Data from a small planet

On November 16, 2021, NASA’s Curiosity spacecraft photographed panoramic images of this scene on Mars twice, approximately eight hours apart. The engineers combined the two scenes to produce this re-creation. (Courtesy of NASA/JPL-CALTECH)

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Mars, the wet planet?

Well, scientists probably won’t be hanging this knob on the fourth rock from the sun and the second smallest planet in the solar system right now. But if they were about 3.5 billion years ago, they might have thought about it.

Information collected by NASA’s Curiosity spacecraft shows that the planet was once a wetter place than it is now. Analysis of the Glen Torridon region in Gale crater, which was formed by a meteorite impact on Mars 3.7 billion years ago, indicates that the basement rocks there were altered by groundwater.

“There is a mass of evidence that when the crater formed, Earth and Mars were similar in water and atmosphere,” said Patrick Gasda of the Space and Remote Sensing Group at Los Alamos National Laboratory. “Mars has undergone climate change. All signs point to a warm, humid Mars in the past. Now Mars is cold and dry. What made Mars shift away from Earth? If we can figure that out, maybe we can prevent it here.”

Crater lakes and hot rocks

Curiosity’s mission was to discover if Mars had the right environmental conditions to support tiny life forms called microbes. The rover obtains samples of rock, soil and air for analysis on board. Looks for rocks that formed in the water and/or show signs of organic matter.

Patrick Gasda, Los Alamos National Laboratory research scientist, is in a lab with the test unit of the ChemCam instrument used by the Mars rover Curiosity to explore the role of water on Mars and the possibility that the planet may have supported life. )

Gasda, 37, is the lead author of a study recently published in a special issue of the Journal of Geophysical Research Planets that describes what Curiosity found in the most chemically diverse part of Gale Crater, which is 96 miles wide and contains a 3-mile-high mountain of sediment. Stratification is called Mount Sharp.

“Gale crater had a lake about 3.5 billion years ago,” Gasda said. “Maybe there was a deep lake there, or maybe a few small or shallow lakes with little 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 Glen Torideon region in the crater likely represents the last stages of wet Mars.

“We want to understand the sediments of the lake in order to provide us with a baseline of what happened before the Martian climate changed,” Gasda said.

Scientists believe that the lake in Gale Crater was formed from percolating groundwater and flowing rain-fed rivers and thaws. Pebbles, sand and silt came with the river water.

Over millions of years these sediments continued to accumulate in the crater of the volcano. Even after Mars began to dry up and rivers stopped flowing, the winds shot sand and dust into the crater, possibly filling it to the brim. But then, the wind began to creep away into the sediment pot, until what remains today is Mount Sharp.

“Wind erosion could have taken about a billion years,” Gasda said. “The base of (Jebel Sharp) occupies between one-third and two-thirds of the crater. It is large. It has been compared to Mount Kilimanjaro (Tanzania).”

Each layer of sediment trapped in the rock records a chapter that reveals the environment in which it was created. Curiosity, using its ChemCam instrument, which was developed at Los Alamos and a French space laboratory, is reading those chapters and reporting back to Earth.

ChemCam records chemistry and images from Curiosity’s four cameras to search for rocks’ physical and chemical changes.

“We see round nodules that are a different color — darker — than the surrounding material,” Gasda said. “The water in the crater will react with the rocks if it’s been there for a long time. It’s the darker substance that gets concentrations of water. That’s how we know these things formed in the water.”

Curiosity has also discovered large veins with strange chemistry, including dark veins high in iron and manganese and light veins rich in fluorine.

“We didn’t expect to find veins with chemistry like this at Glen Torridon,” Gasda said. “Our hypothesis for the way these things formed is that (the meteorite) hits the hot rocks near the crater, the groundwater flows through that rock and it’s possible that this hot water extracted elements like fluorine from these rocks.”

Hot water systems, or hydrothermal systems, will bring elements such as iron, nickel, sulfur, and manganese to the surface of Mars, and microbes use these elements as an energy source.

NASA’s Curiosity Mars rover uses the MAST Camera in March 2020 to capture a view of the planet’s surface. In the background is the top of Mount Sharp, a 3-mile-high mountain the rover has been climbing since 2014 (NASA/JPL-Caltech/MSSS)

“We now think things like this happened all over Mars,” Gasda said. “Anytime there was a major impact, you would have hot water circulating. It is possible that all the craters on Mars would have had similar conditions. Mars would have been a planet-wide friend of life.”

What is life?

Gasda holds 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 space and rock since I was a kid, but I went to college to study chemistry,” he said. “I worked in industry for a while but didn’t like it. Eventually I went back to what I really wanted to do, which was geology and planetary sciences, in graduate school.”

The childlike enthusiasm is still evident when he talks about the exploration of Mars. He thinks it’s crazy to land rovers on a planet farther 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. “I looked for places that were flat so they had a good place to land.”

Initially, Curiosity’s mission was set at two years. But two years have passed, and almost eight years have passed, the rover continues to truck.

The rover’s goal was to discover the role of water on Mars and whether or not the planet could support life. So far, so good.

“There was water and it would have been nice if there was life,” Gasda said. “We have no way of measuring that.”

He said that perhaps the Persevere rover, which landed on Mars in February 2021, will find a fossil that proves that life once existed on the planet.

He’s not talking about something like the bones of a Brontosaurus.

“The most realistic would be the fossils of bacteria, very small specks,” he said. “You can look up the concentrations of carbon, hydrogen, and nitrogen needed for life as we know it.”

But what if there is life as we don’t know it.

“As far as we know, only Earth lives on it,” Gasda said. But we don’t know much about life to be sure. We only have one example of a biosphere. If we can find another example of life, we can understand life on a larger scale.

“If we’re the only ones here, we should do a better job protecting this life.”