NASA's Mars life-detector
With the financial help of NASA, American and European researchers have developed a new sensor to check for life on Mars. It also should be able to determine if traces of life's molecular building blocks have been produced by anything alive. The device has already been tested in the Atacama Desert in Chile. And it should be part of the science payload for the ExoMars rover planned for launch in 2013.
This life-detector has been named Urey, an homage to Harold Urey, "whose pioneering work on isotopes earned him the Nobel Prize in Chemistry in 1934 and later led him to theories of planetary evolution" (Credit: Wikipedia).
Before going further, below is a picture of Urey, this Mars Organic and Oxidant Detector (Credit: NASA/JPL/UCSD). And here is a link to a larger -- and zoomable -- version.
Samples of Martian soil collected by a drill on the rover will be delivered to the Urey instrument. The instrument component called the sub-critical water extractor adds water and heats the sample, getting different types of organic compounds to dissolve into the water at different temperatures. The Mars organic detector uses a fluorescent reagent and laser to detect organic chemicals. The micro-capillary electrophoresis component separates different types of organic chemicals from each others for identifying which ones are present in the sample. The Mars oxidant instrument, part of which is on a separately mounted deck unit not pictured, assesses how readily organic material would be broken down by the radiation, atmosphere and soil chemistry of the site. (Credit: NASA Planetary Photojournal)
So what will be this device capable of?
"Urey will be able to detect key molecules associated with life at a sensitivity roughly a million times greater than previous instrumentation," said Dr. Jeffrey Bada of Scripps Institution of Oceanography at the University of California, San Diego. Bada is the principal investigator for an international team of scientists and engineers working on various components of the device.
And Urey will be really very sensitive, being able to "detect several types of organic molecules, such as amino acids, at concentrations as low as a few parts per trillion."
All life on Earth assembles chains of amino acids to make proteins. However, amino acids can be made either by a living organism or by non-biological means. This means it is possible that Mars has amino acids and other chemical precursors of life but has never had life. To distinguish between that situation and evidence for past or present life on Mars, the Urey instrument team will make use of the knowledge that most types of amino acids can exist in two different forms. One form is referred to as "left-handed" and the other as "right-handed." Just as the right hand on a human mirrors the left, these two forms of an amino acid mirror each other.
Amino acids from a non-biological source come in a roughly 50-50 mix of right-handed and left-handed forms. Life on Earth, from the simplest microbes to the largest plants and animals, makes and uses only left-handed amino acids, with rare exceptions. Comparable uniformity -- either all left or all right -- is expected in any extraterrestrial life using building blocks that have mirror-image versions because a mixture would complicate biochemistry.
For more information, you also can read an earlier description of this life-detector, "A Mobile in situ Subsurface Biotic Detector and Soil Reactivity Analytical Laboratory" (PDF format, 34 pages, 8.98 MB)
Sources: NASA/Ames Research Center news release, March 2, 2007; and various websites
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