Decoding a Dark Splotch
Decoding a Dark Splotch
ESP_016372_1975  Science Theme: Mass Wasting Processes
Geologists aren’t quite sure what to make of the dark splotch in the middle of this image, one of several similar dark splotches that extend east and west for over 100 kilometers. From measurements made in infrared, this and other dark splotches have what we call “high thermal inertia,” meaning that it heats up and cools down slowly. Scientists use thermal inertia to assess how rocky, sandy, or dusty a place is. A higher thermal inertia than the surrounding area means it’s less dusty.

Wavy, banded patterns in the dark splotch (possibly due to cross bedding from sand dunes that once occupied the area) were lithified into sandstone, and then eroded away. These clues could help geologists figure out what’s going on there.

Written by: Kirby Runyon (audio: Tre Gibbs)  (9 October 2017)

This is a stereo pair with PSP_008935_1975.
Acquisition date
23 January 2010

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
279.8 km (173.9 miles)

Original image scale range
from 28.1 cm/pixel (with 1 x 1 binning) to 56.3 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
40°, with the Sun about 50° above the horizon

Solar longitude
41.7°, Northern Spring

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  10.8°
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Black and white
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non-map           (424MB)

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non-map           (561MB)

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RGB color
non map           (549MB)
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Full resolution JP2 download
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Black & white is 5 km across; enhanced color about 1 km
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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.