Ahoy. And here we are back for more interplanetary exploration, although in this case it is monoplanetary. It is local monoplanetary exploration.
Anyway, you will remember from last time (part one) that currently we are floating in the asteroid belt about one hundred and fifty million miles from Earth, next to Ceres, the ice ball. But stuff this place because we’ve been here for ages so let’s go!
230 million miles after Ceres is:
Now, you’ll notice that we just traveled the same distance to get here from Ceres as we did to get to Ceres from the sun. We have left the hot rocky middle behind and are into the gassy section of the solar system, although this by no means means that we are out of hot rocks. Jupiter, the biggest planet, sits there big and fat and hydrogen and it sucks comets and asteroids into itself from the far outer solar system and throws them around, possibly at us. It also sucks itself into itself, mushing its hydrogen into a fluid and then into a metal fluid that conducts electricity at thousands and thousands of degrees temperature. It is unknown what the middle is but it is probably hot rocks.
btw, all the way out here the sun is starting to get quite small although it is still very brilliant.
262 thousand miles after Jupiter is:
Queasy Io is the most volcanic thing in the solar system. It has a dicky tummy because its guts are squashed and stretched around as it is pulled about between Jupiter and the other large moons. It spews up stinky yellow sulphur all over itself. Its inner discontent has caused a breakout of 400 volcanoes and 100 mountains, some taller than Everest, on its otherwise smooth surface. It is as big as our moon.
155 thousand miles after Io is:
Europa is a very smooth icy globe that occasionally spits water because it gets squashed about like Io. This means that there is likely to be a liquid water ocean under the ice and it is therefore an excellent spot to be looking for aliens. Sadly no missions are planned until the 2020s. The ice surface is not solid and still, it slips and slides separate from the rocky middle and it cracks and bulges and bubbles. There could also be lakes under the ice but above the ocean.
248 thousand miles after Europa is:
Bigger than Mercury, Ganymede is unlucky to be strapped to Jupiter when it would make a perfectly nice planet. It is a bit of everything, rock and ice and a metal middle. It is also thought to have a giant internal ocean, although for some reason it seems less exciting here than it does on Europa. Mostly it bullies the other moons around with Jupiter, like Jupiter’s slimy little rat weasel friend.
505 thousand miles after Ganymede is:
Happy to be away from the rumpus of the inner moons, Callisto is peacefully inert and cold. It has an ice coating and a rocky icy inside, like the negative of a malteser. Although its surface is actually very dark. It has an ancient bombed surface, the oldest in the solar system, because there is no geological activity to make nice fresh surface. There is not an inch of it that isn’t part of an impact crater. When a decent asteroid hits it, white ice is exposed.
Jupiter actually has over 60 moons in total, although the rest are not round so we don’t care. Basically that means we’re done here. Next time we’ll visit everybody’s favourite planet and its associated loads of moons. Here is a nice photograph of everywhere we’ve been this time to say bye bye with.