NASA’s robot just landed on Bennu after 2 years — but its mission has only just begun
Secrets of the solar system
Bennu is a Near Earth Asteroid – it has a one-in-2700chance of colliding with the Earthin about 170 years’ 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.
Another surprising find that came from the mapping campaign was that Bennu was not only rich in clay minerals, but thatveins of carbonatewere present. Clay and carbonates require water – lots of it – so these minerals must have formed when Bennu was part of a larger asteroid. There is no running water there now – 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’s gathered.
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.
It was always going to be tricky to collect material from the surface – 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 – the spacecraft approached the asteroid very slowly, hovering only a meter or so from its surface, while an arm was extended to touch the surface to collect a sample.
It did this by blowing a jet of nitrogen gas onto the surface, which was sufficiently powerful to throw material into the collection canister. 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 – hence the relief at mission control at the “back away, burn complete” message, showing that OSIRIS-Rex was moving away from the surface.
We don’t yet know how much material was blown into the canister – and we won’t know untilit arrives back on Earthin September 2023. It might be 60 grams – which is the target – 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 – its uniform motion in a straight line – has changed, which should give a first approximation of the amount collected.
When the sample comes back to Earth, it will be analyzed by an international team of scientists who will measure all aspects of the material’s composition and structure, especially the organic and water contents of the soil.
This is when we’ll get some answers, which will tell us about our own origins as much as about the origin of asteroid Bennu.
This article is republished fromThe ConversationbyMonica Grady, Professor of Planetary and Space Sciences,The Open Universityunder a Creative Commons license. Read theoriginal article.
Story byThe Conversation
An independent news and commentary website produced by academics and journalists.An independent news and commentary website produced by academics and journalists.
Get the TNW newsletter
Get the most important tech news in your inbox each week.
