The global properties of Mars can
here. Things to note are the following:
Speculation about Life on Mars:
- Mars is relatively small, having only about 10% the mass of the
- Mars has an atmosphere made up mostly of Carbon Dioxide but its
pressure is only 1% of the Earth's atmospheric pressure. Thus Mars has
10,000 times less Carbon Dioxide in its atmosphere than Venus.
- The strangest thing about Mars atmospheric content is the high
degree of residual Argon
- Mars is tilted on its axis by 25 degrees, very similar to the Earth
and hence Mars has seasonal variations
- These seasonal variations cause frozen carbon dioxide to sublime from
the Polar Caps thus giving Mars a seasonal atmospheric pressure
This has runned rampant for many years. A few highlights:
Spacecraft Encounters with Mars:
- War of the Worlds by HG Wells in the late 19th century (this
is actually an entertaining social commentary instead of a book about
Martians invading the Earth even though Hollywood disagrees)
- Percival Lowell (late 1920s): A semi-deranged astronomer who thought he saw
canals which connected the polar cap regions to the equatorial regions.
He also saw changing patterns on Mars which he attributed to seasonal
vegetation growth. He made up an elaborate story that Agrarian Martians
built a network of aqeducts to bring water from the polar regions to
irrigate equatorial crops. The New York Times believed him.
- Orson Wells: On Halloween night 1939 he gave a radio broadcast
announcing that the Martians were landing in New Jersey. People believed
him (must be how Rush Limbaugh got his start) - totally amazing. See
the movie "Buckaroo Banzai" for more details on Cherry Hill New Jersey
and John Bigbooty.
Surface Geological Evolution on Mars:
- Mariner 4 crash landed on the surface in July 1965. Limited
images revealed a cratered surface
- Mariner 6 and 7 in 1969 took additional images (before crashing)
which indicated the surface was not uniformly cratered like the lunar
surface. Hence, Mars must have a younger surface
- Mariner 9 in 1971 was the first orbiter mission. Approaching mars
revealed a surface that appeared suprisingly smooth and uniform with
a few black dots. At the time of the approach, Mars was engulfed in one
of its periodic global dust storms and the black dots were the tops of
huge volcanoes sticking above the dust storm. These dust storms account
for the shifting large scale patterns on Mars that Percival Lowell thought
were agriculturual fields. Mariner 9 returned the first evidence that
periodic massive floods (of water) occur on Mars.
- Viking Landers and Orbiters in 1976 took extensive images of Mars
at fairly high resolution (like a few cm in the case of the Landers).
These pictures are quite striking and should be inspected
- No age dataing is available so everything is still a guess.
- Crater erosion is occuring as over time the craters are filled in
with wind-blown dust
- Some evidence for primitive plate tectonics:
- Valley Marineris: Looks like a huge rift valley on Mars as
if crustal separation was occurring
- Tharsis Volcanic Region: Region of 3--4 large shield volcanoes.
Very reminiscent of the Hawaiian Islands as being on a moving plate over
a stationary hot spot (magma source) deep in the interior of the earth.
The large size of these Volcanoes is probably related to the low surface
gravity on Mars (40\% of the Earth's)
- Fluvial Erosion (running water) from two sources. Note that the
current atmospheric pressure on Mars is insufficient for water to exist
as a liquid. However, during volcanic episodes the atmospheric pressure
(mostly provided by carbon dioxide) is sufficient for liquid water to
exist for a short time.
- Much of the Martian topsoil is supported by permafrost.
Periodic melting would cause this support to collapse and on Mars there
does appear to be large scale collapse features (jumbled up terrain if
you want a technical term)
- Many fluvial features are associated with large impact craters.
This suggest that the heat dissipated during the impace melts much
of the permafrost causing a large scale flood. This flooding events
are similar to what occurred in the massive flood 15,000 years
ago that shaped much of Eastern Washington
Searching for Life in the Martian Top Soil:
The Viking Landers primary mission was to test for microbial life in the
Martian soil. They landed at latitudes of 23 and 48 degrees. There
were three identical experiments on board each lander designed to
see if anything in the soil did the following:
- Deposited Waste
The Three Experiments and the results are the following:
- Gas Exchange Experiment: Some soil was put in a small chamber on
board the Viking spacecraft to which water was added. There was a change
in the atmospheric composition in the chamber but this could be entirely
explained via chemical reactions with peroxides (a peroxide molecule has
2 hydrogens and 2 oxygens and is highly chemically reacting).
- The labelled Release Experiment: This was designed to see if anything
in the Martian soil would "eat" some nutrients that were mixed in.
The results can again be explained entire via chemical reactions
- The Pryolictic Release Experiment: This was designed to detect
photosynthesis. When illuminated with light, photosynthesis should deposit
carbon in the soil in the chamber. There was a small increase in the
amount of carbon fixed in the soil which can not be entirely explained
An excellent summary of the Viking Lander Experiments can be found in
a article in Scientific American in 1977 by Horowitz. A brief summary
is given below:
- No Martians were observed standing in front of the Camera
and waving shouting "Hey, we are on TV!".
- Overall the results are ambiguous but most are consistent with
a purely chemical reaction
- The soil of Mars is highly chemically reactive with a high oxidizing
capacity (which of course is why the soil is red)
- A photochemically active surface is evident. However, due to low
temperature and absence of water this surface is maintained in a state
far from chemical equilibrium. Hence, the Viking lander experiments
chemically woke-up some dormant top soil.
- The mass spectrometer aboard each lander carefully analyzed the topsoil
of Mars and found no organic matter down to a level of 10 parts per
The major flaw associated with the Viking Lander experiments is that
they could only access the topsoil. As this is the product of wind blown
dust, it is possible it has become sterile by this process. Hence, it
is desireable to return to Mars and sample deep into the soil, down near
the bedrock, to test for the presence of organic matter.
There is ample scientific motivation to return to Mars with a manned
mission. Here's predicting it will happen before the year 2025.
The Electronic Universe Project