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.
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.
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.
Jupiter and Io have a very interesting symbiosis. Jupiter melts Io to form dusty volcanos. It then magnetically sweeps Io clean of dust. The dust forms a plasma ring that enhances the same magnetic field.
> 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.
1) If those hypothetical mineral resources are rare, organisms would be hard pressed by evolution to start collecting them from the bottom and make it float again.
Animals can make buoyant shells with hard materials that would sink otherwise. Other dress on pods made of glued sand and pebbles. If we find aliens dressed on meteorites they could be colonial, like Sabellaria worms, or individual, like caddisfly larvae.
Fill this cameras with organisms able to extract the energy of chemical links in those rocks, and you have food and refuge in the same packet. It does not matter if you start hosting it to make light or they are just food that reproduces faster than you can eat it.
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2) Maybe we will not need to dig all the way down to find life. Biocenosis will fit every possible niche, so if there is life is 100% guaranteed that the transition "upper ice layer"/"liquid surface" will be colonized
First because it poses a topological advantage (halves the directions of possible attacks by predators, and allows to ambush and hide in irregular ice). Evolution later would select organisms that burrow up in the ice layer. It would be a preferred place to rest and, most of all, to nest so would be a trait selected fast. In places with not much food, we can expect tunnels populated by filterers that create currents to use the energy more efficiently than just swimming around.
If we detect a thin layer in the ice/water frontier that is less dense than ice but more dense than liquid or gas bubbles, and is structurally different than what physics predict for the formation of cracks in the ice, we may suspect the presence of burrowing life. And if there aren't any alterations in this boundary, it may be no life at all, or the points with life will be very isolated.
I am realy excited for the Findings on these missions. Altough I am still missing an Enceladus mission because enceladus is among the most fascinating ocean worlds.
> 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.
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.
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.
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!
> Enceladus is far smaller than the Jovian ocean worlds, roughly the size of Ohio
Why not just say 'has a diameter of about 500 km'? The propensity of astronomers to compare diameters of a small spherical object to a surface patch of a much larger spherical object is intriguing. Similar things happen with 'the Great Red Spot is about two Earths wide'.
When trying to describe sizes and scale, having a reference that one of their readers would be able to go "oh, ... that size, huh?" is useful. There's a meme about "Americans will use anything but the metric system" when describing buildings as "100 school buses back to back" or "3 football fields"; but it's to make numbers real and relatable.
If the article said "500km", someone in the comments would go "that's about as wide as Germany!" or similar.
And, since it was km -> "state size", it was almost certainly for the American audience, since they would have used something like the size of Germany for a European, or "twice the size of South Korea" or something.
For science education, I am strongly for using the units directly to describe everything at first, with these looser comparisons in brackets, rather than inline prose. So I would've instead said, 'is 500 km in diameter (roughly the size of Ohio, or Germany from East to West)'. For extremely large or small values I would use scientific notation only, and expect my audience to understand it, because I'd expect their education to be up to mark.
You said these comparisons are made to make things real or relatable; I personally would expect more out of my audience and give them the magnitude and units directly. I'm not writing for a tabloid; having a strong grounding in units understanding without needing to relate to daily phenomena is in my view critical to not making apparently trivial mistakes that can potentially lead to horrible disasters.
I think that this is more than moderately misleading, because it is ambiguous:
- if they meant "diameter is similar to Ohio dimensions", they are a little bit off, because Ohio is about 355*355 km and Enceladus diameter is around 500km
- if they meant surface area, then they are very off, because Ohio is 116,096 km^2 while Enceladus is about 800,000 km^2. In this case it would be more accurate to say that it is bigger then Texas, but smaller than Alaska (if we want to use US states for comparison)
> - if they meant "diameter is similar to Ohio dimensions", they are a little bit off, because Ohio is about 355*355 km and Enceladus diameter is around 500km
I think they used the diagonal of a hypothetical square Ohio: sqrt(355^2 + 355^2) ≈ 502 km.
The classical definition of diameter of a set is "the largest possible distance between two points". So in this sense your square Ohio has a diameter of 502 km.
(It is still misleading to compare it to the diameter of an almost-spherical object, I agree. Especially because moving on the surface of a sphere it takes much longer than 502 km to walk from one point to the antipodal one.)
> they would have used something like the size of Germany for a European, or "twice the size of South Korea" or something
I don't have a concrete proof, just a gut feeling, but I think that this kind of comparisons are much more common in texts written by Americans and for Americans than in any other culture, that's why:
> There's a meme about "Americans will use anything but the metric system" when describing buildings as "100 school buses back to back" or "3 football fields"
>I don't have a concrete proof, just a gut feeling, but I think that this kind of comparisons are much more common in texts written by Americans and for Americans than in any other culture, that's why:
Those filthy new worlders and their propensity to make technical writing parsable by the unwashed masses. If the masses want to understand science they should just go to Oxford or whatever.
There is much to be said about the irony in said New Worlders refusing to get with the programme, and instead obstinately clinging to an ancient, Babylonian-Roman-Anglo-Saxon-Viking hodge-podge of units instead of something modern and universal.
> make technical writing parsable by the unwashed masses
> If the masses want to understand science they should just go to Oxford
This is a bad strawman. I learnt scientific notation in secondary school. I expect most educated people to understand what is meant by '1.5 × 10^8 km' in an instant. If they don't, then honestly, skill issue, and it is a big indictment of their parent country's education system.
