Ice-cool Mars ‘probably never had warm seas’

SCIENTISTS may have to revise the theory that warm oceans once washed over the surface of Mars, it was revealed yesterday.

New data from the Mars Global Surveyor spacecraft suggest 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, Mars Global Surveyor detected only trace quantities of carbonate in the Martian dust which probably originated from the planet's thin atmosphere, rather than oceans.

The discovery is both a success and a disappointment for scientists. It provides clear evidence that surface water once existed on Mars but not in the quantity researchers hoped for.

A mystery remains, however, over the way features resembling flood plains, river beds and gorges were created on Mars.

Planetary geologist Joshua Blandfield, a member of the US team from Arizona State University, Tempe, said: "What we don't see is massive regional concentrations of carbonates, like limestone. We're not seeing the White Cliffs of Dover."

Carbonates form when carbon dioxide gas comes into contact with minerals and liquid water. Since Mars has an atmosphere largely made of carbon dioxide, scientists have theorised that any large bodies of water on the planet should have left sizeable carbonate deposits behind.

An instrument on NASA spacecraft designed to find carbonates, called the Thermal Emission Spectrometer, was able to search patches of the Martian surface just two miles wide.

It found carbonates everywhere but at tiny levels of just 2% 5%.

Philip Christensen, another of the scientists, said: "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.

"People have argued that early in Mars history, maybe 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."

The new findings, reported yesterday in the journal Science, mean there is less chance of finding evidence of past life on Mars.