Jupiter's melting heart sheds light on mysterious exoplanet

March 22, 2012 By Brian Jacobsmeyer, Inside Science News Service
Credit: Forsetius via flickr

Scientists now have evidence that Jupiter's core has been dissolving, and the implications stretch far outside of our solar system.

Jupiter might be having a change of heart. Literally.

New simulations suggest that Jupiter's rocky core has been liquefying and mixing with the rest of the planet's innards. With this new data, astronomers hope to better explain a recent puzzling discovery of a strange planet outside of our solar system.

"It's a really important piece of the puzzle of trying to figure out what's going on inside ," said Jonathan Fortney, a at the University of California Santa Cruz who was not affiliated with the research.

Conventional planetary formation theory has modeled Jupiter as a set of neat layers with a gassy outer envelope surrounding a rocky core consisting of heavier elements. But increasing evidence has indicated that the insides of gas giants like Jupiter are a messy mixture of elements without strictly defined borders.

This new research on a melting Jovian core bolsters a mixing model of gas giant planets and would provide another avenue for heavier elements to flow throughout the planet.

"People have been working on the assumption that these planets are layered because it's easier to work on this assumption," said Hugh Wilson, a planetary scientist at the University of California Berkeley and a coauthor of the new research appearing in Physical Review Letters.

Although scientists had previously toyed with the idea of melting cores in large planets, nobody sat down and did the necessary calculations, said Wilson.

Scientists have to rely on calculations of Jupiter's core environment because the conditions there are far too extreme to recreate on Earth. Wilson and his UC-Berkeley colleague Burkhard Militzer used a computer program to simulate temperatures exceeding 7,000 degrees Celsius and pressures reaching 40 million times the air pressure found on Earth at sea level.

Those conditions are thought to be underestimates of the actual conditions inside Jupiter’s core. Nonetheless, the authors found that magnesium oxide -- an important compound likely found in Jupiter's core -- would liquefy and begin drifting into Jupiter's fluid upper envelope under these relatively tame conditions.

Researchers believe that similarly-sized gas giant exoplanets -- planets found outside of our solar system -- probably have similar internal structures to Jupiter. Consequently, scientists were baffled earlier this year when they found a planet with approximately the same volume as Jupiter yet four to five times more mass.

Called CoRoT-20b, the new planet was announced in February, and its discoverers searched for a suitable explanation for its unusual density. Using conventional models, the astronomers calculated that the core would have to make up over half of the planet. For comparison, Jupiter's core only represents about between 3-15 percent of the planet’s total mass.

With a core that large, CoRoT-20b presented a huge problem for traditional assumptions surrounding planet formation.

"It's much easier to explain the composition of this planet under a model where you have a mixed interior," said Wilson.

Even the team that discovered the planet noted that a mixing model could allow for a more palatable planet density. Wilson's simulations not only add credence to the mixing model of giant but also suggest that this specific exoplanet's core is probably melting just like Jupiter's.

This melting may help explain why the exoplanet's heavy elements are likely stirred up and distributed throughout its volume, said Wilson.

Santa Cruz's Fortney agrees that most of the exoplanet's heavy elements likely reside in the outer envelope. Nonetheless, he expects other factors played a larger role in how the planet's interior became mixed: "It's more of a planet formation issue."

Several other events, such as two colliding together, might explain the ultra-high density of this new planet, Wilson admits. Certain processes may also limit the effectiveness of the melting and mixing process.

Liquefied parts of a gas giant's core may have trouble reaching the outer envelope due to double diffusive convection -- a process commonly found in Earth's oceans. When salty water accumulates at the bottom of the ocean, its density keeps it from mixing thoroughly with the upper layers. In a similar fashion, the in Jupiter's core may have trouble gaining enough energy to move upward and outward.

Scientists don't know how much this hindrance will affect potential mixing inside Jupiter, and many other questions remain to be answered about the melting process.

"The next question is, 'How efficient is this process?'" said Fortney.

Researchers will have more tools to answer this question once NASA's Juno probe reaches in 2016. With the spacecraft's instruments carefully analyzing Jupiter's composition, Wilson believes that there will be signatures of mixing and erosion.

