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Gas Giants in the Habitable Zone

Because the sky is full of surprises, we can’t afford to be too doctrinaire about what tomorrow’s discovery might be. After all, ‘hot Jupiters’ were considered wildly unlikely by all but a few, and even here in the Solar System, probes like our Voyagers have turned up one startling thing after another — volcanoes on Io were predicted just before Voyager arrived, but who thought we’d actually see them in the act of erupting? So I don’t think we can rule out the idea of habitable moons around a gas giant in the habitable zone, but there are reasons to question how numerous they would be.

We’ve had this discussion before on Centauri Dreams, and while I love the idea of a huge ‘Jupiter’ hanging in the sky of a verdant, life-bearing planet, there are some factors that argue against it, as reader FrankH pointed out recently. One problem is that moons around a gas giant will probably be made largely of ice and rock, because the planet itself would have formed beyond the snow line and migrated into the habitable zone. A Mars-sized moon is going to melt and, given its low escape velocity, will gradually lose its atmosphere in these warmer regions.

We could imagine capture scenarios as a migrating gas giant moves into the warm inner system, but it’s hard to see that as a frequent occurrence. The key question for me would be what factors govern the formation of gas giant moons in the first place, and what is the likelihood of finding moons much larger than Mars? David Kipping’s continuing exomoon work has suggested we could detect a moon of approximately 0.2 Earth masses with existing technology, but this is far larger than Ganymede, and we have no analog in our own Solar System.

ph2_moon

Image: An artist’s rendition of a sunset view from the perspective of an imagined Earth-like moon orbiting the giant planet, PH2 b. The scene is spectacular, but how likely is it that gas giants would have moons beyond Mars size? The answer to the question awaits further work in exomoon detection. Credit: H. Giguere, M. Giguere/Yale University.

So we continue the hunt and the speculation. All this comes to mind because of the discovery of PH2 b-a, the second planet to be confirmed by the Planet Hunters project. The volunteers of Planet Hunters come from all walks of life and use their computers to analyze public domain data from the Kepler mission. The idea behind the project was that humans, with their unique gift of pattern recognition, might see things in light curves that Kepler’s algorithms had missed. Debra Fischer (Yale University), lead scientist for Planet Hunters, champions the idea, particularly in light of the most recent findings, which include a number of other candidates:

“We are seeing the emergence of a new era in the Planet Hunters project where our volunteers seem to be at least as efficient as the computer algorithms at finding planets orbiting at habitable zone distances from the host stars. Now, the hunt is not just targeting any old exoplanet – volunteers are homing in on habitable worlds.”

The estimated surface temperature on PH2 b-a is 46 degrees Celsius, so we are indeed in the habitable zone but without any evidence of moons circling the gas giant. Work with the HIRES spectrograph and NIRC2 adaptive optics system on the Keck telescopes on Mauna Kea has confirmed the existence of the planet, which had been detected by volunteers examining Kepler lightcurves. All told, Planet Hunters identifies in the paper on this work 43 new discoveries, most of which have orbital periods above 100 days. The findings increase the number of gas giant planet candidates with orbital periods over 100 days and radii between Neptune and Jupiter by thirty percent. Nine candidates are members of multi-planet systems. And note this:

Among these new candidates, twenty appear to orbit at distances where the temperature at the top of the atmosphere would be consistent with temperatures in habitable zones. Most of these habitable zone planet candidates have radii comparable to or larger than Neptune; however, one candidate (KIC 4947556) has a radius of 2.60±0.08 R and may be a SuperEarth or mini-Neptune.

Whether or not the imagined habitable moons exist, this is outstanding work and a tribute to the power of ‘citizen science’ in identifying candidates that the Kepler automatic detection and validation pipeline overlooked. The paper on the latest detections runs through the project’s previous candidates and the confirmed planet PH1 b, an interesting world in a 137-day circumbinary orbit around an eclipsing binary in a quadruple star system. The paper adds that Planet Hunters volunteers are most effective at detecting transit candidates with radii larger than 4 Earth radii, while smaller worlds are best retrieved through mathematical algorithms.

For more, see Ji Wang et al., “Planet Hunters. V. A Confirmed Jupiter-Size Planet in the Habitable Zone and 42 Planet Candidates from the Kepler Archive Data,” submitted to The Astrophysical Journal (preprint).

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Comments on this entry are closed.

