ESA Mars Express: Winter in Hooke crater in Argyre basin

Perspective view of Hooke crater in Argyre basin taken by the High Resolution Stereo Camera (HRSC) on ESA’s Mars Express. 

Credit: ESA /DLR

Over billions of years, the southern uplands of Mars have been pockmarked by numerous impact features, which are often so closely packed that they overlap.

One such feature is Hooke crater, shown in this frost-tinged scene, imaged by ESA’s Mars Express during winter in the southern hemisphere.

Hooke crater. Credit: ESA

Hooke crater is located near the northern edge of the 1800 km-wide Argyre basin, one of the most impressive impact structures on Mars, excavated in a giant collision about 4 billion years ago.

Sitting in a flat part of the basin known as Argyre Planitia, Hooke crater has a diameter of 138 km and a maximum depth of about 2.4 km.

It is named after the English physicist and astronomer Robert Hooke (1635–1703).

Hooke crater comprises two different impact structures, with a smaller impactor blasting a depression off-centre in the floor of a larger, pre-existing crater.

High Resolution Stereo Camera (HRSC)

The newer crater in the centre is filled with a large mound topped by a dark dune field. The mound appears to be composed of layered material, possibly alternating sheets of sand and frost.

Dark dunes also spread southwards (to the left in the topographic, main colour and 3D images) from the smaller crater, partially covering the floor of the main crater.

The local topography modifies the airflow, serving as a sand trap for the wind-blown sediments.

Hooke crater topography. Credit: ESA

In these images, much of the low-lying region to the south, as well as the central mound inside Hooke crater, is covered with a thin, white coating of carbon dioxide frost.

At higher elevations and on north-facing crater walls, the frost is largely absent and appears only in areas shaded from direct sunlight by the walls of smaller craters.

Outside the crater, there are a number of linear features visible on the floor of Argyre Planitia, on the south (left) side of the topographic, main colour and 3D images.

These are examples of ‘yardangs’, rocky ridges that have been shaped by prolonged wind erosion.

Most of the yardangs are oriented towards Hooke crater, indicating the prevailing wind direction.

An artist view of the HRSC on ESA Mars Express scanning the Mars mesas. 

Credit: ESA /DLR

Also visible on the floor of the Argyre basin are small areas of chaotic terrain, which resemble depressions containing flat-topped mesas, buttes and hills.

In the topographic, main colour and 3D images, one of these regions can be seen at the top edge, about a third of the way from the left, and another in the lower middle part, down from the left-most edge of the crater.

Chaotic terrains like these are thought to have been created when large-scale melting of ground ice caused the ground to collapse.

Where the terrain has not collapsed completely, the larger mesas may still contain substantial water ice.

ESA’s Mars Express Image: MARS Olympus Mons by the High Resolution Stereo Camera

A portion of the southeastern flank of Olympus Mons as imaged by the High Resolution Stereo Camera on ESA’s Mars Express on 21 January 2013 (orbit 11524), with a ground resolution of approximately 17 m per pixel. 

The image centre is located at approximately 14°N / 229°E. North is to the right. 

The image highlights the stark contrast between the hundreds of narrow, individual lava flows on the flanks of the volcano, and the smooth lava plains that surround it. 

Credit: ESA/DLR/FU Berlin (G. Neukum)

Hundreds of individual lava flows are seen frozen in time on the flanks of Olympus Mons, the largest volcano in the Solar System.

The images, taken on 21 January 2013 by ESA's Mars Express, focus on the southeast segment of the giant volcano, which towers some 22 km above the surrounding plains. This is more than double the height of Mauna Kea, the tallest volcano on Earth at 10 km, when measured from its oceanic base to summit.

Like Mauna Kea, Olympus Mons is a shield volcano, with gently sloping sides that extend outwards at low angles. But unlike other shield volcanoes, it has an abrupt cliff edge, or scarp, separating it from the surrounding plains.

The scarp circles the entire volcano, in places reaching 9 km high. It was likely formed during a number of catastrophic landslides on the flanks of the volcano, during which the resulting debris was transported several hundred kilometres beyond the extent of these images.

