Bright and Dark Slope Streaks
Bright and Dark Slope Streaks
ESP_059261_1950  Science Theme: Mass Wasting Processes
Slope streaks are common in the tropics of Mars. Once thought to be caused by flowing water, most scientists now believe that they are avalanches of dust. They are typically darker than their surroundings and often fan outwards downslope. This suggests that the dust sediment is sticky, so that the avalanche broadens as it flows downhill.

Slope streaks are known to fade over time, but the slope streaks at this monitoring site in Arabia Terra go beyond that. Here, old slope streaks appear to be brighter than the surrounding terrain. A comparison between HiRISE images taken in 2008 and in 2019 shows very few changes in the dark and bright streaks.

We can see three new dark streaks in our more recent image. These were the only changes spotted among the hundreds of streaks observed in the monitoring site, suggesting that new streak formation and fading take place on time scales of at least decades.

Written by: Paul Geissler (narration: Tre Gibbs)  (21 September 2021)
Acquisition date
19 March 2019

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
276.2 km (171.7 miles)

Original image scale range
55.6 cm/pixel (with 2 x 2 binning) so objects ~167 cm across are resolved

Map projected scale
50 cm/pixel and North is up

Map projection

Emission angle

Phase angle

Solar incidence angle
36°, with the Sun about 54° above the horizon

Solar longitude
357.8°, Northern Winter

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  342.3°
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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.