[HN Gopher] Wave activity on Titan strong enough to erode the co...
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Wave activity on Titan strong enough to erode the coastlines of
lakes and seas
Author : wglb
Score : 149 points
Date : 2024-06-25 02:29 UTC (20 hours ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| andrewstuart wrote:
| You'd want to wear your warm jumper to wander those shores.
| EdwardDiego wrote:
| Wonder what the buoyancy would be like, and who will be the
| first surfer on Titan.
| isoprophlex wrote:
| Liquid hydrocarbons? You'll sink like a brick. I don't know
| exactly what methane and ethane do at minus whatever but the
| density is at least 30% lower than water...
| eru wrote:
| Wikipedia says 422.8 g/L (liquid, -162 degC). (See
| https://en.wikipedia.org/wiki/Methane)
|
| So nothing you could swim in, but it would be relatively
| easy to build a boat.
|
| Hmm, come to think of it: Titan's gravity is 0.138 g. So
| you might be able to stay afloat in liquid methane by
| actively swimming upwards, even if you can't float.
|
| Similar to how birds stay afloat in the air, despite being
| heavier than air.
| lazide wrote:
| If you thought huffing was bad for your brain cells
| though....
|
| Wouldn't it dissolve a lot of things, including space
| suit seals? If it wasn't for the extreme cold
| embrittlement anyway.
| kombookcha wrote:
| There is something super raygun gothic about walking on the
| bottom of the liquid hydrocarbon sea in an old timey lead-
| boot diving suit.
| Cyphase wrote:
| My amusing thought was a "kite" boarder pulled by a person in
| some kind of flying gear: https://erikwernquist.com/wanderers
| euroderf wrote:
| I'd bet a modest sum that this hypothetical has been
| addressed in some cyberpunk story or another.
| KineticLensman wrote:
| Stephen Baxter's SF nivel 'Titan' [0] has some astronauts
| build a sort of boat on Titan but the generally depressing
| story otherwise lacks any surfer vibes.
|
| [0] https://en.wikipedia.org/wiki/Titan_(Baxter_novel)
| Something1234 wrote:
| Well that's depressing beyond belief. I don't even have
| words for how sad the novel sounds. I think the best
| thing I can leave is "war pigs" by Black Sabbath
| noisy_boy wrote:
| Thats why Dr. Manhattan is my favorite superhero; he can appear
| anywhere he wants in the universe and observe the glorious
| interactions without any harm to him. What a grand universe and
| how little we can observe with our mortal eyes!
| frr149 wrote:
| And doesn't need to wear warm jumpers.
| escapecharacter wrote:
| We all wish he'd wear something, anything, however.
| BriggyDwiggs42 wrote:
| Ay speak for yourself buddy
| infotainment wrote:
| So hyped for the Dragonfly mission (Titan flying drone probe) to
| get a closer look at this kind of thing:
|
| https://en.wikipedia.org/wiki/Dragonfly_(Titan_space_probe)
| pfdietz wrote:
| Dragonfly is powered by an RTG (with batteries), but higher
| performance nuclear aircraft should be possible on Titan also.
| It's possibly the best place in the solar system for nuclear
| energy (although the fuel has to be imported). The dense, cold
| atmosphere makes open cycle nuclear gas turbines very easy to
| build, even at modest core temperature.
| ceejayoz wrote:
| Is "open cycle nuclear gas turbines" as terrifying as I'm
| reading it to be?
| adrian_b wrote:
| No.
|
| That should be just a gas turbine where the gas is heated
| through a heat exchanger and where the heat source happens
| to be a nuclear reactor.
|
| Normally such gas turbines with external heating use their
| gas in a closed cycle, because air is not a suitable
| working gas (one of the reasons is that it is too oxidizing
| at high temperatures, which can damage the turbine; another
| reason is that it is preferable if the working gas can be
| transformed into a supercritical fluid at a low enough
| temperature and low enough pressure, like carbon dioxide).
|
| In a place where the atmosphere would be an acceptable
| working gas, the cost of the turbine could be reduced by
| using the atmosphere as the working gas in an open cycle.
