NASA had to leave behind its best clue to past life on Mars

A small greenish spot discovered on Mars by the Perseverance rover has piqued the curiosity of scientists. It may be the best sign of past life NASA has found on the Red Planet since the pattern of leopard spots at Cheawah Falls, but the rover couldn’t analyze it.

Green spot. Although NASA has now revealed the discovery, it was August 19, 2024, when Perseverance took a nighttime image of an intriguing greenish patch on rocks in the Serpentine Rapids region of Mars, at the bottom of Jezero Crater, where it was discovered. located like this.

The green blob in question, just two millimeters in diameter, was discovered after the car-sized rover used an abrasive tool to scrape away the rock nicknamed Wallace Butte. This action revealed an amazing palette of colors, including a greenish patch.

Between the red rocks. The image was taken using the SHERLOC WATSON camera, which is located at the tip of Perseverance’s robotic arm. The characteristic green spot with a dark core and blurred outline stands out in a reddish surrounding. These red stones owe their color to oxidized iron.

This is where things get interesting. On Earth, red rocks or strata may develop green spots when oxidized iron is chemically reduced, usually in the presence of liquid water. On our planet, such iron reduction may be associated with microbial activity or the decomposition of organic matter, although it can also occur without biological intervention, due to chemical interaction with sulfur.

Biological factor. Although NASA scientists urge caution, the presence of this anomaly in Martian soil could be evidence that life once existed on the Red Planet. In fact, these green spots will be one of the first tangible signs of the presence of past life on Mars.

What other option is there? The stain could well be the result of ancient interactions between soil minerals and water in the Jezero Crater, where the lake once was, without the intervention of living microorganisms.

A missed opportunity. The complexity of the terrain prevented the rover from placing its sophisticated chemical analysis instruments directly on the green patch. As a result, its composition remains a mystery.

Perhaps Perseverance will find better opportunities where it comes. The rover continues its ascent along the rim of Jezero Crater, negotiating (not without difficulty) steep and dangerous terrain to visit Pico Turquino and Gameizel Hill, two of the most promising regions due to their ancient hydrothermal activity and layered rocks. The search continues, and hope of finding evidence of past life is not lost.

Image | NASA-JPL

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