Scientists have reviewed images taken by the Spirit rover nearly a decade ago, and have concluded that NASA may have previously overlooked evidence contained in them that could point towards them being biosignatures for past early forms of life in outer space on the planet.
A new study published in Nature Communications suggests rocky outcrops and regoliths formed of opaline silica that the rover photographed in the Gusev crater in 2007 potentially have these biosignatures, which are natural traces of current or past life.
Experts Steven Ruff and Jack Farmer, of Arizona State University (ASU), looked at data from the rover's visit to Home Plate, a plateau of layered rocks in the Columbia Hills area of the crater.
It is an ancient area of eroded volcanic ash, thought to still contain an active hot spring, which has formed silica outcrops, including finger-like formations photographed by the rover.
Fossils here on Earth are one example of a biosignature of past life.
They also occur in less obvious forms, including organic molecules which are left trapped in rocks and compacted mats of microbes known as stromatolites - which are the earliest forms of life here on Earth, and are found in Western Australia, and El Tatio in Chile.
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