Fossils of Martian bugs found on meteorite that landed on Earth 13,000 years ago

New evidence has made it more likely that remnants of Martian microbes were transported to Earth in a meteorite, it was revealed today.

A study by scientists from the American space agency Nasa has found chemical signatures in the rock strongly associated with life.

The discovery strengthens the case for believing that worm-like structures in the meteorite are 'microfossils' of ancient Martian bugs.

Skeptics have pointed out that similar-shaped structures could be formed from non-biological processes.

Another unanswered question is whether the microfossils were the result of contamination by Earthly bacteria. This was originally ruled out by NASA but has raised doubts in the minds of other experts.

The meteorite, cataloged as Allen Hills (ALH) 84001, crashed onto the frozen wastes of Antarctica 13,000 years ago and was recovered in 1984.

Scientists believe the rock was blasted off the surface of Mars by an asteroid or comet, reaching Earth after floating through space for around 16 million years.

It would have formed part of the planet's crust at a time billions of years ago when many experts believe water flowed on the surface of Mars, and conditions were suitable for life.

In 1996 Nasa and the White House made the explosive announcement that the rock contained traces of Martian bugs.

Photographs were released showing elongated segmented objects that appeared strikingly lifelike.

However, the excitement did not last long. Other scientists questioned whether the meteorite samples were contaminated. They also argued that heat generated when the rock was blasted into space may have created mineral structures that could be mistaken for microfossils.

The new study was conducted using advanced high resolution electron microscope techniques which were not available 13 years ago.

News of the findings, expected to be released soon by NASA, was leaked to the space news website Spaceflight Now and picked up today by the Sun newspaper.

The research was led by Dr Kathie Thomas-Keprta and members of the original team at the Johnson Space Center in Houston, Texas, that claimed to have found evidence of life in the meteorite.

It focused on a more detailed analysis of magnetite crystals - tiny magnetic particles - and carbonate discs within the rock.

Certain bacteria on Earth are known to contain magnetite crystals, which they are believed to use as tiny compasses to help them navigate.

The crystals form unusual shapes when associated with bacteria which can be seen in ALH 84001, it is claimed.

In addition the scientists say the chemical purity of the features they studied points to biology rather than geology, and a possible interaction with water.

Dr Dennis Bazylinski, from the University of Nevada at Las Vegas, who reviewed the findings submitted for publication in the journal of the Geochemical and Meteoritic Society, told Spaceflight Now: 'I think the paper is really excellent. I work on magnetic bacteria, and one indication there was life on ancient Mars are these particular magnetite crystals in the meteorite that look like they came out of magnetic bacteria.

'At first, I thought there might have been an error. I have no doubt about that now. I know there is no error.

'The big question is can these things be reliable magneto fossils, and that is a matter of debate. But it turns out that the magnetic bacteria make some very unique shapes of magnetite crystals. And one of the organisms we work with on Earth makes particles that look virtually identical to what we see from Mars in the meteorite.'

Spaceflight Now said the data provided "a powerful new case" for believing the meteorite carried traces of extraterrestrial life, according to its sources.

The report added: 'Although not a smoking gun, the new findings considerably strengthen the Mars life arguments that have been hotly and passionately debated for a decade, given that the discovery of life on Mars is the Holy Grail of science.'