Mars Express carries one of the most exciting packages of instruments in the
history of Martian exploration. Using the flood of data expected from the
spacecraft, scientists will be able to unlock the composition of the surface and
the present-day workings of the atmosphere.

They will be able to build a picture of how the planet has changed during the
4000 million years of its history. In so doing, they can answer one of the most
perplexing astronomical questions of the age: was Mars once like the Earth?

Geological investigations with previous spacecraft have revealed ample evidence
that water once flowed across the Martian surface but in exactly what form is
hotly debated. Some believe that flash flooding across a freezing Martian
surface is all; others think that Mars was once warm enough to sustain rivers
and lakes. Some believe that Mars once possessed an ocean.

The High-Resolution Stereo Camera (HRSC) is the best instrument yet sent to Mars
to search for the geological features that betray the presence of water. It will
also keep an electronic eye out for ancient shorelines.

OMEGA will precisely map the composition of the surface of Mars and MARSIS will
make the first ever sub-surface investigation of Mars, using radar to penetrate
down to three or four kilometres below the surface. It may even reveal
underground lakes of ice or water.

Certainly, there is no water on the surface of Mars today. So, why and how did
Mars change? Were those changes sudden or gradual? That is where the atmospheric
instruments come in.

The atmosphere is the buffer between Mars and outer space and the interface
through which most of Mars’s supposed water was probably lost.

The Planetary Fourier Spectrometer (PFS) will measure the global composition and
movement of the atmosphere; SPICAM will look for traces of water and ozone in
the atmosphere and ASPERA will study the way the atmosphere interacts with the
wind of particles given off by the Sun.

Finally, one experiment provides data for free! By analysing the signals sent
back from Mars for subtle, distorting effects, the Mars Radio Science Experiment
(MaRS) will convey information about the interior of Mars and space weather.
Together, all these instruments will reveal Mars and its behaviour as we have
never seen before.

More about …

* Europe goes to Mars

* Mars Express overview

Related articles

* Orbiter instruments

* The search for life

* Chances of life are linked to water

* Water on early Mars?

* Signatures of life

* Geography of Mars

In mid 2000 NASA’s Mars Global Surveyor spacecraft reported what looked like
evidence of water seeping up to the surface relatively recently.

Credits: NASA/MGS