NASA's Spirit Rover may have already found a potential signature of ancient alien life on Mars almost a decade ago.

In a new study published in Nature Communications on Nov. 17, researchers suggest that the outcrops and regoliths made of opaline silica that the Mars rover Spirit encountered in the Gusev crater in 2007 has potential biosignatures of past life on Mars.

Biosignatures Indicate Ancient Or Present Life

Biosignatures are naturally occurring traces that suggest the presence of current or past life. Fossils are an example of a biosignature of past life. Biosignatures also come in more subtle forms such as organic molecules that get trapped in rocks and physical structures such as compacted mats of microbes known as stromatolites.

Stromatolites are formed when microbes form colonies in wet environments and then trap sediments on their sticky surface coatings. The trapped sediments then react to calcium carbonate present in the water and form a buildup of limestone layers.

Home Plate

Researchers Steven Ruff and Jack Farmer, from Arizona State University (ASU), looked at data from the Spirit's study of Home Plate, a plateau of layered rocks in the Columbia Hills of Gusev crater that the golf car-sized rover explored.

Home Plate is an ancient and eroded volcanic ash deposit and is believed to have an active hot spring at some point in the past that produced silica outcrops. The Spirit rover captured images of intriguing finger-like formations at the plateau.

Structures Similar To Those Found In Mars

The stromatolite structures at El Tatio, Chile that were formed in the hot spring deposits by processes involving biological and non-biological activities closely resemble the Martian structures.

Interestingly, El Tatio also has conditions comparable to those on the Martian surface. At 14,000 feet above sea level, temperatures tend to drop below freezing at night even during summers. By day, large amounts of UV rays from the Sun com through the thin and dry air.

The silica deposits in the structures that were influenced by microorganisms in El Tatio were found to be almost identical to those found by the Spirit rover in the Gusev crater eight years ago. This raises the possibility that the structures Spirit found on the Red Planet may have also been influenced by Martian life.

"Our results demonstrate that the more Mars-like conditions of El Tatio produce unique deposits, including biomediated silica structures, with characteristics that compare favourably with the Home Plate silica outcrops," the researchers wrote in their study.

"The similarities raise the possibility that the Martian silica structures formed in a comparable manner."

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