Neptune May Have Eaten a Planet and Stolen Its Moon

jitendraharlalka noted a piece about the origins of Neptune. There is a theory now that it once ate a super-earth in the outer solar system, and kept its moon as some sort of macabre trophy to make sure that Mars and Venus didn't get any big ideas.

Comments

What a bastard

[Pojut]

I always knew he was a slimey fuck.

Re:What a bastard

[nine-times]

You don't even want to know what went into Uranus.

Re:What a bastard

[Cryacin]

Must have given him some pretty bad gas, considering the amount of methane.

Re:What a bastard

[ooshna]

My yes, also in 2015 Pluto was reclassified as a planet after the Texas school board voted to include it despite expert advice because "Without Pluto how would The Planet Song end? Neptune's really windy? Its unpatriotic!"

Silly Goose

[Monkeedude1212]

Kronos is the one that eats babies, not Neptune!

Re:Silly Goose

[Pojut]

Actually, that would be Saturn.

Re:Silly Goose

[DrData99]

Did you even read the article you linked to? "It depicts the Greek myth of the Titan Cronus (in the title Romanised to Saturn), who, fearing that his children would overthrow him, ate each one upon their birth."

Re:Silly Goose

[d34dluk3]

From http://en.wikipedia.org/wiki/Cronus: "Cronus or Kronos"

The article goes on to say that Saturn is the Romanic version of Kronos.

So yeah, the original post was perfectly fine. If you're going to be pedantic, at least be correct.

Re:Silly Goose

[nschubach]

Maybe we should ask Slashdot to lock the whole thread while someone posts a reply to avoid this in the future.

Re:Silly Goose

[eleuthero]

The problem is, that Cronus, Chronos, Kronus ... were all iterations of the same general being (much like we have Batman, Batman Forever, Batman (the series), Batman (the animated series) - we are all referring to the same general being and while the description and artwork (and possibly even pronunciation of Bruce Wayne's name) all change, this doesn't change. The same was true for all the myths...

This should be tagged Om-nom-nom.

[timepilot]

This story should be tagged om-nom-nom.

Re:This should be tagged Om-nom-nom.

[mooingyak]

I went with "badneptunenobiscuit"

Velikovsky

[camperdave]

Looks like someone signed Velikovsky's book out of the library recently.

Can't resist...

[GPLDAN]

' Neptune May Have Eaten a Planet and Stolen Its Moon'

In this way, it is just like Rosie O'Donnell.

Re:amphromoporthizing

[Hatta]

You should never anthropomorphize planets. They hate that.

How many times do I have to tell you

[Locke2005]

Don't anthropomorphize the planets... they hate it when you do that!

Re:Of course!

[Cryacin]

Being a Roman god, he would have thrown it up afterwards.

Re:Next

[oldspewey]

Dude, you're posting AC. You don't have to use the "my buddy" cover.

Re:Nuclear?

[oldspewey]

If you're willing to classify radioisotope decay as a form of "fission," then not only is it likely, it's highly probable.

http://www.physlink.com/News/121103PotassiumCore.cfm
http://en.wikipedia.org/wiki/Radioactive_decay

Copious amounts of maryjoowanna

[bynary]

This "news" article reads like the "pot circle" scenes from That 70's Show:

"Oooh, oooh, I know! First the planets form close to the sun!"

"No way! What if they then moved away from the sun and some of the planets ate the other planets!"

"You're blowin' my mind, man!"

"I could eat a planet right now. Anyone have a Mars bar?"

"Mars bar...Marssss bar...Marrrrrrrssssss bar...that's funny..."

Re:What's that smell?

[Verteiron]

Nonsense, everyone knows Pluto was knocked out of its orbit around Neptune by the impact of an alien craft traveling at extremely high velocity.

First Pluto and now this

[Wiarumas]

First Pluto and now this. Neptune is no longer a planet, but rather a cannibal and a thief.

That's no moon.