| pfdietz wrote:
| The big reason for this cycle on Titan is that at a given
| pressure ratio, the necessary absolute temperature in the
| hot part of the engine is proportional to the absolute
| inlet temperature. So, if the absolute inlet temperature
| is 1/3rd that of Earth's atmosphere, the peak temperature
| is also drastically reduced. All the hot parts could be
| made from cheap materials. The turbine blades wouldn't
| have to be cooled. Lower temperature also reduces the
| speed of sound in the gases, which reduces the velocity
| (and therefore stress) of the compressor and turbine
| blades.
| BoxOfRain wrote:
| Given there's literal seas of hydrocarbons on Titan I wonder
| if there's a source of oxygen that could be liberated,
| allowing probes to operate without the need for fuel from
| Earth?
| pfdietz wrote:
| Without the need to import fission fuel from Earth, you
| mean? Where does the energy to liberate that oxygen come
| from, then?
| pixl97 wrote:
| Depends how tightly bound the oxygen is. If the reaction
| is exothermic then you capture the liberated oxygen to
| make far more oxygen in a feedback loop.
| nick238 wrote:
| I don't get it, are you thinking Titan's just a bomb
| ready to go off? I'm pretty sure that at least one meteor
| has hit Titan in the past with the energy of a nuclear
| weapon, and it's still there. Calculations trying to see
| if a nuclear bomb would ignite Earth's atmosphere were
| interesting, but it feels hubristic to think that any
| nuclear weapon would compare to Chicxulub.
|
| Chemically, things are usually pretty much at equilibrium
| and if there's a giant energetic cliff, they'll fall off
| eventually. Nuclear-wise, sure, all the light elements
| could fuse (hydrogen, helium, carbon, oxygen...) and
| release energy, but that requires some fairly exotic
| conditions.
| maxst wrote:
| Dragonfly's landing site is near equator (Selk crater 7degN),
| but all the lakes coordinates seems to be close to poles, see
| "Lakes of Titan".
|
| Too bad. Would be wonderful to see these rivers and likes up
| close...
| api wrote:
| Titan is actually high on my list of places that could harbor
| life.
|
| I'm not talking about subsurface water though that's possible. I
| mean chemically alien life.
|
| The reason I suspect this is a phenomenon understood in theory of
| complexity and evolutionary informatics circles called the "edge
| of chaos." Oversimplifying a bit you get universal computation in
| the vicinity of a phase boundary.
|
| Titan is loaded with phase boundaries: solid, liquid, gas,
| dynamic changes between them, rain, dissolving and crystallizing
| solids, etc. The solvent is just light hydrocarbons not water.
|
| Life on Titan would be slow and low metabolism compared to us
| (probably). We should be aware of this likely difference when
| looking. What looks like minerals, rocks, weird films of
| chemicals, etc may be alive. We should look for structure,
| metabolism, isomer preferences, etc.
|
| Of course life on Titan is convinced there could never be life
| here. The third planet is a literal hell where it rains molten
| dihydrogen monoxide in an atmosphere of corrosive oxygen. Any
| life there would vaporize and oxidize instantly.
|
| Rumors of a strange disc shaped object being recovered with
| material and isotope ratios pointing to the third planet are
| entirely unfounded, as are rumors of amateur radio enthusiasts
| picking up signals from there.
| abhijat wrote:
| At least we share concepts of hell and amateur radio.
| pfdietz wrote:
| > Life on Titan would be slow and low metabolism compared to us
| (probably).
|
| On the other hand, maybe the chemistry there could be using
| less stable chemicals where less energy is needed to change
| them. It's at a much lower temperature, after all.
|
| I suspect we'll find nothing, though, due to Fermi. If two
| different Origin of Life events happen in the same system, OoL
| (of at least one of those kinds) must be common in the
| universe, and that would remove what I consider the big
| potential obstacle to abundant intelligence in the universe.
| Just an intuition without more data, of course.
| kaibee wrote:
| Its wholly possible for the universe to be teeming with
| single-celled life, but I think the jump to multicellular,
| intelligent, civilization, and space-faring (at least signals
| wise) could still cut it to a factor 1/1000 stars. And we're
| relatively early in the life of the universe still.
| pfdietz wrote:
| Cutting it to 1/1000 stars wouldn't be anywhere near enough
| to get around Fermi, by many orders of magnitude.
