Jupiter when did we realise it was gas

the_monkey

hi
Quick q on Jupiter , I'm reading 2001 a space odyssey and it seems Arthur C Clarke assumed it had a rocky surface under its atmosphere.
That was written in 1968, so I'm wondering when humans discovered it as a gas giant
Thanks


Ps I have goggled it and just info on its general discovery plus I'm away this weekend and only slow 3G phone access ...

BorneTobyWilde

When is started to make everyone laugh

Youngblood.III

From some website...
We do not yet know if a solid surface exists on Jupiter. Jupiter's clouds are thought to be about 30 miles (50 km) thick. Below this there is a 13,000 mile (21,000 km) thick layer of hydrogen and helium which changes from gas to liquid as the depth and pressure increase.

Youngblood.III

the_monkey wrote: »

hi
Quick q on Jupiter , I'm reading 2001 a space odyssey and it seems Arthur C Clarke assumed it had a rocky surface under its atmosphere.
That was written in 1968, so I'm wondering when humans discovered it as a gas giant
Thanks


Ps I have goggled it and just info on its general discovery plus I'm away this weekend and only slow 3G phone access ...

A space oddessy...was that not its moon Europa

Mickeroo

the_monkey wrote: »

hi
Quick q on Jupiter , I'm reading 2001 a space odyssey and it seems Arthur C Clarke assumed it had a rocky surface under its atmosphere.
That was written in 1968, so I'm wondering when humans discovered it as a gas giant
Thanks


Ps I have goggled it and just info on its general discovery plus I'm away this weekend and only slow 3G phone access ...

Don't know how accurate this site is: http://nineplanets.org/jupiter.html

They say it was first visited by Pioneer 10 in 1973 so that would have been after the book. The site also says that it probably has a rocky core amounting to something like 10 to 15 earth masses though, which I wasn't aware of. I don't think there's any confirmation of that though as they say we only have data reaching 150km below the cloud tops (from Galileo).

GerB40

BorneTobyWilde wrote: »

When is started to make everyone laugh

That's the best response in the history of boards..

the_monkey

Youngblood.III wrote: »

A space oddessy...was that not its moon Europa

Europa was a major point in the sequel , but this is the book , and he is talking about Jupiter

ps200306

the_monkey wrote: »

hi
Quick q on Jupiter , I'm reading 2001 a space odyssey and it seems Arthur C Clarke assumed it had a rocky surface under its atmosphere.
That was written in 1968, so I'm wondering when humans discovered it as a gas giant
Thanks

Ps I have goggled it and just info on its general discovery plus I'm away this weekend and only slow 3G phone access ...

The fact that the visible "surface" of Jupiter was dynamic was known to 17th century astronomers almost as soon as the telescope was invented -- if not to Galileo, then certainly to Hooke and Cassini. The bands of Jupiter's upper atmosphere would have been easily visible to 18th and 19th century astronomers. A systematic compilation of 50 years of Jupiter cloud observations was published in book form by Peek in the late 1950s. Ingersoll and Cuzzi used these in 1969 to show that Jupiter's upper atmosphere is a complicated place -- the zonal atmospheric bands show differences in temperature that cannot be explained just by differences in solar irradiation.

It wasn't until astronomical spectroscopy got going in the latter half of the 19th century that we could tell what things were made of, and the first detailed spectroscopic studies of Jupiter along with a model of the planet's atmospheric structure weren't done until 1930 by Rupert Wildt. As well as hydrogen and helium, Wildt discovered that Jupiter's atmosphere contained ammonia and methane.

When a satellite is small compared to the thing it orbits, it's easy to work out the mass of the parent just by the satellite's distance and orbital speed. So Jupiter's moons give us a good idea of its mass. If you take the mass and radius of the planet, and a model of its atmospheric content, you can check via the equations for hydrostatic equilibrium whether this is consistent with a "gas all the way down" scenario.

It's not quite that easy, though. Dalton's law of partial pressures says that the pressure of a mixture of gases is just the sum of the pressures of all the constituent gases. But at very high pressures it's hard to model how all the constituents behave. Hydrogen is believed to form a kind of metal at extreme pressures. Helium forms a liquid and "rains out" above a certain pressure. Neon is soluble in helium, and so it gets rained out too. These and other phenomena imply that the atmosphere cannot be modelled as a simple homogeneous mixture of gases.

All of this assumes we even know what the original mixture of gases was to begin with. Spectroscopy at visible wavelengths only tells us about the tops of the clouds. Infrared spectroscopy has been able to look lower down in the atmosphere. NASA flew an airborne observatory in the 1980s to study the mid-wavelength infrared signature Jupiter's troposphere down to a pressure of 6 bar. But there is still considerable uncertainty about the composition. When comet Shoemaker-Levy 9 crashed into Jupiter in 1994, the spectral analysis of the cloud plume showed sulfur, but no sulfur dioxide, suggesting that the atmosphere is curiously depleted in oxygen.

