Today I heard this on NPR: Exploring a moon by boat

Quick Google search on Dr. Stofan's name found this: What Next for Titan?

Aside from above quote's understandable skepticism of the Discovery-class price tag, where would plutonium for this mission come from? I thought it is all already allocated?

From http://discoverynewfrontiers.nasa.gov/news...ews_051509.html

"Discovery Program investigations may propose the use of Advanced Stirling Radioisotope Generators (ASRGs) for missions enabled by radioisotope power systems. If selected for flight, NASA will provide up to two ASRGs, including the services associated with their provisioning on space missions, as GFE, and their costs will not be included in the cost cap."

ASRGs don't use as much Pu as thermocouple systems. NASA doesn't say where it's coming from, but presumably there is a source (I had thought that production was going to be resumed.)

As for skepticism about cost, IMHO the cost/risk pendulum has now swung to the extreme end of risk aversion and high cost, so anything that might help it swing back is a good thing.

Does anyone know what are the competing proposals for this round of Discovery missions?

Another (possible) proposal is the Io Volcano Observer, which would orbit Jupiter to explore its innermost large moon, Io. Like Titan Lake Explorer, it would use ASRGs for a power source.

I've written a few posts on this proposal on my blog: http://gishbar.blogspot.com/search/label/I...cano%20Observer

I heard this presentation by Dr. Stofan at the Satellites Panel of the Decadal Survey (I was the notetaker). There was a great deal of interest by the Panelists and other members of the audience, but some skepticism as to whether this could ever fit in a Discovery budget. The reason Dr. Stofan's team believe they might have a shot at that $450M cost cap is that for this Discovery AO, the launch vehicle and ASRGs are provided as government furnished equipment. When you subtract those two giant costs out of the equation...you get a nearly New Frontiers-level budget for a Discovery mission. The mission is targeted for one of the larger "seas" at the North Pole and the probe could have a lengthy lifespan (during an extended mission) of possibly as much as 6 months, if memory serves. The instrumentation would be limited with an imager and meteorological/physical properties suite that could do some analysis of the lake fluid and weather conditions. A descent imager and thermometer would also be part of the deal. Comms would be DTE with a slow (but sufficient) data rate.

The IVO also got several eyebrows raised and lots of questions.

This is right. Don't see $425M and then go comparing that to previous Discovery rounds. With the launch and the ASRG's the appropriate comparison value might be something more in the vicinity of $600M.

This ain't your father's Discovery AO. It's a new ballgame.
- Jason

I'm skeptical that if one were to choose to send just one more lander to Titan, that a lake would be the clear place to choose to send it. Is there focus in this proposal of that specific choice? (Land vs. Mare?) It seems to me that if you could predict the weather, you'd almost want it on a solid piece of ground that will see some precipitation. That might be a pipe dream, but it sounds like the "boat" is going to be a meteorology package plus surface characterization tools. Do we have more questions about what's in a lake, or more questions about what makes any other terrain on Titan? I suppose you do learn for certain what part of the aquifer is composed of... and that answers a global question. But as for surface photos, as pointed out in later posts on the same blog, there might not be too much to see. A descent imager would be of great use, but a pancam wouldn't. If you could try to get the boat to drift to shore, though... that would be neat. Maybe give any mast more of a cross-section to the wind and less in the lake to ensure that it does drift.

I personally agree with this statement. A lander in the dunes, for instance, might prove more interesting. But these are very focused missions, and some advantages of the lake are that it's easy to hit, the engineers won't complain that your landing site isn't flat enough, and that there is new science to be done there. Plus since the landscape will be so boring, they won't have to send as much data back to Earth and so can use a cheaper radio link

- Jason

Titan's terrain is pretty varied: If we did pick the land what terrain type would we sample?
The Equatorial bright stuff? the dark dune stuff? the mid-latitude RADAR-bland stuff? or the dark blue ice sand unit (Huygens part II - the taste test), or the Hotei Arcus cryovolcano stuff?

[Now if you could land on just one part of Earth, where would you send it? The white stuff at the poles, the blue stuff, the yellow-brown stuff, or the green stuff?]

