mereka day ago
Set your calendars:
Europa Clipper, launched 2024, starts Europa flybys on March 2031
Dragonfly, hopefully launching July 2028, arriving on Titan 2034
yellowapplea day ago
> This remarkable transformation in our understanding is the result of just three missions: Voyager, Galileo, and Cassini—along with some computer modeling and hard staring by the Hubble and Webb space telescopes.
Seems odd to neglect to mention New Horizons immediately after mentioning the probable existence of liquid oceans under Pluto's surface, a finding made possible thanks primarily to New Horizons.
idlewords7 hours ago
No shade on New Horizons intended, but I was talking about the early 2000's revolution in understanding of ice moons/ocean worlds, and that preceded the Pluto flyby by a lot.
It was a valuable piece of corroborating evidence, but not shocking and unexpected in the way results from those three missions were. We had good reason to believe Pluto would look a lot like Triton, and it does.
yellowapple6 hours ago
Fair enough, though how common was that belief that Pluto would look like Triton? Before the first photos from New Horizons pretty much every artistic rendition of Pluto I'd seen was a solid ball of rock and/or ice, more like Ceres than Triton.
idlewords5 hours ago
Both were known to be Kuiper Belt objects, so it was expected there would at least be a family resemblance. I don't think anyone expected Pluto to be more active than Triton; that was certainly a surprise.
If there are planetologists reading the thread, I'd love to hear a more authorative perspective than mine!
3eb7988a16634 hours ago
I was born in a water moon.
exhilarationa day ago
Great read, other than Europa I wasn't aware of these other candidate ocean moons.
miohtamaa day ago
TIL
> The radiation environment around Europa is punishing; an astronaut standing on the surface would get a fatal dose in about a day
kaseijina day ago
True for all the Galilean Moons more or less. Their orbits all lie within the Jovian equivalent of the Van Allen belts. And Jupiter's magnetic field is much stronger than earth's.
sennalena day ago
Not Callisto. Being within Jupiter's magnetosphere but out of reach of Io's shenanigans makes it one of the mildest radiation environments in the solar system.
stackghost3 hours ago
I'm interested in learning more about "Io's shenanigans". What are you referring to?
delta_p_delta_x34 minutes ago
Io is in orbital resonance with Europa and Ganymede, which causes its orbit to be slightly elliptical. Due to Jupiter's immense gravitational field strength, Io experiences a very high changing tidal force, which causes a changing stress and strain on the entire structure of Io, which causes tidal heating due to friction. This makes it by far the most volcanically active body in the Solar System. Its surface is regularly completely resurfaced, and is covered in sulfur compounds.
idlewordsa day ago
Not true at all, the daily dose on Ganymede (which has a magnetic field of its own) is ~70 mSv/day, and Callisto is 0.1 mSv/day.
Io, meanwhile, is 35 Sv/day. Location really matters among the four Galilean moons.
pvaldesa day ago
Beautifully designed article. Very cool images and diagrams.
> We want rocks in contact with water,
But there is ice compressed between the water column and the xenoceanic bottom, ok. I see the problem.
What about rocks in the surface of the water?. Some volcanic rocks can float.
andrewflnr10 hours ago
> What about rocks in the surface of the water?. Some volcanic rocks can float.
This is... not something you lay plans on. Even on Earth, these rocks are formed at surface pressure, just barely float, and don't float for long (I've tried). If they form in the deep ocean, I'm guessing the pressure isn't going to let the bubbles be big enough to create bouyancy at all. Either way they would be super rare.
Gravityloss11 hours ago
I guess I'm now officially old and cranky, as planetoids receiving glow-ups was just a bit much as a term.
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Ozzie-D5 hours ago
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