Geoscience Reference
In-Depth Information
aluminosilicate rocks. This alteration consumes CO
2
and some of this
carbon is ultimately
found in the ocean in the form of carbonate ions
(CO
3
2-
) due to oversaturation. These will then be transformed into
solid form by the biological processes that create shells and skeletons,
then stored in the sedimentary reservoir. Details on these processes can
be found in Chapter 4, and in Chapter 2 of [MON 14b].
It is unknown how much time the end of this “Venus” phase could
have taken; many specialists on the primitive Earth now believe that
conditions favorable to the emergence of life were already present 4
billion years ago, that is to say, before the late meteoric bombardment,
and it is not impossible that an emergence of life may have taken place
in the ocean from this era [GAR 06]. If it existed, did this life survive a
late meteoric bombardment? Did other emergences, successful or
abortive, take place later? These questions remain largely open.
Figure 1.1.
Diagram of the Earth system at the end of accretion
around 4.5 billion years ago (see color section)