Landing in a lake has the advantage of being relatively homogeneous compared to land terrain. (However, I'll contend that it is possible that the different chemical thingys could segregate out vertically into different goopy layers - sampling different depth might give different results). Another advantage of landing in a lake is that the soluble species (and some of the smaller particulates) from surrounding terrain will end up getting washed into the lakes. So in theory, tasting the lake will give you a taste of all the soluble species from all the terrain types that drain into the lake.

In ignorance of the exact instrumentation, the lake lander will have an easier time acquiring the sample, no digging or scooping, just suck through a straw and shoot into the GC (or whatever). Liquids are much easier to handle than solids. Yet other advantage is that the lake lander will drift over time. So you'll get some spatial coverage as well that a lander won't give you.

My favorite mission is still a Titan balloon that has the capability to touchdown and image and sample multiple points along it's path. Then you could hit a lake, a dune, the mid-latitude bland stuff, etc all with one mission...AND get wind and weather information at different varying locations and altitudes.

You can't hit both dunes and lakes with a balloon. You're at the mercy of the winds. And the lakes are where the giant thunderstorms are that would rip a balloon to pieces.

- Jason

Liquid phase chemistry seems to me the biggest single target for the next Titan surface probe, and there is plenty to learn too about the physical properties and behaviour of the liquid. I do not agree that surface imagery would be boring. We could see any combination of wind waves, precipitation, fog formation, current turbulence, organic scum or other flotsam, lake bed shallows, evidence of diurnal or longer term changes in any of these, and who knows what else. All this and the ability to drift for free to new locations. To me it would be inconcievable to go there yet choose to remain either blind or immobile. So, a lake probe with a chemistry lab and camera: yes please!

EDIT: That's not to discount a balloon - I am just comparing with other possible dry landers.

This is compelling, but someone has to put a figure on what distance over what timescales to make it something than can honestly be considered in pitching the mission. Just seeing a shoreline would be a huge advance over never seeing one.

Many of the arguments for meteorological observations also have an important time component. I'd guess you need meteorology over at least months, especially to quash "Galileo Probe Anisotropy" arguments... what if you plop down into the lake during a supposed rainy time or foggy season, and it turns out that it doesn't fog or rain for a month? Does that just mean you missed the interesting weather? But if you can miss it, does that mean your risk of failing to achieve your mission objectives is high? Do you then get data about a time that everyone after the fact agrees was not representative of the climate you really wanted to sample? Such specific goals for a probe that doesn't have much choice about when it lands or how long it lasts, they scare me. Everyone would love the data from this mission, but the risks of it not really confirming or disproving the climatological theories that we want to confirm or disprove-- those risks need to be quantified. In other words, if you want it to see rain or fog, and we're certain these things occur on Titan, what are the chances it won't? Followed by everyone still believing that those things occur, but have never been observed in situ.

So if you then go back to the objectives that are guaranteed if the probe hits a lake and everything works: photos of a lake, the climate over the lake at one point in time, and the composition of one lake at one point. Everything more ambitious requires guarantees that the boat will work for quite awhile.

My guess is that with the ASRGs, longevity won't be a problem.

- Jason

This has been extensively covered at the Future Planets blog.

See:

Next Discovery Selection
Titan Mare Explorer and TIME
Ilion
Chopper
Venus Balloon
Post with full list of ASRG Discovery Concepts

All Discovery missions get a launch vehicle outside of the $450M PI budget, so no advantage for the Titan Mare Explorer there. A mission that uses an ASRG also gets a free power source, but I don't think that solar panels for competing concepts are likely to be deal busters (and there are lots of other concepts for Discovery missions using ASRGs). I believe that Stofan's proposal also includes a mass spectrometer and gas chromatograph, unless that has been dropped very recently. Not really worth doing the mission in my opinion without that instrument.

The key for this proposal, like a lot of Discovery proposals, is the risk. Depending on how hard you judge it will be to develop the needed capabilities (such as surviving is a frigid place at the interface of two fluid that can suck away a lot of heat fast), a lot of proposals can fit within the Discovery budget. Review boards often seem to judge otherwise, and many a good sounding proposal has been thrown out as too risky for the budget. Whether that applies to this proposal, I have no idea.

