Penitence

Meter-high ice peaks in the summit region of Damâvand, 5604 m, Iran

Penance ice cream at the east summit of Tres Picos del Amor in Argentina

As penitents , penitents or Zackenfirn ( English Snow Penitents or Ice Penitents , Spanish Nieve de los Penitentes ) are up to 6 m high snow and ice pyramids in high mountains of the tropics and subtropics (including the Andes called). Penetration ice up to 30 meters high has been observed on the Khumbu Glacier on Mount Everest .

Penitentice is caused by uneven melting ( ablation ) with strong direct solar radiation and low humidity in the marginal tropical-subtropical dry zone. The tips of the snow pyramids point towards the midday sun. For mountaineers, this type of glacier and firn field surface is usually an insurmountable difficulty.

The formation process probably begins through small depressions in the snow. More reflected light hits their bottom than anywhere else, which means they deepen faster than their higher edges. The effect may be amplified in climates where the dew point is below freezing and at the same time there is strong sunlight. There, snow cannot melt at the tips of the snow peaks, but can only be removed by sublimation . In the wind-protected depressions, however, it is more humid and therefore the dew point is higher, so that the ice can melt. Since more solar energy is required for sublimation than for mere melting, the deepening process proceeds faster there than at the tips.

Penitence may also be found in the equatorial region of Europe , one of the four Galilean moons of Jupiter . At least this is what radar measurements suggest. These structures were also found on the dwarf planet Pluto . There, however, the methane ice peaks can reach heights of several hundred meters.

Web links

Commons : Penitentiary  - collection of pictures, videos and audio files

• Institute for Snow and Avalanche Research: Büsserschnee

Individual evidence

1. ^ MD Betterton: Theory of structure formation in snowfields motivated by penitentes, suncups, and dirt cones. In: Physical Review E. Ser. 3, Vol. 63, No. 5, 2001, ISSN  1539-3755 , 056129, doi : 10.1103 / PhysRevE.63.056129
2. ^ Europa's surface may be covered by blades of ice. In: Physics Today. October 29, 2013. Retrieved September 28, 2017 . 
3. ^ Formation of meter-scale bladed roughness on Europa's surface by ablation of ice. In: Nature Geosciences. October 10, 2018, accessed October 11, 2018 . 
4. ^ Daniel Lingenhöhl: Huge penitent snow thrones on Europe. October 8, 2017. Retrieved October 8, 2017 .