The Presence of Water on Mars
Amy Duggan and Giuliani Lopez
Abstract
The presence of water has made Mars a key area of focus. Current observations and climate
predictions have lead to the theory that liquid water may have once existed. The observations
made by the Mars Exploration Rovers include discovering the presence of minerals such as
hematite, which is often an indicator of the presence of past water as well as jarosite and
goethite which can only be formed in the presence of water. Other observations made by the
Mars Rover included the discovery of shrinkage cracks and cross lamination. Shrinkage cracks
are formed when wet sediments dry out while cross laminations are formed by moving water.
Both characteristics involve liquid water in their formation. Another Martian discovery was the
presence of crystal molds which are made by minerals precipitating out of liquid water. Further
evidence for the presence of liquid water came from the predicted climate changes that are said
to have taken place in Mars’ past. By tracking periodic glaciations and the axial tilt of the
planet, we can calculate the solar luminosity which can give us an approximation of the
temperature that Mars experiences. Predictions of past temperature are in the range at which
liquid water can be present due to the lack of CO2 ice and the lesser degree of axial tilt. As the
climate system on Mars matured, CO2 ice rapidly grew in abundance, decreasing the overall
temperature of the planet making it too cold for there to be liquid water present.
Mars has been the focus of much study in the last couple of years. We are convinced that
there may have once been liquid water on its surface. The possibility of the presence of water
suggests that Mars may have once had an environment that could have supported life. Studies so
far have provided evidence that supports the theory of water being present. NASA sponsored
missions have contributed most of this information. The Mars Lander has uncovered frozen
water on the surface of Mars, the Mars Orbiter has surveyed the surface of Mars and there seem
to be water formed canyons, and the Mars Rovers have discovered minerals that can only be
formed under aquatic conditions. Climate models of Mars have established that the temperature
was once much warmer than what it is today showing the possibility for liquid water to exist
(Nakamura and Tajika, 2001). The past and present climate of Mars as well as the rock
formations and minerals present reveal much about the history of the planet and suggest that
Mars may once have had liquid water.
Upon examination of the data received from the Mars Exploration Rovers several
characteristics were found in the sedimentary rocks that suggest liquid water was involved in
their formation. These two characteristics are shrinkage cracks and cross lamination. The
shrinkage cracks were discovered by the Olympia outcrops and originally several explanations
for their formation existed. It was hypothesized that they could have been formed by the same
impact that formed the Erebus crater but the cracks known to be formed by the impact “postdate
and overprint” the shrinkage cracks (Grotzinger et al, 2006 pg 1087). Also the shrinkage cracks
were found in areas where soft sediment deformation had occurred and in places where plastic
deformation had occurred. These observations do not support the hypothesis that the cracks
were formed by an impact. The cracks however appear to be nearly identical to the shrinkage
cracks found on earth. On earth these cracks are formed by damp sediments drying out and
pulling away from each other. For the sediments to originally have been damp it implies that
liquid water was present at the time to make them so. Also the Martian shrinkage cracks
displayed some prism cracks which are associated with repeated periods of wetness and dryness
which could be caused by small rises and falls in the height of the water table. The only logical
explanation for the formation of these shrinkage cracks on Mars is an oscillation in the height of
the water table and if a water table existed so too did liquid water. The cross lamination in the
sedimentary rocks on Mars also leads to this conclusion. On earth, lamination of the “type and
scale” (Grotzinger et al, 2006 pg 1085) seen on Mars is not known to be caused by eolian flows
or base surges. Also the MI images that were taken of the laminations showed that the layers
were an intrinsic part of the rock and not merely a result of weathering. The only other
explanation is that they were caused by water. The shape, texture and size of the trough cross
lamination suggest that they were caused by shallow water moving at moderate velocities. The
presence of both cross lamination and shrinkage cracks on Mars is highly supportive evidence
that water was once present (Grotzinger et al, 2006).
