High-Altitude Clouds on Mars
High-Altitude Clouds on Mars
ESP_034342_1315  Science Theme: Mass Wasting Processes
The standard color images for this observation look really weird. The reason is apparent by looking at an animation of the color images. These were acquired in a particular sequence: first blue-green (BG), then RED, then infrared (IR), and the animation shows them in this sequence.

What we see are thin condensate clouds moving relative to surface features. They appear to move 200 meters distance over the 0.1855 second between the infrared and blue-green imaging, or 1.08 kilometers per second! Wait, that’s supersonic—can clouds do that? NO!

The MRO spacecraft also moved 603 meters along its orbit in that 0.1885 second frame, so from 260 kilometers altitude, we have a stereo convergence angle of 0.133 degrees. Such a small convergence angle would be useless for stereo imaging of surface features up to only about 1 kilometer high, but clouds can be much higher.

If the clouds were half as high as MRO (or 130 kilometers), they should appear to move 603 meters relative to surface features. Since they only moved 200 meters, their heights must be approximately 42 kilometers. Previous imaging experiments have measured Martian clouds up to 80 kilometers in height. High cirrus clouds on Earth extend up to about 12 kilometers in height, but the lower gravitational acceleration of Mars creates a more extended atmosphere. The high clouds on both Earth and Mars are composed of ice crystals, although on Mars they may be from carbon dioxide rather than dihydrogen monoxide (water).

Written by: Alfred McEwen  (29 January 2014)
Acquisition date
23 November 2013

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
251.8 km (156.5 miles)

Original image scale range
50.7 cm/pixel (with 2 x 2 binning) so objects ~152 cm across are resolved

Map projected scale
50 cm/pixel and North is up

Map projection

Emission angle

Phase angle

Solar incidence angle
80°, with the Sun about 10° above the horizon

Solar longitude
53.3°, Northern Spring

For non-map projected images
North azimuth:  96°
Sub-solar azimuth:  51.8°
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

Black and white
map-projected   (219MB)

IRB color
map-projected   (138MB)

Black and white
map-projected  (103MB)
non-map           (132MB)

IRB color
map projected  (44MB)
non-map           (113MB)

Merged IRB
map projected  (210MB)

Merged RGB
map-projected  (195MB)

RGB color
non map           (101MB)
B&W label
Color label
Merged IRB label
Merged RGB label
EDR products

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

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’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.