There has always been a firm restriction applied to Europa Orbiter designs: no supplementation or change at all in the spacecraft for pre-Europa science. That being said, the new design for the mission -- which uses Earth gravity-assist flybys, and thus allows them to carry fully half a ton of additional payload into orbit around Europa -- would seem to provide some flexibility for this possibility.

I wince at asking this given the tight budget constraints, but has any thought been given to maybe adding a simple surface science experiment to EO? Something like the Deep Space 2 penetrometers with conductivity, salinity and maybe seismic sensors or a sonar transducer/receiver for crust mechanical property measurements could provide a LOT of vital information that is otherwise quite difficult or impossible to interpolate from remote sensing. A low-power low-rate UHF FSK data link would be quite sufficient for the probe support equipment suite, I would think...

Understand that the necessary sterilization procedures might prove too onerous and expensive for this to even be considered, aside from the existing budget problems...but the beauty of this concept is that most of the instrumentation I described has already been engineered to rugged deep-sea oceanographic standards as COTS equipment. NOAA uses this stuff all the time (and, no, I wouldn't expect them to punch through to any hypothetical ocean...but wouldn't that be cool!!!! )

The debate over whether to use that huge new payload margin to put a small piggyback lander on EO was one of the primary subjects at the November COMPLEX meeting, since there has already been quite a lot of design work on possible landers with varying degrees of complexity. (In particular, there was an unbelievably long drawn-out wrangle over whether a seismometer and magnetometer might be worthwhile on a small short-lived lander, which eventually began to resemble that 10-year debate among the savants on Jonathan Swift's Laputa over how long to boil a 3-minute egg.)

The group was nowhere near a recommendation when the meeting ended, but the impression I got was that there wasn't much enthusiasm because it is probably impossible for such a small lander to drill down deep enough into the surface to find any organic compounds that haven't been hopelessly scrambled by Jupiter's radiation -- and without that, the science return from a lander is just not that high. The leader of the team of graduate students who did the hypothetical "Endurance" lander design study described in a poster at the December AGU meeting told me that his group had reached the same conclusion: it would probably be more scientifically productive to put that extra mass into more Orbiter science instruments, a higher bit-rate communications system, and (especially) more shielding to prolong the orbiter's working lifetime in Europa orbit. (It takes 100 kg of shielding to extend the Orbiter's lifeime there by 1 month.)

Oh, well; at least it was considered. Thanks, Bruce!

I am surprised that surface (or just below!) conductivity/permittivity studies wouldn't be considered high priority; we could learn a lot about the amalgam of salts present in the crust--and therefore those present in the possible ocean--that way.

Just to follow up...

In the January 27, 2006, issue of Science, Jeffrey Plescia, of JHU/APL, in one of three letters ("Thinking About NASA's Future") responding to Science Editor-in-Chief Donald Kennedy's Editorial in the November 25, 2005, issue ("NASA: Back to eating seed corn"), closes with the following:

No "fiscal windfall", true. But it strikes me as an exaggeration to say that NASA would "not continue" without a major manned flight component. After all, the things keeping NASA going are (1) its actual valid justifications, and (2) its pork value -- and the latter includes spending on unmanned as well as manned projects. No doubt NASA's total budget would shrink, but it's very implausible that it would "not continue" -- instead, a lot of the Congressional and Presidential hunt for politically useful space pork would be transferred to the unmanned space program, leading to some degree of increase in spending the latter, and quite possibly a large one.

But that takes us to the obvious next question: what if NASA SHOULD vanish, and what if the unmanned space science program should also be radically shrunk after the manned program is eliminated, on the grounds that most space science projects are appallingly low in scientific cost-effectiveness compared to spending on other types of scientific research? We ourselves would certainly regret that, but you would have a hard time coming up with a morally convincing argument against it.

It's hardly surprising, however, that Plescia is pushing the manned program for all he's worth -- he has always done so, although virtually the only argument he's ever been able to come up with for the science value of humans rather than robots on the Moon is that the latter would have more trouble doing deep drilling operations.