| JumpCrisscross wrote:
| > _could still cut it to a factor 1 /1000 stars_
|
| I'm a multicellular rare Earther. We've had on the order of
| 10^40 cells, ever [1]. Symbiogenesis occurred, from what we
| can tell, once [2]. (For comparison, there are 10^11 stars
| in the Milky Way [3] and 10^24 in the observable universe
| [4].)
|
| We might be able to argue that factor should be cut, since
| any late symbiogeneses would be outcompeted into oblivion.
| But that still, optimistically, puts us in the realm of the
| Milky Way's star count.
|
| [1] https://www.cell.com/current-
| biology/abstract/S0960-9822(23)...
|
| [2] https://en.m.wikipedia.org/wiki/Symbiogenesis
|
| [3] https://en.m.wikipedia.org/wiki/Milky_Way
|
| [4] https://en.m.wikipedia.org/wiki/Observable_universe#Mat
| ter_a...
| api wrote:
| The basic idea of rare Earth as an answer to Fermi is
| that if the frequency of advanced life is around 1 per
| galaxy per billion years or something like that then we'd
| likely never meet any aliens.
|
| Intergalactic travel is borderline impossible barring
| unknown physics or travel _very_ close to the speed of
| light. Even at speeds like 0.5c (50% the speed of light)
| the trip would take so long you 'd have problems like
| cosmic rays tearing you apart over such long spans of
| time, and in the vastness of intergalactic space there's
| no place to pitch a tent and chill and repair things.
| 0.5c would get you to the stars but not the galaxies.
|
| Intergalactic flight would require something more like
| 0.95c to 0.99c. The energy requirements for that are
| _insane_ and possibly unachievable, and if you hit a dust
| particle at that speed the yield will be like a
| thermonuclear bomb. The cosmic microwave background also
| becomes a beam of hard gamma rays aimed at your head. All
| kinds of crazy extreme physics things happen.
|
| Lastly, why do it? Galaxies are huge and if you're alone
| then it's all yours. The only conceivable reason would be
| to flee some galactic-scale super-catastrophe like your
| galaxy's central black hole behaving badly and frying
| everything with gamma rays. Even for that it might be
| easier to burrow deeply into planetary bodies instead.
|
| Of course one can imagine ultra-far-future scenarios
| like: what if Andromeda hosts some galactic-scale super
| civilization by the time it hits the Milky Way which by
| then also hosts such a thing. That'd be a hoot.
| pfdietz wrote:
| > Intergalactic flight would require something more like
| 0.95c to 0.99c
|
| Why would it require speeds that high? Sure, it's going
| to take a very long time, but why is that an
| insurmountable obstacle?
|
| There are enough isolated stars in intergalactic space
| that one can even imagining making the trip in smaller
| steps, with colonization in between. At a stellar density
| nine orders of magnitude lower than our galaxy stars are
| still within thousands of light years of each other.
| lazide wrote:
| Because most people go nearly insane in solitary
| confinement? and that isn't even really solitary.
|
| And gov'ts and social structures rarely last a few
| generations, let along 100 of them.
|
| Not to mention inbreeding.
|
| What makes you think any humans stuck in something the
| size of even the most generously sized starships won't go
| full lord-of-the-flies and be unable to effectively
| maintain the ship long before it ever arrives?
| pixl97 wrote:
| Of course I see this as a conflation of life versus
| intelligence.
|
| Do I suspect we'll see life commuting between galaxies,
| seems unlikely life as is fragile compared to how damned
| harsh space is.
|
| But intelligence is a completely different story. We send
| rudimentary intelligences to space and have racked up
| billions of miles on them. It seems far more likely that
| any space faring civilization would look like the
| following.
|
| 1. They would ship the instruction to build life when the
| reach the destination they are heading too. Machines with
| error correction seem much more resilient would be much
| more likely to reach a destination if they had enough
| energy for the trip so they could refurbish themselves
| over time.
|
| 2. Getting rid of the bodies/life part in the first
| place. Who cares if it's a million years if you can just
| pause yourself?
|
| Of course the fact the entire universe isn't filled with
| Von Neumann probes (at least that we see) points out that
| this hasn't happened yet.
