The moon's geology is pretty clear and Cassini has gathered a lot of data.As much as this and many other moons have things that would be awesome to study, I agree that funding is unlikely unless the powers that want sacrifice something else they want to visit, if that.That said, if we really get serious about interplanetary flight, Enceladus as a fuel depot is too good an opportunity to study and utilize. Is there any other moon with as much water ice other than Europa?
Enceladus (and/or Titan) was added recently to the list of candidate missions for the fourth New Frontiers slot.
A flyby probe to capture some of the material from the jets at the tiger stripes would be great, and would be a relatively easy sample return mission
I'd rather we didn't use it as a fuel depot if it does contain life. We've done enough of that nonsense here on Earth without starting in the rest of the Solar System.
no one expected Enceladus to be interesting until Cassini got there
Quote from: JH on 06/23/2016 04:19 amno one expected Enceladus to be interesting until Cassini got there actually, Enceladus was an intriguing little object already after Voyager 2 flew by and revealed its young surface. it was already suspected that something must be going on
A flyby probe to capture some of the material from the jets at the tiger stripes would be great, and would be a relatively easy sample return mission, but it is complicated by the challenges associated with getting a probe out to Saturn within a reasonable budget. RTGs would be much too expensive, so we're talking solar power. It would have to be a very simple probe and it would have to operate on a very small energy budget. There have been several proposals for a flyby sample mission like this or other exploration of Enceladus, https://en.wikipedia.org/wiki/Enceladus#Proposed_mission_conceptsbut none have been funded yet.
Then there's the overall time required for such a mission--approximately 8+ years there and an equal or greater time back, for a total roundtrip of over 16 years.Then there's the fact that if your Level 1 science goals define "success" as "return sample safely to Earth," and your spacecraft unsurprisingly dies in year 17 of its 18 year mission, it fails.
And then there's the issue of how you handle the sample return. I think it's best done above GEO in a telerobotic facility,
No. All laboratory analysis equipment has been designed for use on Earth. There are lots of pieces of equipment--like a cyclotron--that you could not make small and light enough for space use. Doing lab analysis in space would require all new equipment and techniques and would never be as good.
...Is there any other moon with as much water ice other than Europa?
That said, if we really get serious about interplanetary flight, Enceladus as a fuel depot is too good an opportunity to study and utilize. Is there any other moon with as much water ice other than Europa?
Quote from: MattMason on 06/22/2016 07:59 pmThat said, if we really get serious about interplanetary flight, Enceladus as a fuel depot is too good an opportunity to study and utilize. Is there any other moon with as much water ice other than Europa?Yes, from Jupiter outwards, most of the smaller bodies are consisted almost entirely of ice. The ring system of Saturn is as well.Ideally you would want a fuel depot where you aren't going to contaminate any subsurface ocean with Earth life. So you'd choose the ones without oceans, or ones with very thick crusts.An ideal target there would be Callisto in the Jupiter system. It's got a subsurface salty ocean, but thought to be so deep below the surface that there is no chance of contaminating it with surface activities. Also it orbits outside the hazardous radiation of Jupiter. So it would be an ideal place to send humans.In the Saturn system, Titan has an Earth pressure atmosphere permitting aerobraking, but low gravity for take off. It has a subsurface ocean of water also, so it depends on whether there is communication between its subsurface and the surface, which nobody knows. If there isn't any, well modern Earth life couldn't contaminate the Titan seas, far too cold for Earth life. There might be exobiology there, if so it's the one place where humans could actually land and study it in situ without risking contaminating what they study with Earth life .So a base on Titan in the Saturn system would be pretty cool I think. Very exotic location. Would need to look into it carefully but I don't see any major issues with that apart from the issue of possibly contaminating the subsurface ocean.
As for experiments that are designed around presence of gravity - no need for the facility to be in zero g, unless that is required for some reason. Use a counterweight (e.g. spent third stage, or another hab) to spin it to generate artificial gravity (AG). Technically easy to do. Main thing would be how to dock - need a module at the hub of the spin for docking, docking port counterspun.
