Mars mappers fuel water debate

The valleys are in Mars' Tharsis region
Image: Nasa/JPL/Malin Space Science Systems

Scientists who believe Mars has been through warm, wet phases in the past say they have more evidence that water once flowed on the planet.

Water on Mars?

Water held as ground ice in Martian subsurface

Permafrost acts like cap on bottle

Sporadic bursts of internal planetary heat trigger dramatic release of gas and water

Temporary oceans form

Released carbon dioxide warms Martian climate

Snow and rain remove carbon dioxide from atmosphere

Mars cools again

Permafrost reforms

Researchers from the University of Arizona, US, say they have found what could be the largest flood channels on the Red Planet, which is currently covered in frozen desert.

The channels may have been formed by flows of water up to 50,000 times as great as the Amazon river, they say.

Theories of past or present water on Mars are controversial, with many clues but no proof pointing to a wet Martian past.

"Working hypothesis"

"Individual pieces of evidence by themselves represent a weak argument, but collectively they give greater credence to a working hypothesis," said James M Dohm.

The results of our work collectively fit a consistent and coherent picture

James Dohm
University of Arizona

"I am excited because the results of our work collectively fit a consistent and coherent picture," he said.

Mr Dohm and colleagues have been mapping Mars for many years, using data first from the Viking probes and now from the Mars Global Surveyor.

They believe that they have found a northwestern slope valley system in the planet's Tharsis region, 10 times larger than Kasei Valles, the largest previously known outflow channel system on Mars.

They think that the valleys were formed by catastrophic floods generated when hot magma below Mars' surface turned normally frozen water to liquid and started a short wet spell.

Arsia Mons: One of Tharsis' volcanoes
Image: Nasa/Mola science team

"The Tharsis region has had pulses of major magmatic activity that triggered catastrophic floods that sculpted the surface, ponded, perhaps forming oceans and lakes that in turn perturbed the climate," James Dohm said.

He and his colleagues believe that so much water is released by such pulses beneath Mars that a temporary ocean has repeatedly formed over the planet's northern hemisphere.

There is no reason why such an ocean might not appear again, they say.

New mission

The debate about water on Mars will move forward once the Mars Odyssey mission reaches the planet in October.

Launched in April, one of the probe's specific tasks is to look for signs of water.

It will be followed by the European Space Agency's Mars Express mission in 2003, which will carry the Beagle 2 lander, designed by a British-led team.

Beagle 2 will aim for an area on Mars that shows apparent evidence of past flooding and will drill for rock samples to be ground and analysed by its own instruments.

Details of the Arizona findings are published in the Journal of Geophysical Research.