  • Harry R Ray January 10, 2013, 11:09

    If my LOGIC (sorry, I do not have the math skills to back this up) is correct, exomoons have FINALLY been found! Paul Kalas” presentation on the UPDATED orbit of Fomalhut B, to me, indicates that we have discovered a Pluto-like SYSTEM in Eris-like orbit around another star! HERE’S WHY: If Fomalhaut b were a gas giant(or even an ice giant),it would almost CERTAINLY have a strong magnetic field! Since the last impact with Fomalhaut B and Fomalhaut”s Kuiper belt was 1200 to 1500 years ago, the radiation belts would have DARKENED the ice grains around Fomalhaut b to the point where they would NOT be visible to Hubble’s ACFS AT THE PRESENT TIME! Therefore, there must be NO strong magnetic field in the Fomalhaut b system! SO: to get a shell of particles LARGE ENOUGH(app. 1 solar diameter, I predict, although it could be larger), would require the following scenario: FIRST, there must be SMALL moons analagous to Hydra and NIX around the FomaLHAUT B primary, WHICH, UPON IMPACT with with planetessimals in Fomalhaut’s Kuiper Belt, would produce the ice grains necessary to form a LARGE ring system. TWO: CONTINUOS IMPACT between Fomalhaut’s Kuiper belt and the OUTER( app. 400,000 mi from the Fomalhaut b PRIMARY), would creat the “shell” that ACFS is able to image! FINALLY, this shell can only be created and maintained if the orbits of the ice grains are ECCENTRIC(250,000 mi to 1,000,000mi)> This long-term eccentricity can BEST be explained py the presence of a LARGE(Charon-like) EXOMOON orbiting the Fomalhaut b primary! PAPER HERE? I do not know if ANY commenters on this website are GRADUATE STUDENTS or not, obt if there IS one, I strongly suggest they contact Mike Brown re a paper with the POSSIBLE title: Using the Pluto model to best explan Fomalhaut b,with strong evidence for large and small exomoons in the Fomalhaut b system.

  • FrankH January 10, 2013, 13:56

    In “A common mass scaling for satellite systems of gaseous planets” (Canup, R.M., Ward W. R., 2006, Nature 441, 834-839): http://www.nature.com/nature/journal/v441/n7095/abs/nature04860.html
    The maximum mass for a gas giant’s moon is shown to be about 10^-4 times (1/10,000) the mass of the planet.

    You could argue that this is based only on the gas giants in our solar system and that a much larger gas giant could have an Earth mass moon.

    Using the scaling ratio above, A gas giant big enough to have an Earth sized moon would be a brown dwarf -now we’re in a different formation regime, so the rules might be different.

    Lets assume that by chance you get Earth mass moon around a Jupiter-ish gas giant, which then migrates into its star’s HZ. This moon would have a large % of its mass as ice (due to where it formed). If we assume a density of around 2gm/cm^3, (a little higher than Ganymede’s) it would have to be about 1.7x Earth’s diameter just to have the same escape velocity as Earth.

    If this moon has the same diameter as the Earth, it’s escape velocity (6.7km/sex) would just barely be enough to hold on to an atmosphere.

    In the best case scenario above, we would have a water world. If the moon is large, but not quite large enough to hold on to an atmosphere over geologic time, then the ices that make up its bulk mass will vaporize and escape. We would end up with a much smaller, airless rocky moon.

    We’re not even considering other sources of heat which could increase the surface temperature and atmospheric temperature and accelerate atmospheric loss.

    I’m not arguing that we shouldn’t look for exoplanet moons. It’s just very unlikely that they’ll be large and habitable, so when we find a gas giant in a star’s HZ, it’s bad news for habitable worlds.

  • andy January 10, 2013, 14:10

    Meanwhile, some null results from the Hunt for Exomoons with Kepler (HEK) project: the surveyed planets are all sub-Neptunes/super-Earths on fairly close orbits (all less than 90 days) though.

    Kipping et al. (2013) “The Hunt for Exomoons with Kepler (HEK): II. Analysis of Seven Viable Satellite-Hosting Planet Candidates

  • Ronald January 10, 2013, 14:16

    As I also just mentioned in a comment under the recent post Earth-Sized Planets Widespread in Galaxy, there is an interesting recent study on exomoon habitability, by Heller and Barnes in Astrobiology: Exomoon habitability constrained by illumination and tidal heating.
    http://arxiv.org/abs/1209.5323
    There is a complete PDF of the article accessible.

    They discuss the issues of formation (or capture) of a large moon and harmful radiation from the giant mother-planet.

