Arsia Mons

MarsGeo-Mount
name = Arsia Mons


195px|Image Credit: NASA/MOLA Science Team
latitude=9.5
N_or_S=S
longitude=120.5
E_or_W=W
peak = 16 km
discoverer =
eponym = Latin - "Arsia Silva" - classical albedo feature name

Arsia Mons is the southernmost of three volcanos (collectively known as Tharsis Montes) on the Tharsis bulge near the equator of the planet Mars. To its north is Pavonis Mons, and north of that is Ascraeus Mons. The tallest mountain in the solar system, Olympus Mons, is to its northwest. Its name comes from a corresponding albedo feature on a map by Giovanni Schiaparelli, which he named in turn after the legendary Roman forest of Arsia Silva.

Arsia Mons is 270 miles (approximately 435 kilometres) in diameter, almost 12 miles high (more than 9 kilometers (5.6 miles) higher than the surrounding plains [ [http://photojournal.jpl.nasa.gov/catalog/PIA02337 Catalog Page for PIA02337 ] ] ), and the summit caldera is 72 miles (approximately 110 km) wide. [ [http://photojournal.jpl.nasa.gov/catalog/PIA03948 Catalog Page for PIA03948 ] ] It experiences atmospheric pressure lower than 107 pascals [http://www-star.stanford.edu/projects/mgs/sum/s0401131906.html Martian Weather Observation] NASA MGS data 9.2 degrees S 238.2 degrees E 17757 meters 1.07 mbar] at the summit. Except for Olympus Mons, it is the biggest volcano in volume.

A repeated weather phenomenon occurs each year near the start of southern winter over Arsia Mons. Just before southern winter begins, sunlight warms the air on the slopes of the volcano. This air rises, bringing small amounts of dust with it. Eventually the rising air converges over the volcano's caldera and the fine sediment blown up from the volcano's slopes coalesces into a spiraling cloud of dust that is thick enough to observe from orbit. The spiral dust cloud over Arsia Mons repeats each year, but observations and computer calculations indicate it can only form during a short period of time each year. Similar spiral clouds have not been seen over the other large Tharsis volcanoes, but other types of clouds have been seen. The spiral dust cloud over Arsia Mons can tower 15 to 30 kilometers (9 to 19 miles) above the volcano. [ [http://photojournal.jpl.nasa.gov/catalog/PIA04294 Catalog Page for PIA04294 ] ]

The caldera of Arsia Mons was formed when the mountain collapsed in on itself after its reservoir of magma was exhausted. There are many other geologic collapse features on the mountain's flanks. [ [http://photojournal.jpl.nasa.gov/catalog/PIA03799 Catalog Page for PIA03799 ] ]

Possible cave entrances

As of 2007 seven putative cave entrances have been identified in satellite imagery of the flanks of Arsia Mons. [" [http://www.lpi.usra.edu/meetings/lpsc2007/pdf/1371.pdf Themis Observes Possible Cave Skylights on Mars] ." G. E. Cushing, T. N. Titus, J. J. Wynne, P. R. Christensen. Lunar and Planetary Science XXXVIII (2007)] [cite web| url=http://www.planetary.org/blog/article/00000984/| publisher=The Planetary Society Weblog| first= Emily| last= Lakdawalla| title=Windows onto the abyss: cave skylights on Mars| date=2007-05-23| accessdate=2007-05-26] They have been informally dubbed Dena, Chloë, Wendy, Annie, Abbey, Nikki, and Jeanne and resemble "skylights" formed by the collapse of cave ceilings.

*Dena (coord|-6.084|N|239.061|E|globe:Mars)
*Chloë (coord|-4.296|N|239.193|E|globe:Mars)
*Wendy (coord|-8.099|N|240.242|E|globe:Mars)
*Annie (coord|-6.267|N|240.005|E|globe:Mars)
*Abbey and Nikki (coord|-8.498|N|240.349|E|globe:Mars)
*Jeanne (coord|-5.636|N|241.259|E|globe:Mars)

From day to night, temperatures of the circular features change only about one-third as much as the change in temperature of surrounding ground. While this is more variable than large caves on Earth, it is consistent with them being deep pits. However, due to the extreme altitude, it is unlikely that they will be able to harbour any form of Martian life. [cite web|url=http://www.jpl.nasa.gov/news/news.cfm?release=2007-106|title=NASA Orbiter Finds Possible Cave Skylights on Mars|accessdate=2007-09-22|publisher=Jet Propulsion Laboratory]

A more recent photograph of one of the features shows sunlight illuminating a side wall, suggesting that it may simply be a vertical pit rather than an entrance to a larger underground space. [cite news|url=http://space.newscientist.com/article/dn12566-strange-martian-feature-not-a-bottomless-cave-after-all.html| title=Strange Martian feature not a 'bottomless' cave after all|date= 2007-08-30|publisher=NewScientist.com news service| first=David|last=Shiga] Nonetheless, the darkness of this feature implies that it must be at least 78 metres deep.

References

External links

* [http://ic.arc.nasa.gov/ic/projects/bayes-group/Atlas/Mars/features/a/arsia_mons.html NASA/Ames Mars Atlas: Feature entry for Arsia Mons]
* [http://apod.nasa.gov/apod/ap070528.html A Hole in Mars] - Astronomy Picture of the Day for 28 May 2007