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  #1  
Old 07-25-2012, 01:39 AM
Jim B. Jim B. is offline
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Standing On Jupiter.

This question goes back to when I was a child. One time, I mused to myself as a child, why is there such a big to do about possible life on Mars? Why no, say, Jupiter too? (They sent a probe to Mars when I was still a kid. But people still wondered about life, maybe microbal, on Mars.) Then as time went by, I found out more and more about Jupiter. Still not enough, though, to answer what happens if you stood on Jupiter.

My question is simply this: What would happen if you stood on the surface of Jupiter? (You would have to be wearing a space suit first, I assume.) But what would happen? Would you sink? Would you be buoyant and float? Would the surface be solid? And if you sank, would you go all the way to the center, or stop along the way?

Thank you in advance to all who reply
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  #2  
Old 07-25-2012, 01:54 AM
friedo friedo is online now
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Dude, Jupiter's a gas giant. You can't stand on it.
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Old 07-25-2012, 01:55 AM
Jim B. Jim B. is offline
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Originally Posted by friedo View Post
Dude, Jupiter's a gas giant. You can't stand on it.
Which is why one of my questions was, Would you sink? And how far would you sink, etc.
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  #4  
Old 07-25-2012, 01:57 AM
friedo friedo is online now
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Well, the mass of Jupiter is about roughly 380 times that of Earth, so I would guess you'd be crushed under the weight of your own hair.
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Old 07-25-2012, 01:58 AM
friedo friedo is online now
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Err, that's 318 times the mass of Earth, not 380.
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  #6  
Old 07-25-2012, 02:16 AM
Boyo Jim Boyo Jim is offline
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I think, but I'm not a planet-studier-guy, that at some point the gas would compress into a liquid. But you would be crushed before you could stand, float, sink or swim in it.

The gelatinous blob that remains of you would sink until the material below it was denser. But you wouldn't remain a gelatinous blob for long. First, you are not made of uniform material, some blobettes will sink deeper than others. Second, Jupiter's atmosphere is extremely turbulent, so you would be scattered horizontally as well. You might end up something like a kite string, but not nearly as substantial. Or maybe something like a 3-dimensional Jackson Pollack painting.
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Old 07-25-2012, 02:20 AM
coremelt coremelt is offline
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Originally Posted by friedo View Post
Well, the mass of Jupiter is about roughly 380 times that of Earth, so I would guess you'd be crushed under the weight of your own hair.
If you're suddenly teleported into the edge of Jupiters atmosphere and released (in a space suit armored to withstand pressure) you'd be in free fall so you wouldn't be crushed by gravity.

You'll fall until your spacesuit burns up or is collapsed by pressure, it reaches 9500 k pretty quickly:

http://www.universetoday.com/15097/t...re-of-jupiter/
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  #8  
Old 07-25-2012, 02:38 AM
AaronX AaronX is offline
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Originally Posted by friedo View Post
Well, the mass of Jupiter is about roughly 380 times that of Earth, so I would guess you'd be crushed under the weight of your own hair.
But it's more than 10 times the diameter of earth, so gravity on the surface would only be 3 times.
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  #9  
Old 07-25-2012, 02:53 AM
coremelt coremelt is offline
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Originally Posted by AaronX View Post
But it's more than 10 times the diameter of earth, so gravity on the surface would only be 3 times.
the "surface" of the exotic temperature and pressure core (we have no frigging idea what it is) would be 100s of thousands of G's if you could somehow get there.

if you're in the atmosphere you're either in orbit or free falling. Either way you're in zero G.
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  #10  
Old 07-25-2012, 03:19 AM
AaronX AaronX is offline
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I'm thinking the density of the planet would increase as you went deeper, and eventually you'd float or crash, depending if it solidified first or reached your density first. Some people think the density of our oceans increases enough for scrap to float before reaching the bottom too.
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  #11  
Old 07-25-2012, 05:16 AM
coremelt coremelt is offline
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Originally Posted by AaronX View Post
I'm thinking the density of the planet would increase as you went deeper, and eventually you'd float or crash, depending if it solidified first or reached your density first.
My guess is that given the temperature rise, whatever is left of you would be gaseous long before it reached those kinds of densities, and so you'd be dispersed by the winds and stop falling.