Quote from: whitelancer64 on 06/22/2016 07:46 pmA flyby probe to capture some of the material from the jets at the tiger stripes would be great, and would be a relatively easy sample return missionCan you explain what you mean by "easy"?For starters, there's the issue of approach velocity--how do you capture the sample without destroying it with the high velocity impact with the sample collector?Then there's the overall time required for such a mission--approximately 8+ years there and an equal or greater time back, for a total roundtrip of over 16 years.Then there's the fact that if your Level 1 science goals define "success" as "return sample safely to Earth," and your spacecraft unsurprisingly dies in year 17 of its 18 year mission, it fails. Then there's the lifetime cost of a mission that lasts 16+ years, which is not exactly cheap.
Quote from: whitelancer64 on 06/22/2016 07:46 pmA flyby probe to capture some of the material from the jets at the tiger stripes would be great, and would be a relatively easy sample return mission, but it is complicated by the challenges associated with getting a probe out to Saturn within a reasonable budget. RTGs would be much too expensive, so we're talking solar power. It would have to be a very simple probe and it would have to operate on a very small energy budget. There have been several proposals for a flyby sample mission like this or other exploration of Enceladus, https://en.wikipedia.org/wiki/Enceladus#Proposed_mission_conceptsbut none have been funded yet.Actually with modern "labs on a chip" you can do a powerful in situ life finder mission for Enceladus. That would also let you study the plumes at different heights to sample different sizes of particles, and also watch for changes, e.g. if there are algae blooms or similar, or if you get better results at particular times in its orbit. All the mass that would be needed for the sample return could be used instead for extra instruments. With many instrument just a chip and perhaps half an amp of power, that's a lot of in situ study for the mass of a return capsule + fuel to get it back to Earth, and you get the results right away.Also if there is life in the sample, then you don't know how to best preserve it for the journey back, until you know what it's like. And then there's the issue of how you handle the sample return. I think it's best done above GEO in a telerobotic facility, given the rather high chance that there might be exobiology there not based on DNA, with almost no communication with Earth - if life is common in our galaxy, then there may well be exobiology on Enceladus. Impossible to assign a probability of that, but surely it's a few percent at least if life is common? Though almost zero if life is very rare in our galaxy. If returned to Earth's surface, then it's an immensely complex thing to sort out legally, Margaret Race looked into it, you wouldn't believe how many new laws would need to be passed and even quite simple international laws can take many years to pass - it might easily take over a decade to pass all the laws needed for a surface to Earth sample return while a return to a telerobotic facility above GEO can be done within our current legislation. Then return sterilized samples to Earth surface until you know a bit more about it.I see that as possible, but in situ is just far easier to do first, and safest of all the life missions we can do both for Enceladus and for Earth. Almost no possibility of forward contamination and none at all of backward contamination.
Fine, but you're talking about a Flagship-class mission now, requiring an RTG, many instruments, and complex systems on the probe. A simple sample return could easily be a Discovery-class mission.
Because of the much more benign radiation environment, Enceladus is a lot easier place to work than Europa. In my mind, that would be the big "plus" of going there. The big "minuses" are the much greater travel time, and the need for RTGs at Saturn's heliocentric distance.A Cassini-like mission that was designed as an Enceladus orbiter with an advanced chemistry and mass spectroscopy suite for investigating the plumes, plus radar, would be pretty nice. And cost billions of dollars, not including a sure-to-be-SLS launch.
An Ocean lies a few kilometers beneath Saturn's moon Enceladus's icy surfaceSummary:With eruptions of ice and water vapor, and an ocean covered by an ice shell, Saturn's moon Enceladus is one of the most fascinating in the Solar System, especially as interpretations of data provided by the Cassini spacecraft have been contradictory until now. Astronomers recently proposed a new model that reconciles different data sets and shows that the ice shell at Enceladus's south pole may be only a few kilometers thick. This suggests that there is a strong heat source in the interior of Enceladus, an additional factor supporting the possible emergence of life in its ocean.
With news like this tell me again why we haven't got a mission planned already for Enceladus, as in many ways it looks an easier target than Europa other than being further out.
The Enceladus orbiter, which is able to get into orbit around Enceladus equator with excursions to the poles, from the decadal review study in 2010 had a detailed costing of between 1.593 and 1.613 billion in FY2015 dollars. ( page 37 of this report). That was for a launch on an Atlas V 521
Many thanks for the study link, I hadn't seen that before. The basic scope of the mission is about what I'd like to see. Using moon flybys to reduce energy for Enceladus orbit insertion (=fuel weight savings) is awfully clever. One caveat is that there are no ASRGs (that project was cancelled, wasn't it?), so power requirements are going to be difficult to meet. The Atlas is a lot less expensive than SLS, which is good.
