BBC NEWS Americas Africa Europe Middle East South Asia Asia Pacific
BBCi NEWS   SPORT   WEATHER   WORLD SERVICE   A-Z INDEX     

BBC News World Edition
 You are in: Science/Nature  
News Front Page
Africa
Americas
Asia-Pacific
Europe
Middle East
South Asia
UK
Business
Entertainment
Science/Nature
Technology
Health
-------------
Talking Point
-------------
Country Profiles
In Depth
-------------
Programmes
-------------
BBC Sport
BBC Weather
SERVICES
-------------
EDITIONS
Friday, 6 December, 2002, 10:00 GMT
Martian water gone in a flash
Valley, Nasa
Mars: The heavily cratered southern uplands

Asteroid impacts during Mars' early years may have led to brief warm and wet periods when torrential rain carved out the planet's ancient network of valleys.


We envision a cold and dry planet, an almost endless winter, broken by episodes of scalding rains followed by flash floods

The impacts would have melted subsurface ice and thrown water vapour into the atmosphere that would have caused rivers, floods and landslides all over the planet, according to new research.

It would have been bad news, though, for the prospects for life on the planet.

The periods when the water flowed may have been only years or decades long, making it difficult for organisms to establish themselves.

Other research just published reveals frozen water is exposed near Mars' south pole, casting more light on the history of water on the Red Planet.

Sediment-laden rivers

Networks of valleys on Mars cut across the oldest terrain on the planet - the heavily cratered southern uplands.

The valleys formed around the time of the so-called late heavy bombardment by asteroids and comets about four billion years ago.

Research, led by Teresa Segura of the University of Colorado, US, has now produced a new model of the effect of these impacts on valley network formation.

It suggests the larger hits could have resulted in the release of vast quantities of water from the impactors themselves, the ejected Martian material, or exposed ice underneath the Martian surface.

Because of the energy of the impacts, any water would have entered the atmosphere as hot vapour, while the heat spread through the ground would have melted any that was buried there.

The subsurface water would have caused mudflows and led to sediment-laden rivers. Eventually, the water vapour in the atmosphere would have fallen to the ground as rain.

'Challenging for life'

According to the researchers, "there should have been enough water from either source to form the valley networks".

Somewhat controversially, the researchers do not support the idea that Mars had a longer-lasting greenhouse climate earlier in its evolution, which could have allowed life to evolve.

"We envision a cold and dry planet, an almost endless winter, broken by episodes of scalding rains followed by flash floods," they say.

If the new thinking is correct, then Mars would have been wet and warm with flowing rivers for only a few years after the large impacts.

After these brief wet periods, the planet would have returned to the conditions that would have made it "challenging for life to establish itself".

In a second study, also published in the journal Science this week, Timothy Titus and colleagues describe data from the Mars Odyssey Thermal Emission Imaging System (Themis), indicating the presence of frozen water exposed near the edge of Mars' southern polar cap.

The discovery is important for understanding Mars' water cycle, and because someday humans or robots exploring the planet could make use of the water.

Some exposed frozen water had been detected near the Martian north pole, but until now none had been seen near the southern pole.

The Themis data show a uniform region at the south pole that is cooler and brighter than would be expected for dry soil. It is probably water-ice say researchers.

See also:

23 Oct 02 | Science/Nature
29 Oct 02 | Science/Nature
28 May 02 | Science/Nature
23 Jun 00 | Science/Nature
Internet links:


The BBC is not responsible for the content of external internet sites

Links to more Science/Nature stories are at the foot of the page.


E-mail this story to a friend

Links to more Science/Nature stories

© BBC ^^ Back to top

News Front Page | Africa | Americas | Asia-Pacific | Europe | Middle East |
South Asia | UK | Business | Entertainment | Science/Nature |
Technology | Health | Talking Point | Country Profiles | In Depth |
Programmes