back to article New NASA theory: Moon radiation drops so HULK RIP MOON LIKE SHIRT

NASA is now pretty confident its theory that Pluto's moon Charon split apart because of an internal ocean is right. Last October the space agency theorised that deep canyons on Charon were the result of cryovolcanism, or cold volcanic activity to you and I. Now the agency has explained that theory in comic book terms, as …

  1. Mark 85 Silver badge

    They found the ice moon. Now all that's left is to find a salt moon and a tequila planet... margaritaville!!!!

    1. TRT Silver badge


      I decided that I was a lemon for a couple of weeks. Kept myself amused all that time jumping in and out of a gin and tonic.

      Where did you...?

      Find a gin and tonic? I found a small lake that thought it was a gin and tonic, and jumped in and out of that. At least, I think it thought it was a gin and tonic.

  2. Chozo

    Same old NASA

    Any excuse not to send a geologist up to take a a look.

    1. Matthew 17

      Re: Same old NASA

      a very long way to go to conclude that it's a round iceberg in space.

      1. Stoneshop Silver badge

        Re: Same old NASA

        A not quite spherical iceberg of not quite uniform density (probably).

    2. MyffyW Silver badge

      Re: Same old NASA

      I'd be up for a return trip to Mars (although not keen on marooning myself there).

      I'm much less certain I fancy a round trip to Pluto - Charon. I'd certainly want to take my woollen stockings.

  3. jake Silver badge

    To say nothing of the fact ...

    ... that solid H2O banging on the door at a great rate of knots will inevitably raise the local temperature and result in local liquid H2O, at least for the .moment ... Internal radiation, combined with gravitational energy between Charon & Pluto adds into the process (probably) Several dozen millennia later, it should set up enough to become a solid again. Enter plate tectonics, and Bob's-yer-Uncle.

    Energy conversion at the extremes isn't exactly normal to human genetic thought processes.

    1. Tom 7 Silver badge

      Re: To say nothing of the fact ...

      Charon and Pluto are now gravitationally locked (IIRC) so the two face each other with the same sides as they rotate. Even if the orbit it eccentric this means far less energy is released compared with relatively rotating objects.

      However before they locked together the energy release could very well have been, when combined with the radiation, the thing that kept it melted.

  4. Graham Marsden

    @Simon Sharwood - "cold volcanic activity to you and I"

    In a sentence part like this, omit the word "you" and see if it still sounds right: "cold volcanic activity to I". If it doesn't, use the word "me" instead (unless you're from the West Country)

    PS Interesting article, though :-)

    1. Anonymous Coward

      Re: @Simon Sharwood - "cold volcanic activity to you and I"

      Errrm Grammar Nazi Fail, I'm afraid.

      If you omit the "you", then the resultant sentence fragment is "cold volcanic activity and I". That might be a good sequel to Withnail, but otherwise I cannot see that can sounding right to many people.

      I claim the Grammar Nazi crown: ------------------------------------------------->


      1. x 7

        Re: @Simon Sharwood - "cold volcanic activity to you and I"

        "cold volcanic activity and I".

        sounds like sleeping with the ex-wife.....

      2. x 7

        Re: @Simon Sharwood - "cold volcanic activity to you and I"

        " but otherwise I cannot see that can sounding right to many people."

        that doesn't sound right either.

        Fail by the would be grammar-nazi

      3. Michael Wojcik Silver badge

        Re: @Simon Sharwood - "cold volcanic activity to you and I"

        If you omit the "you", then the resultant sentence fragment is "cold volcanic activity and I".

        Utterly wrong.

        As the OP pointed out, and as seen in this thread's topic, the phrase in the original sentence is "to you and I". If you remove "you", you have "to and I". Removing both "you" and the conjunction, as would be more sensible, you have "to I". Why you thought you could remove the preposition without changing the grammatical structure is rather a mystery.

        What we have is a prepositional phrase with the preposition "to" and the phrasal object "you and I". That object is a compound noun phrase, formed from two pronouns and a conjunction. As an object, it has objective case; and pronouns take the case of the phrase they appear in.

        The preferred form of the first-person singular pronoun for the objective case is "me". The OP is correct.

        That said, this is an instance of what has become widespread, if grating, practice: the false elevation of pronouns in the objective case to the conventionally-nominative form, particularly when part of a compound object of a preposition. So I suspect this particular shibboleth - however personally sympathetic I might be to it - is a lost cause.

