Apostrophe Dunes
Apostrophe Dunes
ESP_029660_1350  Science Theme: Aeolian Processes
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

Latitude (centered)

Longitude (East)

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

Emission angle

Phase angle

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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map-projected   (533MB)

IRB color
map-projected   (322MB)

Black and white
map-projected  (230MB)
non-map           (271MB)

IRB color
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non-map           (327MB)

Merged IRB
map projected  (165MB)

Merged RGB
map-projected  (155MB)

RGB color
non map           (323MB)
B&W label
Color label
Merged IRB label
Merged RGB label
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IRB: infrared-red-blue
RGB: red-green-blue
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Black & white is 5 km across; enhanced color about 1 km
For scale, use JPEG/JP2 black & white map-projected images

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