  • Steven Rappolee January 10, 2013, 15:27
  • GaryChurch January 10, 2013, 15:45

    Just find me a planet bigger than Earth, with more land area and less gravity- where it rains alot- and I will go and explore it. Since I am 52 you will only get 10 or 15 years of wandering around from me. And since you would have to freeze me and revive me upon arrival several centuries in the future- we need to get started on freezing people and building starships.

    Oh- and I need a new deer rifle to take with me.

  • Phil January 10, 2013, 17:23

    “…Jovian exomoons never get larger then mars…”

    yes, but…
    Assuming that relation holds outside our solar system
    Assuming no captured or Trojan moons
    Assuming the most common Hz in gas giant moons isnt a Europa-like tidal Hz
    Assuming….

    The existence and size of Triton should give us pause.

    P

  • Leon January 10, 2013, 17:31

    What do you think about the possibility of life on the gas giant itself? After all, life formed on earth´s ocean, a fluid environment, not in the land

  • Ronald January 10, 2013, 20:39

    Further to Heller and Barnes and exomoons: in another recent paper ‘Exomoon habitability constrained by energy flux and orbital stability’, http://adsabs.harvard.edu/abs/2012A&A…545L…8H , Heller states that especially near low-mass stars (M dwarfs!), where the planet/moon combination has to stay very close to the star and hence the moon to its planet, there is a very serious problem of tidal heating, besides radiation and runaway greenhouse effect.
    This sets an absolute lower limit of 0.2 Msun (about average M dwarf), for exomoon host stars, but in case of eccentricity > 0.05 (which will likely be the common case) there will be serious detrimental effects for exomoon habitability up to about 0.5 Msun (upper limit for M dwarfs).

    Conclusion:
    “Although the traditional habitable zone lies close to low-mass stars, which allows for many transits of planet-moon binaries within a given observation cycle, resources should not be spent to trace habitable satellites around them. Gravitational perturbations by the close star, another planet, or another satellite induce eccentricities that likely make any moon uninhabitable.”

    Very sobering conclusion with regard to habitable exomoons around M dwarfs as an often-mentioned alternative for tidally-locked planets there. Together with the recent observations regarding poor prospects for habitable planets around M dwarfs in comments (partic. coolstar) under the recent post ‘Planets Everywhere You Turn’, things do not look good with regard to any habitable worlds near M dwarfs.

  • Ronald January 10, 2013, 20:54

    With regard to large exomoons around large gas giants around solar type stars: 16 Cygni B is a very solar type star, G2.5, about solar mass, 1.3 times solar luminosity. It has a very large planet (b) of about 2.4 Mj at almost 1.7 AU, on the outskirts of its HZ.
    If this planet has a large moon, it would be a good case of an exomoon in the HZ.
    The only thing is that 16 Cygni B is very old, at least 8 – 10 gy, so its HZ has moved outward. Planet b was not always in the HZ, in fact not until rather recently.

  • Ronald January 10, 2013, 21:01

    Gary: yes, a planet somewhat bigger than Earth, but slightly lighter composition to limit gravity (less iron core, more silicon), around a quiet M5/6 star, about half land, half sea, favorable atmosphere and climate, lush vegetation, rich animal life.
    All we need then is suspended animation, life extension and Mach/Woodward/White warp drive.

    Bring the elephant rifle.

  • Rob Henry January 10, 2013, 21:49

    Goodness. In my opinion this whole article seems to exemplify the folly of the paradigm approach to science.

    I will start by noting that we have no statistically valid reason to have any confidence that Earth is typical of life bearing planets. When the day comes when we can say that there is probably no other life around Sol, then we can also say that Earth is probably more typical of the average living-planet than is the most Earth-like planet in a typical multi-planet system. But even that is dodgy.

    I will continue by noting that Earth’s oceans are most productive where they are close to 4C, and most of our surface is sea. Could we possibly have the optimal temperature wrong, even just for our known ribosomal based life on even an Earth-like planet?

    Just look at what happens if we take the evidence of our system, then purely swap Jupiter and Saturn, but scale that system up to Jovian mass. Now escape velocity V(E), is proportional to the product of the cube root of density times M^(2/3), where M is mass. So, even with no increase in density due to compression, Escape velocity from the surface of neo-Titan goes from 2.6km/s to 5.9 km/s. This corresponding to being able to cope with five times as high a temperature, all else being equal. Okay, I admit that I should be talking here of exobase temperature, but these are so complex and require so many assumptions that the results for unknown moons are close to guesswork. But are you confident that this massive inventory of volatiles will just evaporate in a few billion years with a bit more insolation?

