A set of rocks scattered on an historical shoreline on Mars would possibly point out that the Pink Planet was as soon as much more Earth-like than scientists beforehand thought.
The rocks, found by NASA’s Curiosity rover, are unusually wealthy in manganese oxide — a chemical that provides to rising proof that the once-habitable Mars might have sported Earth-like oxygen ranges and life-friendly situations early in its historical past, scientists say.
NASA calls manganese on Earth “an unsung hero within the evolution of life.” Scientists know from our planet’s geological historical past that manganese was ample in rocks and within the oceans earlier than the earliest life-forms emerged roughly 4 billion years in the past and that it paved the best way for oxygen that the majority life now depends on.
The one recognized methods to provide manganese oxide, nonetheless, contain both ample oxygen or microbial life. However there is not robust proof for the previous on Mars, and none for the latter, leaving scientists puzzled by how the chemical shaped within the newfound rocks.
Forming rocks wealthy in manganese oxide “is straightforward to do on Earth due to microbes and due to oxygen — which [also forms] due to microbes — so all of it factors again towards life,” lead examine creator Patrick Gasda, a analysis scientist at Los Alamos Nationwide Laboratory in New Mexico, informed Dwell Science. “We after all don’t have any proof of life on Mars, so if we’re attempting to kind oxygen in a completely abiotic system, our present understanding of Mars would not clarify that.”
The Curiosity rover got here throughout the closely eroded rocks whereas trekking by means of the center of Gale crater, a 96-mile-wide (154 kilometers) historical lake mattress that the rover has been exploring since 2012. The rover’s ChemCam instrument “sniffed” the manganese oxide throughout the rocks by vaporizing tiny bits with a laser after which analyzing the ensuing cloud of plasma. The compound constitutes almost half of the rocks’ chemical make-up, based on the brand new examine, which was printed final week within the journal JGR Planets.
On the website the place Curiosity discovered the brand new rocks, the rover recorded 10 to fifteen meters (33 to 49 toes) of elevation change. Though that is tiny compared with the a whole lot of meters Curiosity has climbed over time, it’s “pointing us towards one thing particular happening in that place,” Gasda informed Dwell Science. The rock texture the place the brand new sandstones had been discovered seems to have transitioned from “curved” to “flat-lined” — a change Gasda and his colleagues are decoding as a river channel opening out right into a lake.
“Meaning we’re on the shore of the lake or close to the shore of the lake,” Gasda mentioned. He famous that this interpretation is unsure on account of restricted information, as a result of Curiosity drove previous the area simply as soon as. “That made the interpretation actually difficult, however that is our greatest speculation,” he added.
If the speculation is right, the rocks might have been dumped within the area when the river water slowed down because it entered the lake, just like manganese-oxide-rich rocks which were discovered on the shores of shallow lakes on Earth.
The newfound rocks are “one other line of proof for liquid water on Mars prior to now, which is useful for all times,” Manasvi Lingam, an astrobiologist on the Florida Institute of Know-how who was not affiliated with the brand new analysis, informed Dwell Science. “This work supplies proof in favor of habitability.”
Nevertheless, not everybody agrees that the newfound rocks point out an oxygen-rich Mars. In line with Jeffrey Catalano, a professor of Earth, environmental and planetary sciences at Washington College in St. Louis, who was not concerned within the examine, the presence of oxidized rocks might assist scientists perceive whether or not Mars, like Earth, went by means of “a punctuated transition” from a lower-oxygen interval and a higher-oxygen interval. “The affect of manganese oxides on our understanding of such a transition, nonetheless, have been overstated, right here and in prior work,” he informed Dwell Science.
Catalano was a part of a 2022 examine that discovered manganese oxide might simply kind beneath Mars-like situations with out atmospheric oxygen. That analysis, which was primarily based on lab experiments, confirmed that components akin to chlorine and bromine, which had been ample on early Mars, transformed manganese dissolved in water into manganese oxide minerals. This discovering supplied a substitute for oxygen that might clarify rocks just like the newfound ones on Mars.
“There are a number of life kinds even on Earth that don’t require oxygen to outlive,” Kaushik Mitra, a geochemist on the College of Texas at San Antonio who led that examine, mentioned in a assertion in 2022. “I do not consider it as a ‘setback’ to habitability — solely that there have been in all probability no oxygen-based lifeforms.”
