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to the fluxes of matter that are exchanged between the internal
components of the Earth system. The former, therefore, has almost no
influence on the latter. Of course, the exceptional impact of a large
meteorite occurs from time to time with important consequences for
evolutionary dynamics, the most well known of them being the
extinction of the dinosaurs, with the exception of the ancestors of birds,
65 million years ago. However, such an event, even if it heavily
impacts the nature of present and future species, has no long-term
effect on the Earth system's general biogeochemical dynamics. Once
the event and its climatic consequences have passed, the system
regains the normal course of its regulations and evolutions, which we
will describe in this chapter and which are also addressed in
Chapter 4, and in Chapter 2 of [MON 14b].
If the Earth has had an exchange with the universe in the pst 4
billion years, it is likely to have been through a flux in radiative energy.
For thermodynamics, this means a non-isolated, but “closed”, system.
The Earth receives a certain quantity of radiative energy from the Sun
and from space and sends an equal quantity back into space, but
increases the average wavelength of its radiation; that is to say it shifts
its spectrum to infrared. The individuality of the Earth system is thus
partly due to the fact that it is a closed system and its perimeter is not
arbitrary since it corresponds to the pragmatic image that we have of it
as an object, well separated from the exterior universe. Moreover, we
will show later that the maintenance of an atmosphere, oceans, a climate
and life, for 4 billion years, is largely due to the fact that the Earth is a
closed system through which energy travels and is transformed. This is
an exceptional situation in the solar system, since we can observe other
neighboring planets, formed at the same time, such as Mars and Venus,
where these characteristics are not present simultaneously.
The atmosphere of Mars is extremely thin and liquid oceans do not
currently exist on Mars nor Venus. The condition of a “closed
planetary system” is therefore necessary, but not sufficient, to explain
the preservation of the principal characteristics of Earth - atmosphere,
liquid water, life - over the course of 4 billion years. The other conditions
stem from adaptive interactions that have been established progressively,
on the one hand between the larger components of the Earth system
(e.g. geophysical, geochemical and biogeochemical exchanges) and on
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