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Life on Mars? Why Not?
Guillaume Filion writes "IEEE spectrum has an interesting article about a new probe sent to Mars searching for life: 'Recent missions to Mars have focused on the search for water, past or present, as a surrogate for life itself. But now a British-led team is working to renew the search for life directly, fueled by doubts about the equipment that prompted NASA to declare Mars a dead world some 26 years ago.'"
I read a book by Stuart Kauffman (hope I spelt that right). He said he was asked by NASA to help design probes to send to Mars to look for life. He told them not to bother, and his reasoning was:
All life takes in energy and matter from the environment, extracts energy, and produces waste. This process causes chemical imbalences in the atmosphere. Therefore to test for the presence of life, you only need to determine whether the atmosphere is in chemical equilibrium. Mars' atmosphere is, and has been for many millions of years.
Apparently this line of reasoning upset NASA, because they wanted to go to Mars, so they made their probes without his help, and when they arrived on Mars, found no traces of current life.
If they send more probes, they could very well find evidence of past life, but there is nothing going on there at the moment.
However I remember reading a story a while ago on Slashdot about how the atmosphere of Venus is operating far from chemical equilibrium, and that there may be some primitive life in the 400 degree acid in the atmosphere. Maybe someone should pay more attention to Venus...
- Water is highly polar, and therefore has the ability to dissolve ions. Without ions, complex chemistry could not take place.
- Water is liquid at a "reasonable" temperature, meaning water in liquid form is not hot enough to destroy most complex molecules.
- The density of ice is slightly less than that of water, so ice floats on top of water. This is vital, because it allows bodies of water to form a frozen cover which protects against further freezing. This is not common among substances.
- Water blocks ultraviolet light, which would otherwise destroy fragile molecules and organisms.
- Water has a very high specific heat, making it ideal for carrying out chemical reactions -- exothermic reactions can dump their heat into the water, and endothermic reactions can draw their heat from the water. This allows energetic reactions to occur without raising the temperature too high.
Basically, water is a very unusual substance with many favorable properties, and it's likely that life will take advantage of water, if it is present.That's not to say that life cannot exist without water, but it certainly makes life much more plausible.
As for non-carbon-based lifeforms, people have been pondering that for decades. Carbon is interesting because it can bond with itself pretty much ad infinitum, forming complicated structures. It also combines readily with oxygen, nitrogen, hydrogen, sulfur, the halogens, and a host of other elements. Complex life based on some non-carbon element would have to have the ability to form long chains of atoms, branching structures, and structured which curl up into specific shapes (i.e. proteins and enzymes). A carbon-silicon combo might work.
How about a BBC article
The fungi that did the damage, Novikova said, included members of the genera Aspergillus, Penicillium, and Cladesporium - all very common on Earth.
Davak