MORE: There has been speculation that evolution on earth took a different path from that on other planets when mitochondria, which were originally free-living organisms like Rickettsia, developed a symbiotic relationship with eukaryotes (cells with a nucleus) and made possible multi-celled organisms. This crucial step may have occurred only once. Or, it may occur in any oxygen rich atmosphere. We should not be surprised to find single cell life on Mars but multicellular life might very, very rare.
I have already posted on the new developments in bacteriology and life forms like Archea. Now, we are starting to see evidence that Mars may host similar organisms. Here is evidence of methane on Mars.
At a NASA news conference this afternoon, a team of scientists led by Michael Mumma of the Goddard Space Flight Center announced the discovery of plumes of methane emanating from the surface of Mars during the planet’s late spring and early summer. Methane is a key component of natural gas, and much of the Earth’s supply of the chemical comes from organisms that release it as they digest nutrients. But the five scientists were cautious to avoid claiming the methane spouts as evidence of life, saying that geologic activity could also put pressure on the methane and blast it through cracks in the surface. Either way, Mumma said, the plumes show that Mars is not merely a dead planet that once may have hosted life or liquid water. “We are entering a new era,” he said. “Now we’re looking at an active Mars.”
I have previously commented on extremophiles and other organisms that might survive in the Martian environment. Here and here.
There is more on this topic here.
To learn whether life could exist in a barren landscape such as that seen on the surface of Mars, where any water present is mostly present in the frozen state, some microbiologists have journeyed to a part of Earth that resembles Mars in some respects: the polar deserts of Antarctica.
Antarctica proves that microbes survive in barren landscapes.
This region of Antarctica has very little water, and most of the year what little water there is exists in the form of ice.
The hole in the ozone layer that has developed over Antarctica allows high levels of ultraviolet radiation to reach Earth’s surface, a condition that would be experienced by any creatures located on the Martian surface.
The level of radiation encountered in Antarctica is not nearly as high as that encountered on the surface of Mars, but it is higher than that encountered on most other parts of Earth’s surface.
Is there life in the polar desert of Antarctica? The answer is an unequivocal Yes. Bacteria and fungi have been found in the Antarctic deserts, not only in the soil of the region but also inside rocks. Scientists speculate that bacteria enter the porous matrix of rocks as a means of protecting themselves from radiation.
The atmosphere on Mars is much thinner than Earth’s.
A major difference between the environment found in the high deserts of Antarctica and that encountered on the surface of Mars is the atmosphere. The Martian atmosphere is much thinner than that of Earth. It consists mostly of carbon dioxide, or CO2 (about 95%), and contains virtually no oxygen (O2). Because many bacteria, archaea, and algae can use inorganic carbon dioxide as their source of carbon (used to build proteins and other cell components), the predominance of carbon dioxide would be a plus. Also, as noted earlier, many of Earth’s microbes do not require O2, so the lack of O2 does not preclude life.
So all these points are permissive. Life could exist on Mars. There is a problem, though.
A more troubling feature of the Martian atmosphere is the very low level of nitrogen (N2). On Earth, N2 makes up 78% of atmospheric gases. On Mars it only composes 3%. Many bacteria can use N2 as a sole source of the nitrogen they need for proteins, nucleic acids, and other cell components, but the low level of N2 would certainly limit the amount of microbial growth. Thus, if there is microbial life on Mars, it is unlikely to be as abundant and as widespread as on Earth and may thus be harder to find.
Different compositions and concentrations of gases may exist in some areas under the Martian surface. Such a possibility would be difficult to prove—unless it is proved indirectly the presence of life in the subsurface regions and in greater abundance than expected.
We may have to consider a life form that does not use Nitrogen. Phosphorus and Arsenic are members of the family of Nitrogen in the periodic table. on Earth, Nitrogen is a gas and a large part of the atmosphere. On Mars, it is a small part. One problem is thinking about Exobiology, the biology of other systems. Phosphorus is abundant on Mars. What does this mean ? I don’t know.
