Planetologists find evidence of brief presence of water in Arabia Terra on Mars


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

Arabia Terra is found in the northern latitudes of Mars. Named in 1879 by the Italian astronomer Giovanni Schiaparelli, this ancient land covers an area slightly larger than the European continent. Arabia Terra contains craters, volcanic calderas, canyons and beautiful rock bands reminiscent of the sedimentary rock layers of the Painted Desert or the Badlands.

These layers of rock and how they formed were the subject of research by Koeppel, along with his advisor, associate professor Christophe edwards of NAU Department of Astronomy and Planetary Sciences, and Andrew Annex, Kevin Lewis, and Johns Hopkins University undergraduate student Gabriel Carrillo. Their study, entitled “A fragile dossier of transient water on Mars, ”Was funded by NASA’s Mars Data Analysis Program and recently published in the journal Geology.

“We were particularly interested in using rocks on the surface of Mars to better understand past environments three to four billion years ago and whether there might have been climatic conditions conducive to life on the surface. “said Koeppel. “We wanted to know if there was stable water, how long there could have been stable water, what the atmosphere might have looked like, and what the surface temperature might have been.”

In order to better understand what happened to create the rock layers, scientists focused on thermal inertia, which defines a material’s ability to change temperature. Sand, with loose small particles, gains and loses heat quickly, while a solid rock will stay warm long after dark. By looking at surface temperatures, they were able to determine the physical properties of rocks in their study area. They could tell if a material was loose and eroding when it looked otherwise solid.

“No one had done a thorough study of the thermal inertia of these really interesting deposits that cover a large part of the surface of Mars,” Edwards said.

To complete the study, Koeppel used remote sensing instruments on orbiting satellites.

“Much like geologists on Earth, we examine rocks to try to tell stories about past environments,” he said. “On Mars, we are a little more limited. We can’t just go out to a rock outcrop and take samples, we’re pretty dependent on satellite data. So, there are a handful of satellites orbiting Mars, and each satellite hosts a collection of instruments. Each instrument plays its own role in helping us describe the rocks that are on the surface.

Through a series of surveys using this remotely collected data, they examined thermal inertia, as well as evidence of erosion, crater condition and minerals present.

“We found that these deposits are much less cohesive than everyone previously thought, indicating that this environment was only able to have water for a brief period,” Koeppel said. “For some people, it sucks the air of the story because we often think that having more water for longer means there’s a better chance that life has been there at some point. But for us it’s actually very interesting because it raises a whole series of new questions. What are the conditions that could have allowed there to be water for a short period of time? Could there have been glaciers that melted quickly with explosions from huge floods? Could there have been a groundwater system that seeped out of the ground for a brief period only to come back down? ”

Koeppel began his college career in engineering and physics, but switched to the study of geological sciences while earning his master’s degree from City College of New York. He came to NAU to work with Edwards and immerse himself in Flagstaff’s thriving planetary science community.

“I got into planetary science because of my enthusiasm for exploring worlds beyond Earth. The universe is incredibly large, 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 starting to study it at levels comparable to the ways we’ve been able to study Earth, and it’s a really exciting time for Martian science.


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