back to article Poor old Jupiter has had a rough childhood after getting a massive hit from a mega-Earth

Jupiter may have started life as a dense rocky planet that only became more gas-like after a massive newborn planet smashed right into it 4.5 billion years ago, according to new research. The paper, published in Nature on Wednesday, describes the scenario. A giant planetary embryo ten times as massive as the Earth, crashed …

  1. Scott 53

    Almost a great article

    until three words from the end when the errant apostrophe spoiled it.

    1. tapemonkey

      Re: Almost a great article

      Whats next an article about Uranus

      1. Sgt_Oddball Silver badge

        Re: Almost a great article

        On my phone that's exactly what I got offered... (the one about boffins probing Uranus' cold ring to be precise).

        Devil icons because this is the reg afterall and I wouldn't expect anything less of them...

    2. Kubla Cant Silver badge

      Re: Almost a great article

      Yes, but what's it got to do with Juno?

      The only scenario that resulted in a core-density profile similar to what Juno measures today...

      I know Jupiter is her husband, but I'm surprised at the close relationship in planetary terms.

      1. Kubla Cant Silver badge

        Re: Almost a great article

        It turns out Juno is the orbiter that produced these measurements. I had to read it in Ars Technica.

    3. Spiz

      Re: Almost a great article


      "The researchers have good reason Jupiter was once solid."

  2. Dr_N Silver badge

    Don't you mean spoilt?

    1. Anonymous Coward
      Anonymous Coward

      Actually, spoiled is the correct term there (in both English and American). Spoilt would be used as the adjective in English; in American, spoiled is used as both the past tense verb and the adjective.

  3. A Non e-mouse Silver badge

    There was an episode of Dr Who where they went back to the formation of the solar system, opened the Tardis doors and watched the solar system form & develop at high speed.

    With all these theories of planetary billiards, I'd love to sit and watch the formation of the solar system. It could be awesome viewing.

    1. Tom 7 Silver badge

      I did some simulations many years ago and you could get some interesting results in a couple of days of 200MHz Pentiums. I imagine now with GPUs and the like you could get some rather spectacular simulations done, The one thing I thought I learned at the time was you really have to assume a relatively uniform disk at the start or all bets are off.

      Anyone know of any current modelling software for this?

      1. Sam not the Viking

        Look up: Universe Sandbox.

        Build your own galaxy.

  4. Blergh


    They are nearly correct Jupiter was previously a rocky planet and even had intelligent beings. However those beings got a bit too clever for their own boots and their weapons a bit too powerful, and it just didn't end very well at all.

    1. ma1010

      Re: Boom

      If Ron were still with us, I'm sure he'd tell us it's just another planet of people that pissed off Xenu. The perished inhabitants exist today, of course, as Thetans, which cause you all sorts of personal problems. For a small fee, we can help you get free of them.

    2. vir

      Re: Boom

      Wasn't there a Charles Sheffield short story about that?

  5. Torben Mogensen

    Alternative explanation

    Another possibility is that, when the core was massive, it had sufficient fissionable material to start a nuclear reaction that pushed the material apart again. This could be an ongoing thing: Fissionable materials collect the centre, react, disperse, collect again, and so on.

    I have absolutely no evidence for this theory, though.

    1. A Non e-mouse Silver badge

      Re: Alternative explanation

      It all comes down to gravity. For a planet/body to ignite to turn into a star, it's more about the mass & density it has, rather than what it's made up of.

      1. Anonymous Coward
        Anonymous Coward

        Re: Alternative explanation

        For a planet/body to ignite to turn into a star, it's more about the mass & density it has, rather than what it's made up of.

        It's a bit of both. Yes, you need enough mass / gravity to produce the pressures required to initiate the nuclear fusion reaction, but you also need enough hydrogen at or near the core to provide the fuel.

        Nuclear fusion of elements heavier than hydrogen only happens naturally in stars, when hydrogen fuel exhaustion allows gravitational collapse of a star's hot core, producing the enormous temperatures and pressures required to initiate fusion of heavier elements such as helium, carbon, oxygen etc.

    2. Brewster's Angle Grinder Silver badge

      Re: Alternative explanation

      If you replace fission with fusion, then what you're describing is how all stars work. It's called hydrostatic equilibrium: the heat rushing outwards balances gravity pressing inwards.

      But Jupiter is not heavy enough to do this. (And it's unlikely it ever has been.) But it's slowly shrinking and those contractions are converted into heat enabling it to emit more "light" than it receives.

