Jupiter: Gas Planet? Landing Possibility & Facts

[Zeref]

How do we know for sure that that it's not possible to walk on Jupiter and that it is a gas planet?
Did something ever land on it?

 

[Simon Bridge]

Welcome to PF;
We can be absolutely certain that Jupiter is a "gas planet" because that is a matter of semantics not Nature.

Have you looked up the internal structure of Jupiter?
http://en.wikipedia.org/wiki/Jupiter#Internal_structure
... Jupiter is thought to have a solid core.

Our level of certainty about the current model for Jupiter, such as it is, actually being a fair representation of the factual Jupiter, rests on well tested Laws of Nature, like gravitation, and the observations that have been possible. There may be some differences in the details but the major brush strokes are pretty solid.

I don't think anyone is saying that walking on the core is "impossible" exactly... it's just that 3000GPa (3000,000,000 atmos) pressure and 35,000K temperatures are a wee bit of a barrier. If we could come up with a structure capable of withstanding that, there is still the matter of the remaining 12-45g gravity. But there should be something to walk on.

A number of objects have "landed" on Jupiter ... most prominently a comet.
Well ... more sort of ... crash... really...

 

[phyzguy]

If you really want to learn about it, there is an excellent review article on the structure of the gas giants that has just been posted on the arXiv:

http://arxiv.org/abs/1405.3752