    We also ignore evidence when it doesn’t fit theoretical expectation. Currently it seems very hard to come up with scenarios that give a high capture probability of exogenous capture of planetary sized objects by Jovians. The fly in the theoretical ointment is Triton. Here we are forced to make the tally of such moons for our system at least one, and we must wonder fleeting (before we remember the *correct* way of thinking) how many other captures we have missed because of their prograde orbits.

  • Arecibo January 10, 2013, 21:50

    I am pretty sure that 1/10.000 limit thing is only sampled our solar system gas giant.

    Our solar system doesn’t have hot neptune, burning jupiter etc where people nearly thrown the planet formation theory when discover its. So stop that bullshit until we get more data, or alternatively we need to change physics theory since apparently a gas planet that formed at 1 million km from its star has the same moon configuration with gas giant that formed at 1 billion km from its star.

  • stephen January 10, 2013, 23:29

    How many of you have read Medea: Harlan’s World? It’s an anthology published in 1985 about the moon of a gas giant orbiting one of the components of Castor. The world was designed by many well-known sf authors, who then wrote stories about it.
    I wonder if anybody has checked for planets of Castor?
    The intense radiation would push the gas and dust farther away, but then the planets would simply form farther away from the star.

  • Eniac January 11, 2013, 0:00

    There appears to be one (1!) paper that says the that moons around gas giants can only get as big as the ones in our system. And the clearly stated motivation for this model is that indeed, in our system, it is true.

    I find that unconvincing.

    Also, we have at least two examples of captured bodies in our system, our Moon and Triton. So, just maybe, captured bodies aren’t really quite as rare as Paul is surmising.

  • Stan January 11, 2013, 2:28

    As per FrankH, there is obviously no point in looking for an Earth-size moon around a Jovian in the HZ.

    But just to play the Devil’s advocate, even if a Jovian with an Earth-size moon in the HZ were extremely rare, and one with two of them unbelievably rare, well, unbelievably rare in a galaxy might mean two or three of them. If we assume the reason we haven’t yet found evidence of aliens is that they tend to suffer from self-induced extinction events on their home worlds before they make it to space, and that a two-Earth moon system would possibly prove to be a huge catalyst toward space-faring, as well as a reducer of self-induced extinction events, then just maybe all it would take is a few of these in a galaxy to begin a galactic civilization.

  • Rob Henry January 11, 2013, 2:52

    Doh! I just realized that I did my above calculations for V(E)^2 not V(E). I should’ve used
    V(E) α M^(1/3) * ρ^(1/6) where
    V(E) = escape velocity, M = mass and ρ = density.

    So – the V(E) of Neo-Titan goes from 2.6km/s to 3.95 km/s. This corresponding to being able to cope with a temperature just two and a quarter times higher. Sorry about that.

  • Michael January 11, 2013, 3:25

    A worry for an Earth like world orbiting a gas Giant would be very high radiation belts, how the two magnetic fields, assuming the Earth like moon had one would interact is bound to be complex,

  • FrankH January 11, 2013, 12:35

    Triton and Neptune are in the outer solar system, where orbital velocities (and energies) are MUCH lower than in the inner solar system.

    A terrestrial planet captured by a gas giant migrating through the HZ would have to loose enough energy to enter a “just right” orbit around the gas giant. It’s more likely that it will be ejected, impact the gas giant or enter an unstable orbit that will eventually cause it to be disrupted.

  • GaryChurch January 11, 2013, 15:22

    “All we need then is suspended animation, life extension and Mach/Woodward/White warp drive.
    Bring the elephant rifle.”

    Actually, suspended animation is the missing technology. If I managed to somehow get my name on some list and get frozen- by the time they woke me up a couple three hundred years or so down the road they would have life extension figured out.

    As for “warp drive”, I am not a believer. All that is required is beam propulsion to accelerate a starship out of the solar system at some fraction of the speed of light and then H-bombs to slow down upon arrival. We should be spending billions on this instead of things like stealth fighters and super destroyers.

  • Alex Tolley January 11, 2013, 18:38

    @Rob Henry

    Earth’s oceans are most productive where they are close to 4C, and most of our surface is sea. Could we possibly have the optimal temperature wrong, even just for our known ribosomal based life on even an Earth-like planet?

    The reason the cold oceans are more productive than the warm ones, is nutrient availability. This has nothing to do with any energetics of life. We also know that terrestrial organisms are more productive in the tropics, especially where nutrients and water are not limiting.

