AGU: Geophysical Research Letters

 

Editors' Highlight

Ring mold craters on Mars: Evidence of subsurface glacial ice

Lobate debris aprons and lineated valley fill, common in the northern and southern midlatitudes of Mars, are believed to have formed either as debris flows mobilized by pore ice or as debris-covered glaciers. To learn more, Kress and Head (2008) defined and analyzed ring mold craters, which are abundant on debris aprons and lineated valley fill but not seen in surrounding terrain. Ring mold craters are concentric crater forms shaped like a truncated torus and named for their similarity to the cooking implement, in contrast to the bowl-shaped craters that are common at such small sizes (hundreds of meters in diameter). On the basis of their similarity in shape to laboratory impact craters formed in ice and the physics of impact cratering into pure ice, the authors interpret ring mold craters to be primary landforms that result from projectiles hitting relatively pure ice below a thin debris layer. These results support the hypothesis that lobate debris aprons and lineated valley fill are debris-covered glaciers and that many hundreds of meters of ice remain in these deposits today on Mars, beneath a veneer of sublimation lag.

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