Astronomy Today@astronomytodayNew modeling led by Richard Anslow of the University of Cambridge suggests comets were probably not the source of the complex molecules life depends on. Most comets hit too fast and at too steep an angle for these molecules to survive.
Survival would have needed impacts below about 33,500 mph (15 km/s), and the rare survivors would have been too scarce to seed early chemistry.
Researchers are increasingly looking at asteroids instead, since a sample from Bennu that OSIRIS-REx brought back contained all the building blocks of RNA.
