Hairy blobs found in acidic hell

June 04, 2008

IN CLOSE-UP, they look like something out of a 1950s B-movie. Colonies of fossilised creatures, dubbed "hairy blobs", have been discovered in one of the harshest environments on Earth. The find may turn out to be crucial for spotting signs of extraterrestrial life in rocks on other planets.

Kathleen Benison, a geologist at Central Michigan University, Mount Pleasant, led a team that studied the sediments formed by acidic and very salty lakes in modern day Western Australia, and those deposited around 250 million years ago in North Dakota. It is very difficult to survive in such a tough environments and few signs of life have ever been found in these sorts of lakes.

Inside the halite and gypsum "evaporate" minerals, which form as the lake waters dry up, Benison and colleagues found previously unknown fossilised blobs at both the modern and ancient sites, ranging in size from 0.05 to 1.5 millimetres. They were made up of a mix of inorganic crystals and "hairs" stuck together in a mass (pictured). They named them hairy blobs.

The team argues that each hair was in fact a separate microorganism because the hair fossils are made of disordered graphite which, unlike inorganic graphite, has irregular layers that suggest it was once a live organism..

Many of the hairs are coated with crystals of gypsum, a calcium sulphate mineral. This link with gypsum suggests that the microorganisms were fuelled by chemical interactions with sulphur in the acidic water - which helped the gypsum to form.

The team also found previously undescribed microorganisms in the lake water, which they say may be the cells that end up as fossilised hairs (Astrobiology, DOI: 10.1089/ast.2006.0034).

Conditions in acidic saline lakes such as those studied by the team are thought to be similar to those on ancient Mars. The many probes currently exploring the Red Planet have discovered that Martian seas and lakes, such as those once found at Meridiani Planum, were strikingly similar in terms of acidity, salinity and the minerals and sediments present.

Benison says the hairy blobs from the Permian halite seem well preserved. "This argues for long-term preservation of microfossils in halite elsewhere, perhaps even on Mars." Had the organisms lived on Mars, she says, the inorganic minerals surrounding them would have acted as protection from the ultraviolet radiation there.

André Brack, an astrobiologist at CNRS, the French National Centre for Scientific Research, says the work "shows life can be preserved for long periods of time from an acidic medium, just like the Martian oceans".

However, he adds that to be certain that the blobs are indeed evidence of life, further tests are needed, such as those to examine whether the carbon isotope ratio in the graphite matches the signature for life.
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