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Nereidum Montes helps unlock Mars' glacial past

The images captured by Mars Express show a portion of the region that displays multiple fluvial, glacial, and wind-driven features.
Nereidum_Montes
High-Resolution Stereo Camera (HRSC) nadir and color channel data taken during revolution 10,736 on June 6, 2012, by ESA’s Mars Express have been combined to form a natural-color view of Nereidum Montes. Centered at around 40°S and 310°E, the image has a ground resolution of about 23m per pixel. It shows a portion of the extensive region, with concentric crater fill in many of the craters towards the east (lower part of the image). Undulations in crater floors are commonly seen in mid-latitude regions on Mars and are believed to be a result of glacial movement. // Credits: ESA/DLR/FU Berlin (G. Neukum)
On June 6, the high-resolution stereo camera on ESA’s Mars Express revisited the Argyre Basin, but this time aiming at Nereidum Montes, some 236 miles (380 kilometers) northeast of Hooke Crater.

The stunning rugged terrain of Nereidum Montes marks the far-northern extent of Argyre, one of the largest impact basins on Mars. Nereidum Montes stretches almost 715 miles (1,150km) and was named by the noted Greek astronomer Eugène Michel Antoniadi (1870–1944).

Based on his extensive observations of Mars, Antoniadi famously concluded that the “canals” on Mars reported by Percival Lowell were, in fact, just an optical illusion.

The images captured by Mars Express show a portion of the region that displays multiple fluvial, glacial, and wind-driven features.
Nereidum_Montes_1
Nereidum Montes seen in broader context at the northern edge of the Argyre Basin. The smaller rectangle shows the region covered in this ESA Mars Express HRSC image release. // Credit: NASA MGS MOLA Science Team
Extensive dendritic drainage patterns were formed when liquid water drained into deeper regions within the area.

On Earth, treelike channels of this kind are usually formed by surface runoff after significant rainfall, or when snow or ice melts. Similar processes are thought to have occurred on Mars in the distant past.

Several of the craters within the region, particularly in the eastern parts, show concentric crater fill, a distinctive martian process marked by rings of surface fluctuations within a crater rim.

The ratios between the diameter and depth of the filled craters suggest that there may still be water ice, possibly in the form of ancient glaciers, present below the dry surface debris cover. Scientists have estimated that the water-ice depth in these craters varies from several tens up to hundreds of meters.
Nereidum_Montes_2
This color-coded plan view is based on an ESA Mars Express HRSC digital terrain model of the region, from which the topography of the landscape can be derived. The color coding enhances the visibility of the rippling sand dunes which formed in the wind-sheltered sides of the mounds and canyons. Centered at around 40°S and 310°E, the image has a ground resolution of about 23m per pixel. Taken during revolution 10,736 June 6, 2012. // Credit: ESA/DLR/FU Berlin (G. Neukum)
The largest crater on the southwestern side appears to have spilled out a glacier-like formation toward lower-lying parts of the region (shown as blue in the topographic image). A smooth area to the east of (below) the glacial feature appears to be the youngest within the image, evidenced by an almost complete lack of cratering.

Another indication of subsurface water is seen in the fluidized ejecta blanket surrounding the crater at the northern edge. These ejecta structures can develop when a comet or asteroid hits a surface saturated with water or water ice.

Finally, throughout the images and often near the wind-sheltered sides of mounds and canyons, extensive rippling sand dune fields are seen to have formed.

In-depth studies of regions such as Nereidum Montes play an essential role in unlocking the geological past of our terrestrial neighbor, as well as helping to find exciting regions for future robotic and human explorers to visit.

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