Probable fresh explanation for a puzzling crater type on the surface on Mars has surfaced. Debris exhumed by an impactor, like other craters, surrounds double-layered ejecta craters (DLE). Two distinct layers formed by the debris – a large outer layer and a small inner layer sitting on top – differentiate DLE from others.
A new research implies that the outcome of impacts onto a surface that was covered by tens of meters thick of layer of frosty ice is DLE.
Senior author James W, Head, Geological Science professor at Brown University wrote in press release, “Recent discoveries by planetary geoscientists at Brown and elsewhere have shown that the climate of Mars has varied in the past. During these times, ice from the polar caps is redistributed into the mid-latitudes of Mars as a layer about 50 meters thick, in the same place that we see that the DLEs have formed. This made us think that this ice layer could be part of the explanation for the formation of the unusual DLE second layer."
In a scenario laid out by Head and first author graduate student David Kutai Weiss, the collision explodes through the ice layer, spattering rock and other ejecta out onto the surrounding ice. However, because that ejected thing is on slippery ice, it moves. They believe the DLE’s appearance occurs when material near the top of an upraised crater rim glides down the ice and covers the lower layer.
"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," according to Weiss. Knowledge of how DLE and other crater types were created could facilitate researchers to recreate the environmental conditions at the time of the collision.
This study will be published in the journal Geophysical Research Letters but an early version of the paper went online on July 25. It was also funded by the NASA.
