The Osiris-Rex spacecraft will soon make a dangerous journey.
–
The asteroid Bennu is not really special in the big picture. It is a pile of gravel and stone held together as it whizzes around in an orbit around the sun.
In scientific articles it is called a rubble pile. This can be loosely translated as gravel pile.
It is classified as an asteroid near Earth, and it is just one of countless small and large things buzzing around the solar system. At the time of writing, scientists know of almost a million different asteroids, but there are many more out there.
And Bennu is one of them. But Bennu has been thoroughly studied for several years. The Osiris-Rex spacecraft has been near the asteroid since December 2018, and its main goal is to take a sample of the surface to be sent back to Earth.
It should go down to the surface with one arm, pick up a small sample, and lift up from the surface again.
The probe also has a lidar on board. This is an instrument that can scan the surface with a laser, and then build up a very detailed height map of the asteroid. The instrument is sensitive enough to bring details down to around 20 centimeters, according to the research article, which is published in the journal Science Advances.
–
Grushaugen
Bennu itself is a mound that is over 500 meters wide and high. The shape is often compared to a spinning bass.
Such a small asteroid has an extremely weak gravity compared to what we know here on earth.
According to NASA, Bennu has a gravitational pull of only a few millionths of the earth, and you do not have to move faster than half a kilometer per hour to escape the surface. Then it holds with a small jump.
On Earth, you have to go up to over 40,000 kilometers per hour to get out into space.
The new survey shows one of Bennus’ distinctive characteristics, namely that the north and south sides are quite different. The southern hemisphere is smoother and has fewer large rocks than the northern hemisphere.
Scientists believe this is due to the fact that Bennu was torn apart from a larger asteroid many hundreds of millions of years ago. Then this asymmetry could arise, and little has changed since then.
But the asteroid itself is much more rugged and rocky than scientists thought beforehand. The probe was initially designed for larger, open areas, but it turned out that these did not exist.
–
This can present problems when the probe is to dive to the surface. In 2019, forskning.no wrote that this could jeopardize the entire mission.
But now NASA will try to take a sample of this asteroid.
Dive to the surface
NASA believes that they have found a suitable place, and the maneuver will take place on 20 October.
The probe is designed to take a sample of fine-grained dust, and NASA has found a slightly more open area in the northern hemisphere. This area is only 16 meters in diameter and there are large boulders on all sides. The probe is actually designed to take samples from areas that are around 50 meters in diameter.
The operation itself is automated, and the probe must interrupt itself if it notices that it is on its way to something dangerous. Osiris-Rex is so far from the earth that it takes over 18 minutes for radio signals to travel back and forth, making it impossible to remotely control a maneuver that needs quick reactions, according to NASA.
This sample will be taken back to Earth in 2023.
Thus, it is only to wait anxiously for the result that will come on October 20.
Reference:
Daly mfl: Hemispherical differences in the shape and topography of asteroid (101955) Bennu. Sci Adv, 2020. DOI: 10.1126/sciadv.abd3649 . Summary
–
