Again, more goodies in Space Science Reviews for the new year (volume 222):
Zhang, R. Zhang, H. Liu, J. et al. Tianwen-2 Mission of China’s Planetary Exploration Program 11 s11214-026-01268-9
The Tianwen-2 mission, launched last year, will rendezvous with asteroid (469219) Kamo’oalewa, an Earth co-orbital, and sample it. After dropping off the sample capsule, the main craft will use the Earth pass as a gravity assist. Tianwen-2 will sling back out to the Main Belt, where it will study its second target. That second body? “Asteroid” 311P/Pan-STARRS, a Main-Belt comet.
That’s right, the object known as Pan-STARRS (after its “discoverer”) orbits in a calm, mostly circular, mostly flat orbit in the Main Asteroid Belt. That would make it an asteroid. Yet it sheds material, forming a tail like a comet. So what is it? It’s an asteroid-comet transition object, and we’re going to see one up close. Granted, there’s the possibility (and Zhang et al. admit this) that the dust loss from 311P is caused by a fast rotation. Material around the equator of the object may be being flung out by centrifugal force alone, not volatile emissions. But we won’t know until we see, eh? Being in the Main Belt, it will take a while to get there- most of a decade. I can barely wait.