Titan Review article |
Titan Review article |
Dec 14 2007, 05:02 PM
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#1
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Member Group: Members Posts: 610 Joined: 23-February 07 From: Occasionally in Columbia, MD Member No.: 1764 |
This just out. Not earth-shattering, but colorful - maybe handy as an up-to-date
Titan intro http://www.jhuapl.edu/techdigest/td2702/lorenz.pdf |
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Dec 28 2007, 03:31 PM
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#2
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Well, I was less than clear (again) in what I meant (sorry!)
Europa certainly needs & deserves attention, but frankly I'm not completely convinced that achieving major scientific objectives--confirmation of an ocean, ice thickness sounding, global high-res photographic coverage, plume search/monitoring--can't be accomplished via one or more Discovery missions in the relatively near term. We pretty much know what to look for at Europa and indeed throughout the entire Galliean satellite system. What we don't know is whether we can get to that putative ocean via any practical technology, but again that seems like something that could be determined on less than a Flagship-class level of effort. I think that the answer to that question is key for planning all future Europa exploration. On the other hand, we've already landed on Titan; we know that we can conduct in situ exploration using reasonable evolutes of current technology, which becomes a trade-off between transit time/launch costs and science return. (Side note: this is why I still wish that there was an ongoing, organized effort by JPL or somebody to identify particularly favorable outer-planet launch opportunities). Titan is quite possibly at least as geochemically complex as Earth (with an outside chance of being more so). Therefore, to me, it seems as if there is a lot more science to be done at Titan than anywhere else in the Solar System -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Dec 28 2007, 08:40 PM
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#3
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
I think the key question, which may come down more to faith than evidence, is: How much more favorable is the very best spot on Europa for landed exploration than the best spot we now know of? Is it possible that if we sent a lander to the best spot we know of now that it would land in an area that last received salty/silty flooding ten million years ago, but if we looked harder we would find a spot that last received salty/silty flooding ten years ago? Or 100? Or... whatever?
This is the main value proposition for a Europa orbiter. If Europa is basically homogeneous on a regional scale (obviously, on a local scale, it is not), then we will gain comparatively little from orbital reconnaissance in detail. But if there is one special place (or 10 or 20 of them) where we get better access to the ocean below (either in terms of a very thin spot in the ice for direct access, or just a much fresher patch of surface ice), then there is tremendous value in mapping the hell out of Europa at great resolution before sending something up there [down there] for a taste. There's no doubt that Europa is going to be vastly more isotropic than Titan. Chromatically, Europa is almost a two-color world, with every spot on the surface distinguished by how much dark stuff is in the ice, and a simple metric that probably correlates with that would be the age of every spot. Think of the Earth -- we have crust that is millions of years old, and we have crust that is 26 years old (Mt. St. Helens) or as fresh as yesterday. But those new areas are very small, and wouldn't turn up after just a few flybys. Titan will be wonderfully more complex than Europa, and is an irresistible target for future flagship missions, and if there were only going to be one more outer solar system mission ever, I would consider Titan the best choice. But as part of a sequence, I think it makes more sense to visit Europa next, then Titan, and then possibly Europa for the mission after that. Or, to direct the competition elsewhere, I might say that when we have gone further down the road of exhausting possible flagship missions to Mars, that Europa might merit some or most of the "astrobiology" coffer that Mars is now monopolizing. |
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Dec 28 2007, 09:34 PM
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#4
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Member Group: Members Posts: 706 Joined: 22-April 05 Member No.: 351 |
John, as usual, nails the subject, at least as I see it.
I think the key question, which may come down more to faith than evidence, is: How much more favorable is the very best spot on Europa for landed exploration than the best spot we now know of? In our lifetimes (or at least mine), we won't have the technology or money to have a probe melt all the way through the ice to reach Europa's ocean. Given this, an Europan lander has to find a place that (1) has subsurface material at or very, very close to the surface and (2) can be landed on with a high probability of the lander surviving. To me, this is the goal of the Europa orbiter -- find those sweet spots. Hence, the orbiter has to have a robust (read heavy, power hungry, and bit intensive) instrument suite to find those spots. I think the goal of a Europa lander is far enough out that I would not favor a Europa-only mission. (Plus there is every chance that the sweet spot for landing doesn't exist: where surface material is near the surface, if such places exist, the terrain may be impossible to land in. If this is the only justification for the mission, it is easy to get skunked.) If the Europa orbiter also does *a lot* of Jovian science, too, then I could favor this mission. Europa plus a dedicated Ganymede campaign, plus Io studies (with a big camera) and maybe a flyby or two, plus Jupiter atmospheric studies, plus maybe magnetospheric studies starts to sound pretty interesting. Titan will be wonderfully more complex than Europa, and is an irresistible target for future flagship missions, and if there were only going to be one more outer solar system mission ever, I would consider Titan the best choice. But as part of a sequence, I think it makes more sense to visit Europa next, then Titan, and then possibly Europa for the mission after that. Again, I agree with John. The Europa mission technology has more than a decade of technology development. A Titan mission will be far more robust with a decade of technology development. So, even though it means that I am not likely to see the final mission(s) in the sequence, I think that Jupiter now, then Titan (with that decade of technology development so it's the best damn mission the money can buy!!!), then back to Europa if the Europa orbiter found those sweet spots for landing. This is the manager in me speaking. But if there is only to be one outer planet flagship mission, do Titan! It is the most interesting body in the outer solar system, in my opinion. This is the (armchair) explorer in me speaking. -------------------- |
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