Planetary Society Charges Administration with Blurring its Vision for Space Exploration

The Planetary Society Cites Cancelled Plans for a Europa and Other Science Missions

Pasadena, CA, — The NASA Budget released today shortchanges space science in order to fund 17 projected space shuttle flights. Despite recent spectacular results from NASA's science programs, this budget puts the brakes on their growth within the agency. It seriously damages the hugely productive and successful robotic exploration of our solar system and beyond.

According to this budget, flight projects that were already underway, such as the Space Interferometry Mission, will be delayed. Others, such as the Terrestrial Planet Finder and a mission to Jupiter's moon Europa, will be deferred indefinitely. Furthermore, the new budget slashes funding for the fundamental space science that makes such missions possible and turns raw data into discoveries.

http://www.planetary.org/about/press/relea...ty_Charges.html

Outrage

Maybe, there will more robot exploration between Earth and Moon. These will be the first robots as a model to conquer to other planets. I bet after that, there will be a leap technology to explore others bodies of our solar system. It is a just a change of aim but the robot technology will continue improving and the there will be no lost time.

Rodolfo

Agreed.

Bet things would be different if JSC & KSC were located in states other than Texas & Florida, respectively...

I suppose I do have something to thank LBJ on in this respect -- even if he was the one who almost single-handedly persuaded JFK to launch the Moon Race (while telling his own friends that he had done so mostly to provide economic pork for the South). The Manned Spacecraft Center was originally supposed to be built in Vallejo, California before he rediverted it to Houston. Had he not done so, it would have been my own state's Senators who were constantly making dishonest jackasses of themselves on the subject of manned space exploration.

Dear ESA,
As you are aware, our current administration has some "issues" with our space budget. Please consider a sophisticated robotic mission to Europa. I mean really, Europe, Europa - the PR writes itself!
Thank you,
Jeff

Spaceflight:

* Europa Mission: Lost In NASA Budget

http://www.space.com/news/060207_europa_budget.html

NASA's newly issued budget has lowered a flagship mission of exploration to
half-mast. Backed by scientists and study groups, a mission to Jupiter's moon
Europa is missing in action within the pages of NASA's Fiscal Year 2007 budget
unveiled yesterday.

Interesting quotes:

One additional payload on Europa Explorer: a simple lander.

Pappalardo said a lander is still being bandied about, but carrying what kind of technology and at what cost are questions awaiting answers.

“We’re not going to search for life with this mission. But just like the Mars rovers in their search for habitable environments…we’re going to characterize the habitability of Europa,” Pappalardo said.

An orbiter to the moon of Jupiter would allow a now sketchy view to become sharp as to how this world works, Pappalardo concluded. This mission, he said, has compelling science and broad community support and “we’re ready to go.”

and:

Also, the European Space Agency (ESA) is currently studying the Jovian Minisat Explorer (JME). The JME focuses on exploration of the Jovian system and particularly the exploration of its moon Europa. The ESA study is also looking into deploying a compact microprobe onto Europa to perform on-the-spot measurement of the moon’s ice crust.


* NASA Seeks 30-Percent Increase for Exploration Program

http://www.space.com/news/060206_nasa_budget.html

Efforts to replace the space shuttle fleet with new Moon-bound spacecraft would
receive big spending increases under NASA's 2007 budget request, while nearly
every other part of the U.S. space agency's budget would be held flat or
decline.


* SPACE NEWS: Policy or Politics? NASA Accused of Intimidating Climatologist

http://www.space.com/spacenews/businessmonday_060206.html

NASA is battling accusations that it tried to stifle its top climatologist, a
man well known for speaking his mind about the causes and consequences of global warming.

Remember this budget is just a request. Congress has the final decision on how much gets allocated to NASA. For several cycles, the Administration allocated no money to New Horizons, but Congress funded it anyway, and now it is on its way to Pluto. And it was Congress that told NASA to prepare to start a Europa mission last year. I would not be surprised if some small part of the 30% boost to ESMD is shaved off and tranferred for a Europa mission. The same goes for SIM. The important thing is that the scientists, advocacy groups and media push for it. That looks to be happening.

