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Sirenum Fossae - False Color (THEMIS_IOTD_20250718a)

Sirenum Fossae - False Color (THEMIS_IOTD_20250718a)

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 a portion of Sirenum Fossae. The linear features are tectonic graben. Graben are formed by extension of the crust and faulting. When large amounts of pressure or tension are applied to rocks on timescales that are fast enough that the rock cannot respond by deforming, the rock breaks along faults. In the case of a graben, two parallel faults are formed by extension of the crust and the rock in between the faults drops downward into the space created by the extension. Numerous sets of graben are visible in this THEMIS image, trending from north-northeast to south-southwest. Because the faults defining the graben are formed perpendicular to the direction of the applied stress, we know that extensional forces were pulling the crust apart in the west-northwest/east-southeast direction. The Sirenum Fossae graben are 2735km (1700 miles) long and stretch from eastern Terra Sirenum into western Daedalia Planum.

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-20250718a

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 18, 2025

Tags:

THEMIS

Thermal Emission Imaging System

ASU

School of Earth and Space Exploration

SESE

odyssey

MSFF

Mars Space Flight Facility

Mars

Mars Odyssey

Sirenum Fossae

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