If you’re going to send a lander to look for life on Mars, you need to choose a landing site with a good chance of harbouring life — preferably a place where water once deposited layers of sediment. "But even with MOC data (MOC is the high resolution camera on board NASA’s Mars Global Surveyor), we don’t know exactly which kind of environment we’re going to meet," Gian Ori from the Universita d’Annunzio, Pescara, Italy told a session of the European Geophysical Society’s millennium conference in Nice, France, last week (25-29 April 2000).
In collaboration with NASA’s Ames Laboratory, he and a colleague are working on a proposal to send a reconnaissance mission to search for suitable landing sites. The Scout mission, consisting of a flotilla of tiny spacecraft, would reduce the risk of sending sophisticated and expensive landers to relatively uncharted territory. It was just one of several new ideas for future Mars exploration presented to the EGS General Assembly.
Scout would probably be too late to help Beagle 2, the lander on board Mars Express, with its choice of landing site: Beagle 2 will arrive at the red planet at the end of 2003. But Scout could be sent in advance of future landers, such as those under consideration by ESA for flight on the flexible mission MASTER, or on a future spacecraft in NASA’s Mars Surveyor series.
MASTER, a mission that would drop a lander on Mars en route to an asteroid, is progressing through the selection procedure for ESA’s next flexible missions, F2 and F3. The final selection will be made in September 2000. To save costs, the lander would probably be a copy of Beagle 2 or one of the French space agency’s (CNES) Netlanders.
The search for life
However, a team of scientists convened by ESA’s Spaceflight and Microgravity Directorate has also drawn up plans for a more ambitious lander that would carry 35kg of instruments compared with 10kg on board Beagle 2. "Our task was to develop and design a package to optimise the search for life on Mars," Andre Brack from the Centre de Biophysique MolÈculaire, CNRS, OrlÈans, France and chairman of the group told the conference.
The main aims of the package are to take microscope images of underground soil and rock samples and to measure the ratio of C12 to C13, which is higher if life is or has been present. Many of these aims will be met by Beagle 2, which Brack described as "the most complete integrated package within such a small mass budget". The greater weight of instruments allowed on a future exobiology lander, however, gives it scope for more
sophisticated imaging, including Raman microscopy, and the possibility of drilling down to 1.5m for samples.
Because of its low weight, Beagle 2 cannot support a drill to take deep core samples from solid rock. Instead, it will use a "mole" to burrow down through soft soil or sediment and a grinder and small drill (supplied by a dentist in Hong Kong) to take samples from just below the weathered rind of hard rock. With the later exobiology lander "we hope to drill through the oxidised layer and then core. But if we can’t — because it’s difficult to core with robots — then we’ll take chips of rock," said Brack.
New ideas on geology and climate The meeting also heard of new ideas for learning more about the geology and climate history of Mars. The MEEM proposal, for example, would build on experience gained with Marsis, the ground penetrating radar on board Mars Express, to mount a synthetic aperture radar on board a future orbiter. P Paillou from the Observatoire Astronomique de Bordeaux, France, told the meeting that MEEM would operate at shorter wavelengths than Marsis and thus penetrate only a few tens of metres to reveal the shape of the Martian crust underneath obscuring sand and dust deposits. Marsis will penetrate a few kilometres underground to search for water.
Several participants at the meeting were looking forward to flying gamma ray spectrometers around Mars because they would reveal the elemental composition of the surface. Omega, the infra red spectrometer that will fly on Mars Express, will reveal the mineral composition. Yet others wanted to sound the Martian atmosphere with microwaves to study water vapour. However, the meeting was not entirely devoted to missions yet to leave the drawing board. Agustin Chicarro, Mars Express project scientist, chaired a session in which the Principal Investigators on several of the spacecraft’s instruments gave updates on their instruments’ progress. They are all in an advanced state of development, within allocated masses and on schedule.
Briefings were also given on the Japanese spacecraft, Nozomi, with which Mars Express is collaborating, and the French space agency’s Netlander mission. Members from some of the instrument teams on board NASA’s Mars Global Surveyor, the only spacecraft now in orbit around Mars, summarised some of their latest findings. These are demonstrating almost daily how a carefully designed and well-executed spacecraft can reveal what an intriguing place Mars is.
Ancient channel of the Nile, revealed by radar
The bottom image, taken with a synthetic aperture radar (SAR) from the Space Shuttle, shows the ancient channel of the Nile which is hidden under sand in the top image taken with a conventional camera. The MEEM proposal, discussed at the EGS, would use SAR to reveal structure hidden under Martian sand. (source: JPL/NASA).