Sitting at the northern edge of Mars' famous Valles Marineris canyon complex, which looks like a gaping wound in the equatorial region of the red planet, is a strange 196 mile (315 kilometer) wide gouge in the landscape called Hebes Chasma. Like Valles Marineris, Hebes Chasma is a scar of Mars' ancient geological upheaval when the planet was volcanically active. Seen here in new observations by the European spacecraft Mars Express, the deep valley is imaged in beautiful high-definition.
Observed by Mars Express' High Resolution Stereo Camera, Hebes Chasma was photographed on eight occasions between 2004 and 2009 to create the new mosaic of the region. Shown here, an elevation model shows how deep the feature is -- nearly 5 miles (8 kilometers) deeper than the surrounding terrain. Strangely, the feature has a unique rise (or "mesa") in its center; no other canyon on Mars is known to posses such a large central hump.
Hebes Chasma and the neighboring canyons are related to the famous Tharsis Bulge -- a huge region on the red planet that dominates the western hemisphere, which was formed in the early volcanic history of Mars. Olympus Mons, the largest shield volcano in the solar system, resides on the bulge, a remnant of the planet's volcanic past. During the formation of Tharsis, Mars' crust was stretched and ripped, creating the Valles Marineris complex, including Hebes Chasma.
Using data from Mars Express, scientists have recreated Hebes Chasma's central mesa with mind blowing precision. Time has not been kind to the mesa, as is evident in this rendering. Material from one edge of the mesa has eroded and slumped to create this horseshoe-like feature. Dark material appears to have "pooled" in the slumped debris, likely darker mineral eroded from an intermediate layer of stratified material. The erosion was likely caused by the freezing and thawing of ices in the rock.
The overriding feature on the mesa is numerous channels etched in the rock, suggestive that the material is soft and easily eroded. Darker bands of material in the mesa slopes also reveal the mineral stratification, revealing some information about the geological evolution of the region. With the help of data from NASA's Mars Reconnaissance Orbiter, both satellites have revealed that many of the minerals inside Hebes Chasma could only have been formed in the presence of water, indicating that many of these mesa erosion features and slumped debris were likely caused by water action.