NASA Press Release

Mars has inspired our imagination over the centuries, and has been the focus of intense scientific interest for many years. Mars has shown itself to be the most Earth-like of all the planets; it has polar ice caps that grow and recede with the change of seasons, and markings that appear to be similar to water channels on Earth. It is a small rocky planet that developed relatively close to the Sun and has been subjected to some of the same planetary processes associated with the formation of the other "terrestrial" planets like Mercury, Venus, and Earth. Martian tectonics-the formation and change of a planet's crust--differs from Earth's. Where Earth tectonics involve sliding plates that grind against each other or spread apart in the seafloors, Martian tectonics seem to be vertical, with hot lava pushing upwards through the crust to the surface. Mars has some remarkable geological characteristics including: the largest volcanic mountain in the solar system, Olympus Mons (27 km high and 600 km across). Volcanoes in the northern Tharsis region are so huge they deformed the planet's shape. There is also a gigantic equatorial rift valley called the Vallis Marineris which is a canyon system that stretches a distance equivalent to the distance from New York to Los Angeles.

The average temperature at surface of Mars is approximately -86oC to -5oC and the atmosphere is composed primarily of carbon dioxide, nitrogen, and argon. From this we find that Mars' atmosphere is now too thin and its temperature too cold to allow liquid water. However, Mars certainly had surface water and groundwater once; liquid water shaped the valley networks in the highlands and the huge flood channels that cut from the highlands to the northern lowlands. How much water was there? Estimates range from the equivalent of an ocean 10 meters deep covering the entire surface to the equivalent of a layer kilometers deep. Where did the water go? It could be underground in pools of groundwater, either small or huge depending on how much water Mars started with. Or it could have escaped to space and been lost completely - the hydrogen from water can escape easily through Mars's low gravity and small magnetic field.

A huge deposit of the mineral hematite extends over 300 miles on the rocky planet. It has led to speculation that there was water on Mars long enough for life to form. The hematite mineral deposit "is really the first evidence we have that hot water was around long enough for a geological period of time so that potentially life could have had an opportunity to form," said Arizona State University Prof. Phil Christensen. Hematite is an iron oxide mineral that forms by a variety of ways that often involve water. The coarse-grained hematite spotted on Mars occurs on Earth around volcanic regions such as Yellowstone National Park. It is evidence that a large-scale hydrothermal system may have operated beneath the Martian surface. Why is this important? "If you want to find out about possible life on Mars, the deposit is a good place to start," Christensen said. "You've got water, you've got heat, got energy."

In April new information was discovered about the planet's north polar cap and its surrounding features, including dune fields that share similar properties to North Africa's sand dunes. The presence of high altitude clouds above the polar cap was also revealed. During the winter, the polar cap was noted as expanding. This suggests that liquid water may or may not be present at certain times of the Martian year.
In addition, a new composite photograph of a crater 25 miles wide and 1 to 1½ miles deep about 3,600 miles south of the Martian equator has been released to the public. The deep, dark area near the middle of the crater appeared to be a frozen pond and there was evidence of water seepage as well. All of this evidence of water and mineral deposits comes into play in our search for answers concerning the mysterious planet Mars.