  • Rob Henry January 11, 2013, 18:46

    FrahkH says “Triton and Neptune are in the outer solar system, where orbital velocities (and energies) are MUCH lower than in the inner solar system.”

    This is true, and he is right that it makes capture very hard for a Jovian migrating in. So, how do we explain it if such events turn out to be common. I think that Frank then gives the key when he subsequently realises that this process is likely to scatter terrestrials into the outer system.

  • Alex Tolley January 11, 2013, 18:57

    @GaryChurch

    Actually, suspended animation is the missing technology. If I managed to somehow get my name on some list and get frozen- by the time they woke me up a couple three hundred years or so down the road they would have life extension figured out.

    There are huge differences between “life extension”, “hibernation” and “freezing”. Life extension will probably happen, but probably not as much as hoped for. I have some hopes for hibernation as there are indications that humans might respond like hibernating animals. But freezing, I very much doubt will ever be possible.

    Now your robot avatar could go as soon as the transport is ready…

  • andy January 11, 2013, 22:20

    Interestingly enough, the satellite systems of the giant planets seem to look remarkably similar to the super-Earth systems that are now being found by missions like Kepler, and which appear to represent the dominant mode of planet formation (>50% of solar-type stars, and perhaps even more frequent around the more common lower-mass stars). So even within our own solar system, the planets appear to represent a minority mode of planet formation. If we’d been taking the regular satellites of the giant planets as the prototypes for planetary systems we wouldn’t have been so surprised by the large numbers of multiple transit super-Earth systems. So there is probably good reason to believe that the giant planet satellites are quite typical.

    On the other hand, observations of exoplanets have had a history of demolishing theoretical predictions, so who knows…

  • James Jason Wentworth January 12, 2013, 13:12

    Rob Henry wrote (in part):

    “We also ignore evidence when it doesn’t fit theoretical expectation. Currently it seems very hard to come up with scenarios that give a high capture probability of exogenous capture of planetary sized objects by Jovians. The fly in the theoretical ointment is Triton. Here we are forced to make the tally of such moons for our system at least one, and we must wonder fleeting (before we remember the *correct* way of thinking) how many other captures we have missed because of their prograde orbits.”

    Indeed–even though they are small bodies, Jupiter’s “middle four” prograde-orbiting satellites (the Voyager and Galileo probes may have found more) that orbit between the Galileans and the outer four retrograde-orbiting satellites were also captured. Mars’ two moons may also be captured asteroids. Given enough time, a captured satellite’s orbit can become quite “regular” (close to circular).

  • Eniac January 12, 2013, 13:54

    FrankH:

    Triton and Neptune are in the outer solar system, where orbital velocities (and energies) are MUCH lower than in the inner solar system.

    True, but what about our own moon?

  • Rob Henry January 12, 2013, 16:54

    Yes Alex Tolley, I meant the optimum temperature a biosphere built on ribosomal life, not ribosomal life itself. If we compare the fastest growth rates of bacteria that have evolved to fill particular microenvironments (and not eukaryotes which are generalists) the best temperature for our known type of life should be around 60C.

  • Holger January 12, 2013, 18:22

    @Eniac:
    “True, but what about our own moon?”

    AFAIK, the accepted theory is that the Moon is the result of a collapsing debris cloud from a collision of two (proto-)planetary bodies, which is quite a different thing from orbital capture.
    A Theia-like body colliding with a gas giant would create a much smaller (if any) debris cloud due to the much higher friction from the gaseous envelope during collision; the body would essentially just be “swallowed whole” by the gas giant. No chance for a planet-sized moon in this scenario.

  • GaryChurch January 12, 2013, 22:25

    “But freezing, I very much doubt will ever be possible.”

    http://www.sciencedaily.com/releases/2006/06/060620171022.htm

    Why would you doubt it? It is the obvious way to travel to other systems. No laws of physics against it. Far more likely than a fusion reactor.

  • Alex Tolley January 13, 2013, 13:09

    @GaryChurch – I doubt it because while no laws of physics are broken, biology is. Just consider the issue of thawing and restarting a heart, let alone a brain.

    The “obvious” way to travel to other star systems is with robots, with or without uploaded minds.

  • GaryChurch January 13, 2013, 21:46

    “The “obvious” way to travel to other star systems is with robots”

    That would not be Human Space Flight. And that is the only kind of space flight that matters. People traveling to other living worlds is what this is all about. For me anyway.

