[HN Gopher] Uranus' moon Miranda may have an ocean beneath its s...
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Uranus' moon Miranda may have an ocean beneath its surface
Author : geox
Score : 21 points
Date : 2024-11-03 19:17 UTC (3 hours ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| munchler wrote:
| > The team set out to explain Miranda's enigmatic geology by
| reverse engineering the surface features, working backward to
| uncover what the moon's interior structure must have been to
| shape the moon's geology in response to tidal forcing.
|
| "Must have been" is doing a bit too much work in that sentence.
| This project is a cool idea and it would certainly be huge news
| if there is liquid water inside Miranda, but this is a long way
| from actual evidence.
| echelon wrote:
| Is there a comprehensive list of all the planets, dwarf planets,
| moons, etc. that we suspect may have liquid water?
|
| How many of them have liquid water without being super saturated
| with salts? What is the level of confidence we have?
|
| Which are most likely to bear life given our current hypotheses
| around the origins of life?
| kevinkeller wrote:
| I have been doing some late-night wikipedia binges on this
| matter, so I consider myself qualified to answer.
|
| > Is there a comprehensive list of all the planets, dwarf
| planets, moons, etc. that we suspect may have liquid water?
|
| Most large moons orbiting the gas giants are suspected to have
| subsurface water oceans, most prominent among them Europa.
| Ganymede, Enceladus, and Triton are other honorable mentions:
| https://en.wikipedia.org/wiki/Planetary_oceanography#Natural...
|
| > How many of them have liquid water without being super
| saturated with salts? What is the level of confidence we have?
|
| We don't know the composition yet, just that a salty ocean
| supports the evidence we've seen. For example, Europa interacts
| with Jupiter's magnetic field in such a way that makes sense
| only if there is a large amount of electrically conducive
| material inside Europa. Given what we know about its formation,
| metallic stuff is unlikely. A salty subsurface ocean is a more
| suitable explanation. We'll know once Europa Clipper gets there
| (one of its missions is to 'taste' the ocean by flying past
| really close).
|
| There are other reasons to suspect a subsurface ocean, such as
| signs of a geologically active body (like Enceladus), which in
| turn implies there is enough heat inside to have an ocean.
|
| > Which are most likely to bear life given our current
| hypotheses around the origins of life?
|
| Europa, maybe Enceladus. Note that our search for life is
| heavily guided (biased?) by our understanding of how we think
| life started here on Earth.
|
| Specifically, we needed these ingredients (non-exhaustive):
|
| * a liquid medium to act as shelter and transport medium
| (liquid water ocean) * a source of energy, something that life
| can 'eat' (hydrothermal vents in the beginning, sunlight later)
| * protection from space-borne threats (atmosphere, magnetic
| field) * a home that isn't geologically dead (like the Moon, or
| Mercury), but also isn't _too_ active (like Io)
|
| Europa checks most of the requirements:
|
| * suspected subsurface ocean * geologically active. This is
| important because Europa and other moons are too far away for
| sunlight to be a big source of energy. There has to be another
| source. Radiogenic heating (released by radioactive isotopes)
| and primordial heating (left over from its formation) aren't
| enough for moons to sustain liquid water (especially 4.5 B
| years after formation). This means tidal flexing is what we
| should be looking for -- something we know Europa has. *
| Europa's thick icy crust blocks pretty much all radiation.
| Barring a thick atmosphere (which only Titan has), a subsurface
| ocean underneath an icy crust is the best life can hope for out
| there, for protection against radiation. * We don't know much
| about what goes on underneath the surface. If the bottom of the
| ocean contains geothermal vents, then that could harbor earth-
| like life.
|
| Saturn's moon Enceladus checks many of these same boxes (tidal
| heating, abundant water, signs of a young surface indicative of
| geological activity).
|
| JUICE and Europa Clipper missions should fill in many of these
| gaps, and help confirm our understanding.
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