[SteeldrivingJon]

Was I really the first person to say that on this thread?

Re:That's no moon.

[tool462]

The Force is weak with these ones today.

Re:wasted opportunity

[radtea]

Yeah, every day this place hits new lows. This is an interesting story on planetary formation and the complex unravelling of the history of the solar system using a mix of precise observation and computer modelling, and the comments are almost exclusively juvenile jokes and complaints that the proposed mechanisms sound stupid.

My question is: is there anywhere that is remotely like /. used to be (say a few months ago, even) when we still got the odd intelligent comment that added something useful to the story?

Some orbital dynamics

[Michael Woodhams]

Some may wonder what need there is for a third body at all - Triton wanders too close to Neptune, it gets captured, right?

The reason is conservation of energy: as Triton wanders near Neptune, it falls into Neptune's gravity well and accelerates, so it is going too fast to remain in orbit. Triton at infinity has more energy than Triton in orbit, so to get captured it has to lose energy, and that energy has to go somewhere.

With a few exceptions, three body interactions (e.g. Neptune, Superearth, Triton) are chaotic, and often end with one of the bodies being expelled and the remaining two left in orbit. The lightest body is the most likely to be expelled. This scenario has Superearth being expelled rather than Triton, which is somewhat unlikely but not impossible. (It is too long since I studied this for me to quantify 'most likely to be expelled'.)

It really doesn't seem to me that you need Superearth to explain Triton. The third body could very easily have been a normal Neptunian moon, which is now unobserved somewhere in the Oort cloud or expelled from the solar system entirely. (Could it be Pluto? This was thought of and rejected a long time ago.)

Disclaimer: All these comments are on the basis of reading the New Scientist summary, not the real paper.

Re:Some orbital dynamics

[simonbp]

The reason we invoked the extra planet was that in these three-body encounters, it's much more likely that the more massive object gets ejected and the smaller captured. However, the surveys of the Kuiper Belt are such that if Triton had larger twin, we'd have found it by now. But noone has, so a different capture method remains plausible. The existence of the extra planet isn't actually the hard part to prove, but rather that it impacted instead of being tossed by Neptune down to Saturn or Jupiter, who could then throw it out of the solar system.

Still lots of work to be done...

-Simon Porter, Coauthor

Re:Some orbital dynamics

[Michael Woodhams]

"...it's much more likely that the more massive object gets ejected and the smaller captured."

How does this work? My memory from a few lectures 20 years ago is the opposite, but clearly you're more reliable than I am. I thought it was an equipartition of energy thing - interactions will tend to divide the energy evenly between the objects, which means the lightest is the most likely to acquire escape velocity. Is it that ejecting the lightest object doesn't usually take away enough energy to leave the other two bound?

If you're trying to drop Superearth into Neptune, then it has to both get very low angular momentum and at the same time high energy (else Triton would not be bound to Neptune). This seems a very narrow target to hit. If you're arguing relative probabilities (it is more likely that the more massive object gets ejected) then you need to establish that the unlikelihood of impact is outweighed by the gain in likelihood of losing the larger rather than smaller object.

It had not occurred to me that the disappearance of the third body could be a two stage process: ejected from Neptune orbit, then secondarily ejected from the solar system by Saturn or Jupiter. What are the odds that an object ejected from Neptune orbit will eventually be ejected from the solar system? My gut feeling is that the odds are pretty good, that falling into a resonance with one of the giant planets or being ejected are the only long term options. (Where 'long term' I'd guess to be thousands or millions of years, not billions.)

Whether absorbed or ejected, this interaction with Superearth would tend to increase Neptune's orbit's eccentricity. How does the expected increase in eccentricity compare to the current eccentricity of Neptune's orbit?

My counter hypothesis is that the third body was a pre-existing but now lost Neptunian moon. Now that I think on it, equally plausible is that Triton was this original moon (originally in a regular prograde orbit) and an outside object came in, formed a 3 body system for a while, and then was ejected.

