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Proctor Crater Dunes - False Color (THEMIS_IOTD_20250730a)

Proctor Crater Dunes - False Color (THEMIS_IOTD_20250730a)

The THEMIS VIS camera contains 5 filters. The data from different filters can be combined in multiple ways to create a false color image. These false color images may reveal subtle variations of the surface not easily identified in a single band image. Today's false color image shows sand dunes within Proctor Crater. These dunes are composed of basaltic sand that has collected in the bottom of the crater. The topographic depression of the crater forms a sand trap that prevents the sand from escaping. Dune fields are common in the bottoms of craters on Mars and appear as dark splotches that lean up against the downwind walls of the craters. Dunes are useful for studying both the geology and meteorology of Mars. The sand forms by erosion of larger rocks, but it is unclear when and where this erosion took place on Mars or how such large volumes of sand could be formed. The dunes also indicate the local wind directions by their morphology. In this case, there are few clear slipfaces that would indicate the downwind direction. The crests of the dunes also typically run north-south in the image. This dune form indicates that there are probably two prevailing wind directions that run east and west (left to right and right to left). Proctor Crater is located in Noachis Terra and is 172km (107miles) in diameter.

The THEMIS VIS camera is capable of capturing color images of the Martian surface using five different color filters. In this mode of operation, the spatial resolution and coverage of the image must be reduced to accommodate the additional data volume produced from using multiple filters. To make a color image, three of the five filter images (each in grayscale) are selected. Each is contrast enhanced and then converted to a red, green, or blue intensity image. These three images are then combined to produce a full color, single image. Because the THEMIS color filters don't span the full range of colors seen by the human eye, a color THEMIS image does not represent true color. Also, because each single-filter image is contrast enhanced before inclusion in the three-color image, the apparent color variation of the scene is exaggerated. Nevertheless, the color variation that does appear is representative of some change in color, however subtle, in the actual scene. Note that the long edges of THEMIS color images typically contain color artifacts that do not represent surface variation.

This martian scene spans 17 x 62 kilometers (11 x 38 miles). To see where on Mars this area lies, and to download high-resolution versions of the image go to themis.asu.edu/zoom-20250730a

See the Red Planet Report at redplanet.asu.edu for updates on Mars research and exploration. For more about Mars geology, check out the Mars-ePedia: marsed.asu.edu/marsepedia

For the latest THEMIS Mars images as received by mission scientists, see themis.asu.edu/livefrommars. To learn more about the THEMIS camera and its Mars images, see themis.asu.edu

This image is in the public domain and may be republished free of charge. If used, please credit it as NASA/JPL-Caltech/Arizona State University.

Taken on: July 30, 2025

Tags:

THEMIS

Thermal Emission Imaging System

ASU

School of Earth and Space Exploration

SESE

odyssey

MSFF

Mars Space Flight Facility

Mars

Mars Odyssey

Proctor Crater

dunes

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