Other observations made by the Mars Exploration Rovers that support the theory that
water was once present included possible crystal molds. Sulfate rich rocks with their surfaces
“crisscrossed by tiny gashes” (Squyres 2005 pg 310) were found by the Opportunity Rover on
the Meridiani Planum. The tiny gashes looked like those formed from crystal molds. On earth
crystal molds form when minerals precipitate out of water that is saturating a rock and crystallize
pushing aside or replacing the rock that is already there. When conditions change the softer
crystals are eroded away faster than the surrounding rock leaving indentations in the rock where
they once were resulting in the scratched appearance of the rock (Squyres 2005). These crystal
molds could also explain something else about Mars. Studies of MgSO4·11H2O have shown that
it could be the crystal that made the molds. If this is true a third of the crystals by volume were
composed of water. It is also possible that the release of water from MgSO4·11H2O resulted in
the some of the outflow channels on Mars (Peterson et al, 2006).
The Mars Exploration Rovers have helped explore the geology of Mars in much greater
depth than was possible with only satellite pictures. One of the instruments in the payload, the
Mossbauer spectrometer was particularly useful in determining the identity of minerals present
on Mars. Three minerals in particular that the Mossbauer spectrometer was able to identify were
hematite, jarosite, and goethite (Squyres 2005). The presence of all three of these mineral helps
substantiate the theory of water once being present on Mars. Hematite is an indicator of water
because it can precipitate out of water and be deposited in layers. Although it can be formed in
others ways and does not provide solid proof of water the hematite found on Mars is a strong
suggestion that it might have been there (Hematite, 2007). Also important was the fact that the
hematite on Mars was found in tiny spherules. These spherules were at first hypothesized to be
either accretionary lapilli, beads of glass, or concretions. The fact that the hematite spherules
were made of a different material than the surrounding basaltic sand disproved the lapilli
hypothisis (Squyres2005) and the distribution and the presence of interlocking spherules makes it
unlikely that they could be anything other than concretions (Minerals in Mars 'Berries' Adds to
Water Story 2004). For the hematite spherules to be concretions they would have to have been
formed by water percolating through rocks and depositing hematite in layers around an initial
point of precipitation. This theory for how the spherules formed involves the actions of liquid
water and thus strengths the argument for the possibility of past water. Two other minerals
discovered on Mars, jarosite and goethite, provide more substantial evidence for the presence of
water. Both jarosite, a sulfate salt, and goethite, an oxyhydroxide, actually have water in their
crystal structure. Therefore water must be present when they are being formed (Squyres 2005).
The climate system on Mars is said to undergo drastic changes in temperature due to
Jupiter’s gravitational interference on Mars’ angle of tilt about its axis. (Kerr, 2003a). These
stages are brought forth every 100,000 years or so as the angle at which the planet tilts fluctuates
between 25.2°, which is the current axial tilt of the planet, and 15° which is the estimated axial
tilt that Mars used to experience several hundred thousand years ago. (Kerr, 2003a). This change
in axial tilt does not increase the amount of light or heat that Mars’ surface experiences but it
amplifies the diurnal and seasonal changes in temperature that Mars experiences. These seasonal
changes in the past would have allowed for a steady temperature state in which liquid water
could exist. Even though there was a presence of water, it was exclusive to the equator where the
C02 pressure was highest. This offers an alternative to labeling Mars as a once liquid water-rich
planet. We do not have to go to the extent and say that liquid water was abundant on early Mars,
but only that it was present.
As the climate system of Mars matured the change in tilt allowed for the accumulation of
CO2 ice through positive feedback. This explains why the 95% of Marsʼ atmosphere and most of
Marsʼ surface is made of either liquid or ice CO2. (Byrne and Ingresoll, 2003). The surface CO2
ice reflected the Sunʼs light and in turn made the planet cooler, eventually leading to the lack of
liquid water. Even though the temperature has long been estimated to be far below the area in
which liquid water can exist, there have been rare occasions that suggest liquid water may still be
running on Marsʼ surface. Photographic evidence shows the minor alterations of craters and
gullies that seem to be formed by erosion. (Reports Detail Rover Discoveries of Wet Martian
History, 2004). This implies that our understanding of the climate system on Mars may not be as
complete as we think and that there may still be subtle traces of liquid water scattered along
Marsʼ surface although if this were so, the amount would be incredibly low because Mars lacks
both the precipitation rates and oceans that drive Earthʼs climate system. (Albee, 2003).
