Ice Penitentes

Penitentes is the Spanish word for someone who is remorseful. Penitentes which form in the Atacama desert are pillars of ice and snow that can range from a few centimeters to 20 or event 30 feet. These pillars often form in a field with other pillars causing them to resemble a group of hooded priests in prayer thereby receiving the name “Penitentes”. But how do these pillars form in the dry and arid Atacama desert, according to local belief the wind in the desert cause ice and snow pillars to rise up from the ground. However through further research it was determined that the Pentitentes instead formed through the process of sublimation.

Charles Darwin was the first western scientist to stumble upon the ice penitentes when he was on his way to Mendoza City in Mexico. His observations sparked great interest in scientists to determine how the ice penitentes were formed. Initially many scientists along with Darwin shared the same belief the locals held in that the ice penitentes were formed by the Andean wind that swept through the desert. However many researchers challenged this belief due to its lack of evidence and explanation. Specifically a biophysicist named Meredith Butterton was intrigued by the Penitentes and determined that sublimation was the main cause of the formation of Penitentes. Sublimation is when ice or snow is turned into water vapor without melting into a liquid state first. Butterton found that for the Penitentes some areas turned into vapor faster than others causing for troughs to form on the surface. Under continued sunlight the troughs become deeper while walls of the ice or snow remain unaffected. As a result tall spikes of ice form, and as it repeats an entire field of ice Penitentes forms.

Nieve penitente is a spike or pillar of compacted snow caused by differential melting and evaporation.

Ice Penitentes usually occur in the Andes and Himalayas on earth, but they could occur in other places within our galaxy. Findings by NASA indicate that Penitentes could be found on Pluto and Europa. Europa is an ice covered moon with a salt water ocean underneath the ice. Through the New Horizons Spacecraft that NASA sent to Europa in 2015, NASA has discovered that Europa possesses a bladed terrain. According to simulations done by NASA, Europa’s equator which receives the strongest sunlight yet has temperatures as low as -200 degrees Celsius contains spires of Penitentes that are much bigger than Earth’s with some as large as 50 feet tall. While a manned spacecraft to Europa is most likely impossible, the future Europa Clipper mission to Europa in 2022-2025 may provide answers for Europa’s Penitentes.

-Allen Shen


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