Curiosity about Uranus

[DerpenWolf]

After hearing about the possibility of KSP's third gas giant having an actual large solid surface I started to think about its real world analog Uranus. As we know Uranus's high axial tilt is suspected to have been the result of a large impact from something that would likely have been made up of a sufficient amount of mass. So long story short I'm wondering if Uranus may have formed a significantly larger core made up of solids and liquids than lets say Neptune from it absorbing the impactor and maybe even a few of its moons (note that Uranus moons are all rather small and a few appear to be torn up! Also aren't the rings rather young?). Could this explain why Uranus seems to be calmer and colder than its neighbors( less circulation, and yes I know it has 400km/hr winds). Does this random theory have any credibility? Or am I going a bit crazy like I suspect I am? Tell me what you think!!

[szputnyik]

Well, Uranus is the most "habitable" gas giant in the Solar System. Its gravity is about the same as that of Venus, and the atmosphere could be accessed with spaceplanes, which would dip down to mine hydrogen and helium, then fly off into space. Making a balloon aerostat like on Venus is impossible, because in a hydrogen/helium atmosphere there are no lighter gases that would be bouyant. The only problem is the extreme cold, which coupled with the thick atmosphere could disable spaceplanes entering it, though it wouldn't be more dangerous than the atmosphere of Titan. Flying machines flying with, instead of against the winds, would experience no dynamic pressure and relative wind.

[Brotoro]

...Making a balloon aerostat like on Venus is impossible, because in a hydrogen/helium atmosphere there are no lighter gases that would be bouyant...

You use HOT hydrogen.

[Armchair Rocket Scientist]

After hearing about the possibility of KSP's third gas giant having an actual large solid surface I started to think about its real world analog Uranus. As we know Uranus's high axial tilt is suspected to have been the result of a large impact from something that would likely have been made up of a sufficient amount of mass. So long story short I'm wondering if Uranus may have formed a significantly larger core made up of solids and liquids than lets say Neptune from it absorbing the impactor and maybe even a few of its moons (note that Uranus moons are all rather small and a few appear to be torn up! Also aren't the rings rather young?). Could this explain why Uranus seems to be calmer and colder than its neighbors( less circulation, and yes I know it has 400km/hr winds). Does this random theory have any credibility? Or am I going a bit crazy like I suspect I am? Tell me what you think!!

Hmm...

Both Uranus and Neptune are believed to be more than 90% rock and ice (mostly ice), with the gas envelope being only a minor component of their masses. This is why they are referred to as ice giants, as opposed to gas giants, which are mostly hydrogen and helium.

NOTE: in the context of planetary composition, "ice" refers to carbon, nitrogen, and oxygen compounds (including water, ammonia, and methane). It does NOT have to actually be in a solid phase.

Now, Neptune is 29% denser than Uranus, which seems to imply that it has the larger core. Uranus's primordial impactor is believed to be about the size of Earth, so I would expect a roughly Pluto-like composition, about 50% rock and 50% ice. This would significantly increase the mass of Uranus's rocky core. However, it's possible that not all of the impactor's mass was absorbed by Uranus. There's also a theory that Uranus actually suffered TWO giant impacts: http://www.scientificamerican.com/article/uranus-axial-tilt-obliquity/

In any case, the impacts would have occurred before Uranus's moons had formed. Also, we can't really say whether Uranus's moons are unusually small because we have no other example of an ice giant's moon system to compare it to (Neptune's regular satellites were all either destroyed or ejected from the system by interactions with Triton).

There is a possibility that the impactor could have dissipated a lot of Uranus's original heat, leading to the blandness of its atmosphere. However, the Uranian atmosphere hasn't been studied in detail over a full year yet, and its weather has become a lot more interesting as it approaches an equinox. It seems that Voyager 2 didn't catch it at a good time.

[lajoswinkler]

Neptune has a much more violent atmosphere because it's colder. There's less friction, so once something starts, it's difficult to stop it. Most of the energy for such processes of our ice giants comes from the interior. Neptune is more massive than Uranus so the core is hotter.

It's difficult to wrap your head around these things because we don't know much about them. One thing is sure - there is no solid surface there. Uranus and Neptune are mostly hydrogen and helium, but they have a higher ratio of ices (water, ammonia, methane) than Jupiter and Saturn, so we call them ice giants. Pressures and temperatures inside them are climbing at such rate that you pass from gas to supercritical fluid which gradually gets more degenerate. In case of Jupiter and Saturn, hydrogen supercritical fluid gradually starts conducting electricity, and in the case of Uranus and Neptune ices play that role, except the conditions are much less extreme.

There is really no concieveable way to navigate the upper atmosphere for the reasons already described by others. Gas giants are like Venus, but a lot more evil. Hellish abyss.

[bigdad84]

I'm a bit out of the loop lately, but "possibility of a third gas giant?". Is there more info on this?

[szputnyik]

The only thing that would be easier than on Venus is keeping the spacecraft that entered its atmosphere at room temperature. Lighting a campfire in a pressurized compartment and periodically supplying it with oxygen and venting the built up CO2 and smoke to the Uranian atmosphere would theoretically be enough, while even the most Earth-like 50km altitude above Venus would experience a temperature of about 55 °C, making some kind of power hungry super-air conditioner necessary.

[zarakon]

XKCD did a what-if a while ago about how well you could fly planes everywhere in the solar system:

http://what-if.xkcd.com/30/

He didn't go into much detail on Uranus though.

Uranus: Uranus is a strange, uniform bluish orb. There are high winds and it’s bitterly cold. It’s the friendliest of the gas giants to our Cessna, and you could probably fly for a little while. But given that it seems to be an almost completely featureless planet, why would you want to?

Venus is a terrible place.

Titan: We’ve saved the best for last. When it comes to flying, Titan might be better than Earth. Its atmosphere is thick but its gravity is light, giving it a surface pressure only 50% higher than Earth’s with air four times as dense. Its gravityâ€â€lower than that of the Moonâ€â€means that flying is easy. Our Cessna could get into the air under pedal power.

In fact, humans on Titan could fly by muscle power. A human in a hang glider could comfortably take off and cruise around powered by oversized swim-flipper bootsâ€â€or even take off by flapping artificial wings. The power requirements are minimalâ€â€it would probably take no more effort than walking.

[NovaSilisko]

NOTE: in the context of planetary composition, "ice" refers to carbon, nitrogen, and oxygen compounds (including water, ammonia, and methane). It does NOT have to actually be in a solid phase.

Thank you for bringing this to attention. Not many realize this!