Explore further: New calculations suggest Jupiter's core may be liquefying

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1.3 / 5 (12) Mar 22, 2012
Would make life most interesting if the scenario painted in the SciFi movie 2010 were to arise, the ignition of hydrogen at the core, given the pressures and mixture of other elements potentially catalytic, one wonders if matter has some more tricks up its collective sleeve under those conditions :-)
1.4 / 5 (9) Mar 22, 2012
Damn, it'd be interesting to drop a probe down into Jupiter's atmosphere to see what's really going on down there. But then again, I'm sure that pretty much anything we send there is just going to be torn apart by the giant planet's gravity, and crushed by its thick, turbulent atmosphere. There must be a way to see through those damned clouds.
5 / 5 (5) Mar 22, 2012
Damn, it'd be interesting to drop a probe down into Jupiter's atmosphere to see what's really going on down there. But then again, I'm sure that pretty much anything we send there is just going to be torn apart by the giant planet's gravity, and crushed by its thick, turbulent atmosphere. There must be a way to see through those damned clouds.

We already have done this. Look up the Galileo mission.
1.4 / 5 (9) Mar 22, 2012
Just wondering. I don't think the Galileo mission released any images or details of Jupiter's interior upon its descent. At least, all I heard was that the probe crashed into Jupiter. And that was it. It's hard to find anything else on the probe's final moments.
5 / 5 (3) Mar 22, 2012
Quite a bit of info is available at
http://nssdc dot gsfc dot nasa dot gov/planetary/galileo dot html#firsts
2.2 / 5 (13) Mar 22, 2012
I understood links were allowed here, so should be http://nssdc.gsfc...l#firsts
seems to work,
5 / 5 (3) Mar 22, 2012
It's a Mixmaster planet. http://en.wikiped...universe .
@ Mike Massen: Brown dwarfs may burn deuterium if they are massive enough, giant planets aren't that massive seems like.

@ Sinister1822: There was no camera on board, it wouldn't have seen anything lower down. That was perhaps lucky, since Galileo was the mission with the main antenna failure, and the data transmission was a bottleneck.

Anyway, there were a lot of instruments that captured ~ 50 minutes and ~ 4 MB of data. Certainly a lot of papers would be analyzing those for model images and details of the interior. (The probe descended some 150 km, sez Wikipedia.) Wikipedia provides an entry point to that, but I assume that there is a Galielo site as well.
5 / 5 (1) Mar 22, 2012
I understood links were allowed here, so should be
seems to work,

I don't know why but when I tried to post the link straight up it was rejected. Thanks for getting it posted so it can just be clicked on. :-)

I just got the notice that my post did not pass the spam filter. I removed the link from your quote and it seemed to work fine without it. Maybe I am just to new here to post links.
not rated yet Mar 25, 2012
I thought that the size issue was already well known and that any more massive planet would be smaller due to matter degernacy, shrinking under pressure, continuing on a scale through white dwarfs.
not rated yet Mar 26, 2012
A giant exoplanet whose core is over half the mass of the planet is definitely an odd beast in my book.

Either heavy elements were in much greater abundance during planetary formation than was the case in our own solar system, or the planet has shed some of its lighter elements after formation.

It might be interesting to simulate what happens to the lighter elements during a collision of two giants. What gets ejected? What is retained? How sensitive to collision velocities is the result?

Heh. Astronomy is way too much fun to leave to the professionals.
1.8 / 5 (5) Mar 27, 2012
Damn, it'd be interesting to drop a probe down into Jupiter's atmosphere to see what's really going on down there. But then again, I'm sure that pretty much anything we send there is just going to be torn apart by the giant planet's gravity, and crushed by its thick, turbulent atmosphere. There must be a way to see through those damned clouds.

Indeed...perhaps, not INTO the gas giant but, THROUGH, it! Two satellites beaming data/transmissions through the planet, looking for timely data flow/energetic-pulse reflections, through a broadband antenna array. They would have to get so close, that they would lose direct contact with each other. But, ELF transmissions could place them in relation to each other and a third probe, at Juno-Synch (Juno, for 'wife' of Jupiter) would relay final data back to earth. I have an idea how to power the beams without harming the data links, or Jupiter. The sats will need SPEED @ such close orbits, but..yes, it can B done.

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