ESA INFO 11-2003 ESA sets ambitious goals for the first European mission to Mars
20 May 2003On 2 June 2003, the first European mission to Mars will be launched. It will also be the first European mission to any planet. Mars Express has been designed to perform the most thorough exploration ever of the Red Planet. It has the ambitious aim of not only searching for water, but also understanding the 'behaviour' of the planet as a whole. However, the most ambitious aim of all may be that Mars Express is the only mission in more than 25 years that is daring to search for life.
Mars has always fascinated human beings. No other planet has been visited so many times by spacecraft. Moreover, it has not been easy to unveil its secrets. Martian mysteries seem to have increased in quantity and complexity with every mission. When the first Mariner spacecraft were sent there back in the 1960s, the public was expecting an Earth 'twin', a green, inhabited planet full of oceans. Mariner shattered this dream by showing a barren surface. This was followed by the Viking probes which searched for life unsuccessfully in 1976. Mars appeared dry, cold and uninhabited: the Earth's opposite.
Now, two decades later, modern spacecraft have changed that view, but they have also returned more questions. Current data show that Mars was probably much warmer in the past. Scientists now think that Mars had oceans, so it could have been a suitable place for life in the past.
"We do not know what happened to the planet in the past. Which process turned Mars into the dry, cold world we see today?" says Agustin Chicarro, ESA's Mars Express Project Scientist. "With Mars Express, we will find out. Above all, we aim to obtain a complete global view of the planet - its history, its geology, how it has evolved. Real planetology!"
Mars Express will reach the Red Planet by the end of December 2003, after a trip of just over six months. Six days before injection into its final orbit, Mars Express will eject the lander, Beagle 2, named after the ship on which Charles Darwin found inspiration to formulate his theory of evolution. The Mars Express orbiter will observe the planet and its atmosphere from a near-polar orbit, and will remain in operation for at least a whole Martian year (687 Earth days). Beagle 2 will land in an equatorial region that was probably flooded in the past, and where traces of life may have been preserved.
The Mars Express orbiter carries seven advanced experiments, in addition to Beagle 2. The orbiter's instruments have been built by a group of scientific institutes from all over Europe, and Russia, the United States, Japan, and China. These instruments are a subsurface sounding radar; a high-resolution camera, several surface and atmospheric spectrometers, a plasma analyser, and a radio science experiment.
The high-resolution camera will image the entire planet in full colour, in 3D, at a resolution of up to 2 metres in selected areas. One of the spectrometers will map the mineral composition of the surface with great accuracy.
The missing water
Data from some of the instruments will be key to finding out what happened with the water which was apparently so abundant in the past. For example, the radar altimeter will search for subsurface water and ice, down to a depth of a few kilometres. Scientists expect to find a layer of ice or permafrost, and to measure its thickness.
Other observations with the spectrometers will determine the amount of water remaining in the atmosphere. They will also tell whether there is a still a full 'water cycle' on Mars, for example, how water is deposited in the poles and how it evaporates, depending on the seasons.
"These data will determine how much water there is left. We have clear evidence for the presence of water in the past, we have seen dry river beds and sedimentary layers, and there is also evidence for water on present-day Mars. But we do not know how much water there is. Mars Express will tell us," says Chicarro.
The search for life
The instruments on board Beagle 2 will investigate the geology and the climate of the landing site. However, above all, it will look for signs of life.
Contrary to the Viking missions, Mars Express will search for evidence for both present and past life. Scientists are now more aware that a few biological experiments are not enough to search for life - they will combine many different types of tests to help discard contradictory results.
To 'sniff' out direct evidence of past or present biological activity, Beagle 2's 'nose' is a gas analysis package. This will determine whether carbonate minerals, if they exist on Mars, have been involved in biological processes. Beagle's nose will also detect gases such as methane, which scientists believe can only be produced by living organisms.
Beagle 2 will also be able to collect samples from below the surface, whether under large boulders or within the interiors of rocks. These are places that the life-killing ultraviolet radiation from the Sun cannot reach. These samples will be collected with a probe called the 'mole', which is able to crawl short distances across the surface, at about 1 centimetre every six seconds, and to dig down to 2 metres deep.
Mars Express will add substantial information to the international effort to explore Mars. "Mars Express is crucial for providing the framework within which all further Mars observations will be understood," says Chicarro.
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