| pfdietz wrote:
| We're not talking about sending a single person, so I
| don't know where the solitary confinement comment comes
| from.
|
| A colonized galaxy will have people mostly living in
| artificial habitats. A starship of sufficient size is
| just an artificial habitat moving at high speed.
|
| One would get around the issues you discuss by just
| sending multiple vehicles. And anyway, this is in
| rebuttal to the idea that intergalactic colonization is
| impossible. The onus on that argument is to show it can't
| work, not argue there are obstacles that would make it
| uncertain in any particular case.
| lazide wrote:
| Eh, the biggest blocker IMO is far more esoteric. Money.
|
| There is nothing we are aware of that is even close to
| expensive/worthwhile enough (except perhaps information)
| to justify the cost in energy to move it that distance.
| Even if the energy is essentially free.
|
| Do the math - rocket fuel isn't very expensive in bulk,
| but even moving 'free' gold, platinum, iridium, etc. is
| not even close to worth it.
|
| And information can be gathered with telescopes or
| transmitted with lasers or radio at faster speeds, so why
| bother with the trek?
| JumpCrisscross wrote:
| > _Do the math - rocket fuel isn't very expensive in
| bulk, but even moving 'free' gold, platinum, iridium,
| etc. is not even close to worth it_
|
| What math are you on? The entire reason moving the "free"
| ore in the asteroid belt to Earth is expensive is
| propellant. If we had cheap interplanetary transport, it
| would absolutely make sense to mine and return matter.
| pixl97 wrote:
| I mean, that's not a great backup plan. If you're not
| running a Redundant Array of Independent Planets then
| you're just one crash away from total data loss.
|
| I mean just looking at the energy expenditure growth rate
| of Earth, you spend as much energy as kings used to in a
| day. And there is still an absolutely massive amount of
| solar energy left to harvest.
| pfdietz wrote:
| Energy could be beamed across interstellar distances. It
| just requires larger apertures than for beaming it across
| shorter distances.
|
| The best way to extract detailed information about a star
| system is to colonize it. Remote sensing only goes so
| far.
| sqeaky wrote:
| I agree with your sentiment but not your specific number.
| The leap from uni- to multi-cellular life might be a "great
| filter" in Fermi-paradox parlance.
|
| But I think it would need to be more like one in a million
| or one in a billion. I think even one civilization becoming
| a slow interstellar (less than 0.1C ships for their)
| civilization could colonize the galaxy in less than a
| million years.
|
| Consider what we could do if we could get a slow ship to
| Alpha Centauri in some absurd time like 1000 years and
| actually settle there. Maybe we try ever If us here on
| Earth and Sol could only do that once every thousand years
| and then if each colony could too. We would only be
| doubling the amount of stars we inhabit every thousand
| years. Presuming this slow pace we would also be adding
| 5~10 light years to our civilization in that time too. But
| in a million years that 5k to 10 light years would be a
| sphere with diameter about 10% to 20% the diameter of the
| galaxy. Allow those jumps to be 50ly and we could get a
| whole Milky Way galaxy in that time.
|
| That is all predicated on very slow stuff, no FTL, slow
| ships or project taking massive time. And since the
| dinosaurs died we had 65 such time periods and another 300
| while the dinosaurs lived...
|
| And I could go on for hours about this stuff. But my point
| is that if unicellular life is common and there is a single
| great filter and that is the jump to multicellular life
| then the odds of that event dictate how often we would see
| other civilizations. A 1 in 1000 we would see civilizations
| all over the place. We would certainly be withing radio
| range of at least a few. So it would need to be much worse
| odds.
| mtlmtlmtlmtl wrote:
| I'm highly sceptical of the Fermi paradox being a meaningful
| paradox at all. I don't think we have nearly enough data to
| make any conclusion at all about the frequency of intelligent
| life in our own galaxy, let alone the universe.
|
| We've only started finding exoplanets in the last few
| decades, and the frequency of exoplanet detection was very
| low for most of that time and is still growing today.
|
| The ability to learn much of anything about the environments
| of these planets is even more recent, just a few years since
| the launch of JWST, and still very limited. It's still only
| "reliable" for fairly large planets, mostly gas giants. And
| even for those planets our ability to model the data is an
| area of active, painstaking research. The number of planets
| whose atmospheres we have any data-backed information about
| is very very low.
