Thaumasia quadrangle
Map of Thaumasia quadrangle from Mars Orbiter Laser Altimeter (MOLA) data. The highest elevations are red and the lowest are blue.
|
|
| Coordinates | 47°30′S 90°00′W / 47.5°S 90°WCoordinates: 47°30′S 90°00′W / 47.5°S 90°W |
|---|---|
The Thaumasia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Thaumasia quadrangle is also referred to as MC-25 (Mars Chart-25). The name comes from Thaumas, the god of the clouds and celestial apparitions.
The Thaumasia quadrangle covers the area from 60° to 120° west longitude and 30° to 65° south latitude on Mars. The Thaumasia quadrangle contains many different regions or parts of many regions: Solis Planum, Icaria Planum, Aonia Terra, Aonia Planum, Bosporus Planum, and Thaumasia Planum. One of the first major networks of stream channels, called Warrego Valles, were discovered here by early orbiters. Another sign of water is the presence of gullies carved into steep slopes.
Gullies are common in some parts of Mars. Gullies occur on steep slopes, especially on the walls of craters. Martian gullies are believed to be relatively young because they have few, if any craters. Moreover, they lie on top of sand dunes which themselves are considered to be quite young. Usually, each gully has an alcove, channel, and apron. Some studies have found that gullies occur on slopes that face all directions, others have found that the greater number of gullies are found on poleward facing slopes, especially from 30-44 S.
Although many ideas have been put forward to explain them, the most popular involve liquid water coming from an aquifer, from melting at the base of old glaciers, or from the melting of ice in the ground when the climate was warmer. Because of the good possibility that liquid water was involved with their formation and that they could be very young, scientists are excited. Maybe the gullies are where we should go to find life.
There is evidence for all three theories. Most of the gully alcove heads occur at the same level, just as one would expect of an aquifer. Various measurements and calculations show that liquid water could exist in aquifers at the usual depths where gullies begin. One variation of this model is that rising hot magma could have melted ice in the ground and caused water to flow in aquifers. Aquifers are layer that allow water to flow. They may consist of porous sandstone. The aquifer layer would be perched on top of another layer that prevents water from going down (in geological terms it would be called impermeable). Because water in an aquifer is prevented from going down, the only direction the trapped water can flow is horizontally. Eventually, water could flow out onto the surface when the aquifer reaches a break—like a crater wall. The resulting flow of water could erode the wall to create gullies. Aquifers are quite common on Earth. A good example is "Weeping Rock" in Zion National Park Utah.
...
Wikipedia