Branched Features on the Floor of Antoniadi Crater
NASA/JPL-Caltech/UArizona
Branched Features on the Floor of Antoniadi Crater
ESP_012435_2015  Science Theme: Fluvial Processes
The dark branched features in the floor of Antoniadi Crater look like giant ferns, or fern casts. However, these ferns would be several miles in size and are composed of rough rocky materials.

A more likely hypothesis is that this represents a channel network that now stands in inverted relief. The channels may have been lined or filled by indurated materials, making the channel fill more resistant to erosion by the wind than surrounding materials. After probably billions of years of wind erosion the resistant channels are now relatively high-standing. The material between the branched ridges has a fracture pattern and color similar to deposits elsewhere on Mars that are known to be rich in hydrated minerals such as clays.

The inverted channels have short, stubby branches characteristic of formation by groundwater sapping. Spring water seeps into the channels and undercuts overlying layers which collapse, so the channels grow headward. These images tell the story of an ancient wet environment on Mars, where life could have been possible. Ancient Martian life was most likely to consist of microorganisms rather than giant tree ferns.

Written by: Alfred McEwen  (29 April 2009)

This is a stereo pair with ESP_012725_2015.
 
Acquisition date
22 March 2009

Local Mars time
15:31

Latitude (centered)
21.356°

Longitude (East)
61.276°

Spacecraft altitude
282.0 km (175.2 miles)

Original image scale range
28.3 cm/pixel (with 1 x 1 binning) so objects ~85 cm across are resolved

Map projected scale
25 cm/pixel and North is up

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Equirectangular

Emission angle
5.2°

Phase angle
61.5°

Solar incidence angle
66°, with the Sun about 24° above the horizon

Solar longitude
232.1°, Northern Autumn

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  331.5°
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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.