Saturday, January 23, 2016

Jupiter and natural satellites

Continuing our exploration of the planets...
Jupiter is the fifth planet from the sun.  It is two and a half times as massive as the other planets combined.  It is not like any of the other planets we've looked at so far.  It is a gas giant, and even though some is known about the outer layers of it, for the simple fact that the conditions are so extreme that the only spacecraft that has ever explored it was only able to survive for the first 150 km of atmosphere before being crushed.

Here's what Jupiter is like as you move in towards the center:
Jupiter has a ring system, this is the first planet with rings.
The very outer layer of the atmosphere is gaseous, but steadily changes into a liquid as as pressure increases.
It is mostly made of hydrogen, but other "fun" chemicals exist, such as hydrazine (corrosive) ammonium hydrosulfide (flammable, toxic), and ammonia ice (generally poisonous and corrosive).  Wind speeds above 100 m/s are common.
As pressure increases further, the hydrogen turns into liquid metallic hydrogen, so named because it is an electrical conductor.   
Much further down is the core of Jupiter.  It is relatively small, but about 12 times heavier than Earth.  It is not know exactly what the core is made of, although it is probably rocky.

Jupiter's gravitational field is 2.54 time stronger than Earth's, and it's average temperature in the outer atmosphere is about -240 F or -151 C.  That, combined with the fact that the pressures would crush almost anything very far down at all, mean that Jupiter isn't very good for any kind of human outpost, much less anything designed for Earth.  Theoretically, some kind of floating station could be built in the very outer atmosphere.

On to the moons of Jupiter!
We'll be skipping the very small moons, because they aren't very interesting.

Jupiter's very nearest moon, Io has over 400 volcanos.  It is very geologically active because of tidal forces from Jupiter and Jupiter's moons.  It's surface is mostly plains, spotted with volcanos and mountains.  It only has traces of an atmosphere, it our stuff wouldn't react much differently than on the Moon, aside from the colder temperatures, due to being further from the Sun.
Europa has a water ice crust over a basic rocky planet.  It is likely, though, that a liquid water ocean exists below the icy crust.  In combination with it's oxygen atmosphere, it is a surprisingly good planet for humans.  Not great, or anything, since it's atmospheric pressure is 10−12 bar, compared to Earth's 1 bar.  The surface temperature at the equator is about −160 C (−260 F).  The sub-surface ocean is probably heated by tidal forces.  An undersea base on Europa would probably be possible, converting the water to oxygen and hydrogen to generate rocket fuel and breathable atmosphere.  Of course, anything from Earth would freeze without protection.
Ganymede is a large lump of icy rock.  It also may have a subsurface ocean.  It has a molten iron core and almost no atmosphere.
Callisto is, again, a large lump of icy rock with a possible subsurface ocean.  Interestingly, below the possible subsurface ocean, the rocket and ice in not stratified like in most planets/moons.  It is probably the best bet for a surface base, being far from Jupiter to minimize radiation, and geologic stability.
And finally, since this post doesn't have a video, here's some robotic falconry: