Life on Mars?

Mars. (Courtesy: NASA)
It is surely ironical that Mars, that desert planet of red dust storms and dry ice caps, might have answers for us regarding the origin of Life. However, recent reports of that claimed signs of life could be detected in Martian meteorites have sparked much interest in the Red Planet, which has long been considered the best candidate for holding evidence of Life beyond Earth.

The presence of the gullies on Mars suggests that Mars has warm events or warm climate periods at times. From analogy with the ice ages on Earth, we might expect astronomically driven alternations of cold and mild periods, since Mars' axis is tilted and since Mars' orbit has substantial eccentricity. (Both tilt and eccentricity produce ice age fluctuations on Earth.) Perhaps, periodically, ancient dormant life forms protected deep within Mars come to life. If so, what kind of carbon chemistry governs their existence? Is there, was there ever, life on Mars? Here is one of the more optimistic answers, from the people who know Mars best:

"Early environments were apparently sufficiently similar on Earth and Mars, and life arose so rapidly on Earth once conditions became clement, that emergence of life on both planets at that time is scarcely less plausible than emergence on only one."
"Exobiological Strategy for Mars Exploration",
NASA SP-530 (April 1995)

"Scarcely less plausible" is about the best we can do at the moment. It is a cautious scientific statement, but hopeful at the same time. The stakes are high:

"...[finding extraterrestrial life] would change everything - no human endeavor or thought would be unchanged by that discovery."
Dan Goldin, NASA Director

Studying Mars as the second test bed after the Earth most likely to have hosted life, even in a primitive form . . . is an obvious step in understanding the development of life in the whole Universe."
Roger Bonnet, Director of Science, ESA

Is there now, or was there ever, water on Mars? Finding evidence for water will greatly increase the chance that Life on Mars, past or present, is a reality.

Our chief interest in Mars' history, again, revolves around the crucial question of whether Mars was always so dry and cold as today, or whether there once were rivers and seas.