Reynolds (crater)
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Reynolds is an
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 crater ...
on
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
, located in the Mare Australe quadrangle at 75.1°S latitude and 157.9°W longitude and is in the southernmost portion of
Terra Sirenum Terra Sirenum is a large region in the southern hemisphere of the planet Mars. It is centered at and covers 3900 km at its broadest extent. It covers latitudes 10 to 70 South and longitudes 110 to 180 W. Terra Sirenum is an upland area nota ...
. It measures 91 kilometers in diameter and was named after British physicist
Osborne Reynolds Osborne Reynolds (23 August 1842 – 21 February 1912) was an Irish-born innovator in the understanding of fluid dynamics. Separately, his studies of heat transfer between solids and fluids brought improvements in boiler and condenser design. ...
.


Spiders

During the winter, much frost accumulates. It freezes out directly onto the surface of the permanent polar cap, which is made of water ice covered with layers of dust and sand. The deposit begins as a layer of dusty CO2 frost. Over the winter, it recrystallizes and becomes denser. The dust and sand particles caught in the frost slowly sink. By the time temperatures rise in the spring, the frost layer has become a slab of semi-transparent ice about 3 feet thick, lying on a substrate of dark sand and dust. This dark material absorbs light and causes the ice to sublimate (turn directly into a gas) Eventually much gas accumulates and becomes pressurized. When it finds a weak spot, the gas escapes and blows out the dust. Speeds can reach 160 km (100 miles) per hour. Dark channels can sometimes be seen; they are called "spiders." The surface appears covered with dark spots when this process is occurring. These features can be seen in some of the pictures below.


See also

* List of craters on Mars


References


Recommended reading

* Grotzinger, J. and R. Milliken (eds.). 2012. Sedimentary Geology of Mars. SEPM. {{Geography of Mars Mare Australe quadrangle Impact craters on Mars