|
| So it seems like the only real argument for the Fermi
| paradox(certainly back in the 50s when Fermi proposed it) is
| that we haven't been visited or received any communication.
| But even that's worthy of doubt. Indeed, our ability to
| detect and characterise very small objects in or passing
| through the solar system is fairly limited even today, and
| was practically non-existent before. It seems very plausible
| that alien probes could have visited our solar system many
| times without us noticing. It could for instance be the case
| that this is only possible by way of technologies that can't
| easily decelerate and so they've only passed through. We'd
| have to be pretty lucky to spot something like that, at the
| size it would likely be, passing through only for a short
| time(given the speed it would have to move at).
|
| As for radio signals, the amount of funding that goes into
| projects like SETI is not exactly earth-shattering and also
| hasn't been going on for very long. It's a pretty fringe area
| of research. The amount of interference from earth-based
| radio sources also makes this research quite difficult.
|
| I'm not some UFO nut, btw. I'm not arguing for conspiracy
| theories involving the US government, alien abductions, yadda
| yadda. I'm just asking what do we _really_ know? Not very
| much, it seems to me.
| api wrote:
| Obligatory XKCD: https://xkcd.com/638/
|
| I completely agree. We haven't been looking very long and
| very hard and we're not even that sure what to look for or
| where to look. All we can say right now is that we do not
| see any unambiguous signs of ETI, but space is called space
| for a reason. We are also searching the vastness of _time_.
|
| I don't completely dismiss ET-origin UFOs. I don't think
| there's anywhere near enough evidence to make such a claim
| as anything more than a hypothesis, but remember that one
| possible answer to the Fermi paradox is that there isn't
| one.
| pfdietz wrote:
| The Fermi paradox isn't a paradox, it's a strong constraint
| that models of ET life have to conform to. In particular,
| models with billions of ET civilizations in the galaxy
| appear to require strong (and I suggest implausible)
| assumptions about the unlikelihood of interstellar
| colonization.
|
| It's also an antidote to baseless presumptions that ETs (or
| even life of any kind) must be common outside our solar
| system.
| exochrono wrote:
| obligatory reference to the dark forest hypothesis
| (https://en.wikipedia.org/wiki/Dark_forest_hypothesis) as an
| alternate explanation for the apparent rarity of life
| Galatians4_16 wrote:
| > light hydrocarbons
|
| Sounds like Titan needs Democracy.
| tshaddox wrote:
| > Of course life on Titan is convinced there could never be
| life here. The third planet is a literal hell where it rains
| molten dihydrogen monoxide in an atmosphere of corrosive
| oxygen. Any life there would vaporize and oxidize instantly.
|
| What are some of the chemicals that would vaporize and oxidize
| instantly in Earth's atmosphere which this hypothetical Titan
| life could be made of?
| dexwiz wrote:
| Almost any light hydrocarbon (4 carbons or smaller) vaporizes
| in the Earths atmosphere. Oxygen is pretty corrosive and we
| have all sorts of biological systems to slow or prevent this.
| buu700 wrote:
| I'm not sure if this is what you meant, but the concept of an
| alien species with a totally different subjective perception of
| time would be interesting. As in all of our
| actions/movements/speech would be experienced as being on e.g.
| 10x fast forward to them, or vice versa.
| 0cf8612b2e1e wrote:
| Dragon's Egg is a story about this concept.
|
| Spoilers from the Wikipedia The rest of the
| story, including almost the whole history of cheela
| civilization, spans from 22 May 2050 to 21 June 2050. By
| humans' standards, a "day" on Dragon's Egg is about 0.2
| seconds, and a typical cheela's lifetime is about 40 minutes.
| lrivers wrote:
| Fetch finally happened!
| abecedarius wrote:
| The most informative sentence was down towards bottom of page:
|
| > The team mapped the shorelines of each Titan sea using
| Cassini's radar images, and then applied their modeling to each
| of the sea's shorelines to see which erosion mechanism best
| explained their shape.
|
| (I feel like phys.org is repeatedly disappointing in reward-to-
| time relative to their headlines.)
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