Titan's surface chemistry has the potential to be beautifully complex. The lake chemistry will allow an easy spot to get an initial taste of some of the simpler components - the kind you could determine with a GCMS. The more interesting complex things will require much more instrumentation, perhaps a follow-on mission once we know how the material behaves. To determine the really fun stuff, you'd need a technique to seperate, isolate, (concentrate?), then analyze by a few detailed methods, like MS-MS, or multinuclear NMR experiments.

I'm looking at the red can of non-halogenated hazardous waste in our lab. It's probably the best analogy of Titan's lake. Like the lake, I can guess at the most likely components in the waste can: methane/ethane/nitrogen for the Titan lake, acetone/water/methanol for the waste can. These could be quickly determined by GCMS (along with H/D ratios). The minor components could also be determined with the same instrument suite: propane, ethylene, acetylene for the Titan lake, and ethyl acetate/heptanes for the waste can.

The really neat-o stuff will be harder to determine (and I guarantee there's lotsa neat stuff in the waste can that won't get picked up by GCMS). Many of the fun heterocylic polymers and life-precursor-looking-things won't fly on a GC and won't give a lot of unambiguous structural information with GCMS (how many molecules can you draw with m.w. 450??). Getting the goodies will require a more complex analytical chemistry instrument suite (heck, sometimes we need multinuclear NMR and we already know what we are looking for.)

In my opinion, a lake mission is a great way to start learning how to analyze Titan stuff under Titan conditions.

(Personally, for the fancier in situ techniques, I'd favor a non-destructive 2-D TLC with two eluants [one being methane], followed by flurorescence and MS-MS and comparing with signatures from a terrestrial laboratory.)

In re landing somewhere that you expect precipitation, I rather thought that the most likely precipitation seasons are winters at the poles -- places where there will be no light, and thus no possibility of pictures. (I don't care if all you get are pictures of a glass-smooth lake surface and the sky, imagery has proven over and over again to be extremely useful, even in places where you would never expect it to be. I won't be happy with a Titan lander, no matter where it's targeted, that has no ability to return images.)

Also, the boat will be an *awful* lot warmer than the boiling point of the liquid in which it's supposed to float. This isn't water, guys, and we're talking about landing a boat that runs on the waste heat from plutonium decay. Just how, exactly, do the designers propose to vent the heat from the probe in such a way that it doesn't transfer *any* of that heat into the liquid? We won't get information on anything like the liquid's natural state if our boat's major impact on its surroundings is to boil away the liquid in which it floats...

-the other Doug

True, at the moment of splash down the probe will be much hotter than the sea 'water'. However, it seems that it would be reasonably straight forward to insulate the surface of the hull that will be in contact with the liquid. As the hull cools down, and the probe drifts about, eventually the liquid touching the probe's hull won't be at a substantially different temperature. Not to be a smart ass, but insulation works in two directions. It is possible to have parts of the probe remain at a comparably higher temperature (such as the RTG) and keep that heat from creeping through the hull and into the sea, thus fouling the sample environment. In fact, having that nice thick Titanian atmosphere makes it easier, because it allows for RTG heat to be dumped into the atmosphere.

Making sure that the instruments that sample the seawater don't introduce any contaminants (such as a profoundly different temperature environment) won't be a minor problem, but it doesn't seem like a deal breaker.

The Venus surface probes have always faced the problem in the opposite direction. Given the several hundred degree and 90 atmospheres of difference from Terrestial experience and the Venusian environment, I'm not entirely sure that we have sampled the Venusian atmosphere and surface with the correct calibration, and in fact have read a few articles that suggest interpretation of some data has been difficult for this very reason. But that didn't stop us (and the Russians in particular) from trying.

Going from a hot environment to a cold environment (like on Venus) will kinetically freeze out the chemistry, kind of like hitting a stopwatch so no bonus chemical reactions take place.

On Titan, you'd be going from a cold environment to a warmer environment. So you will lower the kinetic barriers to chemistry and stuff may react that normally wouldn't react. (Kind of like examining a tree branch after putting it in a campfire - it might be tough to figure out what you started with.)

On Titan, either GC or aqueous-phase based HPLC might be considered a "destructive" method. What you observe isn't what was there.