Quote from: robertinventor on 06/23/2016 04:01 pmThe Enceladus orbiter, which is able to get into orbit around Enceladus equator with excursions to the poles, from the decadal review study in 2010 had a detailed costing of between 1.593 and 1.613 billion in FY2015 dollars. ( page 37 of this report). That was for a launch on an Atlas V 521 caveat is that there are no ASRGs (that project was cancelled, wasn't it?), so power requirements are going to be difficult to meet.
Peter Tsou, who has led the proposals for an Enceladus sample return, stated in a meeting last year that a sample return is at least a New Frontiers-class mission. I don't know if that covers the costs of the sample return facility required on Earth (any life on Enceladus has to treated as dangerous until proven otherwise) or not.The biggest downside to a sample return, as Blackstar pointed out, is that you need to wait 14 to 16 years to get your science.
Now we're also talking about accounting here. If you're going to propose a sample return mission, then the mission is not over until the sample returns to Earth, which means that all those operations costs (18+ years) are included in the prime phase. But if you were to launch a mission to Enceladus that got there in nine years, it would probably include only two years in prime phase. That's 11 years figured into the mission cost. But then if it went into extended phase for another 8 years it would have the same total mission duration as the sample return mission, but the costs are accounted for much differently--it might cost more than sample return in the end, but be more affordable because you have multiple chances along the way to continue funding it or stopping. You don't have those options if you only get your science at the end of the flight.
Two previous comments:"The Enceladus Life Finder is Discovery class.""The ELF proposal uses solar panels. As I remember it, it is believed to be a viable technology out to Saturn."I would caution against using proposals as examples that something is possible. At most they should be used as examples that something is proposable.
And while you might be able to use solar panels at Saturn distances, perhaps they create so many other restrictions on the mission that it is not worth doing.
There are lots of worthwhile targets, and some of them may offer much better return on investment than an Enceladus mission.
Quote from: Blackstar on 06/23/2016 06:44 pmThere are lots of worthwhile targets, and some of them may offer much better return on investment than an Enceladus mission.Fine, let us talk strategy.First, I note that the web available 228 AAS NASA presentation had Jim Greene describe that Enceladus and other ice moons are for free due to The Europa Senator folly, the Administration changed a legislative line. (I think, not being up on US legislative procedures.) Hence they could circumvent both TES's narrow focus and the Decadal Survey propositions who where not based on the latest science. (Europa bad, Enceladus and Titan good.) If NASA is really happy with accelerating outer system exploration while they concentrate on Mars is another thing, they made lemonade.Second, the flyby/orbiter/lander/sample return concept is technologically viable throughout the system, and as the Voyagers show even sample return can be politically/economically viable. You can make a case for Enceladus as an ideal candidate for packaging a flyby/orbiter/"lander". Or even all 4, but likely the first 3 are enough for life detection. So, competitive ROI in comparison with Mars re astrobiology. But superior ROI compared to Europa as a case study of ice moons. Unfortunately Enceladus must eventually be complemented by an Europa mission to assess biopotential over generic ice moons, potentially the largest biosphere volume in the universe.Third, Enceladus is an outstanding test of our best tested emergence theory, vent theory. As I noted in an earlier comment, the oceans looks to be neutral now (unless I am mistaken, have to read the paper). This satisfies the outstanding constraint on alkaline hydrothermal vents as ancestors for life, need the cell potential of alkaline inside and more acidic outside. You may sell others on not going to Enceladus ASAP, but few astrobiologists I think. The still dominant soup theory consensus is happy with Mars exploration. And since the missions are mainly astrobiological...
Oh, there are no guarantees of course. But science teams don't like to play with propositions and have them retracted on technicalities, it is a waste of time.
Quote from: Blackstar on 06/23/2016 06:44 pmAnd while you might be able to use solar panels at Saturn distances, perhaps they create so many other restrictions on the mission that it is not worth doing.Now you are speculating. ELF will do a lot, based on known solar panel technology, so it seems like badly founded speculation to me.
