Icy Mystery
Discovery on Mars
Let’s take an illustrative look at a new study that explored a recently formed crater on Mars. The new icy crater will help scientists better understand the Martian climate and inform future missions to the Red Planet.
Scientists know that Mars has ice. What they’re still trying to figure out is how much there is and where they can find it.
The weather on Mars varies a lot, from negative 200 to 70 degrees Fahrenheit. Although the Red Planet has a similar tilt to Earth’s, it lacks the stabilizing effect of a large moon. Without that tether, Mars wobbles on its axis, which means as its tilt changes, its climate also changes. This wobble affects the Martian climate on relatively short timescales spanning tens of thousands of years and on much longer ones that can reach back millions of years.
As a result, ice on Mars has moved around a lot. Sometimes this movement will leave behind clues in landforms on the surface, like pockets of accumulated sediments called glacial moraines. Although ice that covers the surface of Mars evaporates when it gets too warm, ice just underneath the rocky terrain can persist even when the temperature changes. Scientists know that this underground ice exists, but they can’t easily find it.
That is, until Christmas Eve last year, when a meteorite crashed into Mars at latitude 35 degrees North, (similar to Arizona’s location in the United States), throwing chunks of ice over a quarter of a mile away and forming a crater spanning almost 500 feet in diameter.
Although scientists have studied ice-excavating craters in the past, this crater was significantly bigger and happened to form at low latitudes.
The Mars Reconnaissance Orbiter, a NASA spacecraft sent to study Mars’ surface, monitor its atmosphere, and probe beneath its surface, first detected the impact crater using its onboard camera on December 24, 2021. The impact was later tied to ground shaking measured by the seismometer on the Mars InSight Lander, a robotic explorer sent to study Mars’ crust, mantle, and core.
“This large crater is well-suited to probe the limits of mid-latitude ice, which is deeper below the surface,” Colin Dundas, a research geologist with the USGS, said.
The impact helped Dundas and his colleagues better interpret the history of Martian ice. “There are large bright blocks around the crater’s rim,” Dundas said, “revealing nearly pure ice ejected from deeper beneath the surface.”
However, small secondary craters, which form when chunks from the initial impact create their own craters, do not show much bright ice. “This suggests that the shallowest ice is more a mix of dirt, dust, and ice that previously accumulated on the surface. In contrast, the deeper, nearly pure ice comes from periods when Mars had an accumulation of thicker snow and ice deposits,” Dundas said.
This new impact provides cold, hard evidence that subsurface ice exists closer to the equator than any previous detection. With this new information, scientists can adjust their climate models to capture the Red Planet’s climate history more accurately.
Knowing where ice exists will also help inform future missions to Mars. Ice is an important scientific target because of its value as a resource for human missions. Martian ice can be used to fuel rockets and keep astronauts alive.
In the not-so-distant future, astronauts could find themselves at the very location of the crater, celebrating their landing with some fresh Martian snowcones.
The research was recently published in the journal, https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2022GL100747.
Read story from NASA.
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