| Subject: Re: Jupiter's core |
Author:
luke smith
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Date Posted: 02:45:56 03/21/05 Mon
In reply to:
Blobrana
's message, "Jupiter's core" on 19:11:23 12/14/04 Tue
>Katharina Lodders, Ph.D., Washington University in St.
>Louis research associate professor in Earth and
>Planetary Sciences in Arts & Sciences have proposed a
>new mechanism by which the planet Jupiter formed 4.5
>billion years ago after studying data from the Galileo
>probe.
>
>The widely accepted model for Jupiter's formation
>assumes that its overall composition is similar to
>that of the Sun, with enrichments of oxygen and other
>elements heavier than helium. Jupiter's core was
>believed to be a massive snowball that formed in the
>cold reaches of the outer solar nebula, the gas and
>dust cloud from which the solar system formed.
>However, the Galileo probe mass spectrometer found
>much less water than expected in Jupiter's atmosphere.
>
>Taking the mass spectrometer data and earlier
>Earth-based infrared spectroscopic measurements at
>face value, Lodders calculated that Jupiter is
>depleted in water and thus in oxygen. The Jovian
>oxygen inventory is only about half of the oxygen
>elemental abundance in the Sun. On the other hand, the
>Galileo probe mass spectrometer data show that
>Jupiter's carbon inventory is about 1.7 times larger
>than that in the Sun. Based on these data; it seems
>that Jupiter's core was mainly tar instead of ice.
>
>Jupiter's core formed rapidly relative to the rate at
>which gas was lost from the solar nebula. Once its
>core reached about 10 Earth masses, gravitational
>attraction captured the surrounding nebular gas and
>built up the gas giant planet we observe today. The
>core question is: `If there was a lot of water ice
>that helped to build the Jovian core, where is the
>water now? `
>"However, you need to build a large proto-core fast,
>because otherwise you don't have enough mass there to
>accrete gas and to make a gas giant planet."
>
>However, Jupiter is enriched in carbon, and Lodders
>notes that there is much evidence for carbon being
>locked up in organic material on outer solar system
>planets, comets, and meteorites, and the interstellar
>medium from which our solar system originated.
>
>Lodders' theoretical model assumes an outer solar
>system warmer than previously thought. Her theory
>replaces what astronomers call the "snow line," the
>point in the solar nebula where water ice condenses,
>with the new "tar line," the point where asphalt or
>tar-like material formed, pushing the `snow line`
>farther out in the solar nebula towards the Kuiper
>belt.
>
>Lodders proposes that the Jovian core is originally
>tar and rock, steadily growing to the point where it
>accretes gas from the solar nebula, primarily hydrogen
>and helium. Energy from the accretion heats up
>Jupiter, breaking down the tar and making methane, the
>third most abundant gas observed in the planet's
>atmosphere after hydrogen and helium.
>
>"Up to fifty percent of the carbon in the interstellar
>medium may be in organic solids," she pointed out.
>"Organic solids are abundant out there and Jupiter is
>enriched in carbon, so it makes sense to assume that
>organic solids - instead of water ice - provided the
>glue to rapidly build the proto Jovian core."
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