        Which, of course, is no reason to refrain from complaining about it in the comments section.

  5. Ian 55

    Useless ice

    Doesn't the angle of the Pluto/Charon orbit mean that getting to it is distinctly wasteful of energy unless you do it at exactly the right time?

    It'd be like driving 100 miles to save 1p / litre on fuel.

    1. lawndart

      Re: Useless ice

      That was my first thought too - distance and inclination give you rendezvous problems. Better to use Neptune's moons as refuelling depots if you need to muck about that far away from the inner solar system. You only have to deal with the distance then.

      In delta-V terms the cheapest route to Pluto requires waiting until you can launch from Earth so your ice collector arrives at Pluto as Pluto crosses Earth's orbital plane. You launch into Earth's orbital plane so you only pay the transfer burn cost. The problem here is you can do it twice in Pluto's 239 year orbit. Next is launching when Earth's orbit crosses the orbital plane of Pluto - you launch into Pluto's orbital plane. This happens twice per year but uses more propellant as you have to get the 17 degree inclination change from Earth's trajectory to Pluto's. Some of the angle can be gained for free at launch by selecting a beneficial launch angle, but you will need to make the rest up on the way.

      It's more like waiting three months to save 1p/L on fuel.

      1. Grikath Silver badge

        Re: Useless ice

        not quite.. if you're going out that way you might want to use jupiter or saturn for a slingshot. Them gravity wells is good for making turns y'know..

  6. Brewster's Angle Grinder Silver badge

    Do El Reg's readers really need the word "cryovolcanism" explained?

    1. I ain't Spartacus Gold badge

      Yes. I thought it was support of the theories put forward by Mr Cory O'Vulcan until I read this...

  7. boltar Silver badge

    Just out of interest...

    ... if you expose liquid water to a vacuum, at what temperature does it freeze solid before it gets a chance to explosively boil away into space?

    1. Brewster's Angle Grinder Silver badge

      Re: Just out of interest...

      What was the temperature and pressure of the liquid water before you exposed it to a vacuum? What was the process by which it was exposed? Exactly how pure was it? What were those impurities?

    2. Grikath Silver badge

      Re: Just out of interest...

      The real question is: how much water are you talking about? With masses the size of Charon you're looking at several different other things that happen besides evaporation into vacuum as a surface effect....

      Besides, all the water on Charon arrived frozen already... It didn't start out as a liquid ball...

      1. Brewster's Angle Grinder Silver badge

        Re: Just out of interest...

        "Besides, all the water on Charon arrived frozen already... It didn't start out as a liquid ball..."

        But that was probably formed by vapour deposition of water molecules so never went through a liquid state. (And that would be the fate of any water molecule that couldn't escape Charon's gravitational pull: redeposited as ice.)

        If I'm being picky, the ice may not even have arrived but have been "primordial water" that Charon mopped up duration formation of the solar system.

    3. mr.K

      Re: Just out of interest...

      The freezing point of water is changed very little with pressure when compared to the boiling point. So basically it will freeze as zero degrees as normal.

    4. Alan Brown Silver badge

      Re: Just out of interest...

      " at what temperature does it freeze solid before it gets a chance to explosively boil away into space?"

      Try it and let us know. This is a high school physics/chemistry lab solvable question.

      Just be sure to remove as much of the dissolved gasses from your water sample as possible before starting (there's a fairly easy way to achieve this(*)) or you won't replicate the conditions generally encountered in space.

      (*) You don't even need a lab to do it.

  8. x 7

    So how do we town Charon to Earth to gain access to all that fresh water?

    1. John Brown (no body) Silver badge

      Carefully. With lots of flashing orange lights and a "Wide Load" sign on the back.

  9. Stevie Silver badge


    One last thing: that “something” that was once liquid on Charon appears to have been water. Which makes Charon a splendid spot for a very expensive ice cube. Or a mine for water to be used as fuel for rockets or people. ®

    Other than the fact that because lazy scientists have been too busy remaming stuff to invent the necessary technology we can't actually get to either Pluto or Charon to see if that is in fact true.

    Scientists! Stop fiddling about and do science!

    1. TeeCee Gold badge

      Re: Bah!

      You have the cart before the horse there. You need to know it's true before going there.

      If you wait 'til you get there to find out that actually it isn't true and there's bugger all by way of water, it's way too bloody late to do anything about it.

