Apostrophe Dunes
NASA/JPL/University of Arizona
Apostrophe Dunes
ESP_029660_1350  Science Theme: Aeolian Processes
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While most barchan dunes (also known as crescent dunes) on the Earth and Mars are near-symmetric in shape with two horns pointing down-wind (for example: PSP_007676_1385 or ESP_026745_2540), these dunes only have one pointy horn. Their other “horn” is very rounded and the steep slipface (the smooth slope between the horn and the rounded side that only forms in the sheltered downwind side of the dune) is offset from the middle.

The lack of symmetry within these dunes tells us that there is more than one wind direction acting here. The dominant wind within this region is along the direction of the horns (both the rounded and pointed one), or from the bottom-left of the image. Another wind then alters the basic dune shape. Most likely, a more recent or weaker wind is coming in from the left, thus causing one horn to elongate and the slipface to be offset.

Written by: Serina Diniega  (5 December 2012)
 
Acquisition date
23 November 2012

Local Mars time
15:44

Latitude (centered)
-44.715°

Longitude (East)
331.100°

Spacecraft altitude
255.8 km (159.0 miles)

Original image scale range
from 25.6 cm/pixel (with 1 x 1 binning) to 51.2 cm/pixel (with 2 x 2 binning)

Map projected scale
25 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
1.1°

Phase angle
56.1°

Solar incidence angle
57°, with the Sun about 33° above the horizon

Solar longitude
212.3°, Northern Autumn

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  20.2°
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Merged IRB
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Merged RGB
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RGB color
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map-projected   (533MB)

IRB color
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JP2 EXTRAS
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map-projected  (230MB)
non-map           (271MB)

IRB color
map projected  (82MB)
non-map           (327MB)

Merged IRB
map projected  (165MB)

Merged RGB
map-projected  (155MB)

RGB color
non map           (323MB)
ADDITIONAL INFORMATION
B&W label
Color label
Merged IRB label
Merged RGB label
EDR products
HiView

NB
IRB: infrared-red-blue
RGB: red-green-blue
About color products (PDF)

Black & white is 5 km across; enhanced color about 1 km
For scale, use JPEG/JP2 black & white map-projected images

USAGE POLICY
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/JPL/University of Arizona

POSTSCRIPT
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.