Is Europa really the "highest priority" of the community?, Cleave said it was at LPSC? Options

[mcaplinger]

From Emily's LPSC blog: "Bob Pappalardo would not sit down until he got Cleave to acknowledge that Europa is the consensus highest priority of the planetary science community."

Cleave was obviously poorly prepared for this session, but I don't see that this acknowledgement is either meaningful or particularly accurate. If Europa were the "highest priority" of the PS community as a whole, then one might wonder why we were spending all this money on Mars. I could easily imagine that Europa is the highest priority of the outer planets community, but frankly I was surprised when Europa Orbiter appeared in the '07 budget (presumably the result of some serious lobbying on someone's part.) It was pretty obvious to me then that there would be no money for it, especially in the aftermath of JPL running the old EO project into the ground with cost overruns and engineering upscopes. (And JIMO is best forgotten.)

Don't get me wrong, I would love to be involved with a Europa mission (we did what I think was a good proposal design for EO) but I don't see either the money or the political support being there in the near term. I know it's frustrating, but one has to be realistic, and it might help to avoid the aura of entitlement that I perceive is building in some parts of the community (not referring to you, Bob). Of course, I am just a lowly engineer.

[Guest_BruceMoomaw_*]

Regarding Titan exploration: the PS community currently harbors some hope that a Titan surface-analysis aerobot WITHOUT an accompanying orbiter might be flyable within the New Frontiers budget (e.g., the windblown-balloon version of Titan Organics Explorer). I'll believe it when I see it, though.

Meanwhile, Ralph Lorenz's study group has just concluded that a Titan orbiter with some small additional package (a stationary lander or a fixed-buoyancy balloon) might instead be the best next step. See the last page of http://www.lpi.usra.edu/opag/oct_05_meetin...an_work_grp.pdf . See also pg. 16-30 of http://www.lpi.usra.edu/opag/jun_05_meetin...s/opagtitan.pdf , and the orbiter part of the proposal in http://www.lpi.usra.edu/opag/oct_05_meetin...ngley_titan.pdf .

Such a relatively small stationary lander might very much be worth adding if Cassini can find a location on Titan that is likely to be the result of water cryovolcanism, so that the lander could look for complex water-formed organics. (Or maybe even the remnants of Titanian microbes vomited up from its subsurface water-ocean -- yes, they are thinking about just that in connection with Titan Organics Explorer, and thus one thing it's supposed to do is check any organics it finds for chirality.) That is, the lander would carry the relatively stripped-down science payload planned for TOE, plus maybe a seismometer. (I still think the Huygens team missed a major opportunity by not replacing most of those silly British surface instruments with a short heated core tube hooked up to the GCMS.)

As for a small nonlanding balloon: it might be worth doing too, and not just for weather studies. Titan is one world where cameras on a balloon could do surface observations which CANNOT be done by a camera from orbit, no matter how high-powered -- and Titan's surface is clearly so complex that something of the sort will be needed to understand the place. I also wonder whether such a balloon might carry a subsurface radar sounder -- which is starting to look like something else we will badly need to understand Titan, and which (according to Lorenz) is hard to put on an orbiter because of the difficulty in getting an orbiter down to a low enough altitude for it to work right.

That same extraordinary atmospheric scale height on Titan, though, is indirectly the cause of the one reason why it might be worthwhile flying to Titan before Europa: namely, that (as John Rehling points out) it's a hell of a lot easier place to either land on or orbit. Saturn lacks Jupiter's savage radiation environment; and Titan happens to be the easiest world in the Solar System at which to aerocapture an orbiter -- which would vastly reduce the craft's weight, and which (we were told at the November COMPLEX meeting) we will be completely ready to do for any world in the Solar System once the New Millennium program runs the one proposed Earth-orbital test of the procedure. In short, it may, repeat MAY, be possible to fly a Titan mission which would be fairly close in scientific productivity to Europa Orbiter, but much cheaper -- at which point it WOULD become competitive with EO.

The overall lesson, though, is that it is still way too early to even begin to decide what kind of mission to fly at Titan until Cassini has finished giving the place a far more thorough once-over -- which will take years. And that, in turn, might be a valid reason to delay Europa Orbiter -- if Cassini's later studies of Titan do indicate that it can be explored in a highly scientifically productive way for much lower cost than Europa Orbiter, with or without study of Enceladus thrown in as an addition.