National Geographic:
NASA Budget Diverts Funds From Science to Spaceships
http://news.nationalgeographic.com/news/20...60208_nasa.html

See my post in
Policy and Strategy > The Creature That Ate Nasa Takes Another Big Bite
as to what you might be able to do to help remind Congress about Europa.

Let me suggest a conspiracy theory behind the EO cancelation. While money is sure to be tight, and an axe is going to be aimed somewhere, the choice of EO and TPF may have been performed by someone who wanted to see as little as possible in the way of cuts and reckoned slyly that those two missions are most likely to get a reprieve (by Congressional fiat). If so, putting them in harm's way, which they will, as my theory goes, escape, leads to the least eventual cuts, because putting some other projects in harm's way might have been harder to reverse.

In other words, the sort of campaign that saved NH is not to be considered an extraordinary follow-on to "the system", but part of the de facto system. And in some sense, these missions aren't in jeopardy until a similar movement fails to save them. Warm oceans nearby and earthlike worlds far off should perk some interest, what say...

I hope you are right.

Yeah, that was my thought as well. THe old "close the Washington Monument" trick.

We've always been pretty sure that that's what's going on with the Voyager 'cancellation.' But I think Europa and TPF are different. Europa, at least, will need to be a big, big mission, and it's just not going to work to "save" it every year by congressional action. It really needs to be built in to NASA's very long term plans over more than one decade. Engineers and particularly scientists will need to devote large chunks of their professional careers to getting it going, and despite people's devotion to Europa, I think it would be awfully hard to take the risk to your career to devote so much professional time and energy to a mission that is at risk of being cancelled every year. New Horizons was hard enough to do that way, and it is a much simpler mission. NASA has got to make a long-term commitment to Europa for a mission to work.

--Emily

I agree with Emily. These proposals are simply too big to be subject to this kind of subterfuge to preserve them. Moreover, Congress has already made it clear (with justification) that they are not going to spend any more on NASA as a whole - and the Administration has made it clear that it considers manned spaceflight much more important than unmanned spaceflight and space science.

As for WHY the Administration considers it so much more important -- well, we just got another clue yesterday, when the House GOP (as a consolation prize to Tom DeLay for getting the boot as House leader) gave him seats both on the Appropriations Committee, and on the subcommittee which oversees the Justice Department (which of course is currently investigating DeLay himself) and which also (as a result of DeLay's recent redesign of the House committee system) controls NASA. (The Manned Spacecraft Center is of course now in DeLay's district, and that earlier Washington Post article hinted that he was already the main figure keeping Shuttle/ISS from being trimmed back):
http://news.yahoo.com/s/ap/20060208/ap_on_...wBHNlYwN5bmNhdA

Both the White House and the GOP are still terrified of DeLay -- he is, after all, the one who knows where all the bodies are buried in the gigantic nationwide Tweed Ring that the GOP has now set up in this country -- and it's a safe bet that they will continue to give him everything he wants, if they think they can get away with it, until the moment when he is either indicted or defeated for reelection. After he's gone, we may see some fairly major readjustments in the NASA budget as a side effect.

No argument here, Emily. Frankly, I don't believe any putative "Europa Underground" is going to achieve for Europa Orbiter (EO) what the Pluto Underground effort did in finally getting a Pluto mission launched. As you noted, there are too many fundamental differences between EO, or at least the type of mission recommended by the decadal survey, and a Pluto flyby. No matter how one slices it, EO is going to be a Flagship-class mission (i.e., "Battlestar Galactica"-class). The problem is that, as recommended in the aforementioned decadal survey, NASA will probably be able to fly Flagships only once per decade. With Mars sample return (another Flagship-class mission) preeminent, I don't see how EO can fly before 2020 without some massive amounts of paradigm shifting.

