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Jupiter's Mass

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I need help. I keep reading that Jupiter is a gas giant but I don't really understand what that means. Does that mean its just like clouds? Or Water? How come Shoemaker-Levy 9 didn't pass right through it? What is there to impact? If anyone can help put my mind to sleep I'd be very thankful.


There is no observed solid surface to Jupiter, and by mass it's something like 75% hydrogen, 25% helium, with some other stuff thrown in. To understand how something like Shoemaker-Levy 9 can still "Hit" the planet, remember that gases are still matter, and don't like to be moved around.

For a more everyday experience to compare it to, take a look at a basin of water. You can slosh it around, fill things, submerge things, and it offers little resistance. Now, slap it with an open palm (or do a belly flop) and tell me you didn't hit anything!

If you go fast enough anything will hit back hard. Shoemaker-Levy 9, or any object, falling into Jupiters atmosphere will hit lots of air, be slowed, heated, and if it hits a particularly dense pocket may even explode due to the pressure & shockwaves.

Another example that applies here is supersonic aircraft. For an airplane that isn't designed correctly, going faster than sound is very dangerous as the pressure waves can rip the airframe apart. A cometary impact in an atmosphere is easily going 10 or 20x the speed of sound, and isn't really designed for it. The object will burn, scatter, and disintegrate.

The reason we could see the effects: The comet dumped massive amounts of energy into the atmosphere of jupiter, akin to many large nuclear blasts (how many I don't recall). Each spot you saw was easily comparable in size to that of the entire EARTH!


And once you get deep/low enough into Jupiter, the immense pressure means all that ambient gas is as good as solid.


and in the middle there is probably a few Earth mass core made of compressed rocky material.


MeteorWayne":3fybhr6y said:
Maybe. That is not known with certainty yet.
That's very true, but that is one of the aims of the JUNO mission, measuring the exact shape of Jupiter's gravity well (this was how the internal structures of the Galilean moons were surmized with the Galileo spacecraft, & Mercury with MESSENGER, etc), by getting very close to Jupiter & carrying out atmospheric soundings.

The actual mass of Jupiter is known precisely (approx 318 Earth masses), but what is not so clear is how that mass is distributed within the planet, i.e is it vastly denser at the very center with the outer layers being mostly atmosphere, or is it more uniform closer to the base of the Jovian troposphere.

Evidence so far suggests the former. We'll see, but to be honest, we really do not know. If further clues can be gleaned about Jupiter's formation, i.e did ot start off as a large terrestrial planet, that accumulated a huge amount of hydrogen from a giant annulus within the protoplanetary disk, or did jupiter form from the Jeans Condensation, ie a concentratration of hydrogen from an eddie within the propoplanetary disk. We just do not know. Plenty of ideas & educated guesses, but no hard facts.

Andrew Brown.
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