back to article PLUTO SPACE WHALE starts to give up its secrets

Excited NASA boffins have published yet more imagery of remote dwarf ice-planet Pluto – this time, however, with a bit more geology thrown in. The US space agency's New Horizons probe is now just three days away from its closest flyby of Pluto, having been on its deep space mission for nine and a half years. In the meantime, …

  1. TheProf
    Headmaster

    Shurely Shome Mishtake

    Exogeology.

  2. Anonymous Coward
    Anonymous Coward

    Ouch

    All results of a massive collision that ripped the bottom off and almost broke it apart. Nibiru anyone?

    1. Pascal Monett Silver badge

      Nibiru is supposed to have collided with Earth already, forming the Moon.

      So no, not Nibiru.

      Planet X, though . . .

      1. Jordan Davenport

        Theia is the most popular name given to the planet that collided with the proto-Earth to form the Moon.

        Nibiru is the "Planet X" that a woman who talks with aliens warned will hit us early this century. Certainly can't fault you for not knowing that though.

        1. Anonymous Coward
          Anonymous Coward

          "Earth? I would totally hit it!"

          .. Nibiru

  3. Christoph

    Whale

    Have they spotted the bowl of petunias yet?

  4. Zog_but_not_the_first
    Go

    Call me simple

    But the very fact that Pluto is round must make it a planet. All the comets and asteroids are knobbly and stuff.

    1. Destroy All Monsters Silver badge

      Re: Call me simple

      Ceres is round.

      1. Zog_but_not_the_first
        Pint

        Re: Call me simple

        Simple I am.

        In mitigation...

      2. dan1980

        Re: Call me simple

        As are most of the moons out there. As are basketballs.

      3. helicoil

        Re: Call me simple

        She didn't look all that round when she did her walk of shame -body double or not...

    2. imanidiot Silver badge

      Re: Call me simple

      It has not cleared its direct orbital neighbourhood of debris and is thus NOT a planet.

      1. Destroy All Monsters Silver badge

        Re: Call me simple

        Which?

        1. Jordan Davenport

          Re: Call me simple

          Either. Pluto is a Kuiper belt object.

      2. Robert Helpmann??
        Childcatcher

        Re: Call me simple

        It has not cleared its direct orbital neighbourhood of debris and is thus NOT a planet.

        This is the part of the new definition that bothers me most. Following this reasoning, Jupiter was not a planet while it was busy hoovering up everything in its path and moving toward the sun and didn't become one until Saturn pulled it back from the brink and helped it to settle into its current orbit. While it was doing all of this, Jupiter was a "dwarf planet."

        Two of the criteria of planethood are tied to their relationship to other bodies in their systems (clearing the neighbourhood and orbits the sun) while only one takes into consideration what it is (round-ish from gravitational forces).

        It makes sense to create classifications for things in as much as they are useful as descriptions. How much information does "dwarf planet" convey? In the example of Jupiter above, it would seem that it actually misinforms. On the other hand, there is a complex classification system for stars that identifies them using several criteria. It seems to me that the current classification system for planets does not give enough detail as to what a planet is and would benefit from the addition of information about size and makeup at the very least.

        1. Trevor_Pott Gold badge

          Re: Call me simple

          It seems to me that the current classification system for planets does not give enough detail as to what a planet is and would benefit from the addition of information about size and makeup at the very least.

          This. 10,000 times this. There are some basic classifications that are informally used.

          Brown Dwarf Star: not actually a star, this is a really large gas giant that outputs substantial heat but does not sustain fusion of hydrogen. Brown dwarfs can be extremely heavy and may well undergo hyrdrogen fusion in smallish amounts (in addition to the massive amounts of fission they are undergoing) but never quite "ignite" into burning balls of plasma in the sky. Can range from similar or smaller radius do superjovian to nearly the size of a red dwarf. May actually have a habitable zone, but many questions about radiation belts and magnetospherics remain.

          Superjovian: large enough to output minor radiation and potentially notable heat to its inner moons but not large enough to be classified as a "brown dwarf star". Heat is primarily fission-based, megnetodynamic (depending on stellar flux) gravitational and remnants of its accretion. Can be absolutely huge planets, but don't start getting much bigger than Jupiter until they've gotten to be about 80 Jupiters in mass. Gravitational interaction with most moons will cause internal heating.