At times like these, one can only look back on the now-defunct Outer Planets/Solar Probe (OP/SP) Project with a mixture of bitterness and, believe it or not, humor. Ludicrous as it seems now, under the reign of Captain Crazy (Dan Goldin), the entire OP/SP effort (from cradle to grave), which included three missions (EO, Pluto-Kuiper Express (PKE), and Solar Probe (SP)), was to be cost capped at $750 million. Believe it or not, this also included launch services on EELVs (and the Shuttle for EO), RTG power sources, development of X2000 enabling technologies (which turned out to be vaporware), procurement of science instruments, mission ops, data analysis, yada, yada, yada. Needless to say, OP/SP turned out to be a total fiasco that led to EO being spun off into a separate JPL-led effort, PKE initially getting axed and later brought back to life as a competitively-bid PKB mission, and SP getting axed and re-axed.

Don't forget that the new budget also axes all preliminary research for Mars Sample Return as well -- and the message communicated to the November COMPLEX meeting by Andy Dantzler and Doug McKutcheon had been that Europa Orbiter is definitely higher-priority than MSR for now, and indeed should fly over a decade earlier.

What happened is simply that the continuing attempt to keep Shuttle/ISS going has bled off huge amounts of money from EVERYTHING else -- not just from space science, but from Bush's own manned lunar program (and his tentative moves toward a manned Mars program, which have now been totally eliminated). He wouldn't have done that unless he had been forced to do it.

I was, however, wrong in saying that that Nov. 21 Washington Post article ( http://www.washingtonpost.com/wp-dyn/conte...2301970_pf.html ) said that unnamed Congressional leaders were forcing him to do it. The actual passage is:

"Several sources confirmed that the budget office in the early negotiations proposed stopping shuttle flights altogether. 'It sucks money out of the budget, and it's a dead-end program,' one source said.

"But 'that argument's over,' another source said. 'The political side of the White House said, "We're keeping it." If you kill the shuttle right now, it will be heavy lifting for your foreign policy because of the international obligations' around the space station."

However, that argument -- as Jeffrey Bell points out -- is utter twaddle; we could end the Shuttle/ISS program much more cheaply and cost-effectively by simply repaying our "partners" for their wasted money, especially since they themselves are getting increasing local pressure about flushing money down the ISS rathole. Something else happened -- and the single most likely cause is indeed pressure from Congressional leaders. Specifically, Texan Congressional leaders, since Texas relies specifically on the manned part of the NASA programs, while Florida and the other states could adjust much more easily to NASA spending that was reoriented toward unmanned programs. Feel free to fill in the gaps.



"

Also, historically, note that Captain Crazy's proposals for Mars Sample Return were even loonier than his proposals for OP/SP -- MSR missions starting in 2003, at $500 million per flight -- and COMPLEX, I shudder to report, found that program entirely plausible in a review in November 1998:
http://www7.nationalacademies.org/ssb/marsarchmenu.html

Well, they were only 21 years and $1.5 billion off.

A bit more on Bugsy DeLay's possible hand in all of this at:
http://www.hillnews.com/thehill/export/The...0806/news2.html

As I say, he knows where all the bodies are buried.

A few reality checks here:


* I don't see Mars and Europa in competition, but if they are, I believe that Mars is not being shortchanged any in the mission department lately.

* X2000 successfully produced radiation-hard components, including components flown on Deep Impact. That investment is now awaiting a Europa mission to fly.


* COMPLEX typically reviews the architecture, not the costs.

Actually, I don't think it's a question of which target is being "shortchanged," and I think it's obvious that Europa is getting the shaft, rather it's which target is likelier to convince the politicians (both administration and congressional) to fund a Flagship-class exploration mission, IMO. If one operates under the assumption that only one such mission can be flown per decade, then, I would think, Mars and Europa are indeed in competition, at least in the short term.


Thanks, I wasn't aware of that. BTW, is there is a list somewhere of other realized X2000 products?

There's a nice summary of them (and the remaining problems) on the second page of an LPSC abstract co-authored by none other than Bob Pappalardo:

http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1459.pdf

Where Flagship missions are concerned, NASA's original plan was to fly one per decade to a non-Martian target in addition to its separate Mars program.