    Arguably we could, if we wanted, send a generation ship to another system right now- well, it would take decades to build it, but we could start right now. What makes it extremely difficult (but not impossible) is keeping the humans supplied for several centuries.

    Freezing humans is the trick that makes it far more doable. Just as submarines and flying machines were predicted, suspended animation has been imagined for many decades. I find your inability to see the future of a technology- that is in small parts already working- hard to reconcile with your participation in this discussion. Talk about a defeatist Mantra!

  • Alex Tolley January 14, 2013, 10:51

    @ GaryChurch
    I find it amusing that you feel it necessary to be bombastic with your “space is not cheap” mantra and proceed to inform everyone that the ONLY way to do space missions is with beamed power and bombs because massive radiation shields are needed, but in the next breath indulge in total hand waving regarding freezing humans for travel. Today we have less idea of the path of development needed for such a technology than we do of brain mapping and mind “uploading”.

    One thing we can be sure of, is that it is going to be far easier to send machines to the stars. Which implies that machines will be the dominant agency. If humans, recognizably like us, are to populate the stars, I rather doubt that the means of transport will be pushing their corporeal matter through space.

  • GaryChurch January 17, 2013, 14:18

    “I find it amusing that you feel it necessary to be bombastic”

    Then enjoy.
    I find it amusing also.

  • GaryChurch January 17, 2013, 14:54

    @Alex Tolley

    “-the ONLY way to do space missions is with beamed power and bombs because massive radiation shields are needed, but in the next breath indulge in total hand waving regarding freezing humans for travel.”

    “Space missions” is a generalization; this site is about Star Travel. The best contender for a true starship transporting warm human bodies is in the next century and that is the black hole propelled concept; https://centauri-dreams.org/?p=11751

    But that should not stop us from launching “sleeper ships” near the end of this century. And if not sleeper then generation ships. All we need is a destination- a living planet that is so young it has little life yet and no complex forms. We go there and create another Earth because that is what we must do- or go extinct and join the great silence.

    The question of freezing people goes far beyond possibly saving the human race from extinction in the next couple thousand years. The societal implications are incredible. Freezing a reviving a human being will be the most important event in human history. It will change everything because no one will allow their loved ones to die if they can freeze them until a cure is found.

    Overnight the world will go from accepting death in all it’s many forms to unanimously rejecting mortality. I went from being interested in space to being totally convinced that cryopreservation is the most important issue in the history of the human race.

    So I have been encouraged to start a blog and I think the connection between star flight and cryopreservation and societal change will be the theme. What might be interesting to you Alex is what goes along with this future- the rise of the Artilects as envisioned by Hugo DeGaris.
    http://en.wikipedia.org/wiki/Hugo_de_Garis

    People like David Criswell who ten years ago proposed Lunar Solar Power, and before that Freeman Dyson who worked on bomb propulsion, and long before that John Desmond Bernal and his spheres in space- all of these people saw visions of the future that I believe will come to pass.

    As with Jules Verne and H.G. Wells two centuries ago, the future is being foretold right now- all need to do is choose which future we wish to create.

  • andy January 17, 2013, 15:47

    Any actual biologists around to comment on the prospects of freezing/suspended animation? The few who comment on these kind of discussions tend to be quite dismissive of such ideas (and usually have excellent reasons for doing so), and things like mind uploading as well.

    But I guess they don’t count as actual scientists because they deal with squishy organisms rather than equations and particles and stuff…

  • Ronald January 17, 2013, 19:40

    Andy, the only thing I can contribute here is that cryogenics/freezing is very different from suspended animation/induced hibernation, because the latter does not require freezing cells and therefore avoids a whole lot of risk and damage.
    I simply consulted http://en.wikipedia.org/wiki/Suspended_animation for some refs.
    I understood that there is temperature-induced and chemically induced SA, and that long term SA and SA of large mammals has not been attempted and/or not been successful so far.
    However, at the same time “There are many research projects currently investigating how to achieve “induced hibernation” in humans.”

  • Eniac January 18, 2013, 0:32

    Holger:

    AFAIK, the accepted theory is that the Moon is the result of a collapsing debris cloud from a collision of two (proto-)planetary bodies, which is quite a different thing from orbital capture.
    A Theia-like body colliding with a gas giant would create a much smaller (if any) debris cloud due to the much higher friction from the gaseous envelope during collision; the body would essentially just be “swallowed whole” by the gas giant. No chance for a planet-sized moon in this scenario.

    Is this an established model you are talking about that has this gas vs. rock distinction in it? Where is this written?