          Jovian: Gas giants. They range from large but "fluffy" and not very dense planets (like Saturn) to several time Jupiter's mass. They they do not emit any noticeable radiation or heat past their roche limit, however, they are not massive enough for their megetosphere to deflect stellar radation completely outside their likely moon orbits. Thus most moons will pass through a belt of deadly radiation similar to the Van Allen belts here at Earth. Gravitational interaction with larger moon may cause internal heating of moons.

          Neptunian: These planets have a roche limit that is far enough away from the planet that many planets this size will be capable of supporting ring systems. Planets are large enough to capture smaller terrestrial planets as moons. Gravity is high enough to hang on to hydrogen in the atmosphere. Expect ammonia in the atmosphere as well as water.

          Superterrestrial: Planets larger than Earth but unable to hang on to hydrogen unless it is bound into a heavier molecule like water or ammonia. May have ring systems but highly unlikely. Unlikely to have captured moons. Can potentially be habitable. Very thin atmosphere compared to Neptunians.

          Terrestrial: Planets just large enough to hang on to an atmosphere. Like all planets larger than it, silicates and metals form the planet's core/mantle/crust. Very thin atmosphere. Marginally habitable in that it is continually bleeding away lighter gases into space. These planets require life to be able to continually recycle molecules in order to have an atmosphere that contains lighter molecules that are critical to complex life.

          *****Special case terrestrial: Metal Planet. Metal Planets can form very near a star where metals are hyper-concentrated in the core of a large gas giant as part of the regular formation process. The gas giant's atmosphere is then blown off (typically by the sun expanding to engulf the planet as a red giant for a billion years or so) and the metallic core is left behind, typically orbiting a dwarf star.

          Subterrestrial: rocky planets that are too small to hold on to much of an atmosphere at all. Likely to cool after only a few billion years and not have much of a magnetosphere. May briefly be habitable. May briefly sustain a hydrosphere.

          Dwarf: smaller than a subterrestrial. Not likely to ever have a hydrosphere. Not likely to ever have much of an atmosphere. (Minor outgassings and capturing of an inch or two of solar wind aside.) Dwarfs are separated from subterrestrials mostly because of density. They may be nearly as large as a subterrestrial, but they contain a lot more ices. Some dwarf planets at the fringes of a system may be mostly or all ices.

          The big issues are drawing firm lines between the classifications. While in use by many astronomers, formal definitions require drawing arbitrary lines and this causes much consternation and debate.

          Plus ca change...

        2. imanidiot Silver badge

          Re: Call me simple

          This is the part of the new definition that bothers me most. Following this reasoning, Jupiter was not a planet while it was busy hoovering up everything in its path and moving toward the sun and didn't become one until Saturn pulled it back from the brink and helped it to settle into its current orbit. While it was doing all of this, Jupiter was a "dwarf planet."

          Well no, Jupiter was NOT a dwarf planet while it was doing that. Strictly speaking, as it was not in a stable orbit it wasn't even a planet.

          Personally I find the original definition proposed before all the politics of the object being the dominant body in its orbit to be more appropriate. (What is the definition of clearing its direct orbital neighbourhood anyway. There are thousands of Jovian trojans in the same orbit as Jupiter. Does that constitute "in the neighbourhood"?

          1. Trevor_Pott Gold badge

            Re: Call me simple

            There are thousands of Jovian trojans in the same orbit as Jupiter. Does that constitute "in the neighbourhood"?

            No. They aren't orbiting in Jupiter's orbital path excepting at the Lagrange points. Those asteroids are essentially trapped by Jupiter's gravity. All the rest of the crap that was in it's orbital path has been eliminated. There aren't a bunch of free floating rocks careening out of control behaving willy-nilly. There are a handful of rocks being dragged around at fixed points by Jupiter itself.

          2. Robert Helpmann??
            Childcatcher

            Re: Call me simple

            Strictly speaking, as it was not in a stable orbit it wasn't even a planet.

            I went back and had another look at the IAU's definition (from https://www.iau.org/public/themes/pluto/):

            "[The IAU's] members voted that the resolution B5 on the definition of a planet in the Solar System would be as follows: A celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit."

            So, stability of orbit is not a qualifier, just that it orbits the Sun. This definition is only intended for planets in our system which begs the question of why create one for a class of objects based on such a tiny subset.

      3. Ken Hagan Gold badge

        Re: Call me simple

        That's why we need words that describe *what* and object is and different words to describe *where* an object is. (Suggestion: let the geologists choose the first set of words and the astronomers choose the second set.)