It's a wonderful example of how observing affects the thing being observed.

I'm also just a tiny bit skeptical that you can vent the heat from the boat's warm interior (including waste heat from the ASRGs) up into the air and not have any effect on the temperature or composition of the fluid in which you're floating your boat. At the very least, you will heat a column of air over the boat that will cause chemical reactions in the liquids and gases suspended in the heated air column. Products of those reactions will tend to fall back out of the air column, and if they're heavy enough they'll land in the fluid. Most of this fallout would happen near the boat, I would think. So, anything your vented heat precipitates out of the "humid" air will then change the nature of the air and the fluids you're observing.

Also, what happens if the atmosphere over the lake contains an inversion layer that traps the "superheated" air close to the lake surface? We're talking about a rather thick atmosphere, here. Microclimates might well come into existence in such conditions that we don't know enough to model very well, and they could not only trap hot air for short periods, they would also be disrupted by hot, dry air, making our observations of them resemble Mike's burnt tree branch.

I just keep thinking, even if the heat released is relatively low by our standards (under 100 degrees C), the difference between that and the boiling point of the fluids they're in is much larger than you'd think. I'd imagine that if you applied the same degree of difference to, say, the boiling point of water, it would be something like trying to examine the ocean from a boat that's venting white-hot plasma at 5,000 degrees C. Your water collectors, designed to tell you all sorts of things about the chemistry and properties of the seawater, might just end up picking up a bunch of charred feathers and bird carcasses and leave you trying to understand how those fit in with your model of the oceanic environment...

-the other Doug

It won't be all that warm on the outside -- it will have been falling through hundreds of kilometers of cold atmosphere.

- Jason

Like the idea of a Titan boat? Check this out for a summary of a Titan submersible.

I really, really like the dual floater/submersible idea, as long as the floater can float away for a while, and the submersible can sample all the way down the column.

That is just too cool.

Wow! Just love the concept...a true vessel on a truly alien world...I'm all for it!
Did I read someone saying that the images would be dull?...
Even without the submergible I found it to be one of the most enticing missions-to-be, correct if I'm wrong, this is something that would get launched around 2016 is that it? If there's a way of helping this getting through just let me know...

Hmmm...a vessel, on Titan, how would we call it?...thinking...thinking...
Eos!
(Greek Ἠώς, or Ἕως "dawn") is, in Greek mythology, the Titanic goddess of the dawn, who rose from her home at the edge of Oceanus, the Ocean that surrounds the world, to herald her brother Helios, the sun. (from...ah well...wikipedia).

EDITED: OK, I'll correct myself, according to Ellen Stofan they could launch the probe as soon as 2022.

Maybe the probe could use the residual heat for its advantage. It could slide on a vapour cushion, like a drop of water on a red hot pan, and, if it keeps moving, it could pick samples that are still fresh.

Eos (éole-Venus) was a joint French-Soviet 1970s project to fly balloons in the atmosphere of Venus. It later became the Soviet-only Vega (with French instruments on the balloon)

Yes Paolo, you're right, and there's also NASA's EOS...
I was looking for a name related with the Titans and a feminine one, since vessels are usually female.
Found another Titan godess besides Eos that would fit perfectly:
Eurybia, "godess of the mastery of the seas. She seems to have presided over the external forces which influenced the main, including the rise of the constellations and seasonal weather, and the power of the winds."
http://www.theoi.com/Pontios/Eurybia.html

But this is just a futile exercise...

Yes...a mass spec is part of the surface properties package...that's an instrument suite, not just a single one. The mass spec is currently projected to have a 10^4 resolution max. Not sure on the gas chromatograph. The Decadal Survey panel mentioned that having a mass spec with 10^5 max resolution is desirable since that could possibly see pre-biotic molecules...i.e., amino acids and the like.

Doug...the waste heat is absolutely an issue and was brought up by a Decadal Survey panelist when Dr. Stofan presented. They plan to have the heat radiators on the top of the "boat", but they do recognize that they will be a warm bubble traveling through a very cold liquid. She mentioned that it is an issue that they will address in greater detail for their official Discovery proposal later this year/early next year.

