NASA rover findings released Monday appear to point to a more Earth-like Martian past.
Chemicals found in Martian rocks collected by the Curiosity rover suggest the Red Planet once had more oxygen in its atmosphere than it does now, according to NASA’s Jet Propulsion Laboratory near Pasadena, which built the rover and manages the space agency’s Curiosity mission.
“Researchers found high levels of manganese oxides by using a laser- firing instrument on the rover,” according to a statement released by JPL. “This hint of more oxygen in Mars’ early atmosphere adds to other Curiosity findings — such as evidence about ancient lakes — revealing how Earth-like our neighboring planet once was.”
The manganese oxides were found in mineral veins within a geological setting that the Curiosity mission has placed in a timeline of ancient environmental conditions, linking the higher oxygen level to a time when groundwater was present in the rover’s Gale Crater study area.
“The only ways on Earth that we know how to make these manganese materials involve atmospheric oxygen or microbes,” said Nina Lanza, a planetary scientist at the Los Alamos National Laboratory in New Mexico, which leads the U.S. and French team that jointly developed and operates Curiosity’s ChemCam instrument.
“Now we’re seeing manganese oxides on Mars, and we’re wondering how the heck these could have formed?” Lanza said.
She said microbes seem far-fetched at this point, but the other alternative — that the Martian atmosphere contained more oxygen in the past than it does now — seems possible.
“These high manganese materials can’t form without lots of liquid water and strongly oxidizing conditions,” Lanza said. “Here on Earth, we had lots of water but no widespread deposits of manganese oxides until after the oxygen levels in our atmosphere rose.”
The presence of the same types of materials on Mars suggests that oxygen levels rose there, too, before declining to their present values, she said.
“One potential way that oxygen could have gotten into the Martian atmosphere is from the breakdown of water when Mars was losing its magnetic field,” Lanza said. “It’s thought that at this time in Mars’ history, water was much more abundant.”
Without a protective magnetic field to shield the surface, ionizing radiation started splitting water molecules into hydrogen and oxygen, according to Lanza. Because of Mars’ relatively low gravity, the planet wasn’t able to hold onto the very light hydrogen atoms, but the heavier oxygen atoms remained behind and went into rocks, leading to the rusty red dust that covers the surface today.
Mars’ red iron oxides require only a mildly oxidizing environment to form, but manganese oxides require a strongly oxidizing environment, more so than previously known for Mars, Lanza said.
“It’s hard to confirm whether this scenario for Martian atmospheric oxygen actually occurred,” she said. “But it’s important to note that this idea represents a departure in our understanding for how planetary atmospheres might become oxygenated.”
The high-manganese materials that Curiousity found are in mineral-filled cracks in sandstones in the “Kimberley” region of the Gale Crater that the rover has been investigating since 2012.
NASA’s Opportunity rover, exploring Mars since 2004, also recently discovered high manganese deposits thousands of miles from Curiosity, supporting the idea that the conditions needed to form those materials were present well beyond Gale Crater, scientists said.
–City News Service
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