I object to this mis-use of the word "ocean". If I can't sail there then it's not an ocean. Luckily, Titan still has an ocean. But all the others have iceans.
The possibility of life is what's measured in this article, but what about the sustainability of human colonies?
> The radiation environment around Europa is punishing; an astronaut standing on the surface would get a fatal dose in about a day
This is disappointing to hear because I'd always imagined Europa as the next destination after Mars. Radiation also affects electronics so even a robot couldn't be a permanent visitor.
49 comments
[ 0.26 ms ] story [ 22.5 ms ] thread> The radiation environment around Europa is punishing; an astronaut standing on the surface would get a fatal dose in about a day
Jupiter and Io have a very interesting symbiosis. Jupiter melts Io to form dusty volcanos. It then magnetically sweeps Io clean of dust. The dust forms a plasma ring that enhances the same magnetic field.
> 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.
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.
Animals can make buoyant shells with hard materials that would sink otherwise. Other dress on pods made of glued sand and pebbles. If we find aliens dressed on meteorites they could be colonial, like Sabellaria worms, or individual, like caddisfly larvae.
Fill this cameras with organisms able to extract the energy of chemical links in those rocks, and you have food and refuge in the same packet. It does not matter if you start hosting it to make light or they are just food that reproduces faster than you can eat it.
------------------------------------
2) Maybe we will not need to dig all the way down to find life. Biocenosis will fit every possible niche, so if there is life is 100% guaranteed that the transition "upper ice layer"/"liquid surface" will be colonized
First because it poses a topological advantage (halves the directions of possible attacks by predators, and allows to ambush and hide in irregular ice). Evolution later would select organisms that burrow up in the ice layer. It would be a preferred place to rest and, most of all, to nest so would be a trait selected fast. In places with not much food, we can expect tunnels populated by filterers that create currents to use the energy more efficiently than just swimming around.
If we detect a thin layer in the ice/water frontier that is less dense than ice but more dense than liquid or gas bubbles, and is structurally different than what physics predict for the formation of cracks in the ice, we may suspect the presence of burrowing life. And if there aren't any alterations in this boundary, it may be no life at all, or the points with life will be very isolated.
Europa Clipper, launched 2024, starts Europa flybys on March 2031
Dragonfly, hopefully launching July 2028, arriving on Titan 2034
https://en.wikipedia.org/wiki/Europa_Clipper
https://en.wikipedia.org/wiki/Dragonfly_(Titan_space_probe)
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.
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.
If there are planetologists reading the thread, I'd love to hear a more authorative perspective than mine!
> Enceladus is far smaller than the Jovian ocean worlds, roughly the size of Ohio
Why not just say 'has a diameter of about 500 km'? The propensity of astronomers to compare diameters of a small spherical object to a surface patch of a much larger spherical object is intriguing. Similar things happen with 'the Great Red Spot is about two Earths wide'.
If the article said "500km", someone in the comments would go "that's about as wide as Germany!" or similar.
And, since it was km -> "state size", it was almost certainly for the American audience, since they would have used something like the size of Germany for a European, or "twice the size of South Korea" or something.
You said these comparisons are made to make things real or relatable; I personally would expect more out of my audience and give them the magnitude and units directly. I'm not writing for a tabloid; having a strong grounding in units understanding without needing to relate to daily phenomena is in my view critical to not making apparently trivial mistakes that can potentially lead to horrible disasters.
Although, as it turns out, "orbiter" was a poor choice of name.
This is moderately misleading in some ways, but illustrative enough and also technically valid if somebody wants to model it accurately.
I think that this is more than moderately misleading, because it is ambiguous:
- if they meant "diameter is similar to Ohio dimensions", they are a little bit off, because Ohio is about 355*355 km and Enceladus diameter is around 500km
- if they meant surface area, then they are very off, because Ohio is 116,096 km^2 while Enceladus is about 800,000 km^2. In this case it would be more accurate to say that it is bigger then Texas, but smaller than Alaska (if we want to use US states for comparison)
I think they used the diagonal of a hypothetical square Ohio: sqrt(355^2 + 355^2) ≈ 502 km.
"Ohio isn't actually square, though you wouldn't know that from talking to the inhabitants" or some such.
(It is still misleading to compare it to the diameter of an almost-spherical object, I agree. Especially because moving on the surface of a sphere it takes much longer than 502 km to walk from one point to the antipodal one.)
I don't have a concrete proof, just a gut feeling, but I think that this kind of comparisons are much more common in texts written by Americans and for Americans than in any other culture, that's why:
> There's a meme about "Americans will use anything but the metric system" when describing buildings as "100 school buses back to back" or "3 football fields"
Those filthy new worlders and their propensity to make technical writing parsable by the unwashed masses. If the masses want to understand science they should just go to Oxford or whatever.
> make technical writing parsable by the unwashed masses
> If the masses want to understand science they should just go to Oxford
This is a bad strawman. I learnt scientific notation in secondary school. I expect most educated people to understand what is meant by '1.5 × 10^8 km' in an instant. If they don't, then honestly, skill issue, and it is a big indictment of their parent country's education system.
> But it is a much more exciting place than Ohio, and far more livable.
Maybe just an excuse to make a joke about Ohio.
What would size here refer to surface area? Or diameter? Or circumfence?
> The radiation environment around Europa is punishing; an astronaut standing on the surface would get a fatal dose in about a day
This is disappointing to hear because I'd always imagined Europa as the next destination after Mars. Radiation also affects electronics so even a robot couldn't be a permanent visitor.