{"id":16670,"date":"2020-10-21T15:50:30","date_gmt":"2020-10-21T14:50:30","guid":{"rendered":"https:\/\/ounews.co\/?p=16670"},"modified":"2020-10-21T15:50:30","modified_gmt":"2020-10-21T14:50:30","slug":"asteroid-bennu-successful-touchdown-but-the-scientific-mission-has-only-just-begun","status":"publish","type":"post","link":"https:\/\/www.open.ac.uk\/blogs\/news\/science-mct\/space\/asteroid-bennu-successful-touchdown-but-the-scientific-mission-has-only-just-begun\/","title":{"rendered":"Asteroid Bennu: successful touchdown \u2013 but the scientific mission has only just begun"},"content":{"rendered":"

Following the successful touch-and-go landing on asteroid<\/span>\u00a0Bennu, Monica Grady<\/a>, Professor of Planetary and Space Sciences at The Open University<\/a>, suggests\u00a0that this momentous feat is only the beginning for the OSIRIS-REx team and wider scientific community.\u00a0\u00a0<\/em><\/p>\n

Relief showed clearly on the faces<\/a> of the team of NASA scientists and engineers as they were told: \u201cTouchdown is complete\u201d. Then applause a few seconds later for \u201cback away burn complete\u201d. The most hazardous part of the mission was over \u2013 and seemingly successful, although we will have to wait for a few more days to hear the scale of the success.<\/p>\n

OSIRIS-REx (for Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer)) was launched<\/a> in September 2016, arriving at its target<\/a> asteroid 101955 Bennu<\/a> in December 2018. The purpose of the mission was to characterise the asteroid, then bring some of it back for study on Earth.<\/p>\n

The spacecraft spent two years circling Bennu, making detailed maps of its surface, learning as much as possible about the asteroid before the next phase of the mission: looking for somewhere safe to land. Or, rather, not to land, but to make a very rapid \u201ctouch-and-go\u201d visit to the surface \u2013 where it would collect fragments of material to return to Earth. It was completion of the touch-and-go manoeuvre that prompted the clapping and cheering in mission control.<\/p>\n

Why Bennu? And why the relief? After all, this is not the first asteroid that a spacecraft has visited \u2013 and it is not the first small body that has been landed on. That record is held by the NEAR spacecraft<\/a> that made a controlled crash-landing on Asteroid 433 Eros in 2001<\/a>. And I still remember the emotion in the control<\/a> room when Philae landed on comet 67P\/Churyumov-Gerasimenko in 2014<\/a>.<\/p>\n

The relief was because Bennu is small \u2013 only about 500 metres across – a fact that was known when it was selected as a target. But it is oddly shaped and active \u2013 two things that were not known. It looks a bit like an old-fashioned spinning top, or a rough diamond, pointed at the top and bottom and fatter in the middle. Because it is so small it was assumed that Bennu would be quiescent \u2013 it wouldn\u2019t, for instance, be behaving like a comet and ejecting bursts of gas and rocks.<\/p>\n

But because nothing in the solar system is simple, when OSIRIS-Rex got close to Bennu, it found that the asteroid was throwing small amounts of material<\/a> from its surface. The particles were less than a centimetre across, and most of them landed back on the asteroid \u2013 generally closer to the equator than the poles, which changed its shape over time.<\/p>\n

\n

\"Image

Image of Bennu taken by OSIRIS-REx in 2018. NASA\/Goddard\/University of Arizona<\/p><\/div>

<\/figcaption><\/figure>\n

One of the consequences of the activity \u2013 explained by changes in temperature fracturing larger boulders<\/a> and breaking up the rocks \u2013 is that the surface of Bennu is completely covered in rubble, much more than had been expected. This made selecting a site for sample collection more difficult.<\/p>\n

Secrets of the solar system<\/h2>\n

Bennu is a Near Earth Asteroid \u2013 it has a one-in-2700 chance of colliding with the Earth<\/a> in about 170 years\u2019 time. It is also believed to be rich in the type of organic compounds that might have seeded the Earth to enable life to arise.<\/p>\n

Another surprising find that came from the mapping campaign was that Bennu was not only rich in clay minerals, but that veins of carbonate<\/a> were present. Clay and carbonates require water \u2013 lots of it \u2013 so these minerals must have formed when Bennu was part of a larger asteroid. There is no running water there now \u2013 but there might be small pockets of ice below the surface. While this ice will not be collected by OSIRIS_Rex, the effects of water should be seen in the material it\u2019s gathered.<\/p>\n

Studying these materials will help us understand the primitive dust from which the solar system grew, and the range of organic compounds present. It will also tell us the physical properties of something that might hit the Earth, potentially helping us stop it.<\/p>\n

It was always going to be tricky to collect material from the surface \u2013 any attempt to land would be unlikely to succeed, because the low gravitational pull of Bennu would not grab onto a lander and hold it in place. A lander would bounce off, back into space. This is why NASA used the touch-and-go approach \u2013 the spacecraft approached the asteroid very slowly, hovering only a metre or so from its surface, while an arm was extended to touch the surface to collect a sample.<\/p>\n

It did this by blowing a jet of nitrogen gas onto the surface, which was sufficiently powerful to throw material into the collection cannister. The slow approach to the surface took several nail-biting hours, while the collection operation took a matter of seconds. Collection over, and the spacecraft backed away \u2013 hence the relief at mission control at the \u201cback away, burn complete\u201d message, showing that OSIRIS-Rex was moving away from the surface.<\/p>\n

We don\u2019t yet know how much material was blown into the cannister \u2013 and we won\u2019t know until it arrives back on Earth<\/a> in September 2023. It might be 60 grams \u2013 which is the target \u2013 or it might be as much as a kilogram. An attempt will be made later this week to see how the moment of inertia of the spacecraft \u2013 its uniform motion in a straight line \u2013 has changed, which should give a first approximation of the amount collected.<\/p>\n

When the sample comes back to Earth, it will be analysed by an international team of scientists who will measure all aspects of the material\u2019s composition and structure, especially the organic and water contents of the soil.<\/p>\n

This is when we\u2019ll get some answers, which will tell us about our own origins as much as about the origin of asteroid Bennu.<\/p>\n

\n

I dedicate this piece to the memory of Professor Michael J. Drake, a friend and colleague. He was the original proposer of the mission that eventually became OSIRIS-REx, but died in September 2011, before he could see the mission launched.<\/em>\"The<\/p>\n

This article is republished from The Conversation<\/a> under a Creative Commons license. Read the original article<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

Following the successful touch-and-go landing on asteroid\u00a0Bennu, Monica Grady, Professor of Planetary and Space Sciences at The Open University, suggests\u00a0that this momentous feat is only the beginning for the OSIRIS-REx team and wider scientific community.\u00a0\u00a0 Relief showed clearly on the faces of the team of NASA scientists and engineers as they were told: \u201cTouchdown is […]<\/p>\n","protected":false},"author":19,"featured_media":16671,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[861,1525,1640,1643,1818,2081],"class_list":["post-16670","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-space","tag-faculty-of-stem","tag-news-home","tag-ou-home","tag-ou-news","tag-professor-monica-grady","tag-space"],"_links":{"self":[{"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/posts\/16670","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/users\/19"}],"replies":[{"embeddable":true,"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/comments?post=16670"}],"version-history":[{"count":0,"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/posts\/16670\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/media\/16671"}],"wp:attachment":[{"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/media?parent=16670"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/categories?post=16670"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/tags?post=16670"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}