MARTE: building a better life-detector
A special issue of the peer-reviewed research journal Astrobiology just came out, and it makes interesting reading for those who care about finding life elsewhere in the universe. All the papers of this special issue are devoted to aspects of the Mars Astrobiology Research and Technology Experiment (MARTE), a project to design and test a remote sampling construct that can detect key geochemical features and markers useful in the hunt for life. Not only will MARTE be capable of directly testing Martian regolith with a wide range of chemical life sensors, it will also drill into the Martian surface to seek signs of life meters down.
The Martian surface is very hostile to life in any form, mostly due to radiation, but even a meter or two below the surface would be much more friendly to life. It would be cold, but on Earth there are plenty of microbes that survive – even prosper – under equally stark conditions. On Earth, surface life can power itself by photosynthesis… but on Mars that isn’t a viable option. So the thinking goes that near-surface life might instead derive energy from the reduction of surface iron oxides, which are constantly re-rusting under the onslaught of highly-charged, oxidizing radiation from above. In ice pockets life would be especially likely, using the ice as a haven and a source of water. Where enough heat flows from the deep mantle to liquify water at depth, a cold, salty, moist environment could permeate the sediments just meters below the surface. Even in the Antarctic on Earth, rock warms with depth. On Mars, we have to drill to expect to find anything living.
The MARTE experiment is a wonderful example of NASA research stimulating technological innovations. The working MARTE package is slated to include a robotic drill capable of boring down at least two meters through loose, dry sediment, pull up core samples for better examination, look down and along the walls of the drill hole with multiple sensors, and drill from the main core several tiny mini-cores for high-resolution spectral and chemical analysis. That is an impressive agenda, and will be extremely difficult to pull off successfully.
The challenge is making drills lightweight and energy-efficient enough to fly, says David Beaty, a former exploration geologist in the oil industry who now works for NASA’s Jet Propulsion Laboratory in Pasadena, California. He is organizing a ‘drill-off’ that will take place next February, when a handful of companies developing robotic drills will test their machines at Idaho Falls. Competitors will be charged to build a drill that weighs no more than 40 kilograms, digs 20 metres deep, and runs off the power of a lightbulb.
I expect a few patents will come out of that work, alongside the giant leap forward for the entire human species that will occur when we first discover life beyond Earth.
Testing of the MARTE concept is happening in Rio Tinto, Spain, where acidic groundwater permeates volcanic rock laced with heavy metals and iron sulfide minerals… making it a reasonable approximation of areas of the Martian subsurface, although Spain is warmer, wetter and obviously filled with life. Martian surface sediments include the iron sulfate mineral jarosite, which can only form in acidic water containing iron – the kind of water permeating Rio Tinto rocks. Under Mars, where water can melt, the conditions could be similar, and similarly capable of supporting bacteria that feed on iron and sulfur.
The MARTE drill is only one innovative aspect of the project. Another is its approach to life-detection. MARTE will include the ability to expose bits of sediment to a whole suite of different chemical sensors, including advanced protein microarrays that can directly detect the presence of sugars, nucleic acids, and other distinct biomarkers. Another sensor will measure the presence of ATP, adenosine triphosphate, which is the basic molecular energy currency traded during cellular biochemical reactions. The triphosphate bond is so fundamentally important to the machinery of life that it would probably be used by Martian life too, even if such life had a radically different arrangement of ribonucleic acids making up its machine parts. That’s not terra-centrism, that’s basic chemistry… the manipulation of chemical energy using phosphate bonds is as basic and inseparable from life as is carbon. If ATP is in Mars soil, there’s only one way it can get there; assembly by living cells.
Currently the European Space Agency plans to launch a drill-capable MARTE-style probe to Mars in 2011. Hopefully that means by 2012 we’ll have clear evidence of life on Mars.
But wait… isn’t the world supposed to end in 2012?