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Snow spikes (penitentes) in the Dry Andes, but not on Europa: A defense of Lliboutry’s classic paper
  • Stephen Warren
Stephen Warren
University of Washington, University of Washington

Corresponding Author:sgw@uw.edu

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There is a concern that in the low latitudes of Jupiter’s moon Europa, the ice surface has developed meter-scale bladed roughness, which would pose a hazard to a lander. That concern was inspired by the presence of such structures (“penitents”) on Earth’s subtropical mountains, but their formation requires melting along with sublimation, which cannot occur on Europa. The troughs deepen rapidly by melting while the peaks remain dry and cold by sublimation, losing little mass, because of the 8.5-fold difference in latent heats of sublimation versus melting. Penitents cause a reduction of albedo by ~30% by trapping sunlight. The high albedo of Europa (~0.7 at visible wavelengths) therefore also argues against the existence of extreme surface roughness.