The Aeolis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Aeolis quadrangle is also referred to as MC-23 (Mars Chart-23).〔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.〕
The Aeolis quadrangle covers 180° to 225° W and 0° to 30° south on Mars, and contains parts of the regions Elysium Planitia and Terra Cimmeria. A small part of the Medusae Fossae Formation lies in this quadrangle.
It is famous as the site of two spacecraft landings: the Spirit Rover landing site () in Gusev crater (January 4, 2004), and the Curiosity Rover in Gale Crater () (August 6, 2012).
A large, ancient river valley, called Ma'adim Vallis, enters at the south rim of Gusev Crater, so Gusev Crater was believed to be an ancient lake bed. However, it seems that a volcanic flow covered up the lakebed sediments.〔(Spirit rover follows up on scientific surprises )〕 Apollinaris Patera, a large volcano, lies directly north of Gusev Crater.〔U.S. department of the Interior U.S. Geological Survey, Topographic Map of the Eastern Region of Mars M 15M 0/270 2AT, 1991〕
Gale Crater, in the northwestern part of the Aeolis quadrangle, is of special interest to geologists because it contains a 2–4 km (1.2–2.5 mile) high mound of layered sedimentary rocks, named "Mount Sharp" by NASA in honor of Robert P. Sharp (1911–2004), a planetary scientist of early Mars missions. More recently, on 16 May 2012, "Mount Sharp" was officially named Aeolis Mons by the USGS and IAU.
Some regions in the Aeolis quadrangle show inverted relief.〔Ori, G., I. Di Pietro, F. Salese. 2015. A WATERLOGGED MARTIAN ENVIRONMENT: CHANNEL PATTERNS AND SEDIMENTARY
ENVIRONMENTS OF THE ZEPHYRIA ALLUVIAL PLAIN. 46th Lunar and Planetary Science Conference (2015) 2527.pdf〕 In these locations, a stream bed may be a raised feature, instead of a valley. The inverted former stream channels may be caused by the deposition of large rocks or due to cementation. In either case erosion would erode the surrounding land but leave the old channel as a raised ridge because the ridge will be more resistant to erosion
Yardangs are another feature found in this quadrangle They are generally visible as a series of parallel linear ridges, caused by the direction of the prevailing wind.
== Spirit Rover discoveries ==
The rocks on the plains of Gusev are a type of basalt. They contain the minerals olivine, pyroxene, plagioclase, and magnetite, and they look like volcanic basalt as they are fine-grained with irregular holes (geologists would say they have vesicles and vugs).〔McSween, etal. 2004. Basaltic Rocks Analyzed by the Spirit Rover in Gusev Crater. Science : 305. 842-845〕〔Arvidson, R. E., et al. (2004) Science, 305, 821-824〕
Much of the soil on the plains came from the breakdown of the local rocks. Fairly high levels of nickel were found in some soils; probably from meteorites.〔Gelbert, R., et al. 2006. The Alpha Particle X-ray Spectrometer (APXS): results from Gusev crater and calibration report. J. Geophys. Res. – Planets: 111.〕
Analysis shows that the rocks have been slightly altered by tiny amounts of water. Outside coatings and cracks inside the rocks suggest water deposited minerals, maybe bromine compounds. All the rocks contain a fine coating of dust and one or more harder kinds of material. One type can be brushed off, while another needed to be ground off by the Rock Abrasion Tool (RAT).〔Christensen, P. Initial Results from the Mini-TES Experiment in Gusev Crater from the Spirit Rover. Science: 305. 837-842.〕
There are a variety of rocks in the Columbia Hills (Mars), some of which have been altered by water, but not by very much water.
The dust in Gusev Crater is the same as dust all around the planet. All the dust was found to be magnetic. Moreover, Spirit found the magnetism was caused by the mineral magnetite, especially magnetite that contained the element titanium. One magnet was able to completely divert all dust hence all Martian dust is thought to be magnetic.〔Bertelsen, P., et al. 2004. Magnetic Properties on the Mars Exploration Rover Spirit at Gusev Crater. Science: 305. 827-829〕 The spectra of the dust was similar to spectra of bright, low thermal inertia regions like Tharsis and Arabia that have been detected by orbiting satellites. A thin layer of dust, maybe less than one millimeter thick covers all surfaces. Something in it contains a small amount of chemically bound water.〔Bell, J (ed.) The Martian Surface. 2008. Cambridge University Press. ISBN 978-0-521-86698-9〕〔Gelbert, R. et al. Chemistry of Rocks and Soils in Gusev Crater from the Alpha Particle X-ray Spectrometer. Science: 305. 829-305〕
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