The Spirit and Opportunity rovers, developed by NASA, have been working on Mars for more than a year now. During this time, the rovers have uncovered tell-tale signatures of past volcanic and oceanic activities by studying the various rocks littering the Martian surface. The prospect of finding past/present life on Mars have never been better, and to that end, scientists from the U.S. Department of Energy's Idaho National Laboratory, University of Idaho, and University of Montana are developing a chemical guidebook as part of what they hope will be a definitive method to determine whether extraterrestrial rocks have ever harbored life.

Spirit Rover (Courtesy: NASA)At a fundamental level, all organisms consume resources, and give out waste products. By studying a rock's composition, scientists hope to find signatures of such microbial (or otherwise!) activity within it. The team is using a specialized mass spectrometer to take chemical images of microbes and rocks under conditions close to what might be found on Mars, as well as developing a fuzzy logic computer program to decipher those spectral pictures. By testing and examining local exotic microbes (extremophiles), they expect to develop a guide-book that might point to rocks which might exhibit traces of past or present life.
The scientists will take advantage of two sophisticated research tools:
a) On the hardware side, the LOCI (Laser and Optical Chemical Imager) combines a laser with a mass spectrometer. Already part of the rover repertoire, the laser evaporates the rock surface, and the spectrometer analyses the gas cloud that is formed. Scientists can then study the spectral image to determine what the surface layers were made of – minerals such as iron, say, with a sprinkling of microbial waste products.
b) On the software side, a fuzzy logic computer program called the SIDIE (Spectral IDentification Inference Engine) would supply the Mars rover with some extra brains. Developed at the Idaho National Laboratory, SIDIE uses an open-ended reasoning approach that mimics a human's decision-making abilities and learning.
Thus combined, the two innovations might be able to point to rocks that have a curious chemical signature that might be the product of activities similar to what we call, life! Another bit of good news: NASA has recently extended the operations of the rovers to September 2006; so scientists will be able to test the new software on the rovers to see if they can find some such evidence of past or present life :):).