Valley networks suggest that rivers once flowed on Mars

Science from orbit

20 December 2003

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.

One of the most perplexing astronomical questions of the age: was Mars once like the Earth?

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.

Why and how did Mars change? Were those changes sudden or gradual?

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.

Revealing Mars as never seen before...

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.

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