Detailed imaging of the surface of Mars from orbit has allowed space scientists to produce the most detailed geological map yet of part of the Red Planet. The new map was released on Friday, 12 December, by the U.S. Geological Survey (USGS) to show the structure and nature of rocks in a martian grand canyon. It was produced using data sent back from the High Resolution Imaging Science Experiment (HiRISE) camera on board the Mars Reconnaissance Orbiter which has been studying the planet since 2006. It was launched in August 2005. The map covers a region called western Candor Chasma, which is one of the largest canyons in the Valles Marineris system, often dubbed the "Grand Canyon of Mars". Its creators say its scale gives information as detailed as if a field geologist had been surveying the landscape, and will help answer questions about how the canyon formed. This gave the map a unique feature -- a resolution, or scale, that is detailed enough for the USGS to use the same mapping standards as they would employ for terrestrial geological and structural charts. It is the first time this has been achieved for a planet other than Earth.
The map, which is available for free download online, casts light on past geological processes on Mars and provides new targets for scientists to continue their search for potentially habitable environments. Laszlo Kestay, USGS Astrogeology Science Center Director, said in announcing the new map: "One can see this map as a preview of the kind of geology humans will conduct when we eventually land on Mars. "This also demonstrates how the very high resolution topographic and image data we can obtain from Mars' orbit enables scientific studies on par with rovers and other spacecraft that land on Mars." Previous suggestions for how Candor Chasma collected its deposited material include sediment accumulation in lakebeds, volcanic eruptions beneath glaciers in the canyons and the accumulation of wind-blown sand and dust. The HiRISE images show for the first time detailed structures in the rocks that reveal their origin.
USGS scientist and map author Dr Chris Okubo said, announcing its release: "This new map shows that at the time these sediments were deposited, a part of west Candor Chasma, specifically Candor Colles, contained numerous shallow, spring-fed lakes. "These lakes helped to trap wind-blown sand and dust, which accumulated over time and formed the extensive sedimentary deposits we see today." The conditions observed in the canyon are being compared to those in playa lakes in the American west, such as in Death Valley, California. The mapping study also shows that seismic shaking, or "marsquakes" affected wet sediments in the canyon, and were related to movement along several large faults in the area.
The quakes caused the sediments to liquefy to form features called injectite megapipes, which are now a series of low hills covering the map. They are known as the Candor Colles, after which the new geologic map is named.