Any planetologists here to give a definate answer?
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  #12  
Old 07-25-2012, 05:16 AM
Colophon Colophon is online now
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I must admit I'm a bit hazy about Jupiter's structure, too. Is the "surface" of the planet that we see basically just the outer tenuous reaches of its atmosphere? And then does it basically just get steadily denser down through the atmosphere until you reach the soothing menthol liquid centre (and the enormous diamond, pace Arthur C Clarke )?
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  #13  
Old 07-25-2012, 05:41 AM
Koxinga Koxinga is offline
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By the above logic, couldn't you just as well say that on Earth anyone falling off the side of a boat should inevitably be crushed to death by hydrostatic pressure?

Last edited by Koxinga; 07-25-2012 at 05:43 AM..
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  #14  
Old 07-25-2012, 06:29 AM
Kinthalis Kinthalis is online now
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Assuming you were in free fall, would there be a point in time, before reaching the liquid core where tidal forces might overcome whatever protective shell you were in Ignoring the 9500k heat of re-entry.
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  #15  
Old 07-25-2012, 06:45 AM
Darth Panda Darth Panda is offline
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From wiki:

Quote:
The core region is surrounded by dense metallic hydrogen, which extends outward to about 78 percent of the radius of the planet.[31] Rain-like droplets of helium and neon precipitate downward through this layer, depleting the abundance of these elements in the upper atmosphere.[21][37]

Above the layer of metallic hydrogen lies a transparent interior atmosphere of hydrogen. At this depth, the temperature is above the critical temperature, which for hydrogen is only 33 K[38] (see hydrogen). In this state, there are no distinct liquid and gas phases—hydrogen is said to be in a supercritical fluid state. It is convenient to treat hydrogen as gas in the upper layer extending downward from the cloud layer to a depth of about 1,000 km,[31] and as liquid in deeper layers. Physically, there is no clear boundary—gas smoothly becomes hotter and denser as one descends.[39][40]

The temperature and pressure inside Jupiter increase steadily toward the core. At the phase transition region where hydrogen—heated beyond its critical point—becomes metallic, it is believed the temperature is 10,000 K and the pressure is 200 GPa. The temperature at the core boundary is estimated to be 36,000 K and the interior pressure is roughly 3,000–4,500 GPa.[31]
http://en.wikipedia.org/wiki/Jupiter

My scientific conclusion is that things would end poorly.

Last edited by Darth Panda; 07-25-2012 at 06:47 AM..
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  #16  
Old 07-25-2012, 06:49 AM
Smeghead Smeghead is offline
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Sounds like a good question for xkcd's new feature.
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  #17  
Old 07-25-2012, 07:10 AM
Machine Elf Machine Elf is offline
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Quote:
Originally Posted by AaronX View Post
Some people think the density of our oceans increases enough for scrap to float before reaching the bottom too.
Scrap-what? Metal? Got a cite for that?

Even if some people think that, it's not true. At the deepest part of the ocean, where ambient pressure is around 16,000 psi, the density of the water there is only about 6% greater than it is at the surface. Aluminum will still sink quite readily in this medium.
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  #18  
Old 07-25-2012, 07:26 AM
AaronX AaronX is offline
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Yes it doesn't seem to be true. Can't remember where I read it though, maybe it was science fiction?

I think this point in the discussion depends on the situation. Are you teleported in? Freefall? Do you have rocket boosters to slow you down like our rovers?

I don't get why they call Jupiter "gas" if it's solid inside though. Couldn't you say the same for Earth? The outer layers are gas, then it's rock.
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  #19  
Old 07-25-2012, 07:41 AM
MikeS MikeS is offline
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Quote:
Originally Posted by Koxinga View Post
By the above logic, couldn't you just as well say that on Earth anyone falling off the side of a boat should inevitably be crushed to death by hydrostatic pressure?
You're asking about the effects of buoyancy? Well, we can get a back-of-the-envelope approximation by using the ideal gas law and this chart and assuming that the atmosphere is mostly molecular hydrogen. At the top of the troposphere, the density of the atmosphere should be about 0.02 kg/m3. This increases up to about 0.16 kg/m3 by the time the pressure reaches about 1 bar, which is often considered to be the "zero altitude" on Jupiter. By the time you get down to -132 km, where the Galileo atmosphere probe failed, the density is up to 1.1 kg/m3. Not nearly enough to float in, or even tread water.
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  #20  
Old 07-25-2012, 08:18 AM
Koxinga Koxinga is offline
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That makes sense, thanks.
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  #21  
Old 07-25-2012, 08:31 AM
coremelt coremelt is offline
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Originally Posted by MikeS View Post
Doing a quick and dirty extrapolation from that chart, at -264 km you'd be at approx 10^9 pascals pressure (10000 atmospheres) but only about 800 kelvin.

