Sinus Sabaeus quadrangle

The Sinus Sabaeus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. It is also referred to as MC-20 (Mars Chart-20).[1]

The Sinus Sabaeus quadrangle covers the area from 315° to 360° west longitude and 0° to 30° degrees south latitude on Mars. It contains Schiaparelli, a large, easily visible crater that sits close to the equator.

Contents

White rock in Pollack crater

Within the region is Pollack crater, which has light-toned rock deposits. Mars has an old surface compared to Earth. While much of Earth's land surface is just a few hundred million years old, large areas of Mars are billions of years old. Some surface areas have been formed, eroded away, then covered over with new layers of rocks. The Mariner 9 spacecraft in the 1970s photographed a feature that was called "White Rock.". Newer images revealed that the rock is not really white, but that the area close by is so dark that the white rock looks really white. It was thought that this feature could have been a salt deposit, but information from the instruments on Mars Global Surveyor demonstrated rather that it was probably volcanic ash or dust. Today, it is believed that White Rock represents an old rock layer that once filled the whole crater that it's in, but today it has since been mostly eroded away. The picture below shows white rock with a spot of the same rock some distance from the main deposit, so it is thought that the white material once covered a far larger area.[2]

Pollack crater's white rocks:

Layers

Wislicenus Crater and the Schiaparelli basin crater contains layers, also called strata. Many places on Mars show rocks arranged in layers. Sometimes the layers are of different colors. Light-toned rocks on Mars have been associated with hydrated minerals like sulfates. The Mars Rover Opportunity examined such layers close-up with several instruments. Some layers are probably made up of fine particles because they seem to break up into find dust. Other layers break up into large boulders so they are probably much harder. Basalt, a volcanic rock, is thought to in the layers that form boulders. Basalt has been identified on Mars in many places. Instruments on orbiting spacecraft have detected clay (also called phyllosilicates) in some layers. Scientists are excited about finding hydrated minerals such as sulfates and clays on Mars because they are usually formed in the presence of water.[3] Places that contain clays and/or other hydrated minerals would be good places to look for evidence of life.[4]

Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers.[5]

Craters

When a comet or asteroid collides at a high rate of speed interplanetary with the surface of Mars it creates a primary impact crater. The primary impact may also eject significant numbers of rocks which eventually fall back to make secondary craters.[6] The secondary craters may be arranged in clusters. All of the craters in the cluster would appear to be equally eroded; indicating that they would all are of the same age. If these secondary craters formed from a single, large, nearby impact, then they would have formed at roughly the same instant in time. The image below of Dennin Crater shows a cluster of secondary craters.

Gallery

See also

References

  1. ^ Davies, M.E.; Batson, R.M.; Wu, S.S.C. “Geodesy and Cartography” in Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; Matthews, M.S., Eds. Mars. University of Arizona Press: Tucson, 1992.
  2. ^ http://space.com/scienceastronomy/solarsystem/mars_daily_020419.html
  3. ^ http://themis.asu.edu/features/nilosyrtis
  4. ^ http://hirise.lpl.arizona.edu/PSP_004046_2080
  5. ^ http://hirise.lpl.arizona.edu?PSP_008437_1750
  6. ^ http://hirise.lpl.arizona.edu/science_themes/impact.php