Braided TARs in Syrtis Major
NASA/JPL/University of Arizona
Braided TARs in Syrtis Major
ESP_038227_2020  Science Theme: Composition and Photometry


1080p (MP4)
720p (MP4)
Listen to the text


800  1024
1152  1280
1440  1600
1920  2048
2560  2880


PDF, 11 x 17 in


Transverse aeolian ridges (TARs) are commonly found throughout the Martian tropics, including rocky regions such as Syrtis Major that are largely devoid of dust.

These bright wind-blown ripples most often occur in simple sets of ridges with regular size and spacing. Typical TARs stand a few meters tall and have a wavelength (that is to say, separation) of 30 to 60 meters. HiRISE has not detected any changes among the TARs today, suggesting that they are inactive.

In this scene, we see TARs with a highly unusual morphology. Instead of single ridges, we see sets of small ridges that are separated by about 50 meters. The smaller ripples are spaced only 5 to 8 meters apart. Between the smaller ripples are even smaller striations that are perpendicular to the ridge crests with regular spacings of less than 2 meters.

This image raises a number of puzzling questions. Why are the ripples organized into two distinct wavelengths? Did the different wavelengths result from different processes or from different conditions? When did these wavelength-specific conditions or processes take place? Did they occur together, or did they alternate, or did one take place after the other? Were the processes depositional or erosional, or both?

The complexity of Martian TARs makes us think twice about any single explanation for their origin.

Written by: Paul Geissler (audio: Tre Gibbs)  (3 December 2014)
twitter  •  facebook  •  google+  •  tumblr
Acquisition date
22 September 2014

Local Mars time:

Latitude (centered)

Longitude (East)

Range to target site
279.7 km (174.8 miles)

Original image scale range
56.0 cm/pixel (with 2 x 2 binning) so objects ~168 cm across are resolved

Map projected scale
50 cm/pixel and North is up

Map projection

Emission angle:

Phase angle:

Solar incidence angle
62°, with the Sun about 28° above the horizon

Solar longitude
200.6°, Northern Autumn

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  343.2°
Black and white
map projected  non-map

IRB color
map projected  non-map

Merged IRB
map projected

Merged RGB
map projected

RGB color
non-map projected

Black and white
map-projected   (197MB)

IRB color
map-projected   (115MB)

Black and white
map-projected  (99MB)
non-map           (101MB)

IRB color
map projected  (40MB)
non-map           (107MB)

Merged IRB
map projected  (203MB)

Merged RGB
map-projected  (181MB)

RGB color
non map           (97MB)
B&W label
Color label
Merged IRB label
Merged RGB label
EDR products

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

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

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.