    For the purposes of this discussion, capture is capture, with or without collision. And as long as the two bodies are a similar ratio in mass, I don’t think we have sufficiently precise models to predict that what happened with Earth/moon cannot happen to bigger or gasier bodies.

    According to Rob Henry above, there are many more examples of captures, besides the Moon and Triton. Even if the regular moon formation theories (or should I say speculations?) are correct, they cannot rule out anything, since capture is clearly another common way to get a moon or double planet.

  • Eniac January 18, 2013, 0:38

    Alex Tolley:

    I doubt it because while no laws of physics are broken, biology is. Just consider the issue of thawing and restarting a heart, let alone a brain.

    Well, there are frogs that regularly freeze and revive, such as the Wood Frog (http://en.wikipedia.org/wiki/Wood_frog). From what I understand, the frezing is not 100% complete, but the heart and brain would certainly be temporarily inactive under the circumstances.

    Plus, embryos are routinely deep-frozen and survive completely intact, so there cannot be anything as fundamental as a “law of biology” that would forbid it.

    andy:

    Any actual biologists around to comment on the prospects of freezing/suspended animation?

    Biophysicist, here…

    But I guess they don’t count as actual scientists because they deal with squishy organisms rather than equations and particles and stuff…

    Yup. ;-)

  • Alex Tolley January 18, 2013, 13:02

    @Eniac
    1. You will notice that the only complex life that can freeze (but not solid) are poikilotherms (and small ones at that), not homeotherms like us.
    2. Human embryos are frozen at a very early stage – just a few cells. See this link for more details from an IVF clinic. So we are not talking about complex structures for this process to work.

    If we could even freeze, store and thaw major organs, like hearts and kidneys for transplantation, that would be a major medical advance. So you have a “spin off” technology driver, right there.

  • Ron S January 18, 2013, 15:29

    andy: “But I guess they don’t count as actual scientists because they deal with squishy organisms rather than equations and particles and stuff…”

    Ah, but once you freeze an animal it ceases to be squishy. I suppose that means that freezing either makes biology a ‘hard’ science or that squishy-loving biologists lose interest.

  • GaryChurch January 18, 2013, 16:25

    (The societal implications are incredible. Freezing and reviving a human being will be the most important event in human history. It will change everything because no one will allow their loved ones to die if they can freeze them until a cure is found.)

    http://en.wikipedia.org/wiki/Vitrification_freezers

    I started out helping my wife with a college ethics paper on nuclear weapons- then became interested in space travel after reading “Project Orion, the true story of the atomic spaceship” and finally began to research cryopreservation after I realized the importance of the issues involved. Not dying being the big one.

  • Eniac January 18, 2013, 22:42

    Alex Tolley:

    1. You will notice that the only complex life that can freeze (but not solid) are poikilotherms (and small ones at that), not homeotherms like us.
    2. Human embryos are frozen at a very early stage – just a few cells. See this link for more details from an IVF clinic. So we are not talking about complex structures for this process to work.

    True. The smaller the item to be frozen, the easier it is to cool or heat it in a time short enough to avoid death in the intermediate zone, where the temperature is too low to support life but to high for cryopreservation. This is exacerbated in warmblooded animals where death occurs sooner once the temperature is even just a little off. While a formidable challenge, none of this is a clear showstopper.

    If we could even freeze, store and thaw major organs, like hearts and kidneys for transplantation, that would be a major medical advance. So you have a “spin off” technology driver, right there.

    Good point.

    There are a number of promising reports on cryopreservation of organs, to me it looks like this could become routine within a decade. See, for example http://www.ncbi.nlm.nih.gov/pubmed/15094092 or http://people.ucalgary.ca/~kmuldrew/cryo_course/cryo_chap9_2.html

  • andy January 19, 2013, 9:41

    Ah, but once you freeze an animal it ceases to be squishy. I suppose that means that freezing either makes biology a ‘hard’ science or that squishy-loving biologists lose interest.

    Aha good point! I guess that also explains why the physics nerds love the idea so much… :-)

  • Holger January 19, 2013, 17:51

    @Eniac:
    “Is this an established model you are talking about that has this gas vs. rock distinction in it? Where is this written? ”
    I don’t know how “established” it is. It’s stated implicitly e.g. in http://www.cfa.harvard.edu/news/2008/pr200801.html:

    “[…] 2M1207B might be the product of a collision between a Saturn-sized gas giant and a planet about three times the size of Earth. The two smacked into each other and stuck, forming one larger world […]. ”

    or, more explicitly (but naturally less reliably), in http://answers.yahoo.com/question/index?qid=20100404103910AAUmCJR . (It’s also been stated in a CD discussion some time ago, IIRC.)

