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wet/dry cycled reaction sequence. This dehydration-induced emission of bursts of
UV and visible light, with peak emission
D
365 nm (decaying monotonically
in several hours and several days) from clays, is possibly related to its catalytic
mechanism by means of electronic excitation, creating mobile or trapped holes and
electrons in the lattice (Coyne et al.
1984
,
1985
). So I propose that with a possible
biogeochemical evolution below Martian surface at around 2 Gyrs ago, using clays'
catalytic properties and the light emitted from them, there is a possibility that life
arose at Mars from biomolecules up to a very simple organism form - simpler than
Earth's Archaea organisms - deep within subsurface aquifers.
Such kind of simple organisms, within extreme environments, might have
evolved a two-way form to use energy - one at great depths, using geochemical
energy by sulfur redox, and other near to the surface using the light emitted
from clays at wet/dry cycles. At the surface, gravity would pull colonies of those
microorganisms to underground, and when at depths, plumes of hot water/hydrated
hot molten material would rise those microorganisms near to the surface again, in
long-term periodic cycles. Here on Earth, there are studies of Archaean thermophile
organisms, such as
Sulfolobus shibatae
virus-like particles (SSV1), which exhibit
properties of double ways for the same function (as double proteinic coats, via
DNA decoding) and like to grow at 89
ı
C with UV light (a strong stimulant for
SSV1 production (Martin et al.
1984
)) (Zillig et al.
1992
,
1999
), and other Archaean
which use more than two sources for a common metabolic pathway as
Sulfolobus
acidocaldarius
(growing best in the water of volcanic calderas at about 75
ı
Cand
at a pH range of 1-6), which oxidizes sulfur to sulfuric acid or can use Fe
2C
or
MnO
4
2
as electron acceptors while using glycolysis and the TCA cycle.
The idea of a “simple” microorganism using two different forms of energy
sources is thus not so problematic. That hypothetical life could have lasted for some
hundreds of millions years, 1 Gyr, and now be dormant or, much more possibly,
fossilized inside sediment rocks at the subsurface of Mars.
Future robotic and manned missions to Mars can search for possible biogeochem-
ical signatures of fossilized colonies of such hypothetical microorganisms, below
the Martian surface, within locations with hydrothermal past (and possible present)
volcanic activity, using sedimentary petrological microscopy and NMR - interesting
to astrobiology.
8.6
Biogeochemical Parallels Between Earth and Mars
8.6.1
Geological Comparisons
Well, I make some parallels between what is known about carbonate diagenetic
deposits and petrological studies of arenites, present at the Bauru Group, Brazil,
South America, and what is known about intact rocks in contact with clays, rich in
olivine, exposed at the surface of planet Mars containing carbonate mineral deposits.
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