What kinds of currents and 'sea' surface conditions might be expcted in Kraken Mare? If the 'boat' hit the center of a landing ellipse that was in the middle of the mare, would it just sit there or might we eventually get a view of one of those fabulously dissected coastlines? Might it eventually wash ashore?

P

Thanks! I've learned through long experience that when I assume that people have taken into account things that seem extremely obvious to me, and I never say anything, others invariably have missed the same realization. Of course, when I *do* mention these things, it ensures that someone has already considered it and is taking it into account...

-the other Doug

How about putting some of that "waste" heat to use. Perhaps it could act like a steam engine on earth, and turn a propellor, or turn a fan that fills a sail. Then we could be sure to make it shore at some point.

Maybe we could call it the Clermont, or the Fulton!

David

My understanding is that one of requirements for Discovery-12 mission is that it must be launched no later than December 31, 2016. It would arrive on Titan by 2022.

Yes...those dates sound right. Dr. Stofan mentioned that a 3-5 year time slip (e.g., for the next Discovery AO) would not impact the mission significantly, but after that as the seasons change on Titan, DTE comms will become difficult and the light level at the northern pole will become too dim for useful imagery.

Some recent Cassini radar imagery was presented that showed absolutely no wave-action on the seas. Based on the data..."waves" would be no more than a few millimeters in height...at least at the time of the imagery. Currents are a complete unknown...but the winds should push the boat several kilometers during the primary mission and more during any extended mission. Dr. Stofan said they expect to see the shoreline if there is an extended mission. Washing ashore is a possibility, but she said they don't expect any "traumatic" encounters with the shoreline based on the low wave heights and relatively light winds.

Yes, I thought that also until I read this:
"If NASA does in fact grant the funding, Stofan says they could launch the floating probe as soon as 2022."
From here: http://www.popsci.com/scitech/article/2009...t-methane-titan
Probably a mistake...

Man...I really love this boat idea...

Well when you launch a boat that's usually the time when it goes in the water. Clearly this boat will have two launch dates.

Good to see this topic has stimulated a lot of discussion.

Since Discovery is a competed mission, I will not be saying very much (clearly, I am involved!), but
I think all the concerns raised so far at least are being addressed.

Some remarks on the general question of lakes vs other targets. The landing system is rather simpler
- Apollo didnt do a water landing just for the heck of it, it is simply much easier. More particularly
the chemical sampling for the MS is easier too.

You could probably do a dune lander (and in the 2007 Flagship study, I advocated exactly that,
because the budget permitted inclusion of sampling arms a la Phoenix and a lot of instrumentation)
As the existence of this thread implies, the Disco cap is a challenging one, although much less so
with the ASRGs provided, so the straightforward sampling of a liquid has appeal cost-wise.

Another point is that as the seasons change, the northern lakes will go into winter darkness for a
decade (more particularly, direct-to-earth comm will become impossible) so if any stand-alone
mission to the lakes is to fly, it'll be at this Disco opportunity (launch circa 2016).

Hopefully there will still be a Titan Flagship mission (orbiter + balloon, at least) in my lifetime.

I'm in favour of a lander "boat/submarine" to be parachuted along the shoreline of Kraken Mare in the high northern latitudes. And it might not be the boring place that some of us are imagining.
The question of exobiology in that environment can't be ruled out. We have an exotic solvent, probably a mixture of methane and ethane and of course carbon molecules and an apparently dynamic weather system (giant ethane cloud engulfing the north polar region).
Maybe that the imager of the probe will take emerging animals from the sea or even birds. Birds in such an environment might not have too many difficulties to fly (dense air, weak gravity) as Ralph Lorenz had pointed out in "Lifting Titan's Veil".

I hope, of course, that Kraken Mare won't have dried out during the summer season of the northern hemisphere. If the lakes are too volatile, I admit, however that the exobiology question loses some credibility.

Actually we already have rather a good photo of the birds:

http://www.unmannedspaceflight.com/index.p...st&id=13889

Here is a nice mission summary:

http://www.spacepolicyonline.com/pages/ima...Stofan-TIME.pdf

Also a BBC story (as mentioned in another thread):

http://news.bbc.co.uk/2/hi/science/nature/8409052.stm