Fresh imagery from ESA's Mars Express orbiter has exposed signs of a past ice age in the Coloe Fossae region of Mars. These features include glacial-like patterns in valleys and craters, hinting at climate shifts that spread ice far from the poles. The findings suggest this icy period ended as recently as 500,000 years ago.
The High Resolution Stereo Camera on ESA's Mars Express has captured detailed views of Coloe Fossae, located at 39 degrees north latitude on the Red Planet. This area features long, shallow grooves formed by downward-dropping surface blocks, alongside deep valleys and scattered impact craters of varying ages and shapes—some crisp, others eroded or overlapping.
Within many valleys and craters, swirling, grooved patterns known as lineated valley fill and concentric crater fill indicate the flow of icy debris mixtures across the surface, akin to Earth's glaciers. These textures formed when ice advanced and retreated, eventually buried under rocky material.
Mars experiences climate cycles driven by changes in its axial tilt, leading to colder phases where ice expanded from the poles into mid-latitudes like this region. During warmer intervals, the ice receded, leaving these preserved traces. Scientists believe Coloe Fossae was covered by ice during Mars's most recent ice age, which concluded around half a million years ago.
Similar glacial indicators appear across this latitude band, pointing to a global climate shift. The site lies near the boundary between Mars's northern lowlands and southern highlands, seen as a wide, eroded transition zone called Protonilus Mensae. Comparable features were previously documented in Acheron Fossae.
The camera, developed by the German Aerospace Center, had its data processed at the DLR Institute of Planetary Research in Berlin-Adlershof, with final images produced by Freie Universität Berlin's Planetary Science and Remote Sensing group.
These observations highlight how Mars's ancient climates, much like Earth's—where ice ages over 2.5 billion years stemmed from orbital and tilt variations—have sculpted its terrain, independent of recent human influences.