To progress further, we have to theorise about how and where Jupiter formed. In the solar nebula that surrounded the early sun, it is assumed that there were stratified zones containing different materials depending on their volatility. Volatiles like water, carbon dioxide and ammonia condense at different distances from the sun depending on temperature. The first modern theoretical model of Jupiter's composition based on both observations and theories about solar system formation was done by Zharkov in 1974.

Subsequent theories are based on complicated factors to do with how certain gases are trapped in ices of comets and icy planetesimals that might have been accreted by the early Jupiter. If Jupiter formed in a similar way to the Sun by condensing from the original protosolar nebula, it should have broadly the same chemical composition as the Sun. But an enrichment in certain elements by a factor of several over the solar ratios -- in particular the abundances of the noble gases -- leads to a theory that Jupiter started out as an icy or rocky planet that gradually gained its huge atmosphere by accreting other icy planetesimals.

But we still don't know for sure what the elemental abundances are on Jupiter. The atmosphere is complicated and apart from the zonal layering we don't know much about vertical stratification, i.e. how deep down convective winds go. The Galileo entry probe in 1995 measured them down to a couple of hundred miles depth, but this is still only scratching the surface. Starting in July next year, NASA's Juno spacecraft will answer lots of the questions. It will make gravitational measurements that will shed light on whether there is a rocky core. In fact, it'll make gravity measurements so sensitive that we'll be able to tell how deep down the winds blow, by measuring the density anomalies they cause.

Jupiter's definitely still packing a few mysteries!

(Sources -- a couple of hours of Googling and reading mostly abstracts of academic papers :pac: ).

Tefral

ps200306 wrote: »

.....leads to a theory that Jupiter started out as an icy or rocky planet that gradually gained its huge atmosphere by accreting other icy planetesimals..[/SIZE]

One thing that interests me when I read something like this, is how come it hasn't started some form of ignition by increasing its mass so large? I'snt there dwarf stars out there the same mass as Jupiter?

ps200306

cronin_j wrote: »

One thing that interests me when I read something like this, is how come it hasn't started some form of ignition by increasing its mass so large? I'snt there dwarf stars out there the same mass as Jupiter?

No, the minimum mass for a proper star to get going is believed to be around 0.08 solar masses. Jupiter is 1/1000 solar masses, about 80 times too small. A brown dwarf (by one definition) is a body that manages to fuse deuterium but not hydrogen. I think the lower limit for that is about five times less than for hydrogen fusion, but Jupiter is still too small by a factor of more than a dozen.

GerB40

Considering most stars in the observable universe are binary systems I'd there any chance that Jupiter is a failed second star?

ps200306

GerB40 wrote: »

Considering most stars in the observable universe are binary systems I'd there any chance that Jupiter is a failed second star?

It doesn't seem like it. Binaries form when the collapsing protostellar nebula fragments (i.e. when two regions of it independently exceed the Jeans mass). But from what I've been reading, the evidence from element ratios is that Jupiter formed like the other planets from a protoplanetary disc after the Sun had formed.

Capt'n Midnight

at it core it's rocky but that's a long way down and most of the core may even be made of diamond.

_Tombstone_

What if you released a submarine into Jupiter's atmosphere? Would it eventually reach a point where it would float? Could it navigate?

http://what-if.xkcd.com/138/

JupiterKid

I think that is was widely believed that Jupiter was of a gaseous/liquid composition by 1968. It was believed at one point that the Great Red Spot might be an atmospheric disturbance -like a stagnant zone - overlying a "surface" anomaly but that was pre-1960s. Brad Smith et al in the late 1960s showed that the GRS rotated like a storm - and the Pioneer 10/11 fly-bys in the mid 1970s confirmed this.

If you read National Geographic issues from the mid 1970s, the thinking at the time was that Jupiter had no solid surface. What's interesting about the results of the Pioneer 10 mission is that even then it was believed that the moon Io was unusual - a source of sodium and at the time conjectured to be dusted with salts.

Capt'n Midnight

JupiterKid wrote: »

I think that is was widely believed that Jupiter was of a gaseous/liquid composition by 1968.

or even earlier http://physics.stackexchange.com/questions/35809/was-jupiters-mass-guessed-at-by-kepler-or-galileo

it seems that the first application of Kepler's Third Law to the Jovian satellite system, is found in Newton's Philosophiae Naturalis Principia Mathematica (2nd ed. of 1713), lib. III, prop. 8, resulting in 1/1033 solar mass.

_Tombstone_

Jupiter is made of peddles - New study.

We're starting work this year on a probe to check out it's Moons, especially Europa cuz we think we spotted Water Vapour there.

http://www.natureworldreport.com/2015/08/secrets-unveiled-behind-the-creation-of-gas-giants-like-jupiter/

http://edition.cnn.com/2015/08/21/world/jupiter-juice-mission/index.html