A new study discovers evidence of water on Mars for a brief period of time

NAU PhD candidate Ari Koeppel recently discovered that water was once present in a region of Mars called Arabia Terra, as part of a team of collaborators from Northern Arizona University and Johns Hopkins University

Arabia Terra is located in Mars' northern latitudes. This ancient land, named by Italian astronomer Giovanni Schiaparelli in 1879, is slightly larger than the European continent. Craters, volcanic calderas, canyons, and stunning bands of rock resembling sedimentary rock strata in the Painted Desert or the Badlands can be found on Arabia Terra.

The research focus for Koeppel and his advisor, associate professor Christopher Edwards of NAU's Department of Astronomy and Planetary Science, as well as Andrew Annex, Kevin Lewis, and undergraduate student Gabriel Carrillo of Johns Hopkins University, was these layers of rock and how they formed. Their study, titled "A fragile record of fleeting water on Mars," was funded by NASA and recently published in the journal Geology.

"We were specifically interested in using rocks on the surface of Mars to get a better understanding of past environments three to four billion years ago and whether there could have been climatic conditions that were suitable for life on the surface," Koeppel said. "We were interested in whether there was stable water, how long there could have been stable water, what the atmosphere might have been like and what the temperature on the surface might have been like."

The scientists focused on thermal inertia, which is defined as a material's ability to change temperature, to gain a better understanding of what happened to create the rock layers. Sand, with its small and loose particles, heats up and cools down quickly, whereas a solid boulder will stay warm well into the evening. They were able to determine the physical properties of rocks in their study area by looking at surface temperatures. When a material appeared to be solid, they could tell if it was loose and eroding away.

"No one had done an in-depth thermal inertia investigation of these really interesting deposits that cover a large portion of the surface of Mars," Edwards said.

Koeppel used remote sensing instruments on orbiting satellites to complete the research. "We look at rocks to try to tell stories about past environments, just like geologists on Earth," Koeppel said. "On Mars, our options are a little more limited. We can't just go to a rock outcropping and take samples; we rely heavily on satellite data. As a result, there are a few satellites orbiting Mars, each with its own set of instruments. Each instrument contributes to the description of the rocks on the surface in its own way."

They looked at thermal inertia, as well as evidence of erosion, the condition of the craters, and what minerals were present, in a series of investigations using this remotely gathered data.

"We figured out these deposits are much less cohesive than everyone previously thought they were, indicating that this setting could only have had water for only a brief period of time," said Koeppel. "For some people, that kind of sucks the air out of the story because we often think that having more water for more time means there's a greater chance of life having been there at one point. But for us, it's actually really interesting because it brings up a whole set of new questions. What are the conditions that could have allowed there to be water there for a brief amount of time? Could there have been glaciers that melted quickly with outbursts of huge floods? Could there have been a groundwater system that percolated up out of the ground for only a brief period of time only to sink back down?"

During his master's degree at The City College of New York, Koeppel switched from engineering and physics to geological sciences. He came to NAU to work with Edwards and to become immersed in Flagstaff's vibrant planetary science community.

"I got into planetary science because of my excitement for exploring worlds beyond Earth. The universe is astoundingly big, even Mars is just the tip of the iceberg," Koeppel said. "But we've been studying Mars for a few decades now, and at this point, we have a huge accumulation of data. We're beginning to study it at levels that are comparable to ways we've been able to study Earth, and it's a really exciting time for Mars science."

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