The Beagle has landed...
BY PAUL PARSONS
Posted: May 28, 2003
Well, not quite but the innovative Beagle 2 will soon be on its way to Mars aboard ESA's Mars Express. Once at the Red Planet, it may turn up evidence of past or present life.
Beagle is a lander and holds the record for being the smallest lander ever to be sent to Mars. It has the highest payload fraction of any other Mars lander, with nearly 9 kilos of its 32.7-kilo landed mass devoted to science instruments. Ambitiously it's going to look for evidence of past or present life on Mars. The last probes to attempt that were the twin Viking landers, in the late 1970s, but their findings indicated that Mars is a sterile, lifeless world. Then, in 1996, came the announcement by NASA of what looked like fossilized bacteria found inside a Martian rock. Suddenly, all eyes were back on the Red Planet.
"Colin forced his way into an ESA meeting on Mars Express and told them they were crazy going to Mars without a lander," says Sims. In March that year, Pillinger called a meeting at the Royal Society in London, at which he laid down the challenge to the UK and Europe to design and build a lander for Mars. A three-day workshop followed at the University of Leicester, to develop ideas.
A design and experiment package was put to the ESA Science Programme Committee during late 1998. ESA gave final approval for Beagle 2 on November 10, 1999.
If all goes to plan, Beagle will arrive on the surface of the Red Planet on December 25 this year.
"We've also been careful to pick a place where we think there's been water in the past," says Sims. "But which is flat enough and doesn't have too many rocks, so it's safe to land on."
Once slowed sufficently, a drogue parachute opens and the heat shield is jettisoned by pyrotechnic bolts. The main parachute is then deployed. Two hundred meters above the surface, as measured by a radar altimeter, the airbags inflate, and on first contact with the ground the parachute is released, allowing the lander to bounce away.
The robot arm can reach a surface area of about one square meter. Scientists hope there will be some interesting rocks within that range. "If you go on the Viking and Pathfinder data, then there should be three to four 10-centimeter-size rocks within that one square meter," says Sims.
"The idea is that with the X-ray spectrometer you measure the chemical composition of the rocks," says Sims. "If the chemistry looks right, you look at the mineralogy with the microscope, which gives you the structures, and with the Mossbauer, which tells you how oxidized the rocks are."
Mars looks red because much of the iron on its surface is oxidized -- it's basically rusty. "Oxides destroy organic matter," explains Sims. "So if you're looking for life, ideally you want to pick a rock that isn't too highly oxidized. If that's the case, you cut a core with the corer-grinder and drop it into the gas analysis package in the lander's base."
This instrument, designed by Pillinger's team at the Open University, looks for the key signature of life, which if it's there, will lie in the sample's carbon chemistry. There are two stable isotopes of carbon, one with 12 neutrons in its atomic nucleus and one with 13. Biology prefers carbon-12.
Biologically produced compounds burn at a lower temperature than those that are produced geologically, so the gas analysis package measures the carbon-12 to carbon-13 ratio as the burning temperature is steadily increased. An excess of carbon-12 at low temperature is then a strong indicator of past or present life. "That isotopic signature is preserved over billions of years," says Sims.
The PAW also carries Beagle's mole, a self-burying drill that will be used to probe the Martian subsurface. It's propelled by a compressed spring and drive mass, which can knock the mole across the surface at a rate of one centimeter every six seconds, or hammer it into the soil a millimeter at a time. The mole can reach depths of up to two meters. Tethered, it is recoverable with a winch. A cavity in the tip of the mole can open to grab soil samples, which can then be dropped into the gas analysis package. The gas package will also be used to check for atmospheric methane, which if detected, may also be biological in origin.
Beagle has been thoroughly sterilized prior to its departure; to prevent Earthly bugs contaminating the biology experiments and to prevent terrestrial bacteria settling on Mars. "There's a UN treaty obligation not to wantonly contaminate other planets," explains Sims.
In the air
The suite will run for Beagle's entire 180-Martian-day primary mission, charting the evolution of the planet's atmosphere through the seasons. An extended mission is possible, taking Beagle 2's active stay on the surface to 669 days, or one Martian year -- assuming the lander survives. Even if Beagle's experiments don't detect any biological signatures, life may still be lurking elsewhere. "The problem is that Mars is a big planet," says Sims. "Its surface area is equivalent to the surface land area of the Earth." In its search for life, Beagle will have made a full geochemical characterization of its landing site, adding enormously to our limited knowledge of the planet's surface.
NASA is currently selecting concepts for its Mars Scout missions, due for launch in 2007. "Amongst these are several small landed laboratory approaches that are similar in scientific thinking to the Beagle 2," says Garvin. Sims adds that he believes much of the technology and instrumentation concepts developed for Beagle will be carried forward into ESA's Aurora Programme of planetary missions.
So even if Beagle 2 fails to find evidence for life on Mars, the innovative concepts behind the mission look set to stay. On the other hand, if the mission is a success, it could help scientists write some of the most significant chapters yet in planetary science and evolutionary biology. Darwin would be proud.
A cast of thousands
All of Beagle's instruments, except for the Mossbauer spectrometer, were developed by international consortia. The microscope was developed by a team led by the Max Planck Institute for Aeronomy in Lindau. The stereo cameras come from a consortium organised by the UK's Mullard Space Science Laboratory. Development of the X-ray spectrometer was headed by the University of Leicester. Development of the mole was led by DLR in Germany, with considerable Russian input. The corer-grinder was developed principally by Hong Kong Polytechnic. The Mossbauer spectrometer comes entirely from the University of Mainz. And the gas analysis package comes from the Open University, with some electronics provided by Astrium.
The major software contributions came from Logica, who developed the entry and descent software, and SciSys, who are responsible for the landing software.
Dr. Paul Parsons is a freelance science writer and Astronomy Now's news editor.
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