Contact between the Medusae Fossae Formation and Amazonis Planitia
NASA/JPL/University of Arizona
Contact between the Medusae Fossae Formation and Amazonis Planitia
PSP_006246_1910  Science Theme: Geologic Contacts/Stratigraphy
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Amazonis Planitia (seen in the northern half of this image) is one of the very flattest places on Mars. It is covered by vast floods of lava that have left a smooth lava plain.

The Medusae Fossae formation (seen in the southern half of this image) is a series of young wind-eroded deposits whose origin continues to be debated. It is generally thought to be composed of volcanic ash, perhaps like pumice on Earth. However, some scientists hypothesize that it is an equatorial ice-rich deposit.

In this image, it can be clearly seen that the Medusae Fossae formation is being eroded off of the Amazonis lavas. Pristine lava features can be seen emerging on either side of the ridges of wind eroding material. The thin wiggly ridges on the lava plains are “pressure ridges” formed by bucking of the lava crust while it flowed. The small cones, a few hundred meters or yards in diameter, that dot the lava plains formed when water underneath the lava turned to steam and exploded through the lava flow.

Today, these cones are still partly filled with Medusae Fossae formation materials. At least in this location, HiRISE finds no evidence for ice at or near the surface of the Medusae Fossae formation. Instead, the wind carved slopes are covered with dark streaks that formed as dry avalanches of dust.Written by: Laszlo P. Keszthelyi  (2 January 2008)
 
Acquisition date
26 November 2007

Local Mars time
14:17

Latitude (centered)
11.022°

Longitude (East)
202.659°

Spacecraft altitude
279.5 km (173.7 miles)

Original image scale range
from 28.0 cm/pixel (with 1 x 1 binning) to 55.9 cm/pixel (with 2 x 2 binning)

Map projected scale
25 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
0.1°

Phase angle
36.9°

Solar incidence angle
37°, with the Sun about 53° above the horizon

Solar longitude
353.2°, Northern Winter

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  344.9°
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HiView

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RGB: red-green-blue
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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/University of Arizona

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.