FIG. 353 shows that, during the Viking primary mission
period, large areas of the martian surface were above 273░K when an albedo
of 0.25 and a thermal inertia of 6.5 were applied. Although the maximum
temperature contour drawn for the Viking landing sites is 270░K, that
surface temperature would be exceeded where, because of rocks or dark
colorations, the albedo was less than 0.25 and/or the thermal inertia was
greater than 6.5. Under these conditions, water would be in liquid form.
"Thermal observations made half a century ago54,55,56
established that midday equatorial temperatures rose above the melting
point of water."57 Within large geographic areas, the upper
layer of the martian soil exceeds the triple point temperature and
pressure for water which, thus, would occur in liquid form at least
transitorily in diurnal and seasonal cycles.
LR tests performed on the Death Valley sand dunes,
shown in FIG. 4, detected microorganisms in the top one or two millimeters
of the sand within one hour, as did tests performed on bare rock.
Antimetabolites applied to duplicate samples as controls were effective in
preventing evolution of gas, confirming the biological nature of the
response. Samples of the top 2 mm of the sand were taken and analyzed by a
NASA Jet Propulsion Laboratory (JPL) soil microbiologist. The moisture
content and microbial populations reported58 were 0.9%, and
5.10 x 103 aerobic cells per gram, respectively.
The above considerations address the presence of
liquid water in terms of the more familiar terrestrial biological needs.
Other factors concerning water and biology may apply. Even before the
announcements of probable evidence for life in the martian meteorites, the
possibility that life once existed on Mars was gaining favor.59
It was generally believed, however, that any such early life forms would
have become extinct when liquid water was thought to have become
unavailable. Alternatively, it was proposed, some organisms might have
retreated to discrete "oases" deep below the surface where liquid water
might still exist. Recent findings question the presumption that water
activity on Mars is too low to permit aqueous moiety reactions. For
example, chlorofluorocarbons are adsorbed onto stratospheric ice crystals
which provide a liquid-like moiety for the chlorine to react with
ozone.60 Such ice activation may accompany the diurnal frost
depositions Viking observed on Mars, making biological reactions possible.
Alternatively, water vapor rising from the Mars permafrost may be adsorbed
on soil particles to form "double donor waters." These are reported to
exist commonly in ice where they expose very large surfaces as thin films
and clusters.61,62 An atomic force microscopy
study63 of thin films of water indicates a solvating monolayer
of phase I ice on adsorbing surfaces. This water might be available for
biological reactions. Duracrust formations on Mars are
attributed64 to the solvation and transportation of sulfate to
the surface by the vapor flux from the Mars permafrost. This water of
solvation might also accommodate biological reactions. Current
availability of this solvating factor on Mars was indicated by the Viking
GCMS results, which were cited65 as evidence for the
availability of water to form the duracrust.
Since Viking, life has been found thriving in extreme
environments heretofore believed deadly, including high temperatures and
pressures, and even in non-aqueous environments.66 A
variety of microorganisms, including synergestic combinations such as
lichen, live inside rocks in the dry valleys of the
Antarctic67, where precipitation is rare and occurs only as
light snow. Aseptically removed from within the rock, scrapings produced
the positive LR response included in FIG. 6.
Under extraordinarily harsh environments, many species
of bacteria can enter a state in which they catabolize slowly, but neither
grow nor divide68 until nutrient concentrations, temperature,
and other conditions become favorable. A review69 cites many
mechanisms for survival, including some for completely anhydrobiotic
cells. Examples70,71 of dormant microorganisms indicate
survivals approaching geologically significant time periods. Indeed,
bacteria have been reported to have been resuscitated72 after
30 million years of dormancy under highly desiccating conditions.