Glaciers, not some ancient timekeeper, most likely etched this hourglass-like feature into the surface of Mars.

This southeastward-looking view of a region called Promethei Terra at the eastern rim of the Hellas Basin was compiled by imagery taken by the European Space Agency’s (ESA) Mars Express spacecraft.

Shown here are the effects of a ‘block’ glacier – a glacier containing a large amount small rocks, or scree – which flowed from a flank of the nearby mountains into an already full impact crater nine kilometers wide. A downward slope led the glacier to then flow into the larger, 17-kilometer wide crater some 500 meters below.

Glaciers must have formed on Mars until about a few million years ago during a time that was warmer and possibly also had a thicker atmosphere, ESA researchers said. The icy formations may have become inactive or retreated due to the lack of continued supply of ice. Since then  they may have been protected from sublimation by layers of dust, almost ubiquitous on Mars, which would explain why ‘fossil’ ice present at depths of only a few meters could not be detected by other instruments such as spectrometers.

Mars Express used its High Resolution Stereo Camera (HRSC) to generate this image.

• New Signs of Recent Glaciers, Volcanoes and Flowing Water on Mars

-- SPACE.com Staff

Credit: ESA/DLR/FU Berlin (G. Neukum)