# Tag Info

120

(*) Jupiter, for all intents and purposes, doesn't have a solid surface to stand on. Not any more than you could say that Earth's atmosphere has it, before you hit Terra Firma. It's an enormous ball composed of mostly Hydrogen and Helium, but also other heavier elements in smaller parts, and it's so massive that its own gravity compresses these gases into ...

50

The trajectory was not only "unhindered" - it was enhanced! Knowing mass of the planet you can calculate very precisely how the trajectory of a probe flying by will be affected. You modify the trajectory on arrival in such a way, that the departure trajectory will be exactly as desired. And due to some rather unintuitive physics caveats, you can make it so ...

46

Jupiter being a gas giant is not about its appearance, as another answer stated. It's only about the mass distribution of a planet. Jupiter's mass is 320 Earth masses, while we know from the Juno mission that the rock/ice in the core account for 5–25 of these Earth masses. So the rest of about 300 Earth masses is gas. Thus Jupiter is a gas giant. It is ...

25

They did not ! This is the trajectory of Voyager 1 at Jupiter. credits wikipedia

23

This is a pretty broad questions, as it would depend on which gas giant you have in mind. Excluding Uranus and Neptune as ice giants, this leaves us with Jupiter and Saturn in our own Solar system, and they're still hard to directly compare in terms of how hazardous environment they'd represent to an orbiting space station. But they have one deadly thing in ...

14

One reason they are called gas giants is because they are mostly composed of elements that are gaseous at Earth like temperatures and pressures. Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, though helium comprises only about a tenth of the number of molecules. Jupiter's upper atmosphere is about 88–92% hydrogen and 8–12%...

14

My 1965-vintage copy of Sourcebook On The Space Sciences has this to say: The model developed by DeMarcus in 1958 is regarded at present as the most acceptable for the interior of Jupiter. It postulates that the planet consists of 78% by weight of hydrogen molecules and the remainder helium ... calculations indicate that at a distance of about 0.8 times the ...

14

There is an answer on wikipedia: Rogue planet: It is calculated that, for an Earth-sized object at a kilobar hydrogen atmospheric pressures in which a convective gas adiabat has formed, geothermal energy from residual core radioisotope decay will be sufficient to heat the surface to temperatures above the melting point of water.[13] Thus, it is proposed ...

10

At JPL I participated in several studies concerned with telecommunication from depth at Jupiter (and other giant planets). In general, with radio telecom from within Jupiter's atmosphere, the lower you go in frequency, the deeper you can penetrate. But there is a practical limit. Above about the 100-bar level (the depth in the atmosphere where the pressure ...

9

Live, yes. Thrive? No. The ISS and stations like it are not "benign environments" - that is, they are life sustaining, but not safe for long term habitation on the order of years. They lose air, they admit both EM and particulate radiation, and are only minimally protected from magnetic induction. The NASA lifetime space exposure limit is under 5 Seiverts ...

6

Eventually, yes but I don't think that it has much to do with the sun. Jupiter's magnetosphere shunts all of the solar wind (plasma) from the sun and Jupiter's atmosphere was also found to be quite turbulent. This indicates that Jupiter's winds are driven in large part by its internal heat rather than from solar input as on Earth. -nineplanets.org ...

6

No, you can't fly through the rings you can see without hitting lots and lots of dust-sized ice particles at high velocity. Your vehicle will not fare well. The ring material is not sparse in that sense. There is a wide distribution of particle sizes from boulders to dust. There's a lot more dust-sized, so that's what you need to worry about. (I wouldn'...

6

As I remember, Saturn was often described as being less dense than water and thus able to float in a giant ocean, long before the probes. The orbiting natural satellites were used to measure the total masses and thus densities of the gas planets. James Blish coined the term "gas giant" to describe the outer planets about 1952 in a science fiction story, ...

5

The term "Ice Giant" is given to planets which are thought to have formed from materials in their ice phase, not because they are made of ice. The ices changed to gas and liquid during planet formation.

5

This formula assumes a constant gravitational acceleration over the whole height of the gas column - a reasonable assumption for Earth, as the atmosphere is thin compared to to the size of the planet. For a simple argument, if you assumed composition is the same, it's clear that the altitude change needed for pressure to change by a certain factor is less ...

