The case for life on Mars, hangs heavily on the existence of water, since it’s considered to be one, if not the crucial element necessary. What has been discovered in and under the surface in recent years, is more and more supportive of the theory that Mars at one time, had water in liquid form, and that it was abundant enough to flow and re-shape the landscape.
Gullies: In September of 1999, the Mars Orbital Camera snapped shots of a meteor impact crater in Noachis Terra. Shown in the photos, are the wall of the crater, eroded by gullies, which are associated with groundwater seepage or surface runoff. The debris at the perimeter of the gullies, and the fact that there are no other craters overlaying the channels, would seem to indicate features that are “young” from a geological standpoint. Whether liquid water exists sub-surface is open to question. What experts surmise, is that at some time, the surface of Mars experienced the movement of liquid water.
Sediment: An examination of the central mound in the Gale Crater, by the combined assets of the Mars Orbital Camera and the Mars Orbiter Laser Altimeter, gave scientists a very clear charting of the phases that the surface of Mars has passed through. In places, the layers of the mound are as much as 1.4miles thick, however the base shows hundreds of layers only 6-10 feet thick, a feature the mound has in common with other areas of Mars. One item that did stand out dramatically was that of a “filled” channel, considered evidence of past water movement. The channel developed, was filled with sediment, then completely buried, after which erosion lowered the surrounding rock, making one end of the channel into a ridge standing above it. Nearby, is what scientists have labelled a “partly-exhumed” crater. It shows an eroded surface that lay exposed to the elements before another deposit dropped lighter colored material over a portion of it. The remainder of the crater, shows the typical pock marks of meteorite strikes, whereas the area showing “erosion”, does not; further proof that Mars experienced cycles of deposit/erosion activity.
Layered Formations: As far back as 1972, the Mariner 9 mission, found that there were layers to some of the formations inside what is known as the Martian “Grand Canyon”. This layering was attributed to possible repeated deposits of volcanic ash, or the sediments that can be laid down in lakes. Either were grounds for speculation that fossilized proof of life on Mars might be found in them. With the Mars Global Surveyor mission of the late 90s, higher quality images showed not only the original layered formations, but new ones in areas where the surface material was not expected to have that kind of structure. New theories suggested that they may have been the result of material deposited in craters, which had then been buried and re-exposed. A .9 by 1.8 mile area of the Candor Chasma, revealed more than 100 layered beds, each of almost uniform thickness at 11 yards, and each being solid enough to form sharp cliffs at their extremities. The regularity of size and thickness, indicates that the deposition of materials that form the beds, was interrupted on a regular, ongoing basis. On Earth, such beds would be formed at the bottom of lakes where there was continuous and strong water movement. On Mars, it is currently impossible to confirm this possibility, or the one that surmises the beds could also have been the result of dust deposits occurring with the cyclic nature of atmospheric pressure, and then cementing themselves into cliff type formations.
Water trails: Gully land depressions, which are put forth as evidence of water channels, occur in the most unexpected locations. Typically, they are found high on the walls of the south polar pitted plains, on the side facing away from the sun. Their latitude would place them in Antarctica on Earth. On Mars, they are located where winter last six months, with temperatures that would freeze carbon dioxide. The channels start about 1/3 of the way down the wall, tapering from wide at the top, to narrow at the bottom, typical of water runoff trails. Above the channels, the wall is layered, and has been eroded into chutes and ridges with the movement of debris. All of which leaves the question of whether the water trails were the result of surface activity that was buried by the subsequent layers shown above the visible gullies, or whether water was trapped below the deepening surface crust, and only seeped out on the violent displacement of rock by meteor impact.
Ice and Water: Contrary to popular belief that Mars is a desperately cold and barren place which can’t possibly contain life supporting materials, we find water…just not liquid water. Mars has ice caps at both poles. In summer, the carbon dioxide ice recedes from the northern pole, enabling water to be detected, where none is found at the southern pole. The caps themselves are striated layers of dust and ice, likely formed due to atmospheric conditions during dust storms. While frost covers the layers year round at the north pole, it is possible when the frost recedes in the south, to see such unusual features as the crater which has a partly pock marked surface, and partly smooth, proving that the dust/ice layers that are even now accumulating there, are geologically new, having never been subjected to meteor strikes. If thermodynamics (air pressure and temperature) were different, the frost and ice might release their secrets.