Mars TV series
A still from National Geographic's Mars TV seriesNational Geographic

During its wheeled treks on the Red Planet, NASA's Spirit rover may have encountered a potential signature of past life on Mars, report scientists at Arizona State University (ASU).

To help make their case, the researchers have contrasted Spirit's study of "Home Plate" — a plateau of layered rocks that the robot explored during the early part of its third year on Mars — with features found within active hot spring/geyser discharge channels at a site in northern Chile called El Tatio.

The work has resulted in a provocative paper: Silica deposits on Mars with features resembling hot spring biosignatures at El Tatio in Chile.

As reported online last week in the journal Nature Communications, field work in Chile by the ASU team — Steven Ruff and Jack Farmer of the university's School of Earth and Space Exploration — shows that the nodular and digitate silica structures at El Tatio that most closely resemble those on Mars include complex sedimentary structures produced by a combination of biotic and abiotic processes.

"Although fully abiotic processes are not ruled out for the Martian silica structures, they satisfy an a priori definition of potential biosignatures," the researchers wrote in the study.

"Our results demonstrate that the more Mars-like conditions of El Tatio produce unique deposits, including biomediated silica structures, with characteristics that compare favorably with the Home Plate silica outcrops. The similarities raise the possibility that the Martian silica structures formed in a comparable manner" read a part of the paper as reported by Fox News.

Spirit landed on Mars in January 2004, a few weeks before its twin, Opportunity, touched down in a different part of the Red Planet. Both golf-cart-size rovers were tasked with looking for signs of past water activity during their missions, which were originally planned to last three months.

Spirit encountered outcrops and regolith composed of opaline silica (amorphous SiO2nH2O) in an ancient volcanic hydrothermal setting in Gusev crater.

An origin via either fumarole-related acid-sulfate leaching or precipitation from hot spring fluids was considered possible. "However, the potential significance of the characteristic nodular and [millimeter]-scale digitate opaline silica structures was not recognized," Ruff and Farmer noted in the new study.

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