Even within its hoped-for yearly funding for the Mars Program alone, however, NASA had been having trouble fitting MSR into the Mars schedule -- which is why they ended up bumping it all the way to 2024. About a billion dollars worth of its total estimated cost (now roughly $4 billion) must be poured into preliminary R&D starting a decade or more before launch.

http://www.washingtonpost.com/wp-dyn/conte...0100022_pf.html

Is NASA in Outer Space?
Not After a Surprise Round of Budget Cuts

By Michael Benson
Washington Post
Sunday, April 2, 2006
page B02
© 2006 The Washington Post Company

In her NOVA interview, Carolyn Porco made it clear she would prefer to forgo Europa and take another stab at Enceladus.

As fascinating as Saturn is, I would prefer a fully-loaded Jovian mission first. There is much to learn.

Feel free to list those components; I'm extremely skeptical that any of the X2000 components ended up being megarad hard if they ever saw silicon at all. See http://centauri.larc.nasa.gov/outerplanets/Dscr_X2000.pdf for what these looked like for the first EO. The microcontroller was abandoned; the NVM slice never existed at anything like the hardness levels intended; and if the DC-DC converter was ever developed I've not heard of it. So just what are you referring to?

The coloration on the cracks of Europa is especially interesting to me. Far-fetched theory, but perhaps some sort of algae that turns brown after exposure to UV radiation?
More likely just some chemical oozing up from below, but who knows.

I guess the benefit of Enceladus is that the water's just spewing out into space from open cracks. Europa's got a helluva thick crispy crust protecting its water.

You know, that's a good point -- Enceladus has geysers and Europa does not, at least not at present.

And yet, Europa's cratering record shows that its surface has been reworked pretty extensively over time -- there just isn't anything like the crater count that you find on, say, Callisto or portions of Ganymede.

On Enceladus, it's pretty obvious that the resurfacing is happening via the geyser activity. Older, more rugged terrain is being buried in massive "snowfalls" on Enceladus.

But on Europa, the relatively young surface isn't simply a visually homogenous covering layer of snow. It is a very complexly cracked surface that appears to have, at least at some pont, been a pretty thin covering over a large liquid ocean. As I understand it, it's hard to explain the cycloidal (I think that's the term) cracks if the ice layer has always been kilometers-thick.

But the Europan resurfacing *appears* to have had everything to do with repeated release of liquid water onto the surface and nothing to do with plume-deposited ice crystals. All slosh, no whoosh.

So, does this mean that Europa hasn't really seen geyser activity in the geologically recent past (i.e., since its last major resurfacing)?

And if so, what does the lack of such eruptions tell us about Europa?

-the other Doug

Rule 3.5 - un-needed quote removed - Doug

I could have sworn there was an article in a circa 1980 issue of Sky & Telescope
magazine that showed what might have been a plume on Europa. Does anyone
have the details/image?

There was some speculation by one researcher that that photo MIGHT show a plume -- but later study did not bear him out. Cynthia Phillips, in particular, has been going over every damn spacecraft photo of Europa ever taken looking either for plumes, or any signs at all of visible changes in surface features -- and, so far, she hasn't found a thing.

The evidence continues to grow that Europa undergoes cycles of varying levels of tidal heating, over periods of 50-100 million years, as it and the other Galilean moons slowly shift their precise orbital relationships -- and that at the moment it is in one of its cool periods, with a thicker crust and thus no cracks or vents punching through the ice (but with solid diapirs of warm ice, perhaps accompanied by local pockets of briny meltwater, slowly creeping up through the current thick ice layer to produce the "lenticulae" and chaotic terrain, which seem to exist on the fresher areas of Europa's crust).

I remember that. The problem was that it was a single pixel in a lone opnav frame. Therefore, the probability of it being noise, especially given that there were no other frames showing it, is too high to reach any conclusions.

Have a careful read of the Enceladus Science papers (specifically Porco et al vs. Spencer et al.) and you will see that the evidence for water is equivocal, and arguably circular. The prime piece of evidence for liquid water (Porco et al) is the inferred high ice/vapor ratio of the plume (top of p. 1398). This is inferred from scattering models and assumptions of plume particle sizes and argued unlikelihood of particle entrainment in sublimating gas (briefly explained in note 30). Should we hang our conclusions and exploration strategies on that? Instead (Spencer et al), the fractures of Enceladus may simply expose warm (T ~ 180K) ice which sublimates like a comet (p. 1405). Show me the water. (Perhaps discussion appropriate to a different thread.)

