New Type of Impact Crater on Mars Identified, Explained

By studying the effects of underground nuclear tests and volcanoes, researchers have pieced together a new theory behind the creation of a class of unusual impact craters on Mars.

Nadine Barlow, a professor of physics and astronomy at Northern Arizona University, refers to the formations as Low-Aspect-Ratio Ejecta (LARLE) Craters based on their thin layer of outer deposit extending far beyond the normal range of ejecta.

Barlow first identified the craters while examining high-resolution images of Mars' surface taken by the Mars Odyssey Orbiter and the Mars Reconnaissance Orbiter (MRO).

"I had to ask, 'What is going on here?'" Barlow said in a statement.

To come to an answer, the researcher and her colleagues turned to "explosion literature," where they learned more regarding a phenomenon known as base surge.

In base surge, a large explosion is followed by a cloud formed by fine-grain material, which then moves along the surface, eroding it and picking up more material. The result is a far reaching outer deposit.

An adjustment of equations derived from volcano research so as to reflect Martian conditions yields an accurate explanation for the "thin, sinuous, almost flame-like deposits," Barlow said.

Furthermore, the craters are mostly found at higher latitudes, which correlates, according to the press release detailing the study, "with thick, fine-grained sedimentary deposits thick with subsurface ice."

This combination "helps vaporize the materials and create a base flow surge," Barlow explains.

With it six meters per pixel, the MRO was especially helpful in examining the finer detail needed for the study.

"We're looking in more detail at these deposits to find out what their characteristics are," Barlow said. "We can see dune-like structures and the hollows that occur in the outer deposit."

Going forward, the researcher said she welcomes any future surprises that may arise as she continues to study Mars' surface.

"That's part of the fun of science, to see something and say, 'Whoa, what's that?'" she said. "Projects like this end up leading to proposals."