HiRISE | A Sinuous Ridge in Mareotis Fossae (ESP_088990

NASA/JPL-Caltech/UArizona

A Sinuous Ridge in Mareotis Fossae
ESP_088990_2150 Science Theme: Volcanic Processes

This curious sinuous ridge is located on the floor of Mareotis Fossae, a system of canyons/fractures that trend in a radial direction from Alba Mons.

The sinuous ridge is approximately 10 meters wide and several kilometers long. The floor surrounding this ridge has been eroding laterally, forming pits and circular features suggestive of removal (sublimation) of subsurface ice. However, landforms such as channels or moraines that might suggest the presence of water or ice are lacking, so the ridge itself does not appear to have formed by fluvial or glacial processes.

Perhaps this curious feature is an exhumed dike formed from magma emanating from Alba Mons in subsurface fractures.

Written by: Ginny Gulick (16 February 2026)

Acquisition date
21 July 2025

Local Mars time
15:21

Latitude (centered)
34.556°

Longitude (East)
267.972°

Spacecraft altitude
286.8 km (178.2 miles)

Original image scale range
57.7 cm/pixel (with 2 x 2 binning) so objects ~173 cm across are resolved

Map projected scale
50 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
5.7°

Phase angle
50.9°

Solar incidence angle
45°, with the Sun about 45° above the horizon

Solar longitude
113.6°, Northern Summer

For non-map projected images
North azimuth: 97°
Sub-solar azimuth: 5.5°

JPEG
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

JP2
Black and white
map-projected   (208MB)

IRB color
map-projected   (122MB)

JP2 EXTRAS
Black and white
map-projected (110MB)
non-map           (141MB)

IRB color
map projected (40MB)
non-map           (100MB)

Merged IRB
map projected (217MB)

Merged RGB
map-projected (200MB)

RGB color
non map           (93MB)

ADDITIONAL INFORMATION
B&W label
Color label
Merged IRB label
Merged RGB label
EDR products
HiView

NB
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

USAGE POLICY
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-Caltech/UArizona

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.