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Entries in "Europa"

Hydrothermal activity on Europa

Lowell, RP and M DuBose, Hydrothermal systems on Europa, GRL, 32, L05202, doi:10.1029/2005GL022375, (2005), Article.

Europa is so fascinating, icy tectonics, subsurface oceans, tidal interaction, and who knows, maybe even some microbes... One of the open questions with regard to Europa is how to form "chaos" type regions and features that look like cryovolcanism. The two basic ideas out there are (1) warmer water from the ocean induces a melt-through event in the overlying (thin) ice, (2) tidal dissipation is focused in the (thick) ice shell which is convecting on its own, creating surface features. This paper focuses on the first of these two ideas and tries to understand the heat output from hydrothermal activity in the rocky layer beneath the ice and water ocean. They take estimate for Europa's total heat output from the literature on tidal dissipation and radiogenic heat output and calculate the portion of the heat flow carried by hydrothermal activity by analogy with Earth oceanic crust (seems reasonable to first-order). The punch line is that the total hydrothermal heat flux is similar to earth's, but the output of any given vent is about 10 times less than black-smokers on the bottom of the Earth's oceans. That leads them to conclude that there just isn't enough energy in the thermal anomalies created in the overlying ocean to rise up and melt through the overlying ice... in accord with other papers on the subject.

What strikes me though is that Europa's ocean must be salty, so it is conceivable that it is somewhat stratified like the Earth's oceans, and this may reduce even further the mass/buoyancy flux through the oceans. Also, the input parameters in this study are pretty liberal with the heat available, and yet their models don't predict plumes capable of melt-through, which seems like maybe another nail in that idea. Of course, if Europa's hydrothermal vent systems were more localized (along the trace of the sub-Jovian point or something like that) maybe a bit more energy would be available, but the salt-induced stratification may trump it anyway...