Lakes on Mars
In the summer of 1965, the first close-up pictures from Mars revealed a cratered desert with no signs of water. However, over the decades, as more parts of the planet were imaged with better cameras on more sophisticated satellites, Mars showed evidence of past river valleys, lakes, and ice in glaciers and in the ground. It was discovered that the climate of Mars displays huge changes over geologic time because its axis is not stabilized by a large moon like our Earth. Also, some researchers maintain that water could exist for periods of time due to geothermal effects or asteroid impacts.Besides seeing features that were signs of past water, researchers found other types of evidence for past water. Minerals detected in many locations needed water to form. An instrument in the Mars Odyssey, an orbiting spacecraft, mapped the distribution of water in the near surface. When the Phoenix spacecraft fired its rockets to land in the far north, ice was exposed.When water enters a large body of water, like a lake, a delta may form. Many craters and other depressions on Mars show deltas that resemble those on Earth. In addition, if a lake lies in a depression, channels entering it will all stop at the same height. Such an arrangement is visible around places on Mars that are supposed to have contained large bodies of water—including around a possible ocean in the North.Lake formation has been proposed by various researchers for quite some time. One study found 205 possible closed-basin lakes in craters on Mars. The basins have an inlet valley that cuts the crater rim and flows into the basin, but they have no visible outlet valley. The total volume of the basins equals water to 1.2 meters in depth spread evenly over Martian surface. However, this amount is a small fraction of the modern water ice stores on Mars. Another study, found 210 open-basin lakes. These were lakes with both an inlet and an outlet; hence water must have entered the basin, and reached the height of the outlet. Some of these lakes had volumes similar to Earth's Caspian Sea, Black Sea, and Lake Baikal.Moreover, some basins on Mars are part of long chains of lakes. The Naktong/Scamander/Mamers Valles lake-chain system is about 4500 Km long and a drainage area similar to the Earth's Missouri-Mississippi River's. Another, the Samara/Himera Vallis system is 1800 Km long. Many of the long chains of lakes are found in the Margaritifer Sinus quadrangle.Some of the lakes appear to have had a high volume as compared to their drainage area; hence, it is believed that some of the water was groundwater. Further evidence is the existence of knobby material on the basin floors. These knobs can be formed when large amounts of water left the ground. This article will describe some of the places that could have held large lakes. Perhaps, the lakes held water long enough for life to form.