5

Combustion requires a fuel (hydrogen), an ignition source (your enormous explosive), and an oxidizer. There's a very small amount of oxygen in the atmospheres of the gas giants, almost all of it already bound up in water -- i.e. all the oxygen has already combusted with some of the hydrogen. Without the introduction of a lot more oxygen or other oxidizer, ...

4

There are two factors at work here: The rings of Saturn are made of much more reflective material (water ice) than those of Jupiter, Uranus or Neptune. They simply have much more matter in them. This wikipedia article and this one suggest a mass for Saturn's rings ($1-3\times 10^{19}$kg) which is at least 1000 times greater than that of Jupiter's rings ($10^... 4 This image shows that the rear side of Saturn rings is dark. These images show the variation of the rings' brightness: the closer Saturn is to Earth, the brighter its rings appear. The rings of Saturn consist of 99% of water and the remainder are various impurities. The water is in the form of water ice. Since ice is a crystalline structure, it reflects and ... 4 For a spherically symmetric mass distribution in hydrostatic equilibrium:${dP\over dr}=-g\rho$where$P$is the pressure,$r$is the radius,$g$is the gravitational acceleration as a function of$r$, and$\rho$is the density of the gas as a function of$r$. Then you integrate up or down from some known conditions.$g$as a function of$r\$ is ...

4

Yes, and that's believed to be the source of Jupiter's gigantic magnetosphere. It is also a possible explanation for bizarre cooling of Cassiopeia A. So that's at least two immediate effects of large quantities of metallic hydrogen present in a celestial body; formation of a magnetosphere and faster cooling of their outer cores. Both of these effects are ...

4

I've seen it in viewgraphs, but not in a serious proposal. I suspect that there will be more traditional probes (entry vehicles on parachutes) to Saturn and one of Neptune or Uranus, since we haven't done those yet, before a balloon would be attempted.

4

@SteveLinton gave the primary investigations for determining a giant planet's internal structure: gravity field structure and magnetic field structure. One minor correction: while the round-trip propagation times ("ranging" data) are useful, the most accurate data are Doppler data of the spacecraft's velocity vs time, as described in Arv Kliore's paper on ...

4

That's a tricky question, if you want to go into enough detail. Generally, the gas giants consist mostly of gas, and you can derive the density and thus gravity if you know the equation of state of the gas (that's the tricky bit). A random treatise on the exploration of Saturn's internal structure based on gravity data could be this article as found in ArXiv....

4

I'll make a simplifying assumptions that the giant planets are very close to spherical and that the density inside these planets depends only on radial distance from the center of the planet. (This is not quite correct as the giant planets rotate rather quickly, making the planets oblate spheroids rather than spheres. But the differences are small.) These ...

3

Just about any data concerning a planet can contribute to our understanding of its internal structure one way or another. That said, probably the most powerful techniques at the moment are observation of the planets gravitational and magnetic fields and how they vary in space and time. Observing the gravitational field amounts to accurately tracking the ...

3

The orbital period of a satellite tells you the mass of the object it's orbiting. Thus we could weigh the gas giants and know that they were so light they had to be almost all gas.

3

Actually Mazura is wrong, Callisto the moon of Jupiter has a mean temperature of 134 Kelvin, Jupiter has a cloudtop temperature of 165 Kelvin. So it is warmer, but just by 30 degrees. The Jupiter's internal heat really shows below the top clouds, with the core being 36000 Kelvin hot. The freezing point of hydrogen is 13.99 Kelvin. Any "gut feeling" is wrong ...

3

If the right chemical bath spews from hydrothermal vents on the floor of an ocean on this moon, then perhaps it could host creatures like the ones found around such vents on Earth. Here is a quote from an article on the subject in NASA Science News: Instead of photosynthesis, vent ecosystems derive their energy from chemicals in a process called "...

3

We can probe this matter a little more in-depth. This introductory reference describes all the giant or Jovian planets, noting that only the two more massive ones, Jupiter and Saturn, are made primarily of hydrogen and helium. Uranus and Neptune, which did not have as much material to work with and did not become powerful enough to draw large proportions ...

3

If we ignore the atmospheric effects for a moment, let's see what gravity does as you descend into a planet (and this goes for all planets, rocky or gaseous). According to Newton's Shell theorem, inside a sphere of uniform density, gravity is proportional to your distance to the center. Gravity is highest when you're on the surface, with all of the planet'...

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