Re:Some orbital dynamics

[simonbp]

what happens in these binary captures is that you have two objects orbiting around each other and falling at essentially escape velocity towards Neptune. If it were just one object, it would either hit Neptune or zoom past and leave Neptune's sphere of influence. But since there are two objects, one is going slightly faster than escape velocity, and the other slightly slower. If there is no collision, then one that is going slower can be captured, while the other is ejected from the system. If the two objects are not of equal mass, then the smaller is going to be moving faster than the larger, and thus there is much wider window of opportunity for it to be captured. So, it's not impossible for the larger to be captured, just much less likely.

In the case of a collision, it is more like likely that the larger will impact, as the center of mass is closer to it, and impacts are the merging of centers of mass. In this case, we think that Triton would be in a sufficiently wide orbit that it would watch the impact from a distance, and then either ejected (if its orbital velocity was in the impact direction) or captured (if its orbital velocity was in the opposite direction). So, Amphtrite could have had multiple moons, but Triton was the one on the correct quarter of the orbital phase to be captured.

Simon Porter

Re:Worlds In Collision

[spacemandave]

Ugh. Every time one of these stories comes up, someone has to bring up Velikovsky. As someone who studies early solar system evolution, I've had the "pleasure" of talking with Velikovsky supporters on numerous occasions. What Velikovsky wrote about was wide-scale rearrangements of the architecture solar system WITHIN HISTORICAL TIMES, based on nutty interpretations of classical mythology. What the article here discusses is a hypothesis for the formation of Triton during an event called the Nice model that is thought to have happened about 3.9 billion years ago (based on dating of large lunar basins from Apollo samples). During this time, a much more massive precursor to the Kuiper belt fueled the migration of the outer four giant planets, disrupting stable reservoirs of small bodies throughout the solar system. Once the ancient Kuiper belt was depleted of mass, the migration stopped (so the "fuel" is gone, and therefore this process can only occur once in the lifetime of the solar system). Had planetary migration occurred within historical times, then we would currently be in the midst of a massive bombardment of comets and asteroids, and the Earth's oceans would currently reside in the atmosphere (along with perhaps some rock vapor clouds). The Nice model and Late Heavy Bombardment is backed up by observations of the structure of the Kuiper belt, observations of other solar systems around other stars, radioisotope dating of lunar rocks (in a variety of isotope systems, but most especially K-Ar, and U-Pb), observations of the structure of the asteroid belt, dynamical models based on plausible initial conditions for the early solar system (constrained by aforementioned observations), observations of zircon crystals found in ancient Earth rocks, cratering chronologies of the rocky planets, the Moon, and icy satellites. Basically it's a preponderance of evidence pointing toward plausible models for the early history of the solar system. Velikovsky has tortured interpretations of ancient literature. Who do you think is more likely to be closer to describing reality?

Re:Next

[Anonymous Coward]

He better. I don't want him sullying my good name.

Cannibal?

[Mick R]

Which planet did it eat? Planet Kenny? The bastard!

Re:amphromoporthizing

[bh_doc]

The theory doesn't anthropomorphize the planet. The article describing the theory does, because that makes it more accessible and interesting to general readers.

Remember, not everyone is an emotionless nerd. Some of us like allegories.

Re:Nuclear?

[Bigjeff5]

Indeed, without the earth's magnetic field the Sun would be blasting us with a constant supply of nastiness to go along with the life-giving radiation it currently provides.

It is well known that the Earth's core is liquid and made almost entirely of iron. It has been shown that rotating a mass of liquid metal generates a significant magnetic field. It's where Earth's field comes from. Mars also has an iron core, but it is solid all the way through, which explains the lack of a magnetic field.

With no magnetic field Mars gets no filter - it gets the full blast of the Sun's radiation, which pretty much destroys any chance of life at the surface. Without the magnetic field to re-direct some of the Sun's rays, more of Mars's atmosphere also gets launched into space.

In other words, you are absolutely correct sir!