Just out from Nature Geoscience (15 January 2026):
Kitazato, K. Sakurai, S. Hyodo, R. et al. Surface rejuvenation of stony near-Earth asteroids triggered by planetary shadows s41561-025-01907-w
We see active asteroids, including at least one (maybe multiple) that give us a meteor shower. We finally saw, up close, asteroid Bennu shedding macroscopic debris, courtesy of the OSIRIS-REx probe. In some cases, these “asteroids” are truly asteroid-comet transition objects (hence the creation of the term “small Solar System body”), with activity driven by volatile emission. In some other cases, mass loss is ejecta after a meteor impact, and just temporary. Meteor impacts can happen anywhere, any time, and this is a lot less interesting. In other cases, YORP spinup causes bodies to fling out loose bits.
There’s yet another case: thermal cycling and cracking. But asteroids rotate, and if they go through a thermal cycle every “dawn” and “dusk”, then why aren’t we seeing, oh, almost every asteroid become active? Some rock compositions may be more susceptible than others, but we’ve got some of a handle on mineralogy (courtesy of meteorites). Now, an interesting hypothesis: asteroids go into deep cycling when they pass behind a planet, and into/out of its shadow. Kitazato et al. consider the severity and length of these eclipses, and find that asteroids can be “primed” for future cycling.