Gullies on Mars.

According to University of Melbourne geologist Dr Nick Hoffman, gullies near the Red Planet's south pole form as the seasonal ice cap retreats in the Martian spring.

"In itself the observation of active flows is a dramatic discovery since no movement has yet been seen on Mars, except for some dry dust avalanches," he told BBC News Online.

But contrary to the common idea that such features were carved by liquid water, Dr Hoffman says the flow is most likely gaseous carbon dioxide which, if true, would deal a blow to the prospects for life on Mars.

Writing in the latest edition of the journal Astrobiology, Dr Hoffman presents evidence for the first in-action flow events on Mars and argues that liquid water is not to blame, in fact no liquid is.

"In the Martian Spring," he says, "carbon dioxide frost and snow at temperatures of minus 130 degrees Celsius fill the valleys, yet the flow events are occurring.

Nasa researchers believe water can explain the grooves in the sides of craters "But at such low temperatures everything turns to concrete so whatever is moving cannot be a liquid," he told BBC News Online.

"Nothing based on water can flow at these temperatures, so the culprit must be avalanches of gaseous carbon dioxide and rocky debris."

This is because carbon dioxide does not melt on Mars: it boils directly from the solid - a process called sublimation.

"The boiling dry ice acts like a armada of miniature hovercraft carrying a shower of sand, dust, and tumbling rocks down the slope, carving out the gullies as it goes," Dr Hoffman says.

Life would find it more difficult to take hold on Mars without supplies of liquid water.

"Without liquid water there cannot be life and despite recent reports of more and more ice on the Red Planet, Nasa has yet to find liquid water," he says.

Although many US space agency scientists are doubtful about Dr Hoffman's observations, the geologist says that at a meeting of the American Geophysical Union held last month, they struggled to find arguments against the evidence he presented.

To Dr Hoffman the possibility that the gullies are formed by gas flows emphasises how different Mars is from the Earth.

Geologically it may have more things in common with some of the ice-crusted moons of the outer planets than our own world.

"Mars is not a cold Earth. It is a different world, it works in another way. It is more like a warmer version of Europa, a moon of Jupiter, than our Earth," he says.

We Earthlings have problems with gaseous products right here on Terra firma, as will be noted in the following

[Bloomberg News Service]: A terrible diet and room without ventilation are being blamed for the death of a man who was killed by his own gas. There was no mark on his body and an autopsy showed large amounts of methane gas in his system.His diet had consisted primarily of beans and cabbage (and a couple of other things).It was just the right combination of foods.

It appears that the man died in his sleep from breathing the poisonous cloud that was hanging over his bed.; Had he been outside or had his windows been opened, it wouldn't have been fatal. But the man was shut up in his near airtight bedroom.According to the article, "He was a big man with a huge capacity for creating "this deadly gas."

Three of the rescuers got sick and one was hospitalized.

Sorry, its an Urban legend... Snopes.com reports:

FALSE!
Origins:
In August 1996 this story was included in a "Darwin Awards" mailing, marking its first appearance on the Internet. It's a gas, gas, gas! No attribution to a specific news source from which this account might have been harvested from was given, but the date of the unfortunate sleeper's demise was pegged as 25 March 1993. The story has since circulated on numerous "dumb deaths" lists, sometimes with a specious "Bloomberg News" tag attached.

Disabuse yourself of any notion that such a death occurred. Not only don't any bona fide news accounts detailing this bucket-kicking exist, but it would be impossible for anyone to die in such a situation. The gas expelled from the body isn't poisonous; it wouldn't kill anyone. (As for the room's filling up with bodily emissions that somehow "used up all the oxygen" and resulted in the sleeper's dying of suffocation instead of poisoning, the volume of air that would have to be replaced for this scenario to be real is simply way too large.)

In other words, this was all just a made-up story. That it circulates as a "This is true!" shocker shouldn't be taken as proof of anything other than the sender's gullibility.

From a folklorist's point of view, a far better tale is the venerable Fart in the Dark. In that story, the gaseous emissions of the victim don't kill her, though she fervently wishes they had (anything to be spared the embarrassment of the moment!).

Barbara "gas masked" Mikkelson

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