Scientists find ‘penitentes’ on Pluto

Sublimation on Pluto is forming a unique ice formation only previously found on Earth. Photo by NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

TORONTO, Jan. 5 (UPI) — Scientists have discovered unique snow and ice formations on Pluto — formations previously only found in the Andes. The formations are ice ridges known as “penitentes.”

Penitentes — or nieves penitentes, Spanish for “penitent-shaped snows” — are blade-like spires of compacted snow or ice surrounding a hollow depression. The ridges and depression are formed by erosion.

On Earth, they are only found in the Andes above 13,120 feet, where the air is thin and the dew point is never above freezing. Snow and ice doesn’t melt, but sublimates. As the hollow depression begins to form, a positive feedback loop is formed. Radiation is concentrated downward and reflected between the walls of the spires. Air circulation decreases, lowering the dew point and encouraging more sublimation and melting.

Analysis of Pluto images captured by the New Horizons spacecraft suggests a similar set of circumstances have yielded penitentes on the dwarf planet. On Pluto, however, the spires are more than 1,600 feet tall and separated by as many as three miles.

“This gargantuan size is predicted by the same theory that explains the formation of these features on Earth,” John Moores, a professor of planetary sciences at York University, said in a news release. “In fact, we were able to match the size and separation, the direction of the ridges, as well as their age: three pieces of evidence that support our identification of these ridges as penitentes.”

Moores and his colleagues shared their findings in the journal Nature. The paper’s authors suggest the solar system may host a diversity of penitentes yet to be discovered.

“Exotic differences in the environment give rise to features with very different scales,” Moores added. “This test of our terrestrial models for penitentes suggests that we may find these features elsewhere in the solar system, and in other solar systems, where the conditions are right.”


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