Too Hot to Handle: Io and Enceladus

Two moons in the solar system are turning up the heat on beliefs that they could be billions of years old.

Jupiter’s Io: The most volcanic body in the solar system, Io, continues to stump planetary scientists.  “A new study finds that the pattern of heat coming from volcanoes on Io’s surface disposes of the generally-accepted model of internal heating,” announced a Science Daily article (see JPL press release) summarizing new findings published in Icarus.  “The heat pouring out of Io’s hundreds of erupting volcanoes indicates a complex, multi-layer source.”  Further reading suggests that tidal heating remains insufficient to account for the volcanic activity.  “The fascinating thing about the distribution of the heat flow is that it is not in keeping with the current preferred model of tidal heating of Io at relatively shallow depths,” said Ashley Davies.  One good puzzle deserves another: “Instead, the main thermal emission occurs about 40 degrees eastward of its expected positions.”  So is the heating deep or shallow?  Both, said Dennis Matson of JPL.    Then the team really poured the heat on:

A mystery has also emerged. The team found that active volcanoes accounted for only about 60 percent of Io’s heat. This component mostly emanates from flat-floored volcanic craters called paterae, a common feature on Io. But where is the “missing” 40 percent? “We are investigating the possibility that there are many smaller volcanoes that are hard, but not impossible, to detect,” said Veeder. “We are now puzzling over the observed pattern of heat flow.“

These findings show that Matson and his JPL colleagues have made little progress explaining how Io’s volcanoes could last for billions of years since our first story on Creation-Evolution Headlines 12 years ago (see 8/16/2000).

Saturn’s Enceladus:  Saturn’s geyser moon Enceladus (a.k.a. Cold Faithful) continues to baffle planetary scientists who need to keep the activity going billions of years (see photo gallery on PhysOrg from Cassini’s 19th flyby May 3).  Now, as reported by New Scientist, PhysOrg and other media outlets, the geysers produce a plasma unlike anything seen before: tiny dust grains that pick up negative ions from water molecules pumped out the geysers.  Moreover,  “It seems that Enceladus provides most of the plasma in the magnetic bubble, or magnetosphere, surrounding Saturn,” an astonishing influence for an Arizona-diameter moon to have over billions of cubic miles. Has this been going on for 4.5 billion years?  Planetologists are typically reluctant to invoke special conditions that allow phenomena to commence near the time humans became available to observe them.

Observers of planetary scientist psychology are sure to notice two conditioned responses peculiar to that sub-population of Homo sapiens: (1) an eagerness to connect any mention of water with life, and (2) a reluctance to discuss the age implications of small active bodies like Io and Enceladus.  Peculiar, indeed.