The Martians are Coming, The Martians are Coming

• HG Welles wrote an interesting story about it
  

• The telescopic appearance of Mars can show "subtle" changes over time. This is due to wind blown dust changing the large scale features and reflective characteristics. In the late 19th century Schiaparelli imagined he saw linear features which he called "canals"
  

• Schiaparelli's atlas of Martian Canals captivated the imagination of Percival Lowell who greatly popularized the idea of Life on Mars. Lowell imagined a system of canals that the Martians would use to transport water from the Polar Caps to the more arid regions. One of the results of his obsession was Lowell Observatory in Arizona. He constructed an elaborate globe of mars to illustrate this:
  

  Orson Welles 1939 broadcast of Martians invading New Jersey only served to perpetuate the mythology of the Martians. Unfortunately, the media really does have a powerful effect on people.

• Looking Around
• Looking around some more
• Nice Panorama

The Viking Lander Mission on Mars (1976) sampled the soil and found evidence of a highly chemical reactive soil and environment. There was no unambiguous evidence for biological processes. Worse still was the mass spectrometer measurements which detected no organic molecules down to a concentraction of less than 1 part in 10 million.

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:

• Ate
• Breathed
• 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 Pyrolytic 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 through chemistry.

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 but recent re-analysis of the data states otherwise.

• 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 billion.

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.

So what about the Martian Meteorite?

• Microscopic examination showed morphological peculiarites?

• once you find one you can find many
• Age dating suggests the following sequence
  • The rock itself is 4.6 billion years old (this by itself is highly unusual)
  • The concentration of carbonates is dated to between 3.6 -- 4.0 billion years ago. This suggests that carbonates were deposited inside the rock as liquid water found its way into cracks
  • The rock was part of a large cloud of Martian debris that was blasted off the surface by a large impact 16 million years ago
  • Landed on the Antarctic Ice Sheet 13,000 years ago
  • Discovered over 30 years ago.

If there was liquid water in the rock, then there is the potential for life. Why? By analogy with the development of early life on the earth, starting which chemical processes that synthesized organic molecules and rained them into the oceans, we believe that oceans are required for the development of early life:

• Water shields sensitive Organic Molecules from UV radiation
• Water acts as a transport medium that facilitates interaction between molecules, eventually leading to early forms of DNA and cells.

The most probable explanation of the morphological features seen in the Martian Meteorite is a chemical reaction. Factors that work against the biological interpretation are the following:

• The structures are 10--20 times smaller than similar "micro fossils" seen on the earth. This is a real problem - the structures aren't really big enough to "hold" DNA

• Carbonate concentrations in meteorites can easily be produced by chemical reactions that happen when the rock is shocked. This happens at high temperature (700 C) -->definitely not conducive for biology

• Magnetic fields have played a role in the evolution of bacteria on the earth. They use the magnetic field to sense their position. On Mars there is no global magnetic field --> there might have be one in its early history (when the core was molten) but it would have been very weak.

• All of the evidence remains morphological and not physical.

  Was there water on Mars?

  • Yes, there is now
  • There is evidence of flooding
  • More evidence
  • Agent for Water Production

  The ability for liquid water to exist on the Martian surface depends upon the atmospheric pressure. Current atmospheric pressure is 1/1000 that of the earth - too thin of atmosphere for water to exist. But the current theory from the latest satellite and lander findings is that oceans did exist for the first billion years.

  NASA radar measurements (from July 2007) indicate that there is enough frozen water on mars to flood it uniformly to a depth of 11 meters. This is approximately 10 times more available water than previously thought.

  However, in the early history of Mars there was enough Carbon Dioxide present to form an atmosphere that was at least 20 times as thick as the present day atmosphere.

  At this pressure, water could exist as a liquid on the surface, but the the temperatures couldn't get above freezing. The question is, how long did these "oceans" exist. On earth we know it took 800 million -- 1 billion years for the first cells to evolve. If Mars indeed had oceans for the first billion years, then the idea of ancient martian cells is possible based on this idea. However, Mars has a fairly elliptical orbit which would contribute to much lower temperatures periodically in it's orbit and thus keeping water frozen.

  Where does the atmosphere go?

  • Freeze out at the Poles but the more recent measurements suggest very low concentration of frozen CO₂ in the Martian polar caps. This is a critical blow to the idea that Mars was once warm and wet. Recent findings hint at subsurface water. But this has yet to be confirmed by more missions to the planet.

  • Gradual escape - Mars is a very small planet; has only 1/2 of the earth's gravity and therefore has difficulty holding on to atmospheric gases.

The soil about one-inch into the surface layer is alkaline, with a pH between 8 and 9 and it appears to contain magnesium, sodium, potassium, and chloride this is highly similar to many soils on the Earth.

Overall, the soil appears to have sufficient nutrients to potentially support microbial life.

But the most encouraging aspect of potential microbial life on Mars comes from our increasing understanding that life thrives in hydrothermal ocean vents.

The principle energy source is the processing of hydrogen sulfide (H₂S) by bacteria. This leaves behind rich deposits of sulfur.

The most significant aspect of this is that its now clear that life can form in a way that is independent of the Energy of the Sun This is a Big Deal because if subsurface water does exist, this means that the heat from the planet (which keeps the water in the liquid state) could provide an environment for Martian extremophiles to thrive.

But of course, its only true if its on YouTube.

And this is very much an Alien world, on the Earth, which should remind us all that there is much more to know.