Abstract: Comets and asteroids may have contributed much of the Earth’s water and organic matter. The Earth accretes approximately 4×10(exp 7) Kg of dust and meteorites from these sources every year. The least altered meteorites contain complex assemblages of organic compounds and abundant hydrated minerals. These carbonaceous chondrite meteorites probably derive from asteroids that underwent hydrothermal processing within the first few million years after their accretion. Meteorite organics show isoto…