Mars Astrobiology: Recent Status and Progress - Planetary Exploration and Science: Recent Results and Advances - page 209

Lagoon, whose water is rich in iode (I), some meters ( 10 m) distant from the
sea water (which is very rich in phyto- and zooplankton), inside an environmental
protected area, Setiba State Park, Brazil. I measured the temperatures of the
subsurface sediments (mud) at different depths, ranging from 0 to 0.5 m, and
took measurements at different locations in the lagoon area. I also measured those
temperatures at different times during day 1, at 8 A.M., 12 A.M., 4 P.M., and 8 P.M.,
in February 2003 (summer season in Brazil).
I collected small quantities of the subsurface mud at those range in depth,
analyzed the color and particulate consistency of it, and froze the samples at 10 ı C
(using a portable thermal insulator). The temperature of the subsurface sediments
and their color, smell, and particulate consistency are simple and good indicators of
possible microorganisms' catalytic activity. The vertical temperature profile shows
that at 12 A.M., at the surface (0 m), T D 20 ı C, and at 0.05 m, T D 25 ı C. At
0.30 m, T D 30 ı C. Between and below these depths, there was a noticeable drop
of temperature ( T D 18 ı C) and the same occurring below 0.20 m.
The color of the sediments at 0.05 and 0.30 m are black-dark gray (mud), and
the color of the sediments between and below those depths are gray. The odors of
the collected material at 0.05 and 0.30 m are strongly of hydrogen sulfide (H 2 S),
and the odors of the material between and below those depths are lightly of H 2 S.
The particulate consistency of the material collected at 0.05 and 0.30 m is
of very wet clay (mud), and the material between and below those depths shows a
silt consistency. All those above four biogeochemical characteristics united display
a strong possible evidence of microbiological metabolic activity at 0.05 and
0.30 m. H 2 S is known to be the by-product of sulfate-reducing bacteria, and the
black color of the very wet clay also reinforces this behavior (Mudryk et al. 2000 ).
This vertical temperature profile is maintained at different horizontal places of
the lagoon area. But the vertical T profile varies with time during the day (probably
linked to the variation of the solar energy flux by insolation unit area during a day,
since the Sun's infrared and ultraviolet energy are metabolized by microorganisms)
in a cyclic pattern - T oscillates from a minimum recorded at the surface (0 m),
T D 18 ı C at 8 A.M., to a maximum recorded at 0 m, T D 35 ı Cat4P.M.And
the depths of the subsurface material exhibiting the above characterized possible
microbial metabolism (black, hot, clay mud with strong odor of H 2 S) alternated by
subsurface regions with these smaller physicochemical parameters also vary in a
time-dependence cyclic behavior.
These sites with possible microbial mats are spatially (vertically and horizon-
tally) arranged in the form of “hot spots,” or “hot clusters,” not scattered as small
clusters but they are more concentrated in regions, and they exhibit temporal cyclic
behavior. At the surface of the sediments (0 m), there were microscopic green algae,
deposited there by the tidal sea water. Perhaps these photosynthetic microorganisms
could be supplying O 2 and nutrients (S, P, others) to the possible subsurface bacteria
communities.
And it was also noted that the boundaries between those sites exhibit scale-
invariance of those above biogeochemical properties, i.e., there were ensembles
of mud material near to ensembles of mud material near the boundaries at 0.05