    On the other hand, I’ve never heard of collisions being considered as a kind of capture, either.
    The big difference between a collision and an orbital capture is that the former only puts a small fraction of the inpactor’s mass into orbit in the end (even for rocky bodies – the Moon has only 10% of Theia’s estimated mass). And (if Earth’s Moon is a typical case) the debris is expected to be a quite homogenous mixture of the impactor’s material and the impacted planet’s outer layer.
    (So even if you assumed no qualitative difference between gas giant and rocky planet impacts (and proportionality between impactor mass and “debris moon” mass), you’d still need an impactor much more massive than Earth to produce a moon >0.25 M_Earth, and the moon would predominately consist of H and He, which it could not keep over billions of years.)

  • Rob Henry January 19, 2013, 19:29

    Lets say the problem of thawing without killing is soluble, and work backward as to how it was done. All that I can see is that the cryogenic carcass must be impregnated by an extensive lattice of thin pipes of high thermal conductivity. I assume that they were put there during the freezing process, and not drilled later. I can’t even see if that warming mechanism is flowing hydrogen or electricity. Hydrogen would be simpler wouldn’t it?

  • Alex Tolley January 20, 2013, 14:29

    @Eniac
    The work by Fahy is on rabbit kidneys. These are small (< fingertip in size). Having said that, their results are intriguing. However since that work has been done, I can find no further work by Fahy, other than with oocytes, or references to his work suggesting progress.

    The 21st Century Medicine corp. (at which Fahy works/worked) described in the Calgary course material ref appears to be doing nothing/defunct based on perusing their web pages.

    In their chapter 15 I note this sentence:

    […] it must be declared that current cryonic techniques are almost certainly destroying many of the neural structures that are necessary for full recovery, probably irreversibly. This is not to say that cryonics will not work, just that the likelihood of current techniques providing adequate preservation is slim.

    Other references I have read suggest that general cryo-preservation is going to be extremely hard to solve, as different tissues require different conditions. While that might work for isolated organs, freezing an intact body is going to be extremely hard.
    I think that expecting even successful kidney cryo-preservation in 10 years is extremely optimistic. If anything, the technology is pointing to stem cells to rebuild organs, rather than donor transplants.

    However I do note this point from the course materials:

    There are now many cases of severe hypothermia (from immersion in ice water) where human brains have been chilled to near freezing temperatures and breathing suspended for hours with complete mental recovery following resuscitation. Ground squirrels have taken this even further, allowing their brains to cool below the freezing point for up to six weeks at a time, with complete function upon rewarming. Clearly it is possible to slow the clock in the brain appreciably without any loss of function.

    This seems more like a state above freezing, but well beyond hibernation. If this extreme hypothermic state can be induced and recovered from without injury over several years, this might possibly be the way to travel, at least within the solar system.

  • Eniac January 20, 2013, 20:41

    Alex: Great analysis. I was perhaps not sceptical enough.

    The ground squirrels are interesting, though. Perhaps starting from this “almost-frozen” state, full freezing without damage (vitrification?) could be achieved in some way. Using http://en.wikipedia.org/wiki/Magnetic_refrigeration, perhaps?

    Rob:

    All that I can see is that the cryogenic carcass must be impregnated by an extensive lattice of thin pipes of high thermal conductivity.

    Or, use microwaves?

  • Eniac January 20, 2013, 21:00

    Holger: Good points. I wonder what would happen if two gas giants collided on a high angular momentum trajectory, i.e. a “glancing” impact. Is one possibility the formation of a double planet with the two cores remaining separate, but the gas thoroughly mixed? Could much of the gas be evaporated from the heat of impact, leaving only the cores behind?

    I think there are way too many possibilities for large moons out there, and our models are too naive to conclude with any confidence that they all must be rare.

  • Alex Tolley January 26, 2013, 14:31

    Final piece on hibernation.

    This news article http://abcnews.go.com/Technology/story?id=97509&page=1
    has a piece on the arctic ground squirrel. It hibernates with a body temperature of – 3C, so its blood and tissues must be supercooled.

    I looked at some of Barnes’ papers in this area, and there are some interesting genomic changes during hibernation of this creature. If humans could be made to mimic this hibernation using drugs, this would definitely be a good solution for deep space missions in the solar system. It would even be very interesting for organ storage as metabolism is very low.