Thursday, January 22, 2009

Nature Sides with Titan Mission and Finally, Which Mission Does Jason Support?

As I mentioned in the last post, Nature has a news article by Eric Hand on the run-up to the downselection of the destination of the next Outer Planets Flagship Mission. The article provides quotes from the the study teams on the strengths of both mission. Bob Pappalardo points out that the Europan mission design and the technology needed for it have almost a decade of heritage after at least five mission studies. Quoteth Pappalardo, "Are you going to pick the brightly colored horse, or are you going to ask, 'Is that horse ready to run?'" Ralph Lorenz, a member of the Titan study team, disagrees and states that, "With its atmosphere, its hydrological cycle and even its potential for cryovolcanism, Titan would mobilize a much wider scientific community."

Nature also has a short editorial covering more of the shortfalls of both mission concepts and finally comes out in favor of one of the missions. Nature cites the lengthy lifecycle of these concepts (if selected, TSSM, from mission start to the end of that mission, will cover half my life to that point) as a major factor in deciding which mission to put its hat in with. While TSSM takes longer to reach its target, the implied need for a follow-on lander for Europa is seen as a problem for that mission concept. Nature also agreed with some of my criticisms, that the orbital mission doesn't really address the habitability issue as much as the Summary Report would make you think it does. Again, that issue would require a lander (and perhaps a submarine) to more fully answer. According to Nature, the Titan mission is more self-contained as it goes further towards answer the important scientific questions at Titan without necessarily requiring an immediate follow-up mission. So Nature sides with the Titan mission.

Okay, so which mission do I support? Well, let me first say, that to be quite honest, I think I will be happy either way. EJSM would examine my favorite world in the Solar System fairly extensively, even if Io isn't the primary target. It would serve as a fine contingency plan in case the Io Volcano Observer is not selected as a Discovery mission. TSSM would more extensively study my second favorite celestial body, Titan. I have friends and colleagues I admire greatly on both study teams. On the basis purely of its study of Io alone, I would favor EJSM being selected. I also feel that EJSM's science would be far less impacted if the mission became NASA-only (because ESA decided not to go with JGO as their Cosmic Visions mission, for example) than TSSM would.

Van Kane has a nice post on his blog on a thought experiment on the potential options for the losing side. He states that because of that analysis, he feels that selecting Titan as the target for the next flagship mission as Europa could be studied reasonably with a New Frontiers mission budget, whereas it would be impossible for a Titan mission to do the same (in his experiment, he presumed, if Europa was selected and Titan lost, that NASA and ESA could pool their funds from a New Frontiers AO and from the funds gained by ESA cancelling JGO, the latter not being a real option).

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