RE: New Issue: Bands on Europa ----- Original Message ----- From: Gary McMurtry To: [EMAIL PROTECTED] Sent: Tuesday, November 26, 2002 9:07 AM Subject: RE: New Issue: Bands on Europa
This is interesting! Looks like the "fast" upwelling zones would be the best place to search the surface ice for clues to the ocean composition. The center fault of a "slow" rift might be the best place to punch through the crust. It's a little disconcerting that Europa seems to be slowly solidifying. This may mean any internal heating mechanisms, like volcanism, have ceased long ago. But at least some surface compounds may be slowly, but consistently, reintroduced due to subduction? _______________________________ A moon that size should have cooled its internal, gravity-friction furnace long ago. What probably sustains a liquid ocean is seafloor volcanism fed by heat from tidal friction in the core/mantle induced by Jupiter's pull, supplemented by natural radioactive decay. Recall Io is Europa's neighbor moon. Now, it gets really interesting when you consider that the net tidal pull can vary with changes in the relative orbits of the moons, so that the heat "engine" may slow and rev over time, causing the liquid ocean to shrink or grow. ___________________________________ YES -- this is starting to look like the central key to understanding Europa. All indications are that not only is its current surface just a few tens of millions of years old, but that, during that short period, the fundamental nature of its geological activity has radically changed -- from the cracks, faults, ridges and bands whose formation one would expect in a thin ice crust, to the "lenticular" bumps and chaotic terrain one would expect as a result of warm-ice diapirs slowly plowing upward through a thick ice crust. Ergo, during that geologically very short period, Europa's crust has radically thickened -- which means that it must go through this same cycle every few tens of millions of years, due to the repeated changes in the tidal tuggings of Io, Europa and Ganymede on each other (as a result of their slow changes in their orbits) that Gary talks about. This same factor may explain why Io is currently much hotter than its current degree of tidal massaging should be able to produce -- it's still cooling off from a geologically recent era of much stronger tides and resultant heating. And it may even explain Ganymede's magnetic field -- some calculations suggest that a billion years ago it went through a period of having a relatively eccentric orbit and REALLY dramatic tidal heating, which could have produced both a central core that's still hot enough to be molten rock, and the strange "ridged" terrain covering much of its surface which is about a billion years old, and which seems to have been the result of the very thick surface ice layer expanding and then contracting due to a temperature change. Of couse, this also means that the Europan "bands" are the products of an earlier period of thin-crust geological activity on Europa, and that they haven't been active for several tens of millions of years -- and that, in turn, means that Jupiter's radiation has long since hopelessly modified any organic compounds that they carried up to the surface from the ocean. However, if you drill a moderate distance you should be able to get below that radiation-modified layer -- and even in the current thick crust, those rising ice diapirs (like the blobs in a lava lamp) are still carrying material from the ocean slowly up to the surface (maybe in a period of just a few hundred thousand years), which means that they are even better sites to look for relatively recent oceanic material. == You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] Project information and list (un)subscribe info: http://klx.com/europa/
