Mars Sea Discovery Ups Odds of Red Planet Life, Scientists Say
for National Geographic News
|March 16, 2005|
Since NASA's twin robot geologists Opportunity and Spirit landed on Mars in January 2004, a steady trickle of scientific analysis has confirmed that water once soaked the red planet, raising the possibility of life there.
Now, scientists may know where to look for life first.
Images recently taken by the European Space Agency's Mars Express spacecraft, which is orbiting Mars, show a frozen body of water, about the size of Earth's North Sea, beneath the surface of Mars (see enlarged image).
"I believe this makes the possibility of the discovery of life on Mars much closer than was previously thought," said John Murray, a research scientist at the Open University in Milton Keynes in England. Murray led the research group that made the discovery of the frozen sea.
Scientists now say that Mars has been shaped by flowing water, lava, and ice in the recent geological age. The sea formed within the last few million years, as volcanic eruptions or tectonic activity caused the area to flood.
A separate study shows that explosive eruptions about 350 million years ago created depressions on the flank of the Martian volcano Hecates Tholus. Glacial deposits formed inside those depressions as recently as five million years ago.
"It indicates that Mars is still a geologically active planet, and geological activity is generally agreed to be important to the development and continuance of life, which requires such a source of energy," Murray said.
The discoveries are reported this week in the science journal Nature.
The first camera images taken of Mars and atmospheric data collected from the red planet in the 1960s led scientists to believe that Mars had been continuously cold and dry.
This view changed in the 1970s, when pictures taken from the Mariner 9 and Viking orbiters revealed river valley networks and huge channels carved by cataclysmic floods.
However, scientists long believed that hydrological events were limited to the time of Mars's formation, between 3.8 and 3.5 billion years ago.
The latest discoveries show the oppositethat such geological activity on Mars is recent and ongoing.
"[These studies] provide an overwhelming case for new thinking about recent geological activity on Mars," Victor Baker, a geologist at the University of Arizona in Tucson, writes in an accompanying article in Nature.
In a third paper, scientists describe how recurring glacial activity has left its mark at what are now tropical and mid-latitude regions on Mars.
Ernst Hauber of the Institute of Planetary Research at the German Aerospace Center in Berlin says the surface of Mars today is not stable, so the glaciers must have formed in a different climate and are protected now by a dust cover, which may be several meters thick.
"That would mean the climate has changed within the last few million years, which is nothing for planetary time scales," said Hauber, a co-author on all three studies.
Scientists believe the Martian poles contain ice. And for some time researchers predicted they would find water close to the surface of the equator too.
The frozen body of water fills a low-lying region in the southern Elysium region, five degrees north of the equator. It is 800 by 900 kilometers (about 500 by 560 miles) wide, and averages 45 meters (147 feet) deep. On the surface it is covered by traces of pack ice.
The theory is that water erupted less than five million years ago from the Cerberus Fossae, deep cracks on the Martian surface. These cracks opened up and tapped a huge reservoir of liquid water deep beneath the surface.
Pack ice formed on top of that water. It then broke up, before freezing rigid. A crust of dust and volcanic ash, perhaps just a few centimeters thick, has prevented sublimation, the process by which ice erodes over time into water vapor.
Scientists say the same eruptions of vast amounts of water have occurred throughout geological time elsewhere on Mars.
"The fact that they are still occurring today means that we have had huge pockets of liquid water beneath the surface of Mars for thousands of millions of yearsplenty of time for life to develop," Murray said.
If life can develop in these subsurface oceans, as many scientists believe, this frozen sea may be the ideal place to look not just for fossils of past life, but for the actual frozen organisms themselves, Murray said.
"We now need to land there and drill into these deposits, which hopefully will happen in 2011, when both the European Space Agency and NASA have plans for landers," he said.
"This mission has certainly utterly changed my ideas about Mars and the possibility of finding life there now, let alone the remains of past life."
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