Craters and channels in Hephaestus Fossae

Hephaestus Fossae lies at about 21° North and 126° East on the Red Planet. Named after the Greek god of fire, it extends for more than 600 km on the western flank of Elysium Mons in the Utopia Planitia region.

Obtained on 28 December 2007, the images have a ground resolution of about 16 m/pixel. They show that the region has channel systems of unknown origin.

The images cover 170 x 80 sq km, an area almost as large as Montenegro. The surface is mostly smooth, and is covered by several small impact craters 800-2800 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.

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.

This ortho-image was rectified using elevation data derived from a high-resolution Digital Terrain Model, or DTM (obtained from HRSC data), such that distortions introduced during imaging are corrected. Such an image can be used to derive maps. Elevation data from the DTM has been colour-coded and overlain on the ortho-image so that elevation data and the image itself are displayed in a single scene. The scale is in metres. High resolution image (1.7 MB). Credit: ESA/DLR/FU Berlin (G. Neukum)




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. High resolution image (1.3 MB). Credit: ESA/DLR/FU Berlin (G. Neukum)




High resolution image (1.4 MB). Credit: ESA/DLR/FU Berlin (G. Neukum)




High resolution image (1.4 MB). Credit: ESA/DLR/FU Berlin (G. Neukum)

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.

Since the smaller impact craters show neither a blanket of ejecta nor any kind of outflow channel, they did not impact the surface strongly enough to reach the subsurface ice. It is possible to calculate the depth of a possible frozen water reservoir beneath the surface by determining the depth of the impact craters.

The colour scenes have been derived from the three HRSC-colour channels and the nadir channel. The perspective views have been calculated from the digital terrain model derived from the stereo channels.

Source: European Space Agency
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