Lava flows cover the base of the volcano, punctuated by a handful of pointy and flat-topped blocks that were either rotated or uplifted during the collapse. The transition from the towering heights of the volcano down onto the flat lava plain at the base of the scarp can be easily seen in the colour-coded topography image.

Lava once flowed down the flanks of the Olympus Mons volcano, spilling out onto the surrounding plains.

Here, the paths of numerous individual lava flows can be seen curving around natural obstacles and cascading like waterfalls over cliff edges. 

Random pointed and flat-topped blocks protrude from the flank edges, rotated or uplifted as the sides of the volcano collapsed. 

Only a few very faint traces of ancient lava channels can be seen in the surrounding plain, which was flooded by a later outpouring of lava.

The image was taken by the High Resolution Stereo Camera on ESA’s Mars Express on 21 January 2013 (orbit 11524), with a ground resolution of approximately 17 m per pixel. 

The image centre is located at approximately 14°N / 229°E. 

Credit: ESA/DLR/FU Berlin (G. Neukum)

In the leading colour image and perspective views, extensive networks of narrow, overlapping lava flows are proof of an extremely active volcanic past.

The lava, long since solidified, once spilled down the natural contours of the volcano, spreading out into broad fans as it reached the scarp and plains below.

Flows that ended before reaching the scarp did so with rounded tongues, as the lava cooled and crept to a stop.

Some lava flows are bounded by steep channel walls, while others were contained in lava tubes. Zooming in to the top left portion of the flank in the leading image reveals one example of an ancient lava tube, its winding track partially exposed in channel segments where the roof of the tunnel has since collapsed.

The chaotic lava flows on the flanks provide a stark contrast to the smooth plains seen surrounding the volcano.

ESA Mars Express - Deep faults and disrupted crater at Acheron Fossae

This is an image taken by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express of the Acheron Fossae region, an area of intensive tectonic (continental ‘plate’) activity in the past.

Other images of this region are available here at ESA website.

Acheron Fossae marks the northern edge of the Tharsis plateau. It is part of a network of extensional fractures that radiates outward from their central focus in the Tharsis ‘bulge’, a huge area of regional uplift where intensive volcanic activity occurred.

Mars Tharsis Plateau

These curved ‘faults’ were caused in the process of this uplift: cracks in the crust formed when the hot material rising from deep in the mantle of Mars pushed the overlying ‘elastic’ lithosphere (surface layers of rock) upward.

When the distorting tensions became too strong, the brittle crust on top of the lithosphere broke along zones of weakness.

The image, from orbit 37, are dominated by these curved features, showing a highly fractured, faulted and deformed area in the central part of the Acheron Fossae.

The feature is situated at approximately 35º-40º North and 220º-230º East, about 1000 kms north of the large Olympus Mons volcano.


Credits: ESA/DLR/FU (G. Neukum)

ESA MARS Express: Hi-Res Image - Volcanic ash in Meridiani Planum

Hi-Res images from ESA's Mars Express.

Meridiani Planum, at the northern edge of the southern highlands of Mars, lies between the volcanic Tharsis Region to the west and the low-lying Hellas Planitia impact basin to the south-east.

Through a telescope, Meridiani Planum is a striking, dark feature, close to the martian equator.

It extends 127 km by 63 km and covers an area of roughly 8000 sq km, about the size of Cyprus. This dark material probably resembles volcanic ash, which is predominantly composed of minerals such as pyroxene and olivine.

Deposits of volcanic ash colour this view of the Meridiani Planum, as seen by the Mars Express High Resolution Stereo Camera. They also give clues to the prevailing wind direction in this region of Mars.

Meridiani Planum, a plain at the northern edge of the southern highlands of Mars, is half way between the volcanic Tharsis Region to the west and the low-lying Hellas Planitia impact basin to the south-east.
 
Through a telescope, Meridiani Planum is a striking, dark feature, close to the martian equator.

For more information and images go to ESA Mars Express website: Hi-Res images from ESA's Mars Express.