ESA Science & Technology30-Jun-2005 14:15:52


Last Update:  07 Jul 2003

Is there - or has there ever been - life on Mars? Mars Express will set off in 2003 to find out. It will carry a payload capable of conducting the most thorough search of the red planet yet for liquid water, which is essential for life as we know it. It's been known for nearly 100 years that there's frozen water at the Martian poles; and previous space missions have found water vapour in the thin Martian atmosphere. There's also plenty of evidence that liquid water - possibly lots of it - existed on Mars way back in its early history about 3.8 billion years ago when its atmosphere was much denser than today

Artists impression of water on Mars

Features in the Martian landscape resembling valleys and dried-up river beds could only have been shaped by large quantities of flowing water, possibly mixed with other substances. Some features even suggest catastrophic floods.

But sometime about 3.5 billion years ago, the Martian climate changed rapidly. "Something happened within 100 million years (which is a short time in geological terms). The atmospheric pressure and temperature decreased very quickly. Why? No-one knows," says Agustin Chicarro, ESA project scientist for the Mars Express mission. The water disappeared and Mars changed from a relatively warm, wet planet into a cold, dry one.

Where did all the water go? There are two possibilities: it could have evaporated and been lost to space along with most of the atmosphere; or some of it could have been trapped in rocks underground where the increase in pressure and temperature could be sufficient to keep it liquid.

One of Mars Express's tasks will be to assess these possibilities. "Water can either sink or escape," says Marcello Coradini, Solar System missions coordinator at ESA. "If there is any liquid in the subsurface, then it's no more than a few kilometres down. We need to know the total surface and subsurface distribution of water. To know whether it escapes outside the planet, we need to look at the escape processes from the atmosphere."

The spacecraft will carry eight instruments, all of which will make a contribution to solving the mystery of the missing water. Just before it arrives at Mars six months after launch, the spacecraft will jettison one module, a lander called Beagle 2, which will head for the Martian surface where it will take in situ measurements of rocks and soil. The other seven instruments will make observations from the main spacecraft as its polar orbit gradually moves round to give global coverage over the mission's expected lifetime of nearly two Earth (one Martian) years.

When Mars Express has performed its core mission, it will continue in orbit helping subsequent lander missions relay data back to earth for at least another Martian year.

For further information please contact: