The Enduring Charm of Martian Spiders
The Enduring Charm of Martian Spiders
ESP_056927_0940  Science Theme: Seasonal Processes
Araneiform terrain (colloquially: spider-like terrain) is located in the south polar region of Mars and evolves in appearance over the spring and summer. In the season shown here, the thin bright lines on the surface (the spider legs) are troughs and many of these features have dark fan-shaped markings emanating from them.

Our current theory for how these patterns are formed is that during winter a carbon dioxide ice layer develops over the surface. When sun rays strike this surface, this carbon dioxide ice acts in a similar way to our atmosphere: it allows the sun light to penetrate but traps the infrared radiation creating a greenhouse-like effect.

The trapped heat transforms the ice at the bottom of the layer to gas, building up pressure until it bursts through. When that happens, the gas flows out in geyser-like fashion and carries dust with it, which falls back to the surface to form the dark fans.

Written by: M. Ramy El-Maarry  (10 December 2018)
Acquisition date
18 September 2018

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
245.7 km (152.7 miles)

Original image scale range
24.6 cm/pixel (with 1 x 1 binning) so objects ~74 cm across are resolved

Map projected scale
25 cm/pixel

Map projection

Emission angle

Phase angle

Solar incidence angle
66°, with the Sun about 24° above the horizon

Solar longitude
252.2°, Northern Autumn

For non-map projected images
North azimuth:  128°
Sub-solar azimuth:  43.1°
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Black & white is 5 km across; enhanced color about 1 km
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All of the images produced by HiRISE and accessible on this site are within the public domain: there are no restrictions on their usage by anyone in the public, including news or science organizations. We do ask for a credit line where possible:

NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA’s Science Mission Directorate, Washington. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona.