Life-on-Mars still fantasy

It may have been the discovery of the century when scientists claimed ten years ago that they found what was believed to be trace of life on a Martian meteorite. But now "Life-on-Mars" still remains a fantasy as the results have not been verified.

The National Aeronautics and Space Administration (NASA) presented magnified pictures of a 1.8-kg Martian meteorite riddled with wormy blobs that looked like bacterial colonies.

Scientists said they had obtained numerous clues from the rock, all supporting their contention that microscopic creatures once existed in its nooks and crannies.

But no breakthrough has been made toward the finding of life on Mars. Non-biological explanations have been found for every piece of evidence that was presented. Even though NASA scientist are still trying to defend their claim, more and more have given up the belief.

The rock in question was discovered in Antarctica. Its name, ALH84001, indicates that it was the first meteorite found during the 1984 research season in the Allan Hills. At first ALH84001 was misclassified, so it was not until 1993 that researchers even realised the rock came from Mars. But ALH84001 also turned out to be much more ancient than the other known Martian meteorites. At 4.5 billion years old, it dates from a period of Martian history when liquid water probably existed at the now barren planet's surface.

It made sense to ask: Could there be fossils of ancient Martian microbes preserved in the cracks of ALH84001? And the NASA scientists' answer is "Yes." Four reasons to support the claim have been put forward by researchers.

First, chemical analysis showed that the meteorite contained organic molecules known as polycyclic aromatic hydrocarbons (PAHs). PAHs can be produced by biological processes. But they are also commonly found in asteroids, comets and meteorites. Sceptics dismissed the importance of PAHs in the Martian meteorite.

Second supporting evidence is that the elongated blobs in the electron microscope images could be fossils of ancient Martian bacteria. But the problem was that those blobs were much smaller than any bacteria observed on the earth.

The other two lines of evidence survived longer. Both revolved around minerals sprinkled through the meteorite that could have been produced by microbes.

The first mineral, carbonate, is formed on the earth by remains of living organisms. So finding carbonate in ALH84001 could indicate the presence of ancient microbes in the rock.

Some bacteria produce extraordinarily small and pure magnetite crystals. Some of the most evolutionarily ancient bacteria on the earth produce magnetite.

(www.chinaview.com)