What is the latest evidence for life on Mars

asks Mayastar:
A. Researchers who are looking at the data from the Pathfinder mission to Mars in 1997 believe that there may be chlorophyll in the soil close to the landing site.

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Q. How can they tell
A. When the Pathfinder mission landed in the Ares Vallis region of Mars, it took thousands of images of the surrounding area.

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The Nasa team has looked at the so-called Superpan, a high-resolution, highly processed series of superimposed images produced by Pathfinder's camera, which was able to examine a range of spectral wavelengths. A detailed analysis of the images has revealed two areas close to Pathfinder that have the spectral signature of chlorophyll. Experts say that this could be highly significant - or just be an area of coloured soil.

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Q. What's a spectral signature
A. The scientists wrote a computer programme for chlorophyll that systematically scanned the Superpan for any pixels of interest.

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Q. Why wasn't this done before now
A. It was. The scientists searched for chlorophyll in the images shortly after Pathfinder landed on Mars. There were a few indications seen, but they were later dismissed as 'possible image misregistration'.

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Q. Why is chlorophyll significant
A. Chlorophyll is the molecule used by plants and some algae and bacteria that allows these organisms to extract energy from sunlight. This energy is used to drive photosynthesis, a process that converts carbon dioxide and water into the simple sugar glucose.

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Photosynthesis is the starting point for nearly all life on Earth. It is the huge amount of chlorophyll in leaves that makes plants appear green.

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Q. When will we know of this is really chlorophyll
A. This discovery is controversial and research is at an early stage, so the researchers say they cannot make definite claims until they've done more work and prepared a detailed paper for submission in a scientific journal.

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By Sheena Miller