That does make it helpful in the sense you don't have to drill down as much (and the fact that no one really cares about Europa ). So the material you want is much more accessable. However, if you want to land, there isn't much choice on where you can land as only a very small percentage of the surface has a resonably access water body beneath it (assuming of course that a sub-surface body of liquid water generates the plumes). Europa would presumably have a far greater number of acceptable landing sites.

But that still leaves the problem that no one cares about Europa.

Okay, I'll stop messing with vexgizmo now.

Is the number of sites a big problem? One is enough, as long as it's not so small as to be hard to target.

I think a bigger problem, even in the best case, the engineering task becomes difficult/uncertain:

Supposing Enceladus does have a pocket of H2O "magma" that spritzes out of a few cracks, the exploration strategy isn't totally clear. There must be some artesian pressure working to force that water out, and whether you want to go in via the existing aperatures or make your own, I don't see how that would work. I see a lander getting fatally blasted by a rocket-fast stream of H2O coming the other way. Maybe we should send two and have one take video of the other one. But that doesn't get us a submarine in that lake.

Or maybe a lander could study from nearby the gush of vapor/ice from a vent, but then what's the point of being on the surface at all?

Even if the optimists are right (and I think they are), I don't see the exploration strategy.

Maybe the way to go is to identify a place where the ice is a desired thickness, like 100 m, and then use a melt-down approach that counts on the tunnel re-freezing behind the probe. Then when it finally taps into the high-pressure soda water, it'll have nowhere to get rocketed back into except the ice at its butt end.

That mission would require a precursor of some sort.

I'd say we might just want to put a lander or even the very same class of lander onto both Enceladus and Europa in the locales of most likely water access and perform a Viking-equivalent mission analyzing the ice for nonice content, and using seismic/sonar means to investigate local ice depth/structure.

It seems like the superset of options would be:

Europa Orbiter
Europa Icepick Sample Return
Europa Surface Lander
Europa Subsurface/Submarine Mission

Enceladus Orbiter
Enceladus Plume FlyThrough Sample Return
Enceladus Surface Lander
Enceladus Submarine Mission

Enceladus science needs to age like a wine before the sense of those missions can be evaluated. Europa Orbiter is clearly a need, even if it's not clear that it's the top need. The two Surface Landers could merit identical design. I can sense Europaists getting itchy at the idea that the two worlds getting anything like a unified approach, but if the two worlds both have the water endgame feasible, then I think the plans ought to converge. On the other hand, we may have an Enceladus without actual liquid... or we might have Europa with a crust so thick as to indefinitely discourage access to the ocean. It would seem that Europa has the advantage of getting the next move, but Enceladus is more likely to get to the endgame this century.

I suggest that, since most of the water spewed off Enceladus' plumes immediately falls back onto the moon, the logical course is to touch down a modest distance from the plumes, just collect the falling snow, and then periodically melt, filter and analyze it for organic remains.

After all, even if (as Bob Pappalardo suggests) the plumes may just be due to ice sublimating off the surface of Enceladus, when that surface is heated from underneath by warm liquid water, you're going to get a conveyor-belt recycling over geological time -- the snow will reaccumulate on top of the ice near the plumes, and its weight will cause more of the ice on the bottom layer to sink down to depths where it in turn will be melted before later being refrozen into the bottom of the ice layer. And since Saturn, unlike Jupiter, does not have an intense radiation environment, there's a good chance that any biological or prebiological remains in the warm liquid water will survive for a long time on the surface after having been frozen into the bottom ice, slowly carried upwards by the solid-state convection in the ice, and then expelled onto the surface. (This, after all, is precisely why we're hoping for frozen biological remains in Europa's near-surface ice, once you dig down the relatively short distance below its radiation-damaged upper layer. In the case of Enceladus, the sampling is easier. And if Titan's cryovolcanism is as strong as it currently appears likely to be, a similar search for frozen biological remains in the surface ice from its probable subsurface ocean also makes sense -- and, in fact, the instrumentation for the suggested Titan Organics Explorer WOULD look for chirality in any surface organics that it finds.)