        Pluto's orbit is actually a rather neat feature of orbital mechanics. It's in a resonance with Neptune, which means that the Plutonian system is in a region of space near Neptune that Neptune cannot clear. It's not a moon of Neptune, but the relationship has something of the same flavour.

      4. Martin Budden Silver badge

        Re: Call me simple

        It has not cleared its direct orbital neighbourhood of debris and is thus NOT a planet.

        Neptune has not cleared Pluto from its orbit, so is Neptune not a planet?

        1. Anonymous Coward
          Anonymous Coward

          Re: Call me simple

          Come to that, Earth hasn't cleared its neighbourhood of asteroids, hence we have concerns about possible impacts. Does that mean Earth isn't a planet? That's always seemed to me one of the least satisfactory bits of the new classification scheme. And what if a system were found with a couple of co-orbital Jovians (eg; in each others Trojan points)? Would they not be planets simply because neither had cleared the other out? Or would common sense reign and they be described as co-orbital planets?

    3. Trevor_Pott Gold badge

      Re: Call me simple

      Vesta, Ceres, Orcus, Quaoar, Eris and Makemake are, of the top of my head, round. Eris is bigger than Pluto. Sedna is suspected to be round. Haumea is an oval. Eris, haumea, Quaoar and Orcus - at a minimum - all have moons.

      Do we have 8 planets and many dwarves? Or do we have dozens of planets? With 8 planets + dwarves we accept that "planet" comes in gradations and we start to be able to reasonably classify them in a useful fashion.

      With "there are dozens of planets" we're just lumping anything that happens to be round and orbiting a star - as opposed to another planet - as a planet.

      For that matter, Pluto isn't a planet even by the "forget the orbital path clearing" criteria. Vesta, Ceres, Orcus, Quaoar, Haumea, Eris and Makemake all are, but Pluto isn't. It's a double planet. Or a double moon, depending on how you want to look at it.

      Pluto and Charon both rotate around a common barycenter that it outside of Pluto proper. Pluto is Charon's moon. Charon is Pluto's moon. Add in Styx, Nix, Kerberos and Hydra and it's not really so much "planet" or "double moon" as "pile of rubble that somehow hasn't all collapsed in on itself yet".

      Now let's have a conversation about Luna. And the Galilean moons. And Titan. And Triton. These are all worth considering as "planet-sized" bodies in some definition or another. Titan as a denser atmosphere than Earth. Triton is almost certainly a "captured planet". Hell, Staurn alone has 7 moons in hydrostatic equilibrium!

      Being round does not make a ball of space debris special.

      Anywho. The solar system, eh? Endless wonder. Endless debats to have about categorization and classification.

  5. Destroy All Monsters Silver badge

    "Our 1st pics must use moonlight of Charon"

    "Moonlight'f Charon"

    The last time she saw Pluto's south pole

    Carried away by a moonlight'f Charon

    It passed on blackened and frozen still

    Carried away by a moonlight'f Charon

    Lost in a riddle that Tuesday night

    Far away on the other side,

    It was caught while speeding to Kuiper belt

    And she flew by and radioed home

    1. M. Poolman
      Thumb Up

      Great, one of my favourite tunes of all time. I can hear Maggie Reilly's voice even as I type.

      1. M. Poolman

        And another thing

        Photography by the moonlight of Charon?!

        Awesome, maximum respec !

  6. Omgwtfbbqtime
    Terminator

    That stripe... can just about make out...

    - Police Line - Do Not Cross -

    1. Mage Silver badge
      Alien

      Re: That stripe... can just about make out...

      Or a panning giant Ion Cannon / Rail gun weapon on automatic. I'd not like to meet the lads that did that.

  7. TonyWilk

    Oh oh...

    That's no moon dwarf planet !!!

    1. Destroy All Monsters Silver badge

      Re: Oh oh...

      It ... it is an orc planet!!

      (Gets massacred by a brutal axe throw)

  8. Will Godfrey Silver badge
    Alien

    Disturbing

    An I the only one who thinks there is a remarkable resemblance to the Death Star?

    We need a really, really scared icon!

    1. Anonymous Coward
      Anonymous Coward

      Re: Disturbing

      Sadly, you ARE the only one.

      (Then Disney rings up JPL)

  9. Sgt_Oddball

    Are you ready for you close up?

    Smile for the camera now Pluto, not long now.

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