| Mars: icy and frozen always
Aug. 22: The possibility that life ever existed on Mars was dealt a blow today by evidence that seems to dash suggestions that there were once warm oceans on the Red Planet.
The quest to find evidence of life is linked to that for liq- uid water. After a decades- long scientific quest, scientists analysing data from Nasa’s Mars Global Surveyor spacecraft have concluded that large bodies of water never existed on the planet.
If they had, they should have left large deposits of carbonate minerals, such as the limestone rocks on Earth.
Instead, the spacecraft detected only trace quantities of carbonate in the Martian dust, which probably origina- ted from the planet’s thin atmosphere, rather than oceans.
The discovery is both a success and a disappointm- ent, providing clear evide- nce that surface water once existed on Mars — but not in the quantity that researchers had hoped for.
“We’re not seeing the white cliffs of Dover or anything like that,” said Dr Joshua Bandfield of Arizona State University, one of the team wh- ose work is reported today in Science.
“We’re seeing ubiquitously low levels,” Bandfield added.
Because there are known to be deposits of frozen water on Mars, the findings could have important implications for Mars’ past climate history.
“This really points to a cold, frozen, icy Mars that has probably always been that way, as opposed to a warm, humid, ocean Mars sometime in the past,” said Professor Philip Christensen, co-author.
“People have argued that early in Mars’s history, may- be the climate was warmer and oceans may have formed and produced extensive carbonate rock layers. If that were the case, the rocks formed in those putative oceans should be somewhere. But they don’t seem to be.”
Britain’s Beagle 2 probe, carried by the European Sp- ace Agency’s Mars Express spacecraft, is due to land on the planet on Christmas Day and will search for evidence of life.