Water on Mars
Water on MarsWater on Mars exists almost exclusively as water ice. The Martian polar ice caps consist primarily of water ice, and further ice is contained in Martian surface rocks at more temperate latitudes (permafrost). A small amount of water vapor is present in the atmosphere. There are no bodies of liquid water on the Martian surface. Current conditions on the planet surface do not support the long-term existence of liquid water. The average atmospheric pressure and temperature are far too low, leading to immediate freezing and resulting sublimation. Despite this, research suggests that in the past there was liquid water flowing on the surface, creating large areas similar to Earth's oceans.
There are a number of direct and indirect proofs of water's presence either on or under the surface, e.g. stream beds, polar caps, spectroscopic measurement, eroded craters or minerals directly connected to the existence of liquid water (such as goethite), grey, crystalline hematite, phyllosilicates, opal, and sulfate. With the improved cameras on advanced Mars orbiters such as Viking, Mars Odyssey, Mars Global Surveyor, Mars Express, and the Mars Reconnaissance Orbiter pictures of ancient lakes, ancient river valleys, and widespread glaciation have accumulated. Besides the visual confirmation of water from a huge collection of images, an orbiting Gamma Ray Spectrometer found ice just under the surface of much of the planet. Also, radar studies discovered pure ice in formations that were thought to be glaciers. The Phoenix lander exposed ice as it landed, watched chunks of ice disappear, detected snow falling, and even saw drops of liquid water. Today, it is generally believed that Mars had abundant water very early in its history during which snow and rain fell on the planet and created rivers, lakes, and possibly oceans. Large clay deposits were produced. Life may even have come into existence. Large areas of liquid water have disappeared, but climate changes have frequently deposited large amounts of water-rich materials in mid-latitudes. From these materials, glaciers and other forms of frozen ground came to be. Small amounts of water probably melt on steep slopes from time to time and produce gullies. Recent images have also detected yearly changes on some slopes that may have been caused by liquid water. Although Mars is very cold at present, water could exist as a liquid if it contains salts. Salt is expected to be on the Martian surface. Details of how water has been discovered can be found in the sections that follow on the various orbiting and landing robots that have been sent to Mars. In addition, many bits and pieces of indirect evidence are listed here. Since several missions (Mars Odyssey, Mars Global Surveyor, Mars Reconnaissance Orbiter, Mars Express, Mars Opportunity Rover and Mars Curiosity Rover) are still sending back data from the Red Planet, discoveries continue to be made. One recent discovery, announced by NASA scientists on September 27, 2012, is that the Curiosity Rover found evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars.
An artist's impression of what ancient Mars may have looked like, based on geological data
Water on Mars
Interactive maps of MarsThe following interactive map of the planet Mars has embedded links to geographical features in addition to the noted Rover and Lander locations. Click on the features and you will be taken to the corresponding article pages. North is at the top; Elevations: red (higher), yellow (zero), blue (lower).