Fallen Meteorites Found to Preserve Microfossils

A group of researchers from several Australian universities teamed up to study how meteorites can preserve evidence of life in a paper which was recently published in the journal Astrobiology. The team, which included researchers from Monash University, University of Queensland, and Australian National University, studied meteorites from the Nullarbor Plain in South Australia to find out how they could preserve microfossils.  

“By studying how meteorites on Earth are altered by weathering and microbial activity, it may help to know what chemical signatures to look for when we study the same meteorite material that fell on Mars, which could have been weathered and potentially altered by any life there. Looking at meteorite chemistry as an environmental record, and as a potential way to compare processes on Earth and other planets, is a new idea and really exciting,” said co-author Dr Jessica Hamilton.

The team’s research revealed that a variety of fossil microorganisms, diatoms, bacteria, and fungi, were entombed and preserved within veins of calcite and gypsum. Using x-ray fluorescence microscopy at the ANSTO’s Australian Synchrotron, they determined that redox-active metals were mobilised in vein-like cracks of the meteorites due to environmental or microbial activity.  

“The location and quantity of calcium, iron and manganese can be delineated in the sample by the ultra-sensitive technique. It revealed that the manganese enrichment occurred at the rim of calcite-gypsum veins,” said Dr Hamilton.

This means that when a meteorite falls to the surface of a planet, the meteorite undergoes mineral changes in order to find a chemical equilibrium with its new-found environment. During this process, the forming minerals within the meteorite can trap microorganisms, preserving them as microfossils. 

Co-lead author Dr Alastair Tait from Monash University’s School of Earth, Atmosphere and Environment said, “This is an original finding and it is important because it shows us that microorganisms can interact with Astro-materials in a way that is vital to their metabolism.”

“Essentially, they provide a time capsule of past biological activity, or, in the case of samples from the Nullarbor Plain, meteorites can serve as a refuge for life,” said fellow co-lead author Professor Gordon Southam of the University of Queensland’s School of Earth and Environmental Sciences.

“They act as lifeboats for life on a hostile surface, where there are not many bioavailable minerals,” said Dr Andrew Langendam, a beamline scientist and planetary geochemist who was part of the fieldwork team which collected meteorite samples for this study.  

While the team studied meteorites which had fallen to Earth, these findings could potentially be applied to meteorites elsewhere in the Solar System. 

“This adds a new dimension to the search for life on Mars, targeting comparable meteorites on the red planet,”  said Professor Southam.

In their research, the team suggests that if samples were to be returned from Mars, an overall picture of the volcanic and sedimentary history of Mars could be built, possibly including evidence of past life on the Red Planet. Meteorites, therefore, could be key to finding life on Mars.