From - Sky & Telescope, By - Jeff Hecht, Edited by Amal Udawatta, This mosaic of asteroid 101955 Bennu was created using data from NASA’s OSIRIS-REX spacecraft, which visited the asteroid from late 2018 to mid-2021. NASA GSFC / University of Arizona Small asteroids are called rubble piles because they come in pieces, but close-up observations show the near-Earth asteroid 101955 Bennu is far from a random accumulation of interplanetary debris. Scientists analyzing data from NASA’s Osiris-REX spacecraft say they’ve found evidence it has an inner shell: a compacted layer a few meters thick made of small particles. The results will appear in Icarus . Most asteroids larger than tens of kilometers appear as single bodies, held together by gravity despite cracks and impacts. However, asteroids in the kilometer range or smaller are more often loose aggregations of smaller objects. The latter, so-called “rubble piles,” often have a low overall density and appear to be porous. Examples