Arandas is a crater in the

Mare Acidalium quadrangle The Mare Acidalium quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is located in the northeastern portion of Mars’ western hemisphere ...

of Mars, located 42.77° North and 15.17° West. It is in diameter and is named after the town of Arandas in

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. Gullies are visible in Arandas. On the basis of their form, aspects, positions, and location amongst an apparent interaction with features thought to be rich in water ice, many researchers believed that the processes carving the gullies involve liquid water. However, this remains a topic of active research. As soon as gullies were discovered,Malin, M., Edgett, K. 2000. "Evidence for recent groundwater seepage and surface runoff on Mars". ''Science'' 288, 2330–2335. researchers began to image many gullies over and over, looking for possible changes. By 2006, some changes were found. Later, with further analysis it was determined that the changes could have occurred by dry granular flows rather than being driven by flowing water. With continued observations many more changes were found in Gasa Crater and others. As further observations have been made, still more changes have been noted; since the changes occur in the winter and spring, experts tend to believe that gullies were formed from dry ice. Before-and-after images demonstrated the timing of this activity coincided with seasonal carbon-dioxide frost and temperatures that would not have allowed for liquid water. When dry ice frost changes to a gas, it may lubricate dry material to flow, especially on steep slopes. Wikisklodowskamola.jpg, MOLA map showing Arandas crater and other nearby craters. Color indicates elevation. Wikiarandas.jpg, Arandas crater, as seen by CTX camera (on MRO). Wikiarandasgullies.jpg, Gullies in Arandas, as seen by CTX camera. Note: this is an enlargement of the previous photo. WikiarandasESP 034907 2230.jpg, Gullies in Arandas, as seen by HiRISE under

HiWish program HiWish is a program created by NASA so that anyone can suggest a place for the HiRISE camera on the Mars Reconnaissance Orbiter to photograph. It was started in January 2010. In the first few months of the program 3000 people signed up to use HiRIS ...

Impact crater An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...

s generally have a rim with

ejecta Ejecta (from the Latin: "things thrown out", singular ejectum) are particles ejected from an area. In volcanology, in particular, the term refers to particles including pyroclastic materials (tephra) that came out of a volcanic explosion and magma ...

around them, in contrast volcanic craters usually do not have a rim or ejecta deposits. As craters get larger (greater than in diameter) they usually have a central peak. The peak is caused by a rebound of the crater floor following the impact. Sometimes craters expose layers that were buried. Rocks from deep underground are tossed onto the surface. Hence, craters can expose what lies deep under the surface.

References

{{Portal bar, Solar System Impact craters on Mars Mare Acidalium quadrangle

See also

References