Clearly the first step is to try to (1) get more detailed information on the trace components in Enceladus' plumes; and (2) try to get a measurement of the precise surface temperature at the central source of the plumes. Which, of course, is prcisely what Cassini will be trying to do in its super-low 2008 flyby, which is why its controllers have decided to run that risk. (Notice how Enceladus, so far, has been the ONLY thing found in the Saturn system that has made Cassini's controllers change their original mission plan?) Only then -- and only after Cassini has also told us a lot more about Titan's global surface layout -- will we be able to make any reasonable judgement as to what to do about these three worlds, and the order in which we should do it.

If Enceladus does indeed have a conveyor-belt snow recycling system, then it might also be that we'd find analogous sites to the Antarctic locations where meteorites fetch up. By sampling along such a 'shoreline' where fresh snow gets trapped and sublimates away, we might have access to the greatest repository of objects from other worlds anywhere we've yet found!

Bob Shaw

You misunderstand me. Once the snow lands a certain distance away from the warm regions where the ejection of water vapor occurs (either by direct geysers or by sublimation of ice from the top surface of the warm regions), it stays in place permanently. And the only debris carried up with the water, even if geysering occurs, is possible rocky material from Enceladus' interior -- and then it won't be kicked a long way from the geysers unless it's quite fine material. (If the plumes consist of water vapor just sublimating off a warm ice surface, no other material at all will be spread farther by the plumes, except of course for the trace gases mixed with the water vapor -- but the glacially slow convective "conveyor belt" of warm ice creeping upward in the central warm region, and descending again in the cooler peripheral regions where the snow is accumulating, might carry some rocky debris from the interior up to the surface in the plume regions.)

In any case, those trace gases that get expelled along with the water vapor explain the frozen CO2 and other "light organics" which the VIMS HAS seen spread on the surface for some distance from the vents, along the Tiger Stripes -- and getting a better look at the composition of those other substances with the VIMS must be yet another urgent goal of the coming super-close 2008 Enceladus flyby. (Bob Pappalardo, by the way, obligingly sent me copies of the "Science" articles on the VIMS and mass spectrometer findings, which I'm reviewing right now and will report on later.) If it turns out that the plumes ARE just due to vapor boiling gently off the surface of a quite wide area of relatively warm ice, then it would almost certainly be safe for a lander to touch down right in the middle of the plume region -- and analyze the ice right there to see what else was oozing up from Enceladus' interior along with the warm ice.

I just have to ask this question: When it comes to Scientific information, would a mission to Enceladus provide more information than a mission to Europa assuming no life, or complex organics, are found?

I know the liquid water = life argument is trotted out with regularity, but that is still pretty uncertain. At least a Europa Orbiter, or some analagous mission, would provide us with lots of extra information on the Galilean Moons, but this proposed Enceladus mission seems totally focused on life,life,life. If the life does not show up, then it would seem that the mission would be mostly a waste. It seems a bit risky to me.

I would hope that the people at NASA can conceive that -there may be liquid water there-, and -we may get clues to the formation of the solar system- are not the only good reasons to send out space probes. Io, for example, is a fascinating place. There is also a certain satisfaction is getting the first good images of an object that was previously just a dot or a smudge, at least to me. That's pure exploration.

So what I am saying is that I find throwing away a mission that will return valuable, non-search-for-life science , in return for a mission with a remote chance of hitting the jackpot, rather reckless.

I must respectfully disagree with you, James. Although finding life on Enceladus via a lander mission would of course be the scientific coup of Western civilization, in situ observation of the plume processes and associated chemistry would still be valuable in its own right, and certainly enlightening in a wide variety of ways.

Consider: We don't really understand why Enceladus is even active at all at this time. Pure tidal influences seem inadequate; is there something unique about the moon's geochemistry? This is a valid research question with profound implications for the formation of the Saturnian system that alone would justify a lander.