The important figure of merit for an orbital spacecraft is specific power.MMRTG has about 2.2-2.5W/kg.SoA solar at Earth has 150W/kg. Divide by 90 (yes, I am aware of other effects from low light levels), and you have 1.7W/kg, so nearly the same but a LOT cheaper. Additionally, ROSA arrays currently under development can approach 1000W/kg at 1AU, so about 11W/kg at Saturn, FAR exceeding MMRTG's performance for a given mass.If you're in orbit, then solar power is fantastic. Keep the RTGs for surface missions and missions well beyond Saturn.
Not sure whether this is the best thread but I thought that Enceladus mission proposal deserves a mention Enceladus Orbilander: A Predecadal Mission Concept Studyhttps://www.lpi.usra.edu/opag/meetings/opag2020fall/presentations/MacKenzie_6019.pdf
No Single Life Detection InstrumentOrbilander would rely on a complex suite of instruments to determine whether Enceladus’ water has a blend of chemicals conducive for life as we know it, and search for amino acids, lipids, and cells. The instruments include mass spectrometers to weigh and analyze molecules, a seismometer, a microscope, and a DNA sequencer.
Yep. And of course a key question in all of this is what do you want to do with the spacecraft? And that's related to the power issue and all the rest. While you can put a brick in orbit there and power it with big solar panels, that doesn't do anything. It is possible that one of your science requirements might be for a certain amount of power for a certain amount of time, coupled with high pointing accuracy--and solar panels might allow for two of those things, but not all three. That's a long-winded way of saying that it all depends. I sat through a recent explanation about the trades for Europa Clipper and they were fascinating. Some interesting stuff about how the Europa orbiter approach required near continuous communications back to Earth and that drove the power requirements rather high. But the flyby approach enabled them to operate instruments at one point, then do the communication back later at a lower data rate and that lowered the power requirements a lot and enabled solar. There were other aspects to it as well, but once you hear about all these trades you realize that designing a spacecraft is a lot like trying to squish a balloon and if you push on one side it bulges out on the others, so you have to address multiple issues simultaneously.
Quote from: leovinus on 09/30/2020 06:53 pmNot sure whether this is the best thread but I thought that Enceladus mission proposal deserves a mention Enceladus Orbilander: A Predecadal Mission Concept Studyhttps://www.lpi.usra.edu/opag/meetings/opag2020fall/presentations/MacKenzie_6019.pdfAnd a nice write-up at planetary.org Meet Orbilander, a Mission to Search for Life on Enceladus. In the context of "What is life?", I like the broad detection approach which will be relevant for other missions as well.QuoteNo Single Life Detection InstrumentOrbilander would rely on a complex suite of instruments to determine whether Enceladus’ water has a blend of chemicals conducive for life as we know it, and search for amino acids, lipids, and cells. The instruments include mass spectrometers to weigh and analyze molecules, a seismometer, a microscope, and a DNA sequencer.
Quote from: Blackstar on 06/24/2016 08:17 pmYep. And of course a key question in all of this is what do you want to do with the spacecraft? And that's related to the power issue and all the rest. While you can put a brick in orbit there and power it with big solar panels, that doesn't do anything. It is possible that one of your science requirements might be for a certain amount of power for a certain amount of time, coupled with high pointing accuracy--and solar panels might allow for two of those things, but not all three. That's a long-winded way of saying that it all depends. I sat through a recent explanation about the trades for Europa Clipper and they were fascinating. Some interesting stuff about how the Europa orbiter approach required near continuous communications back to Earth and that drove the power requirements rather high. But the flyby approach enabled them to operate instruments at one point, then do the communication back later at a lower data rate and that lowered the power requirements a lot and enabled solar. There were other aspects to it as well, but once you hear about all these trades you realize that designing a spacecraft is a lot like trying to squish a balloon and if you push on one side it bulges out on the others, so you have to address multiple issues simultaneously.More on Enceladus Life Finder (ELF) and its solar power ideas. https://twitter.com/ltelkins/status/1339950883178643457
There's a good open access new paper in The Planetary Science Journal on the science case for returning to Enceladus:https://iopscience.iop.org/article/10.3847/PSJ/abfb7a
https://www.esa.int/Science_Exploration/Space_Science/Saturn_s_moon_Enceladus_top_target_for_ESA