Strange Mars Craters Created By Ice?

Double-ringed craters on Mars, like the one above, could have formed when ejected material slides down steep crater walls and across ice, forming a radiating top layer. Credit: NASA

A four-decade long Martian mystery surrounding the origins of double-rimmed craters may have been cracked.

New research suggests that their strange spill patterns seen around some impact sites on Mars may be directly linked to giant ice sheets that could have blanketed the Red Planet sometime in its ancient past. (Related: Ancient Mars Was Snowy, New Model Suggests)

Pouring over hundreds of orbiter images taken by the orbiting spacecraft—some of which date back to the 1970s—planetary geologists from Brown University  believe they have finally learned how these distinctive double-layer ejecta (DLE) patterns around the craters may have been created.  (See also: Mysterious Martian Grooves Carved by Dry Ice Chunks?)

As their theory goes, when material from the original meteor impact blast was thrown onto the surface, it would spill over the steep crater walls and slip down the lower slopes, which were covered by a sheet of ice. This then created a set of unique features on the surface.

Similar features are seen on glacial landslides here on Earth. The similarities between the two made researchers think ice was somehow involved on the Martian soil.

Another clue? The climate of Mars billions of years ago is believed to have been quite different from today and varied considerably over time. Research has also shown that ice from the polar caps may have migrated to lower latitudes at one point in its history—straight into same geographical locations where these DLE craters are now found.

This global climate model fits perfectly with the new landslide theory being proposed for creating DLEs, say the researchers. By combining steep crater slopes and a slippery layer of surrounding ice, the telltale two-layered appearance of the DLEs can be explained.

“I think for the first time since DLEs were discovered in the 1970s we have a model for their formation that appears to be consistent with a very wide range of known data,” said David Weiss, the co-author of the new study and graduate student at Brown University, in a press statement.

The research team hopes this new insight into crater formation will help lead them to a better understanding of how the environment may have changed  on the Red Planet over time. (See more Mars pictures.)

“There are over 600 DLEs on the Martian surface, so reconciling how they formed with our knowledge of the climate of Mars is pretty important,” Weiss said. “It could tell us a lot about the history of the Martian climate on a global scale.”

This double-rimmed crater study will be published in an upcoming issue of the journal Geophysical Research Letters.

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Changing Planet

Meet the Author
Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.