The Perseverance rover has uncovered an unusual red rock on Mars with drop-like green spots that provide clues about its composition.
The “mysterious rock,” as NASA described it in the press release, could not be examined in detail because the rover’s instruments did not have enough space to work with it. However, its controllable features provide clues that this rock formed on an older, wetter Mars.
When Perseverance reached Mars in February 2021, its goal was to survey a dried river delta at the edge of a billion-year-old lake for signs of ancient microbial life. Although it experiences much more extreme temperature fluctuations and is much drier than our Earth, scientists believe there were large lakes of liquid water on the surface of Mars billions of years ago. One of these lakes was in Jezero Crater, where Perseverance touched down three years ago.
Since landing on the planet, Perseverance has circled the western edge of Jezero, taking images of the planet and collecting rock cores and some Martian atmosphere that will be sent back to Earth by a future mission.
Perseverance’s astrobiological research is based on the idea that if life had existed on Mars in the past, it would have been similar to the first forms of life on Earth, that is, consisting of microbes that survived in shallow water. While these microbes survive, they form sedimentary concretions (rock layers) and then fossilize with distorted patterns. These rock fossils are called stromatolites, and they continue to form on Earth today.
In July, Perseverance found “leopard patterns” in hematite and calcium sulfate bands on Mars. NASA scientists believed this could indicate that the rock was once mud containing organic compounds.
The mystery of the red rock with green dots
Perseverance has now examined another intriguing target, a red rock with green dots. Although this rock is not clear evidence for alien life, it provides an important glimpse into Mars’ iron-rich past.
Although the rock’s red color was likely due to oxidized iron, the Perseverance team wanted to examine the rock more closely. The rover used an abrasive tool to cut a circular piece 5 centimeters wide from its surface to see the interior of the rock that had not been eroded or otherwise altered by windy conditions on the Martian surface.
Green spots on the rock were “relatively common,” NASA reported. These spots form when water penetrates iron-rich sediment before it turns into rock, oxidizing the metal and turning it green. On Earth, microbes can catalyze this reaction, but it can also occur due to decaying organic matter or interactions between sulfur and iron.
Whatever the reason, examining the rock will provide information about Mars’ watery past, potential life on the planet, or how the planet evolved. Although further examination of this green-speckled sediment was desired, a more detailed examination could not be made because there was not enough space around the rock sample for Perseverance to deploy its instruments.
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