We could probably build a suit to withstand 800 kelvin for a while, but could we build a suit to withstand 10,000 atmospheres pressure? My guess from that chart is you'd be squashed before you fried.

Last edited by coremelt; 07-25-2012 at 08:32 AM..
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  #22  
Old 07-25-2012, 08:51 AM
TriPolar TriPolar is offline
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Originally Posted by Machine Elf View Post
Scrap-what? Metal? Got a cite for that?

Even if some people think that, it's not true. At the deepest part of the ocean, where ambient pressure is around 16,000 psi, the density of the water there is only about 6% greater than it is at the surface. Aluminum will still sink quite readily in this medium.
How does water get denser at all? I thought it was an incompressible fluid.
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  #23  
Old 07-25-2012, 08:56 AM
md2000 md2000 is offline
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The characteristic of liquid is that it is virtually incompressible. So in the depths of the ocean, or in Jupiter's non-surface, you would have the gaseous parts squashed flat - lungs, sinuses, inner ear, miscellaneous bubbles in the intestines... But your basic body would remain intact.

Whether we're talking body or scrap metal, it's still denser than water and sinks in the ocean. Metal (solid) also does not compress (significantly), so relatively the density ratios are still the same - metal and bodies sink in water.

Compressed hydrogen or liquid hydrogen or supercritical fluid hydrogen is still much less dense than organic or regular metal materials - so you keep sinking.

Note the extreme prssure and temperature at depth in Jupiter's "oceans". This is where the non-hydrogen tends to accumulate. Life (Jim, but not as we know it) is made up of complex chains of molecules. In the case of carbon organics, the ones that we use require a very precise range to remain intact and perform the functions that keep us alive (plus we need a specific mix in our environment).

The theory is the convection and general environment deep in Jupiter is not stable or friendly enough to allow the complex molecules, whatever they are based on, to form and remain intact and functioning. There have been scince fiction stories of life floating in the clouds of Jupiter and such, but note the earlier post that much of the non-hydrogen elements precipitate down out of the upper atmosphere.

Finally, gravity does not increase as you descend. Once you are well towards the core, gravity becomes less. In fact, a though experiment will show that in the exact center, you sould be weightless.

Last edited by md2000; 07-25-2012 at 08:58 AM..
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  #24  
Old 07-25-2012, 08:59 AM
Boyo Jim Boyo Jim is offline
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FYI, according to several sources, including this one, the gravity of Jupiter is about 2.5 times Earth's, so if you were in a suit that could stand the pressure, the gravity alone wouldn't crush you down to a pancake. Military pilots are routinely subjected to higher g forces than that while maneuvering their planes.
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  #25  
Old 07-25-2012, 09:19 AM
MikeS MikeS is offline
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Originally Posted by Colophon View Post
... (and the enormous diamond, pace Arthur C Clarke )?
Clarke also wrote A Meeting with Medusa, a novella about a manned descent into Jupiter's atmosphere. In the story, the craft was essentially a hot-air balloon, with rockets in order to ascend and return to an orbiting spacecraft.
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Old 07-25-2012, 09:35 AM
AaronX AaronX is offline
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Originally Posted by TriPolar View Post
How does water get denser at all? I thought it was an incompressible fluid.
"Incompressible" is an oversimplification, like clearly dividing things into solid, liquid and gas, saying solids have fixed shapes, etc.
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  #27  
Old 07-25-2012, 09:40 AM
TriPolar TriPolar is offline
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Originally Posted by AaronX View Post
"Incompressible" is an oversimplification, like clearly dividing things into solid, liquid and gas, saying solids have fixed shapes, etc.
I thought water would certainly have some amount of 'free space' in it under the conditions we normally experience it. But I am curious what is happening under great pressure. A 6% density increase isn't all that great, but is the pressure just squeezing it down to maximum density at that point, or is there some other change?
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Old 07-25-2012, 10:44 AM
Machine Elf Machine Elf is offline
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Originally Posted by TriPolar View Post
I thought water would certainly have some amount of 'free space' in it under the conditions we normally experience it. But I am curious what is happening under great pressure. A 6% density increase isn't all that great, but is the pressure just squeezing it down to maximum density at that point, or is there some other change?
It's progressive. Water (and other liquids) is incompressible in the same way that steel is inflexible - which is to say that it is, in fact, very slightly compressible. Not enough to matter for most practical purposes (which is why high school science teachers can safely teach that water is incompressible), but for some purposes (e.g. density calculations at very high pressures), it matters. Oils have a greater compressibiliy (lower bulk modulus) than water, so the compressibility matters at lower pressures I've worked with 7,000-psi hydraulic systems where the choice of hydraulic fluid had a measurable effect on efficiency: the fluid with greater compressibility fostered lower efficiencies. Liquid compressibility is also a factor in the power consumption of the latest and greatest diesel injector pumps, which operate at pressures upwards of 25,000 psi.

