EU Space Probe Photographs Pack Ice on Mars

LONDON, UK, February 28, 2005 (ENS) - The discovery of a frozen sea close to the equator of Mars by an international team of scientists has brought the possibility of finding life on Mars one step closer. They say the sea of ice photographed by the European Space Agency's Mars Express probe is "the first evidence of recent liquid water" on the red planet.

The 3D images of pack ice near the Martian equator were taken by the high resolution stereo camera on board the Mars Express probe. Higher levels of methane over the same area mean that primitive micro-organisms might survive on Mars today, the scientists say.


3D images of pack ice near the Martian equator taken by the European Space Agency's Mars Express probe. (Photo courtesy ESA)
The findings by the team of scientists from 10 countries led by Jan-Peter Muller of University College London (UCL), John Murray of the Open University, and Gerhard Neukum of the Free University of Berlin were presented at a European Space Agency Mars Science Conference in The Netherlands on February 21, and are to be published in the scientific journal "Nature" next month.

“This is a historic moment for Mars exploration when a previously neglected region reveals its secrets," said Muller of UCL's Department of Geomatic Engineering.

"Speculations that this area might have water close to the surface have been shown to be correct," he told colleagues at the European Space Research and Technology Centre in Noordwijk, the design hub for most European Space Agency (ESA) spacecraft and technology development.

“The fact that there have been warm and wet places beneath the surface of Mars since before life began on Earth, and that some are probably still there, means that there is a possibility that primitive micro-organisms survive on Mars today," said Murray, of the Department of Earth Sciences at the Open University.

"This mission has changed many of my long-held opinions about Mars," he said. "We now have to go there and check it out.”

Mars Express, Europe’s first space mission to another planet, entered the orbit of Mars on Christmas Day 2003, and since January 2004 the high resolution stereo camera on board has been taking images of the surface from altitudes as low as 270 kilometers (167 miles), showing details down to 10 meters (33 feet).

Images of 23 percent of the Martian surface have now been taken in 3D and full color. The images provide a wealth of information on past climate and water, as well as the relative ages of the surface from crater measurements on Mars, the evolution of volcanism, potential resources, characteristics of present and future landing sites.

The water that formed the frozen sea appears to have originated beneath the surface of the planet, the Mars Express scientists say.

Erupting about five million years ago, from a series of fractures known as the Cerberus Fossae, the water flowed down in a catastrophic flood, collecting in an area 800 x 900 kilometers and was initially an average of 45 meters deep - about the same size and depth as the North Sea.

The pack ice, which formed on the surface of the sea, drew the attention of Mars Express team.

Although formed at the time when early hominids on Earth were evolving from apes, this is very recent in geological terms, the scientists said. It suggests that vast flooding events, which are known to have occurred from beneath Mars’ surface throughout its geological history, still happen.

The presence of liquid water for thousands of millions of years, even beneath the surface, is a possible habitat in which primitive life may have developed, and might still be surviving now. "This must now be considered as a prime site for future missions looking for life," the scientists said.

The pack-ice floes have drifted into obstacles, and in places have become grounded on islands when the water level dropped, but the very flat surface - similar in slope to water surfaces in estuaries on Earth when the tide is coming in - and the thick ice within enclosed craters suggests that most of the ice is still there.

Ice is unstable at the surface of Mars because of the low atmospheric pressure, and changes straight from ice to vapor without passing through the liquid state - moving off into the atmosphere. But the scientists say the frozen sea appears to have been protected from this by a layer of volcanic ash and dust.


The pack ice location is shown by a white square near the Mars equator. (Map courtesy ESA)
The Mars Express probe will be deploying its MARSIS experiment in May, a radar instrument which is specifically designed to look for ice or water beneath the surface by penetrating the ground of the red planet.

If water ice is confirmed, this site represents a prime target for Mars landers from the European Space Agency planned for the end of this decade.

"This is one of many discoveries that we expect the European Space Agency to make with Mars Express and the Aurora program," Muller said, "given future UK support."

Muller helped to develop the 3D mapping system in association with the German Space Agency more than 10 years ago. This 3D mapping system worked immediately with the first pictures relayed back from Mars.

The high resolution stereo camera experiment is planned to image the entire surface of Mars at 10-20 meter resolution over 50 percent of the surface for the two year nominal mission and 100 percent over an extended mission of four years, with selected targets at 2.5 to four meters resolution.

"In other words," said Muller, "we will have better knowledge of the surface of Mars than we do of the Earth."