The surface of Mars

Researchers have calculated that carbon dioxide snow particles on Mars are roughly the size of a human red blood cell. Martian snow is depicted in this artist's rendering as a mist or fog that eventually settles to the surface.

A TextureCam analysis of a Mars image is able to distinguish rocks from soil.

A Martian dust devil roughly 12 miles (20 kilometers) high was captured winding its way along the Amazonis Planitia region of northern Mars on March 14, 2012 by NASA's Mars Reconnaissance Orbiter. (NASA/JPL-Caltech/UA)

This image mosaic taken by the Mars Exploration Rover Spirit's panoramic camera shows a new slice of martian real estate southwest of the rover's landing site. The landscape shows little variation in local topography, though a narrow peak only seven to eight kilometres away is visible on the horizon. A circular depression, similar to the one dubbed Sleepy Hollow, can be seen in the foreground. Compared to the Viking and Pathfinder landing sites, the terrain at Gusev Crater, Spirit's landing site, is flat and speckled with a sparse array of rocks. The picture was released by the Jet Propulsion Laboratory in Pasadena, California Janaury 10, 2004. EDITORIAL USE ONLY (CREDIT : REUTERS/NASA/JPL/Arizona State University/Cornell University/Handout)

A view of Eberswalde crater containing a rare case of a martian delta, with well preserved channels which fed the lake in the crater, located in the southern highlands of Mars, seen in this handout photograph acquired by Mars Express at approximately 25S / 326E during orbit 7208 on August 15, 2009 and released September 2, 2011. The delta deposits and channels together provide a clear indication of liquid surface water during the early history of Mars. The images have a ground resolution of about 22 m per pixel. Reuters

A close-up of the sunset on Sol 24 as seen by the Imager for Mars Pathfinder was released by the Jet Propulsion Labratory August 27. The red sky in the background and the blue around the Sun are approximately as they would appear to the human eye but the color of the Sun itself is not correct -- the Sun was overexposed in each of the 3 color images that were used to make the picture. The true color of the Sun itself may be near white or slightly bluish.

Mars' Victoria Crater at Meridiani Planum is seen in this image taken by NASA's High Resolution Imaging Science Experiment (HiRISE) camera in this picture released October 6, 2006. NASA officials gave conflicting views during a meeting of space scientists on December 13, 2006, on whether the construction of a moon base will mark a great leap in planning for a manned mission to Mars or prove a wasteful diversion of funds. FOR EDITORIAL USE ONLY REUTERS/NASA/JPL/Caltech/Handout (UNITED STATES)

A portion of the west rim of Endeavour crater sweeps southward in this color view from NASA's Mars Exploration Rover Opportunity released by NASA August 10, 2011. This crater has a diameter of about 14 miles (22 km). This view combines exposures taken by Opportunity's panoramic camera (Pancam) of the rover's work on Mars August 6, 2011. Opportunity arrived at the rim during its next drive on August 9, 2011. Endeavour crater has been the rover team's destination for Opportunity since the rover finished exploring Victoria crater in August 2008. Endeavour offers access to older geological deposits than any Opportunity has seen before. The lighter-toned rocks closer to the rover in this view are similar to the rocks Opportunity has driven over for most of the mission. However, the darker-toned and rougher rocks just beyond that might be a different type for Opportunity to investigate. The ground in the foreground is covered with iron-rich spherules, nicknamed "blueberries," which Opportunity has observed frequently since the first days after landing. They are about 0.2 inch (5 millimeters) or more in diameter. REUTERS/NASA/JPL-Caltech/Cornell/ASU/Handout (UNITED STATES - Tags: SCI TECH) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS

A handout of the European Space Agency ESA shows a visualisation of Mars, created from spacecraft imagery. ESA's first mission to the Red Planet is Mars Express. It comprises an orbiter carrying seven scientific instruments to probe the planet's atmosphere, structure and geology, including a search for evidence of hidden water. The main spacecraft will also release the UK's small Beagle 2 lander to gather and test rock and soil samples on the surface. British space probe Beagle 2 failed to broadcast a signal on December 25, 2003, to confirm it had landed on Mars, but scientists said they were waiting for a second contact opportunity later on Thursday. REUTERS/Ho/European Space Agency ESA

In this image released January 19, 2005, NASA's Mars Exploration Rover "Opportunity": has found an iron meteorite on Mars, the first meteorite of any type ever identified on another planet. The pitted, basketball-size object is mostly made of iron and nickel. This composite combines images taken through the panoramic camera's 600-nanometer (red), 530-nanometer (green), and 480-nanometer (blue) filters REUTERS/NASA/JPL/Cornell/Handout SSM

NASA's Phoenix Mars Lander's Surface Stereo Imager shows two trenches dug by Phoenix's Robotic Arm in this image taken June 8, 2008, the 14th Martian day after landing. Soil from the right trench, informally called "Baby Bear," was delivered to Phoenix's Thermal and Evolved-Gas Analyzer, or TEGA, on June 6, 2008. Picture taken June 8, 2008. REUTERS/NASA/JPL-Caltech/University of Arizona/Texas A&M University/Handout (UNITED STATES). FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS.

A cliff, up to 4,000 m high, located in the eastern part of Echus Chasma, one of the largest water source regions on Mars, is seen in this image taken by the High-Resolution Stereo Camera (HRSC) on board ESAís Mars Express and made available July 14, 2008. Echus Chasma is the source region of Kasei Valles which extends 3,000 km to the north. The dark regions REUTERS/ESA/DLR/FU Berlin/G.Neukum/Handout. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS.

The High-Resolution Stereo Camera (HRSC) on board ESA?s Mars Express has returned images of Echus Chasma in this image made available on July 14, 2008. Echus Chasma is an approximately 100 km long and 10 km wide incision in the Lunae Planum high plateau north of Valles Marineris, the ?Grand Canyon? of Mars.

One of the first color images from the Phoenix Mars Lander shows the surface of Mars after the Phoenix Mars Lander spacecraft landed successfully in the first-ever touchdown near Mars' north pole May 25, 2008. REUTERS/NASA,JPL, Caltech, University of Arizona/Handout. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS.

An artist's conception shows what NASA's Mars Reconnaissance Orbiter has revealed, vast Martian glaciers of water ice under protective blankets of rocky debris at much lower latitudes than any ice previously identified on the Red Planet. Scientists analyzed data from the spacecraft's ground-penetrating radar and report in the November 21, 2008 issue of the journal Science that buried glaciers extend for dozens of miles from edges of mountains or cliffs. REUTERS/NASA/Handout (UNITED STATES) QUALITY FROM SOURCE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS.

This magnified look at the martian soil near the Mars Exploration Rover Opportunity's landing site, Meridiani Planum, shows coarse grains sprinkled over a fine layer of sand, in this image released by NASA's Jet Propulsion Laboratory in Pasadena, California, February 4, 2004. The image was captured on the 10th day of the rover's mission by its microscopic imager and roughly approximates the color a human eye would see. Opportunity, NASA's second of two roving Mars probes, rolled ten feet off its lander onto Mars on January 31.