14 DAY TRIAL // The recent findings of water existence proofs on Mars inflamed the imagination of scientists chasing proofs of the existence of former or current life forms on Mars.
"Hunting for traces of life on Mars calls for two radically different strategies," said Jack Farmer, a professor of geological sciences and head of the astrobiology program in Arizona State University School's of Earth and Space Exploration.
"Of the two, with today's exploration technology we can most easily look for evidence for past life, preserved as fossil "biosignatures" in old rocks. Searching for extraterrestrial life must follow two alternative pathways, each requiring a different approach and tools," Farmer says.
"If we're looking for living organisms, we are doing exobiology. But if we are seeking traces - biosignatures - of ancient life, it's better to call it exopaleontology."
But the technology to make exopaleontology research in Mars needs 10-15 years more of technological advance from the current one.
"To find living organisms on Mars," says Farmer, "you need to find liquid water. Because liquid water is unstable on the Martian surface today, that means going deep into the subsurface. Water saturates the ground in high latitudes north and south, and around both poles, only a few inches below the surface," Farmer explains.
But the surface or shallow waters in Mars are frozen the entire year.
"Environments with liquid water will likely lie far deeper, perhaps miles below the surface."
On Earth, scientists found biological communities formed by bacteria in fractured rock, thousands of meters below the Earth's crust, even under sea.
But the deep drilling requires complex, heavy technology which is difficult to employ even currently on Earth.
"We'll be lucky if, in the next decade or so, robotic drilling on Mars reaches a depth of a couple yards."
Thus, the exopaleontology on Mars is by now more within reach.
"Finding the signatures of an ancient Martian biosphere means exploring old rocks that might preserve traces of life for millions or billions of years," Farmer notes.
"Among the best places to look on Mars are deposits left by springs and former lakes in the heavily cratered highlands. The rocks there date from a period in Martian history when liquid water was common at the surface."
In fact, conditions on ancient Mars could have been similar to those on early Earth, when life emerged.
"The Mars Exploration Rover Opportunity found ample evidence for water in ancient rocks at Meridiani Planum, but the rovers' instruments can't detect organic materials."
NASA's next rover, the Mars Science Laboratory, planned for 2009, will be able to investigate for traces of organic substances.
Finding life traces in Mars is not looking for ancient bones or shells, but it's more like searching for stromatolites (structures formed in shallow oceans, lakes, or streams by microbial colonies wrapped in old sediments), the oldest life forms found on Earth.
Stromatolites display microscopic cellular structures and organic chemical traces left by microbes.
"For hunting Martian fossils, we will need robotic microscopic imagers capable of viewing rocks in many wavelengths as well as seeing details as small as a hundredth of a millimeter across. Also needed are organic chemistry laboratories to analyze promising rocks. That will help us avoid mistaking non-biological features for biological ones," he says.
Farmer has studied microbial communities living in extreme habitats around the world, from Iceland to New Zealand, Yellowstone National Park, and Mono Lake, California, in order to see how these microorganisms fossilize.
"Their environments span physical and chemical conditions believed to be representative of early Mars. Studying how microbes become fossils is a key step in developing an effective strategy for exopaleontology. It will help us find the best places to explore on Mars and how to look."