<P> In this timeline, Ma (for megaannum) means "million years ago," ka (for kiloannum) means "thousand years ago," and ya means "years ago ." </P> <P> 4000 Ma and earlier . </P> <Table> <Tr> <Th> Date </Th> <Th> Event </Th> </Tr> <Tr> <Td> 4600 Ma </Td> <Td> The planet Earth forms from the accretion disc revolving around the young Sun with organic compounds (complex organic molecules) necessary for life having perhaps formed in the protoplanetary disk of cosmic dust grains surrounding it before the formation of the Earth . </Td> </Tr> <Tr> <Td> 4500 Ma </Td> <Td> According to the giant impact hypothesis, the Moon was formed when the planet Earth and the hypothesized planet Theia collided, sending a very large number of moonlets into orbit around the young Earth which eventually coalesced to form the Moon . The gravitational pull of the new Moon stabilised the Earth's fluctuating axis of rotation and set up the conditions in which abiogenesis occurred . </Td> </Tr> <Tr> <Td> 4404 Ma </Td> <Td> First appearance of liquid water on Earth . </Td> </Tr> <Tr> <Td> 4280 Ma </Td> <Td> Earliest appearance of life on Earth . </Td> </Tr> </Table> <Tr> <Th> Date </Th> <Th> Event </Th> </Tr>

When did the earliest organisms appear on earth