Bulk modulus tends to increase (i.e. compressibility tends to decrease) as you move to higher and higher pressures. Take water from 14.7 psi to 16,000 psi, and you get about 6% increase in density; take the pressure from 16,000 to 32,000 psi, and you won't see another 6% increase; you might see (shot in the dark here) a 4% increase.
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  #29  
Old 07-25-2012, 12:45 PM
QuanSu QuanSu is offline
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Quote:
Originally Posted by MikeS View Post
Clarke also wrote A Meeting with Medusa, a novella about a manned descent into Jupiter's atmosphere. In the story, the craft was essentially a hot-air balloon, with rockets in order to ascend and return to an orbiting spacecraft.
Poul Anderson also did the short story "Call me Joe" ("Avatar" used the same idea) which involves Jupiter.
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Old 07-25-2012, 01:11 PM
FUTBOL! FUTBOL! is offline
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Originally Posted by QuanSu View Post
Poul Anderson also did the short story "Call me Joe" ("Avatar" used the same idea) which involves Jupiter.
Asimov produced at least two stories connected to the subject of Jupiter's surface conditions.

In Victory Unintentional, a humorous comedy, three very special robots are sent to Jupiter to attempt to persuade a very xenophobic and aggressive race that they should have peaceful relations with the humans on Ganymede and "the inner worlds" rather than wage war against them.

I say "special" because this is one of the few robot stories with a departure from his more typical robots. These robots are very squat and non-humanoid in appeareance, besides being virtually indestuctible in materials and design.

I recommend reading this short story, appearing in "The Rest of the Robots" and elsewhere, because it is so funny, with a very surprising ending.

- - -

There is a non-robotic prequel Not Final! is which the xenophobia of the Jovians is discovered, but at first the supposed inability of anyone to develop a stable atmosphere-containg force-field leads the humans to breath a sigh of relief.

Unfortunately, a technician discovers a way aroung the supposed invincible production barrier and the theoreticians and leaders realize that they cannot be sure that the Jovians will not be able to duplicate the discovery, and that leads them back to their original fears.

ISTR an extensive discussion of why the Jovians could not be defeated in war, nor could a preemptive genocidal strike be carried out against them.
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  #31  
Old 07-26-2012, 03:15 AM
eburacum45 eburacum45 is offline
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Originally Posted by coremelt View Post
the "surface" of the exotic temperature and pressure core (we have no frigging idea what it is) would be 100s of thousands of G's if you could somehow get there.
The gravity of the core is zero at the exact centre; at which distance from the core do you calculate the gravity to be 100,000 times that of Earth?

If the solid core has a mass of 10 x Earth (as seems likely) and the average density of the compressed core is ten times that of our planet, so that the core is the same size as the Earth, then the gravity will only be ten gees. Even though the core is compressed very considerably I doubt it will be much more than ten times as dense as the average density of the Earth.

Last edited by eburacum45; 07-26-2012 at 03:16 AM..
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  #32  
Old 07-26-2012, 09:01 AM
hibernicus hibernicus is offline
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Originally Posted by Kinthalis View Post
Assuming you were in free fall, would there be a point in time, before reaching the liquid core where tidal forces might overcome whatever protective shell you were in Ignoring the 9500k heat of re-entry.
Tidal forces are just the difference between the force of gravity at your head and at your feet. Since these are only 6 feet apart at any given time, I can't imagine you would notice any tidal forces during your descent.
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  #33  
Old 07-26-2012, 12:07 PM
MikeS MikeS is offline
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Originally Posted by hibernicus View Post
Tidal forces are just the difference between the force of gravity at your head and at your feet. Since these are only 6 feet apart at any given time, I can't imagine you would notice any tidal forces during your descent.
You can actually show that the gravitational tidal forces between your head and your feet as you fall freely through the fluid will be proportional to the density at that level, assuming that the body is spherically symmetric and you're falling in feet-first. The density of Jupiter's core isn't known, but even if Jupiter's core is as dense as the core of the Sun (which it probably isn't), the differential acceleration between your head and your feet is about 0.2 mm/s2. That's a hundred time larger than the tidal effect between your head and your feet here on Earth's surface, but you'd still never notice it.
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