    3. Michael Maxwell

      Re: Alternative explanation

      The other responses have been about fusion, which of course Jupiter is too small for. But the OP was about fission. Fission still occurs in the Earth, and is the source of the heat flow from the interior; this heat flow powers plate tectonics, in the sense that it causes melting.

      The supply of fissionable isotopes was much higher in the early solar system, since most of those isotopes with relatively short half lives have by now fissioned away (with the exception of some that are themselves products of fission of longer-lived isotopes, like radon). So presumably the heat production due to fission (not fusion) was much higher in the planets of the early solar system.

      Give that, plus the fact that massive planets might be more effective at separating out heavy elements--rather like a centrifuge (with heavier elements being more likely to be fissionable), your idea does seem plausible to me. But I'm no geophysicist...

    4. Esme

      Re: Alternative explanation

      @Torebn Mogensen: Nah. there wouldn't be enough energy to do that against that much gravity.

      Also, even if enough fisionables collected in one spot to go boom, let alone create heat a la Oklo reactor, that'd have negligible effect on a Jupiter sized object even if there were hundreds of thousands of such happening all at once (highly unlikely).

      To create the sort of effect you have in mind would need such huge concentrations of such rare material coming into close proximity at the same time in such a precise manner that, in essence it's highly unlikely to ever occur naturally during large multiple of the universe's current lifespan.

      As for "it's the aliens wot dunnit" theories - if they had the capability to arrange that sort of thing, I can;t think of any reason why they'd want to do so - building a Dyson swarm instead would be a better use of their time and effort. Of course, if the sacred tome of HHGTTG actually is correct, then it might've been one of Slartibartfast's chums on the piss wot dunnit.

      1. A.P. Veening Silver badge

        Re: Alternative explanation

        Of course, if the sacred tome of HHGTTG actually is correct, then it might've been one of Slartibartfast's chums on the piss wot dunnit.

        That deserves (and got) an upvote.

  6. Graham Jordan

    I've just finished watching Brian Cox's Our Planets and I'm pretty sure that was the idea anyway? Jupiter formed roughly the same time as the sun, started migrating inwards and took a massive beating by proto planets on the way until Saturn's gravity pulled it back?

    1. Brewster's Angle Grinder Silver badge

      According to the paper, that would fall under "planetesimal enrichment and vaporization" and the verdict is "...relevant models typically cannot produce an extended diluted core [as is seen in Jupiter and, to a lesser extent, Saturn]."

      Translation: proto-planets would have disintegrated, and their metals sunk to the centre and been deposited on a conventional rocky core. (Think growing salt crystals.)

      Whereas Jupiter's core hasn't fully condensed into a solid lump. (Although it might do eventually.) And the authors' model model suggests a head-on collision that happened at a very late stage in planet formation would produce that.

      1. Anonymous Coward
        Anonymous Coward

        Theories are theories?

        Is it not also just as likely some pressure/fluid/heat dynamics is spreading things about too. I mean, it has super diamonds and metallic hydrogen. For certain, there are still uncertainties of the exact mechanics at the size and densities of what we get with Jupiter... so saying it's most likely a (unprovable/testable past event) planetary collision is all well and good... but how do we know it's the "better" theory compared to any other?

        1. Mark 85 Silver badge

          Re: Theories are theories?

          but how do we know it's the "better" theory compared to any other?

          We don't. Until a theory is proven valid*, it's just a guess and there's lots of guesses about Jupiter.

          *Some guesses are probably just too improbable to be real. Reference the post above about 'Ron".

    2. Symon Silver badge

      " Saturn's gravity pulled it back" and after that, things could only get better.

      1. Will Godfrey Silver badge

        Yeah, good old Saturn. Jupiter didn't realise the gravity of it's situation.

        Hang on mate, I'm coming along too.

  7. Brewster's Angle Grinder Silver badge

    There must have been one helluva drunk driver in the early solar system. They crash into Jupiter and whip up its atmosphere, and then bash into the earth to create the moon.

    I know there's no evidence Theia was a fragment of the object that collided with Jupiter.

    1. Michael Maxwell

      I think the best analogy is the night that Sven's wife called him on the cell on his commute home. Lena said, "Now Sven, you be careful out dere. The news says dere's somevun driving de wrong vay on de freevay." Sven replies, "Ya, sure, if dere's one, dere's a tousant."

      I propose that we name whatever hit proto-Jupiter and proto-Earth, Sven.

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