An error in past and present understandings of Mars’ surface has been in identifying CO2
ice and H2O ice properly. There are vast areas of CO2 ice caps that are believed to cover the
majority of H2O ice on Mars. Thermal identification of frozen H2O has been observed to have
problems identifying items through dust particles and thick sheets of CO2 ice which throws off
the estimates of H20 ice on Mars. (Titus et al, 2003). The importance in these miscalculations is
that CO2 determines the atmospheric pressure of Mars, surface which can affect the levels of
H2O present. (Byrne and Ingresoll, 2003). However, if we assume that current atmospheric
conditions where CO2 ice and CO2 gas are the highest in abundance are the reason for no liquid
H2O, we can predict that atmospheric conditions were at one point optimal for the presence of
liquid H2O before the process of CO2 ice sheet positive feedback occurred.
Although no liquid water has yet been found the body of evidence supporting this theory
is extensive. The evidence shows that liquid water is the most probable cause for the formation
of the shrinkage cracks, cross lamination, crystal molds and hematite spherules. This evidence
coupled with the probability of a warmer mars derived from climate models suggests the
presence of liquid water. The evidence of water has lead to a deeper understanding of Mars’
past, increase present interest in Mars and may pave the way for future discoveries. Currently
there are hypotheses working off the theory that liquid water was present which suggest that
there may be bacteria on Mars and that in the past Mars may have had an environment capable of
supporting life.
References
Albee, A.L., The unearthly landscapes of Mars, Scientific American, Vol 288, No. 6, 4453, 2003.
Byrne, B. and Ingersoll, A.P., A sublimation model for martian south polar ice features.
Science, p 1051-1054, 2003.
Grotzinger J. et al “The Geological Society of America” Sedimentary textures formed by aqueous
process, Erebus crater, Meridiani Planum, Mar. http://www.gsajournals.org/perlserv/ ?request=
get-document&doi=10.1130%2FG22985A.1 (9-20-08)
Kerr, R.A., Iceball Mars?, Science, 234-237, 2003.
Peterson, R., and Wang R., Crystal molds on Mars; melting of a possible new mineral
species to create Martian chaotic terrain Geology, Vol. 34. No. 11, 957-960 November
2006
Nakamura, T., Tajika, E., Stability and evolution of the climate system on Mars, Earth
Planets Space, 53, 851-859,2001.
“NASA” A Patch of Spherules on Mars 2-16-04
http://apod.gsfc.nasa.gov/apod/ap040216.html (10- 18-08)
“NASA” Mars exploration Rover Mission 8-17-02
http://mars.jpl.nasa.gov/mer/fido/sol18-image1.html (10-11-08)
“NASA” Hematite 7-12-07 http://www.jpl.nasa.gov/releases/2004/88.cfm (10-11-08)
“NASA” Minerals in Mars 'Berries' Adds to Water Story 2004
www.jpl.nasa.gov/releases/2004/88.cfm (10-11-08)
Squyres S. Roving Mars: Spirit, Opportunity, and the Exploration of the Red Planet.
Hyperion 2006.
Titus, N.T., Kieffer, H.H., Christensen, P.R., Exposed water ice discovered near the
South Pole of Mars, Science, 1048-1052, 2003.
Webster G. Savage D. “NASA” Reports Detail Rover Discoveries of Wet Martian
History, 2004 12-2-04 http://www.nasa.gov/centers/jpl/news/mer-120204.html (9-23-08)
Image A is of trough cross-lamination found
on Mars. Image B is an example of trough
cross-lamination found on Earth (Grotzinger
et al, 2006).
This is an image of the hematite spherules found
on taken by the rover Opportunity (A patch of
Spherules on Mars, 2004).
Shrinkage cracks on Mars (Mars Exploration
Rover Mission).