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If we are the only ones here, we should do a better job of protecting this life — Patrick Gasda, Los Alamos National Laboratory research scientist
Mars, the Wet Planet?
OK, scientists probably are not going to hang that handle on the fourth rock from the sun and the second-smallest planet in the Solar System now. But if they had been around 3.5 billion years ago, they might have considered it.
Information collected by the NASA Mars rover Curiosity shows that the planet was once a much wetter place than it is now. Analysis of the Glen Torridon region in the Gale crater, created by a meteor impact on Mars 3.7 billion years ago, indicate that bedrock there was altered by groundwater.
“There is a block of evidence that when the crater was formed, Earth and Mars were similar in water and atmosphere,” said Patrick Gasda of Los Alamos National Laboratory’s Space and Remote Sensing Group. “Mars underwent a climate change. All signs point to a warm, wet Mars in the past. Now Mars is cold and dry. What made Mars divert from Earth? If we could figure that out, maybe we could prevent that here.”
Crater lakes, hot rocks
Curiosity’s assignment was to discover if Mars ever had the right environmental conditions to support small life forms called microbes. The rover acquires rock, soil and air samples for onboard analysis. It looks for rocks that formed in water and/or show signs of organics.
Gasda, 37, is the lead author of a study, published recently in a special issue of Journal of Geophysical Research Planets, that describes what Curiosity found in the most chemically varied part of Gale crater, which is 96 miles wide and contains a 3-mile-high mountain of layered sediments named Mount Sharp.
“Gale crater had a lake approximately 3.5 billion years ago,” Gasda said. “There could have been a deep lake there, or maybe just a few small or shallow lakes with small rivers in between. It would have been a friendly place for life – like bacterial life. But we haven’t found any evidence of life yet.”
He said the crater’s Glen Torridon region likely represents the last stages of a wet Mars.
“And we want to understand the lake sediments in order to give us a baseline for what happened right before Mars’ climate changed,” Gasda said.
Scientists believe the lake in Gale crater was formed by groundwater seeping in and rivers, fed by rain and melting snow, flowing in. Gravel, sand and silt came in with the river water.
Over millions of years these sediments continued to build up in the crater. Even after Mars started drying out and rivers ceased to flow, wind blew sand and dust into the crater, possibly filling it to the brim. But then the winds begin to claw away at the bowl of sediment, until what remains today is Mount Sharp.
“Erosion by wind could have taken about a billion years,” Gasda said. “The base (of Mount Sharp) takes up between a third and two-thirds of the crater. It’s big. It’s been compared to (Tanzania’s) Mount Kilimanjaro.”
Each layer of sediment locked into the rock records a chapter that reveals the environment that created it. Curiosity, using its ChemCam instrument, which was developed at Los Alamos and a French space laboratory, reads those chapters and reports back to Earth.
ChemCam registers chemistry and imagery from Curiosity’s four cameras to look for physical and chemical changes to rocks.
“We see rounded nodules that have different color – darker toned – than the surrounding material,” Gasda said. “Water in a crater will react with rocks if there for a long time. It is the darker material that gets concentrations of water. That’s how we know this stuff formed in water.”
Curiosity also discovered large veins with peculiar chemistry, including high iron and manganese dark veins and fluorine-rich lighter veins.
“We did not expect to find veins with chemistry like this in Glen Torridon,” Gasda said. “Our hypothesis for the way these things formed is that the initial (meteor) impact heated rocks near the crater, groundwater flowed through those rocks and this hot water likely extracted elements such as fluorine from these rocks.”
Heated water, or hydrothermal, systems would bring elements such as iron, nickel, sulfur and manganese to the surface of Mars, and microbes use these elements as a source of energy.
“We think now things like this happened all over Mars,” Gasda said. “Any time a large impact occurs, you would have hot water circulating. It is possible all craters on Mars had similar circumstances. Mars could have been friendly to life planet wide.”
Gasda has a bachelor’s degree in chemistry from Ursinus College in Pennsylvania and a doctorate in geology from the University of Hawaii.
“I’ve been interested in all things related to space and rocks since I was a kid, but I went to college to do chemistry,” he said. “I worked in industry for a while but didn’t like it. Eventually I came back to what I really wanted to do, which was geology and planetary science, in graduate school.”
A kid-like enthusiasm is still evident when he talks about exploring Mars. He thinks it is crazy exciting that we are landing rovers on a planet that is farther away from Earth than Earth is from the sun.
Curiosity was launched in November 2011 and landed on Mars in August 2012.
“Curiosity had its own camera and took pictures on the way down,” Gasda said. “It looked for places that were flat so it would have a good place to land.”
Initially, Curiosity’s mission was set at two years. But two years came and passed nearly eight years ago and the rover keeps on trucking.
The rover’s goal was to discover the role of water on Mars and whether or not the planet could have supported life. So far, so good.
“Water was there and it would have been nice if there was life,” Gasda said. “We just don’t have a way of measuring that.”
He said that perhaps the rover Perseverance, which landed on Mars in February 2021, might find a fossil that would prove life once existed on the planet.
He’s not talking about something like Brontosaurus bones.
“The most realistic would be fossils of bacteria, tiny little specks,” he said. “You could look for concentrations of carbon, hydrogen, nitrogen, which are required for life as we know it.”
But what if there’s life as we don’t know it.
“As far as we know, only Earth has life on it,” Gasda said. “But we don’t know enough about life to be sure. We have only one example of a biosphere. If we could find another example of life, we could understand life more broadly.
“If we are the only ones here, we should do a better job of protecting this life.”