team performs their roles remotely.
The mission is scheduled to perform a second rehearsal on Jun. 23, taking the spacecraft through the Matchpoint burn and down to an approximate altitude of 82 ft (25 m). OSIRIS-REx's first sample collection attempt is scheduled for Aug. 25.
воскресенье, 5 апреля 2020 г.
Огромный астероид 1998 OR2 безобидно пролетит мимо Земли 29 апреля
Огромный «потенциально опасный» астероид 1998 OR2 находится всего в нескольких неделях от его близкого сближения с Землей, и вы можете наблюдать за приближением гигантской космической скалы онлайн или с помощью небольшого телескопа. В то время как астероид 1998 OR2 достаточно велик, чтобы нанести ущерб Земле, если он ударит по нашей планете, но он не допустит столкновения, когда пролетит 29 апреля. «29 апреля астероид 1998 OR2 благополучно пройдет в 6,2 миллиона километров (20 световых секунд)», - заявили ученые из программы НАСА «Астероидные часы» в своем обновлении в Твиттере, опровергая сообщение Daily Express, предупреждающее о пролете. «Нет никаких предупреждений об этом астероиде», - добавили они в другой пост в Твиттере. По оценкам НАСА, ширина астероида составляет от 1,8 до 4,1 км. Согласно Asteroid Watch, 1998 OR2 пройдет на безопасном расстоянии, которое более чем в 16 раз превышает среднее расстояние между Землей и Луной. В то время как НАСА классифицирует астероиды, которые находятся на расстоянии менее 7,5 миллиона км от Земли, как «потенциально опасные», с OR2 1998 года не о чем беспокоиться. «Орбита хорошо изучена, и он безопасно пройдет на расстоянии в 16 раз дальше от нашей луны», - пишет НАСА в Twitter. «Никто не должен беспокоиться об этом астероиде».
В настоящее время астероид слишком слабый, чтобы его можно было увидеть в домашний телескоп, но какое-то время назад он был виден в большие телескопы. Проект «Виртуальный телескоп», удаленная обсерватория, основанная астрофизиком Джанлукой Маси из Астрономической обсерватории Беллатрикс в Италии, около месяца следит за астероидом, периодически выпуская новые снимки космического камня, когда она проносится по космосу со скоростью 31 000 км/ч.
Астероид 1998 OR2 в настоящее время виден только в профессиональный телескоп, подобных тем, которые Маси использует в проекте Virtual Telescope. Тем не менее, астрономы-любители будут иметь возможность увидеть астероид, когда он станет видим в небольшие телескопы во время его близкого сближения.
Согласно EarthSky, ожидается, что астероид 1998 OR2 достигнет визуальной величины 10 или 11 (величина является мерой яркости объекта). Это означает, что он будет виден как минимум в 6- или 8-дюймовых телескопах, если конечно позволит погода.
Астероид 1998 OR2 в настоящее время виден только в профессиональный телескоп, подобных тем, которые Маси использует в проекте Virtual Telescope. Тем не менее, астрономы-любители будут иметь возможность увидеть астероид, когда он станет видим в небольшие телескопы во время его близкого сближения.
Согласно EarthSky, ожидается, что астероид 1998 OR2 достигнет визуальной величины 10 или 11 (величина является мерой яркости объекта). Это означает, что он будет виден как минимум в 6- или 8-дюймовых телескопах, если конечно позволит погода.
Комета «Атлас» показала свой прекрасный хвост
У кометы «Атлас» (C/2019 Y4 (ATLAS) появился хвост — и это впечатляет! Джеральд Реман сделал эту анимацию 27 марта в своей обсерватории на заднем дворе дома в Айхграбене в Нижней Австрии. По его наблюдениям, длина хвоста кометы — 1,2 градуса, что составляет 3,3 млн км (более чем в 2 раза больше ширины Солнца). Внешние края хвоста все еще блеклые, но на анимации Ремана их можно заметить в виде тонких ниток, словно из паутины. Реман отметил, что сделал эти изображения при помощи 12-дюймового телескопа. Комета Атлас сияет на небе, как звезда 8-й величины — слишком тусклая, чтобы ее можно было разглядеть невооруженным глазом (звездная величина самых ярких объектов отрицательна). Однако при этом комета является легкой целью для телескопов. Ожидается, что комета станет намного ярче. В конце мая она приблизится к Солнцу ближе, чем Меркурий, и тогда она сможет соперничать с Венерой на вечернем небосводе.
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