ESA - Mars Express Mission patch.
Feb. 10, 2014
The flood after the impact
Large and small, hundreds of thousands of craters scar the surface of Mars, hollowed out by a multitude of asteroids and comets that impacted the Red Planet throughout its history.
This image shows a region of the planet’s northern hemisphere known as Hephaestus Fossae – after the Greek god of fire – that was imaged by the high-resolution stereo camera on ESA’s Mars Express orbiter on 28 December 2007. The image has been coloured to indicate the elevation of the terrain: green and yellow shades represent shallow ground, while blue and purple stand for deep depressions, down to about 4 km.
Scattered across the scene are a few dozen impact craters that cover a wide range of sizes, with the largest boasting a diameter of around 20 km.
The long and intricate canyon-like features that resemble riverbeds are the phenomenal aftermath of the same fierce impacts that created the largest craters.
Artist's view of Mars Express spacecraft
When a small body such as a comet or an asteroid crashes at high speed into another object in the Solar System, the collision dramatically heats up the surface at the impact site.
In the case of the large crater seen in this image, the heat produced by such a powerful smash melted the soil – a mixture of rock, dust and also, hidden deep down, water ice – resulting in a massive overflow that flooded the surrounding environment. Before drying up, this muddy fluid carved a complex pattern of channels while making its way across the planet’s surface.
The melted rock–ice mixture also gave rise to the fluidised appearance of the debris blankets surrounding the largest crater.
Based on the lack of similar structures near the small craters in this image, scientists believe that only the most powerful impacts – those responsible for forging the largest craters – were able to dig deep enough to release part of the frozen reservoir of water lying beneath the surface.
Hephaestus Fossae perspective view
This image of Hephaestus Fossae was obtained by ESA’s Mars Express orbiter on 28 December 2007. The region is dotted with craters and channel systems and lies at about 21°N and 126°E on the Red Planet. Named after the Greek god of fire, Hephaestus Fossae extends for more than 600 km on the western flank of Elysium Mons in the Utopia Planitia region.
The surface is mostly smooth, and is covered by several small impact craters measuring 800 to 2800 m in diameter. Smaller craters are scattered across the entire region. The left side of the image shows a large impact crater measuring 20 km in diameter. Covering an area of approximately 150 sq km, a crater of this size on Earth could harbour cities such as Bonn or Kiel. In contrast to the smaller craters, it shows a blanket of ejecta with flow forms surrounding the rim.
Hephaestus Fossae perspective view
This image of Hephaestus Fossae was obtained by ESA’s Mars Express orbiter on 28 December 2007. The region is dotted with craters and channel systems and lies at about 21°N and 126°E on the Red Planet. Named after the Greek god of fire, Hephaestus Fossae extends for more than 600 km on the western flank of Elysium Mons in the Utopia Planitia region.
The surface is mostly smooth, and is covered by several small impact craters measuring 800 to 2800 m in diameter. Smaller craters are scattered across the entire region. The left side of the image shows a large impact crater measuring 20 km in diameter. Covering an area of approximately 150 sq km, a crater of this size on Earth could harbour cities such as Bonn or Kiel. In contrast to the smaller craters, it shows a blanket of ejecta with flow forms surrounding the rim.
Hephaestus Fossae perspective view
This image of Hephaestus Fossae was obtained by ESA’s Mars Express orbiter on 28 December 2007. The region is dotted with craters and channel systems and lies at about 21°N and 126°E on the Red Planet. Named after the Greek god of fire, Hephaestus Fossae extends for more than 600 km on the western flank of Elysium Mons in the Utopia Planitia region.
The surface is mostly smooth, and is covered by several small impact craters measuring 800 to 2800 m in diameter. Smaller craters are scattered across the entire region. A larger impact crater measuring 20 km in diameter is a prominent feature. Covering an area of approximately 150 sq km, this crater could harbour cities such as Bonn or Kiel. In contrast to the smaller craters, it shows a blanket of ejecta with flow forms surrounding the rim.
The large craters were formed when loose, soft material was ejected due to impact, and the smaller ones formed due to secondary impacts, when consolidated material was ejected in a ballistic path and impacted the original crater at varying distances. Most martian water exists in the form of subsurface ice. The presence of a blanket of ejecta and outflow channels around the crater suggest that the primary impact may have penetrated the surface enough to melt a buried frozen water reservoir.
For more information about Mars Express Mission, visit: http://www.esa.int/Our_Activities/Space_Science/Mars_Express
Images, Text, Credits: ESA / DLR / FU Berlin (G. Neukum).
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