Snow spikes (penitentes) in the Dry Andes, but not on Europa: A defense
of Lliboutry’s classic paper
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.