Sources of Heat...

Before NASA's Voyager robotic explorers flew by Jupiter in 1979, scientists believed that Jupiter's moons – so far from the sun's heat – were cold, frozen places. The Voyagers rather dramatically showed otherwise, spotting sulphur volcanoes on Io and the ice-encrusted oceans of Europa (at right).

Soon a new scientific consensus formed around the notion of tidal forces as the source of the heat needed to produce these observed phenomena. Now scientist Robert Tyler has published a paper that first shows that tidal forces aren't powerful enough to provide the heat needed, and proposes a different mechanism that would produce the necessary heat.

Tyler's paper is unusual for being a single-author paper – most papers in his field are team efforts.

The source of heat that Tyler proposes derives from the fact that these moons rotate on an axis that's oblique to their orbital plane. This produces Rossby waves (which I had never heard of until this morning) that are energetic enough to explain the observed heat on Europa (the subject of Tyler's study). It will be very interesting to see if this same source of energy can explain observations on other moons in our solar system.

For more, see here, here, here, and here.

The most obvious consequence of Tyler's discovery is this: there may well be many planets and moons (around our Sun and around other stars) that are too far from their sun for solar heat to provide the conditions for life, but which nonetheless have enough heat to provide liquid water and energy. We have forms of life right hear on earth that could survive and even thrive in several environments within our solar system...