Quadrangle map of Oxia Palus labeled with major features. This quadrangle contains many collapsed areas of Chaos and many outflow channels (old river valleys). Crommlin Crater is found at the lower right. Crommlin Crater contains a large mound that shows dozens of regular spaced layers. These layers are similar to layers in other major craters such as Gale Crater and Henry Crater.
|Eponym||Andrew C. Crommlin, a British astronomer (1865–1939)|
Crommlin Crater is an impact crater in the Oxia Palus quadrangle of Mars. It is located at 5.1° north and 10.2° west. It was named after Andrew C. Crommlin, a British astronomer (1865–1939). Parts of Crommlin crater display many thin layers. These may reflect different climates in the past--some of which were much wetter.
Many places on Mars show rocks arranged in layers. Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers.
Many craters once contained lakes.    Because some crater floors show deltas, we know that water had to be present for some time. Dozens of deltas have been spotted on Mars.  Deltas form when sediment is washed in from a stream entering a quiet body of water. It takes a bit of time to form a delta, so the presence of a delta is exciting; it means water was there for a time, maybe for many years. Primitive organisms may have developed in such lakes; hence, some craters may be prime targets for the search for evidence of life on the Red Planet. 
Crommlin Crater with important parts labeled, as seen by CTX camera (on Mars Reconnaissance Orbiter).
Crommlin Crater Layered Deposit, as seen by HiRISE. The color blue in the photo is a false color.
Why are Craters important?
The density of impact craters is used to determine the surface ages of Mars and other solar system bodies.  The older the surface, the more craters present. Crater shapes can reveal the presence of ground ice.
The area around craters may be rich in minerals. On Mars, heat from the impact melts ice in the ground. Water from the melting ice dissolves minerals, and then deposits them in cracks or faults that were produced with the impact. This process, called hydrothermal alteration, is a major way in which ore deposits are produced. The area around Martian craters may be rich in useful ores for the future colonization of Mars. 
- Grotzinger, J. and R. Milliken (eds.) 2012. Sedimentary Geology of Mars. SEPM
- "HiRISE | High Resolution Imaging Science Experiment". Hirise.lpl.arizona.edu?psp_008437_1750. Retrieved 2012-08-04.
- Cabrol, N. and E. Grin. 2001. The Evolution of Lacustrine Environments on Mars: Is Mars Only Hydrologically Dormant? Icarus: 149, 291-328.
- Fassett, C. and J. Head. 2008. Open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.
- Fassett, C. and J. Head. 2008. Open-basin lakes on Mars: Implications of valley network lakes for the nature of Noachian hydrology.
- Wilson, J. A. Grant and A. Howard. 2013. INVENTORY OF EQUATORIAL ALLUVIAL FANS AND DELTAS ON MARS. 44th Lunar and Planetary Science Conference.
- Newsom H. , Hagerty J., Thorsos I. 2001. Location and sampling of aqueous and hydrothermal deposits in martian impact craters. Astrobiology: 1, 71-88.
- Planetary nomenclature
- Impact crater
- List of craters on Mars
- Water on Mars
- Climate of Mars
- Groundwater on Mars
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