      1. Stevie Silver badge

        Re: Bah!

        No, y' don't. You just have to have the will and the curiosity and not be fixated on ultimately pointless reclassification of stuff to the exclusion of all else.

        Pluto didn't need reclassifying, it needed a few people standing on it. Still does. Why else is space out there if it isn't for human beings to play with?

  10. Joe Gurman

    Charon smash!

    That's all, nothing to see here. It's Friday, innit?

  11. Palf

    If you licked Charon, would your tongue stick to it?

    1. Arthur the cat Silver badge

      If you licked Charon, would your tongue stick to it?

      Probably, but as you'd have to open your space suit's helmet to do so you wouldn't worry about it for long.

    2. Malcom Ryder 1


  12. Mikel

    Gas stations

    Apparently the gas stations go all the way out. And no, you don't stop at Pluto on the way out. You launch the fuel from Charon on an intercept trajectory. Probably with a railgun assist.

    Neptune has a huge gravity well. Stopping there is probably a bad idea.

  13. Arthur the cat Silver badge

    If Pluto is like the Hulk

    why isn't it wearing a huge pair of underpants?

  14. Anonymous Coward
    Anonymous Coward


    Quite. It's difficult to see the point of the lower image because it just seems to be the ordinary image with a height-map overlaid upon it using an alpha channel. The problem this causes is that the shadows and highlights in the underlying image are distorting the height-map colours and the height-map colours are burning out areas of the underlying image. Just the height-map, on its own, would've been more meaningful.

  15. YARR

    I don't buy...

    So if a (evenly distributed) sub-surface liquid is freezing into a solid state, that exerts an near-enough even force across the whole surface of the moon. Are we to believe that there is such surface tension that the surface is held together like a shell, and the single point of weakness resulted in a crack which expanded to a canyon while the rest of the shell remained intact? Frankly I would have expected expansion cracks to appear all across the surface.

    Unless, perhaps the freezing process is uneven, starting at the poles with the equatorial region freezing last...?

  16. Cynic_999 Silver badge

    Water cannot provide fuel. Reaction mass perhaps, but not fuel ...

    1. allthecoolshortnamesweretaken Silver badge

      You could separate the H from the O ---> fuel and oxydizer

      1. John Brown (no body) Silver badge

        That far from the sun you'd need nuclear to generate power to separate H and O and if you already have that much nuclear then you probably don't need fuel and oxidiser, just reaction mass will do.

        1. cray74

          That far from the sun you'd need nuclear to generate power to separate H and O and if you already have that much nuclear then you probably don't need fuel and oxidiser, just reaction mass will do.

          I'm usually a fan of nuclear power anywhere in space, but some nuclear applications are better than others. Nuclear power for electricity (to be used for in situ resource production and/or ion engine propulsion) has a great deal more flight experience than nuclear-thermal rockets suited for water propellant.

          Notably, no one has actually run a nuclear-thermal rocket with water reaction mass. Rooskie and American tests used hydrogen and ammonia, and both saw significant corrosion and fuel loss even with those reaction mass options. The NERVA NRX prototype blew 17 pounds of fuel out its tailpipe in just 2 hours of rocket firing with relatively inert hydrogen. Though fuel corrosion was reduced by up to a factor of 3 in lab testing and NASA was satisfied enough for space use, that's still a maintenance problem when you're 40AU from home and thinking about running something highly corrosive like water through the engine.

          On the other hand, if you've got an abundance of usable resources like on Charon or Pluto, then you don't need to be ultra-conservative with specific impulse. You've got fuel to burn, so to speak. Once you have the equipment needed to mine dirty water ice and clean it sufficiently for use in a nuclear rocket, then you're only a small step away from being able to crack it into hydrogen and oxygen. Quite likely you'll already have one electrolyzer in the life support system, so you're already flying one unit to the Pluto system - another larger one for in situ fuel production will be easy, unlike the novel task of proving, flying, and operating a novel water reaction mass nuclear rocket.

          Though it would be nifty to see a bimodal nuclear rocket puttering around the outer solar system.

    2. Michael Wojcik Silver badge

      Yep. Water doesn't provide fuel for people, either.

      (And splitting water into hydrogen and oxygen isn't using it as fuel; it's using it as a chemical storage medium. We don't claim batteries are "fuel". Well, unless we're burning a lot of them in a furnace, I suppose. Which I can't really recommend.)

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