Penitente (snow formation)

First description

Penitentes were first described in scientific literature by Charles Darwin in 1839. On March 22, 1835, he had to squeeze his way through snowfields covered in penitentes near the Piuquenes Pass, on the way from Santiago de Chile to the Argentine city of Mendoza, and reported the local belief (continuing to the present day) that they were formed by the strong winds of the Andes.

Formation

Penitentes are tall, thin blades of hardened snow sculpted by the sun. As the sun hits the snow, it transforms it directly into vapor without melting it, through sublimation. Initially smooth, the snow surface thus develops depressions, hills, and hollows as some regions sublimate faster than others. As the carved surfaces then continue to concentrate sunlight, they help to speed up the process. This results in icy snow columns that look like towering spikes.

Louis Lliboutry noted that the key climatic condition behind the differential ablation that leads to the formation of penitentes is a dew point that remains below freezing. This combined with dry air will cause snow to sublimate. A mathematical model of the process has been developed by Betterton, although the physical processes at the initial stage of penitente growth, from granular snow to micropenitentes, still remain unclear. The effect of penitentes on the energy balance of the snow surface, and therefore their effect on snow melt and water resources, has also been studied.

Non-terrestrial

Penitentes up to 15 m high are suggested to be present in the tropics zone on Europa, a satellite of Jupiter. According to a 2017 study, NASA's New Horizons mission discovered penitentes hundreds of meters high on Pluto, likely composed primarily of methane ice deposited seasonally from Pluto's thin atmosphere. The structures occupy a region named Tartarus Dorsa, a name that was formally accepted by the IAU in August 2017.

References

References

1. "Penitentes ESO Australia".
2. (1954a). "Le Massif du Nevado Juncal ses penitentes et ses glaciers". Revue de Géographie Alpine.
3. (1954b). "The origin of penitentes". Journal of Glaciology.
4. Lliboutry, L.. (1965). "Traité de Glaciologie, Vol. I & II". Masson.
5. (1997). "Preliminary study on the shape of snow penitents at Piloto Glacier, the Central Andes". Bulletin of Glacier Research.
6. Darwin, C.. (1839). "Journal of researches into the geology and natural history of the various countries visited by H. M. S. Beagle, under the command of Captain Fitz Roy, R.N., 1832 to 1836". H. Colburn.
7. (28 May 2012). "The Penitentes, Stunning Snow Formations".
8. (2001). "Theory of structure formation in snowfields motivated by penitentes, suncups, and dirt cones". Physical Review E.
9. Corripio, J.G.. (2003). "Modelling the energy balance of high altitude glacierised basins in the Central Andes". University of Edinburgh.
10. (May 2018). "Climate and Hydrology in Mountain Areas". Wiley & Sons.
11. (9 October 2018). "Jupiter moon may have huge, jagged ice blades that complicate the search for alien life".
12. (2013). "Europa's surface may be covered by blades of ice". Physics Today.
13. Talbert, Tricia. (2017-01-04). "Scientists Offer Sharper Insight into Pluto's Bladed Terrain". NASA.
14. (2017-01-12). "Penitentes as the origin of the bladed terrain of Tartarus Dorsa on Pluto". Nature.
15. (2017-08-08). "Tartarus Dorsa".