New research of lunar samples shows that asteroids (a combination of carbonaceous chondrite-type materials), not comets, were responsible for the majority of water and nitrogen delivered to the Moon ~4.5–4.3 Ga. The study places important constraints on the origin of water in the inner Solar System.

See the source article by following the link below:
New research of lunar samples shows that asteroids (a combination of carbonaceous chondrite-type materials), not comets, were responsible for the majority of water and nitrogen delivered to the Moon ~4.5–4.3 Ga. The study places important constraints on the origin of water in the inner Solar System.