By comparison, Europa does not seem to demonstrate any recent cryovulcanism (although I acknowledge that the Galileo dataset may not have been sufficient to rule it out completely) despite the fact that it's much more massive than Enceladus and also exposed to significantly greater tidal stress.

Therefore, if forced to choose (as we must given the newly austere budget environment), it seems rational to study the more geologically active target in detail first. Finding life would be nice, but it cannot be the entire rationale for such high-risk missions.

[size=2]


Back to the subject of the Europa Orbiter, I think that we need to call
Griffin on his remarks last week at the NSS (National Space Symposium).
He suggested that we wait 10 years until the heavy-lift CLV and CaLV
are available. Then, NASA could fly a Jumbo mission to Europa.

This is the same old trick that Goldin, and company, tried in 2000 when
NASA wanted to cancel a mission to Pluto. At that time, it was suggested
that we wait until an advanced nuclear ion propulsion system becomes available.
Then we could launch a Pluto probe on a really fast trip to that planet.
Fortunately, Congress saw through the "smoke-and-mirrors" and added
funds to NASA's budget for the New Horizons probe. As the UMSF community
can see in another post on this site, the advanced propulsion effort, Project
Prometheus, has been cancelled.

I hope that Congress is not tempted to believe that there is merit in Griffin's
suggestions at the NSS. We need to reject Griffin's siren call to wait, and
instead get on with a mission to Europa using technology already in hand.


Another Phil

As if flying a scientific mission on a man-rated mammoth booster would ever be an option. How many unmanned probes did we launch on the Saturn boosters? Even when they they were ordered and payed for, they were send to a museum rather than to Jupiter or Saturn. Mr. Griffin's suggestions are starting to sound pretty desperate, if you ask me. I still hope ESA can play a leading role in a Europa orbiter, it seems such a logical next step.

Pluto was a special case - the atmosphere is a ticking bomb waiting to go bye bye - we needed to get there by X to have a good chance of investigating it before it froze out.

I agree that Enc and Eur can 'wait' as it were. But only for financial reasons (i.e. we can't afford them at the moment) however - there is no need or requirement for the new heavy LV for those missions. If what you're building busts an Atlas V Heavy, Delta IV Heavy or any other LV mass budget, then you need to be more creative with your mission - slingshots, ion prop - whatever it takes.

Doug

Doug

Do you really think ESA can afford funding such a grand mission? From what I gather, Venus Express is their last planetary mission (for the time being) and they're now shifting towards astronomical observatories.
Any involvement in EO would likely be in the form of a joint NASA/ESA mission and I don't know how likely that is given the current state of NASA and its unmanned space exploration. ESA already was once in a position of rescuing a mission from being cancelled (Cassini) and it's questionable whether they are willing to take the risk again and see the U.S. folks bail out on them halfway through the development phase. IMHO, NASA (arguably not due its own fault) just currently can't be taken as a reliable partner.

Saturn V was never a launch vehicle that went into serial production. Contracts were made to build 15 or so of them and then the industrial infrastructure and manpower was laid off. In the end they winded up with a couple of surplus ones and used one to lift Skylab as it was one of the uses a Saturn could have been used as a heavy lift booster. It was much too expensive and useless to continue production because their capability was pretty much overkill once the moon race ended.
Even today, think about its capability - IIRC 30 metric tons to Earth escape velocity. Building a probe that heavy and capable would probably take billions (along with the cost of the vehicle itself) and its obvious these days one can't get even a measly billion for a flagship mission. You'd have an ultra-heavy booster that the market just doesn't need. In that light, it'll be interesting to see where Delta IV Heavy will end up.

The Skylab booster was the Apollo 20 Saturn 5. The abandoned flight vehicles were the boosters for 18 and 19. However, there are 3 Saturn 5's on display!

All of them incorporate parts from something that LOOKS like a Saturn 5 but was never a flight vehicle: the "Facilities checkout vehicle"... used to test VAB/Crawler/Launch-Umbical Tower/Pad equipment, including fueling exercises. But it didn't have real engines or lots of other stuff.

Things are a bit more complicated than that IRL, but you'd need to read the exhaustively detailed new book on Saturn 5 to find out.