During the same relative time period, other clues indicate more oxygen was present in the atmosphere thanfound currently
Space news (planetary science: Martian rocks containing manganese oxide minerals; indicating a wetter surface with more atmospheric oxygen than presently found on Mars) – Mars (the Red Planet), 154 million miles (249 kilometers) from Sol, or 141 million miles (228 million kilometers) from Earth, on average –
NASA’s Curiosity Mars rover has found rocks at a place called Windjana containing manganese oxide minerals according to reports from planetary scientists studying samples from the region. On Earth rocks of this type formed during the distant past in the presence of abundant water and atmospheric oxygen. This news added to previous reports of ancient lakes and other groundwater sources during Mar’s pastpoints to a wetter environment in the study region Gale Crater during this time.
Planetary scientists used the laser-firing instrument on the Curiosity Mars rover to detect high levels of manganese-oxide in mineral veins found at Windjana. “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 Los Alamos National Laboratory in New Mexico. “Now we’re seeing manganese oxides on Mars, and we’re wondering how the heck these could have formed?”
Planetary scientists are looking at other processes that could create the manganese-oxide they found in rocks in Mar’s Gale Crater region. Possible culprits at this point include microbes, but even optimistic planetary scientists are finding little fan fair accompanyingtheir ideas. Lanza said, “These high manganese materials can’t form without lots of liquid water and strongly oxidizing conditions. Here on Earth, we had lots of water but no widespread deposits of manganese oxides until after the oxygen levels in our atmosphere rose.”
Geologists have found high concentrations of manganese oxide minerals is an important marker of a major shift in Earth’s atmospheric composition, from relatively low oxygen levels during the distant past, to the oxygen-rich environment we live in today. Planetary scientists studying the rocks they found in Gale Crater suggest the presence of these materials indicates oxygen levels on Mars rose also, before declining to the present low levels detected. The question is how was Mar’s oxygen-rich atmosphere formed?
“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,” said Lanza. “It’s thought that at this time in Mars’ history, water was much more abundant. Yet without a protective magnetic field to shield the surface, ionizing radiation started splitting water molecules into hydrogen and oxygen. 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. Much of this oxygen went into rocks, leading to the rusty red dust that covers the surface today. While Mars’ famous red iron oxides require only a mildly oxidizing environment to form, manganese oxides require a strongly oxidizing environment, more so than previously known for Mars.“
Lanza added, “It’s hard to confirm whether this scenario for Martian atmospheric oxygen actually occurred. But it’s important to note that this idea represents a departure in our understanding for how planetary atmospheres might become oxygenated. Abundant atmospheric oxygen has been treated as a so-called biosignature or a sign of extant life, but this process does not require life.“
The Curiosity rover has been investigating Gale Crater for around four years and recent evidence supports the possibilityconditions needed to form these deposits were present in other locations. The concentrations of manganese oxide discovered were found in mineral-filled cracks in sandstones in a region of the crater called “Kimberley”. NASA’s Opportunity rover has been exploring the surface of the planet since 2004 and recently reported similar high manganese deposits in a region thousands of miles away. Supporting the idea environments required to form similar deposits could be found well beyond Gale Crater.
What’s next for Curiosity?
NASA’s Curiosity rover’s currently collecting drilled rock powder from the 14th drill site called the Murray formation on the lower part of Mount Sharp. Plans call for NASA’s mobile laboratory to head uphill towards new destinations as part of a two-year mission extension starting near the beginning of October.
The rover will go forward about a-mile-and-a-half (two-and-a-half-kilometers) to a ridge capped with material rich in the iron-oxide mineral hematite first identified by observations made with NASA’s Mars Reconnaissance Orbiter. Just beyond this area, there’s also a region with clay-rich bedrock planetary scientists want to have a closer look.
NASA has been exploring these key exploration sites on lower Mount Sharp as part of an effort to investigate evidence the Red planet was once a much wetter environment, which contrasts with the pictures of Mars we have received from our orbiters and rovers. A wetter environment where life could have taken root and grown.
“We continue to reach higher and younger layers on Mount Sharp,” said Curiosity Project Scientist Ashwin Vasavada, of NASA’s Jet Propulsion Laboratory, Pasadena, California. “Even after four years of exploring near and on the mountain, it still has the potential to completely surprise us.”
Planetary scientists found the Murray formation consists primarily of mudstone, which on Earth would form from mud accumulated on the bottom on an ancient lake. This seems to indicate any lake environment that existed on the Red Planet lasted awhile, but we’ll need to investigate this possibility more. Plans are for Curiosity to investigate the upper regions of the Murray formation, ahead, for at least one year of the mission.
“We will see whether that record of lakes continues further,”Vasavada said. “The more vertical thickness we see, the longer the lakes were present, and the longer habitable conditions existed here. Did the ancient environment change over time? Will the type of evidence we’ve found so far transition to something else?”
Vasavada said, “The Hematite and the Clay units likely indicate different environments from the conditions recorded in the older rock beneath them and different from each other. It will be interesting to see whether either or both were habitable environments.”