From: LARRY KLAES (ljk4_at_msn.com)
Date: Wed Jul 28 2004 - 08:34:39 PDT
http://seattlepi.nwsource.com/national/183801_space28.html Wednesday, July 28, 2004
Jupiter is churning inside, scientist says
By SUE VORENBERG
Jupiter might look like its mellow twin, Saturn, on the outside, but inside it feels nothing but turmoil.
That's the diagnosis from a scientist at New Mexico's Los Alamos National Laboratory who led efforts to create mathematical models of the inner workings of hydrogen in the two gas giants. A group of lab scientists found that while the two planets are similar in composition, both made up mostly of hydrogen, they might have formed in different ways.
In fact, Jupiter might have experienced so much internal mixing it might not even have a planetary core, said Didier Saumon, the Los Alamos scientist who led the group.
"We'd expect to find two similar planets with similar planetary cores, but the modeling doesn't support that," Saumon said. "That means that if they started the same way, something changed in the formation process for Jupiter that didn't happen in Saturn."
The lab scientists developed several mathematical models of something called the equation of state, or EOS, of hydrogen. It describes how the element will behave in different temperatures, densities and pressures, Saumon said.
Essentially, the models let them build their own versions of the planets.
Through tests done with the equation, Saumon says he believes Saturn formed a solid core of heavier rocky elements as gas and dust collected around it in the early solar system. Jupiter should have a similar core, but the models show it doesn't.
"Jupiter appears to have a very small core -- maybe five times the size of the Earth instead of 10 to 20 times the size of the Earth -- or it could have no core at all," Saumon said.
"Why is that? We don't know. Some are speculating that the core inside of Jupiter might have dissolved and mixed in with the surrounding gas in the early history of the planet."
Think of a cup of milk, Saumon explained. If you pour coffee into the milk, the two substances swirl together until they appear to be a single substance. A similar process might have dissolved Jupiter's core, he said.
If there's no solid rocky core inside Jupiter, it probably means pressurized liquid metallic hydrogen is swirling throughout the center of the planet, with other heavier elements mixed throughout, Saumon said.
The equation was originally developed to help lab scientists better understand how hydrogen behaves in nuclear weapons explosions, but the work is also a big help to the planetary science academic community as it tries to understand how our solar system is put together, said Bill Hubbard, a planetary science professor at the University of Arizona. Hubbard is an independent expert who isn't part of the lab team.
"The Los Alamos models give us a more accurate picture of the gas giants than anything we had before," Hubbard said. "We know of about 100 planets outside of our solar system now, and they are all basically like Jupiter and Saturn. In order to understand what we're seeing there, we need to understand the gas giants in our own solar system and how they evolved."
The models also could help NASA scientists calibrate experiments on the Cassini mission, which reached Saturn on July 1. Those experiments, in turn, could feed back into the Los Alamos model to make it more accurate, Saumon said.
"There are similar missions proposed for Jupiter in the future, and this work can also help those make better measurements to understand its interior," Saumon said. "Right now, the best data we have from that is from Voyager (which passed Jupiter in 1979)."
Hubbard said he finds the model interesting but isn't entirely convinced it's true.
"To say that Jupiter doesn't have a core -- that's still a controversial topic in my view," Hubbard said. "The work we've done suggests Saturn and Jupiter have very similarly sized cores. I think it's still a bit up in the air."
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: Wed Jul 28 2004 - 08:42:26 PDT
Outside, it may look mellow like Saturn, but lab model shows a mixed-up planet
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