Protonilus Mensae
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| Coordinates | 43°52′N 49°24′E / 43.86°N 49.4°ECoordinates: 43°52′N 49°24′E / 43.86°N 49.4°E |
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Protonilus Mensae is an area of Mars in the Ismenius Lacus quadrangle. It is centered on the coordinates of 43.86° N and 49.4° E. Its western and eastern longitudes are 37° E and 59.7° E. North and south latitudes are 47.06° N and 39.87° N. Protonilus Mensae is between Deuteronilus Mensae and Nilosyrtis Mensae; all lie along the Martian dichotomy boundary. Its name was adapted by the IAU in 1973.
Map showing the relation of Deuteronilus Mensae to other nearby regions Colors refer to altitudes.
The surface is described as fretted terrain. This terrain contains cliffs, mesas, and wide flat valleys. Surface features are believed to have been caused by debris-covered glaciers. These glaciers are termed lobate debris aprons (LDA) when surrounding mounds and mesas. When glaciers are in valleys, they are called Lineated valley fill (LVF). Parts of the surface show flow patterns that start in numerous alcoves located within the walls of plateaus. Small flow lobes on top of main flows demonstrate that there was more than one glacial period, just as on Earth. It is strongly believed that beneath a thin layer of rock and dust lie vast reservoirs of ice. Radar data from the SHAllow RADar (SHARAD) on board MRO have found pure ice under LDA and LVF.
Some places in Protonilus Mensae display lines of pits. These pits may have formed when ground ice converted to a gas, thus leaving a void. When surface material collapses into voids, pits are created.
Wide view of dunes in Moreux Crater, as seen by HiRISE under HiWish program
Enlarged view of dunes on the bottom of the previous image, as seen by HiRISE under HiWish program
Close view of one large dune from the same location, as seen by HiRISE under HiWish program
Close view of white spot among the dark dunes showing ripples and streaks
Many features on Mars, including ones in Protonilus Mensae, are believed to contain large amounts of ice. The most popular model for the origin of the ice is climate change from large changes in the tilt of the planet's rotational axis. At times the tilt has even been greater than 80 degrees Large changes in the tilt explains many ice-rich features on Mars.
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