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| OSIRIS REX |
Osiris-rex has been in orbit around the asteroid Bennu for around a year now Bennu is the smallest object ever orbited.
Osiris rex orbits only several hundred meters above its surface. Being so close to the asteroid means it can examine minute detail about asteroid Bennu.
The most unique things about this mission is the fact that a Osiris Rex is orbiting Bennu which is only 500 meters wide.
A 500 meter wide object barely has any gravity at all which means one orbit of Bennu takes 62 hours at an altitude of 1.75 kilometers.
However orbiting Bennu was necessary to map its surface accurately as the spacecraft orbits and the asteroid rotates as Osiris Rex is scanning the surface creating the highest resolution map of any celestial body.
To date this detailed examination is to find the best landing site for a Osiris Rex which is actually a sample return mission.
Scientists want to retrieve 60 grams from the surface of Bennu and return it back to earth in pristine condition while there are a lot of meteorites that land on the surface of earth and we have many many samples these meteorites pass through our atmosphere heating up to incredible temperatures which alters the delicate materials in the meteorite upon impact.
They are also then exposed to the surface of earth making it hard for scientists to distinguish what was there from before and after the impact.
A sample directly from an asteroid protected in a box from contamination which occurs during the re-entry process can give a much greater insight to the nature of asteroids than anything we have observed before.
With this sample scientists will be able to search for organic compounds like amino acids hydrated materials like clays and other substances that would otherwise be hard to detect.
But as the Osiris Rex found anything interesting during its preliminary scans as Osiris Rex isn't just taking photos of the asteroid but it is also mapping the global properties chemistry and mineralogy of this primitive carbonaceous asteroid to characterize its geologic and dynamic history to provide context for the returned samples it's doing, this to help pick the best site for the sample return part of the mission.
Scientists are looking for the most geologically interesting site that can provide the most interesting sample. Spectroscopic surveys have already revealed that there are hydrated materials or in other words clays on the surface of Bennu.
This is significant clays contain water and Bennu was not a type of body where scientists expected to find traces of water.
Scientists are still of the belief that a body as small as Bennu could never have held its own water but what this does imply is that liquid water was likely present on the body been who would have originated from and all that remains of it is what been locked away in these clays.
Scientists had a rough idea of what Bennu who looked like before Osiris Rex even arrived, thanks to radar imaging from ground-based telescopes.
However what they didn't expect is just how much the surface is covered with large boulders. Many asteroids have been described as rubble piles in the past but I don't think anyone was expecting it at this scale just to give you a sense of scale the largest Boulder on the surface is 20 meters high and about the size of a football field.
Other boulders you see here are about the size of a horse this makes picking a landing site a little tricky when ideally you are looking for a patch roughly 25 meters in diameter containing particles no bigger than a centimeter so your sample collector can retrieve a sample safely.
However for smaller landing sites were eventually chosen named Osprey, Kingfisher, Nightingale and Sandpiper. Even though they are smaller sites than originally hopeful the sites are relatively free from boulders.
Scientists have had to adjust and refine their plans to make sure a Osiris Rex will hit its mark as the difficulty of the maneuver is exasperated by the small size.
The landing sites which are no bigger than a few car parking spaces with large and dangerous boulders surrounding them Osiris Rex won't be long before the final sample site is picked and within a few months of that mission controllers will attempt the sample collection.
All being well they'll be successful on their first attempt but they do have the fuel to try again should they not get anything the first time and if they don't crash considering Bennu is seemingly an inactive pile of rocks floating in space.
Scientists surprised greatly when Osiris Rex spotted some dynamic activity on the asteroid, occasional ejection events were spotted where some material was flung away into space.
Some of these particles were even captured in orbit around the asteroid for a few orbits before eventually returning to the asteroid surface.
This is likely due to the fast rotation of the asteroid and the Osiris Rex has already been able to detect that this rotation is speeding up very gradually due to the Yarkovsky effect, this effect is caused by the slight pushing effect from solar radiation acting on an irregularly shaped object causing it to rotate faster over very long periods of time.
The speed of the rotation can already be seen due to the build-up of rocks along the equator through centrifugal forces. If the rotation continues to speed up then the asteroid might eventually disintegrate altogether when centrifugal forces overcome the gravity of the asteroid.
Bennu had a lot of surprises waiting for scientists when a Osiris Rex arrived, it was a lot more lumpy than expected with giant boulders comprising almost the entirety of the surface.
It contains clays and other hydrated minerals and dynamic activity originating from Bennu was witnessed up close.
We still have the sample collection part of the mission to go and can't wait to see what else Bennu has in store for us.