Surprise – Again! Asteroid Bennu

[Unitron48]

"After analyzing data gathered when NASA’s OSIRIS-REx spacecraft collected a sample from asteroid Bennu in October 2020, scientists have learned something astonishing: The spacecraft would have sunk into Bennu had it not fired its thrusters to back away immediately after it grabbed dust and rock from the asteroid’s surface."

"The asteroid presented its first surprise in December 2018 when NASA’s spacecraft arrived at Bennu. The OSIRIS-REx team found a surface littered with boulders instead of the smooth, sandy beach they had expected based on observations from Earth- and space-based telescopes. Scientists also discovered that Bennu was spitting particles of rock into space."

Complete article here: https://www.nasa.gov/feature/goddard/20 ... c-ball-pit.

The spacecraft is due to deliver its sample in September 2023.

Dave

[seigell]

Well, that really stands to reason - assuming Bennu is the type of asteroid developed by accretion of smaller masses - boulder-sized to dust-speck sized. After all, what would be the mechanism for compaction and affixing those accumulated particles except for the weak gravity of Bennu itself?? In the absolute cold of space, very few chemical reactions occur which would produce any cementing effect that might firm-up the outer layers of such a mass.
It seems that there should be two basic structures for asteroids that we encounter - those which are weakly-held accumulations of smaller bodies and those which are the product of fragmentation of larger astroidal bodies where much stronger gravitational forces might have previously melted/fused the progenitor's mass into truly solid form.