Gully features

Gully features

. The gullies on Mars have three parts the alcove, the channel and the apron. Water seeps out from high up on the wall of a crater or other type of depression and the alcove (right center) forms by collapsing into the material removed by the seepage. Water and debris run down the slope from the seepage area, cutting channels below the alcove and depositing rock, soil and ice into a fanlike apron (bottom middle). This image, taken from the Mars Global Surveyor, covers an area of 1.3 kilometers wide by 2.0 kilometers long. It is located on the south-facing wall of an impact crater in Noachis Terra near 54.8 degrees south and 342.5 degrees west. (Courtesy of NASA, JPL and Malin Space Science Systems.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University