Bizarre TARs
NASA/JPL/UArizona
Bizarre TARs
ESP_042124_1665  Science Theme: Aeolian Processes
These strange features in Syria Planum are still being widely debated. They have the same general form as transverse aeolian ridges (TARs) elsewhere on Mars; windblown deposits that are common in the Martian tropics. Their height and spacing are similar to the more familiar looking TARs in other places, and they are similarly bright. Unless Nature is perverse, they were both made by the same process.

Yet the TARs here in Syria Planum appear different than typical TARs elsewhere on the planet. They have blunt edges, in contrast to the tapering ends of typical TARs. The ridge crests are serrated, unlike the smooth crests of most TARs. They are layered on their upwind faces and scoured on the downwind sides, whereas TARs are usually smooth and symmetric. Why are these TARs bizarre?

A possible answer is that the features here in Syria Planum are at a different stage of evolution than TARs elsewhere, and are either younger or older than typical TARs. We can look at an enhanced color cutout* to see whether this can be the case.

Our cutout covers the width of the color strip (1 kilometer) and is centered on a bare patch in a field of bright TARs. The illumination direction is from the top left, and the wind direction is from top to bottom. At first glance, these TARs look like they could be old, degraded versions of the TARs with which we are familiar. However, erosion tends to smooth things out and not create sharp edges where none existed previously. More likely, we are seeing TARs in the process of formation. The distinctive features of the TARs in Syria Planum — the blunt edges, serrated ridges, and the asymmetric appearance of the surface — are features that are more easily removed than created by erosion.

*Note: the cutout is non-map projected, so approximate north is down.




Written by: Paul Geissler  (16 September 2015)
 
Acquisition date
22 July 2015

Local Mars time
14:38

Latitude (centered)
-13.339°

Longitude (East)
253.784°

Spacecraft altitude
252.3 km (156.8 miles)

Original image scale range
25.3 cm/pixel (with 1 x 1 binning) so objects ~76 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
4.9°

Phase angle
40.3°

Solar incidence angle
44°, with the Sun about 46° above the horizon

Solar longitude
16.7°, Northern Spring

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  31.2°
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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.