March 15, 2006
Clues to Mars Life May Lie Underground: Scientist
By Irene Klotz
HOUSTON (Reuters) - To learn if Mars ever supported life, researchers should look underground, a scientist presenting results of the Mars Express mission said at a conference this week.
The European Space Agency's orbiter has mapped almost the entire planet for minerals that bear chemical fingerprints of past encounters with water.
Less than 1 percent of the planet's surface bears signs of hydrated minerals, said Jean-Pierre Bibring, the lead investigator for the Mars Express Omega instrument, which splits and analyzes visible and near-infrared light radiating from the planet's surface.
"We initially thought hydrated minerals would be everywhere," Bibring said in an interview. "That turned out to be not the case."
For the past two years, Bibring and his team have been mining Omega data for minerals that contain water in their crystalline structure. Two types of hydrated minerals have been found: phyllosilicates, which, like clay, develop from rocks that have prolonged contact with water; and sulfates, which form as deposits from saltwater.
In general, the clays are more likely habitats for life than sulfates because they needed more time to interact with water to form, Bibring said.
The search for life beyond Earth is shaped by the fact that life, at least forms of terrestrial life, needs water to develop. So on Mars, and elsewhere in the solar system, researchers have focused on finding suitable habitats for life to evolve, namely sites that have or had liquid water.
On Earth, life has been found in a vast array of hostile environments, including around deep-sea vents.
"You don't need to be on the surface to have life appear," Bibring said.
He suspects that a much richer supply of hydrated minerals exists just beneath the martian crust.
"As soon as you have a way to drill, you might find the entire crust was exposed to water," Bibring said.
In a presentation to scientists at the Lunar and Planetary Sciences Conference in Houston, Bibring said he believes the phyllosilicates developed first on Mars. That layer was covered by red-hued soil due to a massive global disturbance. The sulfates formed later.
"Whatever happened on Mars modified the entire climate," Bibring said.
Scientists expect to get a much better understanding of the mineral makeup of Mars when NASA's Mars Reconnaissance Orbiter, which arrived at Mars last week, begins its mission later this year. The orbiter has a spectrometer that that has 10 times better resolution than Mars Express' Omega instrument.
The Mars Reconnaissance Orbiter is scheduled to reach its operational orbit in November and then begin a detailed search for signs of water.