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Planet Ceres is an 'ocean world' with sea water beneath surface, mission finds

theguardian.com

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Re: Planet Ceres is an 'ocean world' with sea water beneath surface, mission finds

#171

Post by Twisol »

overflow_error wrote: post #148
ceejayoz wrote: post #4

Earlier quoted context omitted.

The first paragraph uses the term “dwarf planet”. https://en.wikipedia.org/wiki/Dwarf_planet

yeah but dwarf planet is not a planet, this is like saying method is a function, outrageous

If that bothers you, you'll love the nLab's page on the red herring principle :)

> The mathematical red herring principle is the principle that in mathematics, a “red herring” need not, in general, be either red or a herring.

> Frequently, in fact, it is conversely true that all herrings are red herrings. This often leads to mathematicians speaking of “non-red herrings,” and sometimes even to a redefinition of “herring” to include both the red and non-red versions.

https://ncatlab.org/nlab/show/red+herring+principle

Re: Planet Ceres is an 'ocean world' with sea water beneath surface, mission finds

#172

Post by HeadsUpHigh »

elliekelly wrote: post #20
abledon wrote: post #7

spaceX when? 2048?

Somewhat related I saw it’s going to take NASA’s new Perseverance rover about 7 months to get to Mars and it’s traveling at something like 25,000 MPH. Since NASA had to take the planetary orbits and launch timing, etc. into account I’m assuming that’s the fastest ideal velocity for the rover but not necessarily the fastest possible. So I guess my question is, given that Ceres is so much further away than Mars, what’s…

The 7 month trip is not the fastest, it's the most fuel efficient because it needs the least amount of dV. Hoffman transfer orbits are what you should google about( and they exist for every planet).

Re: Planet Ceres is an 'ocean world' with sea water beneath surface, mission finds

#173

Post by simonh »

henearkr wrote: post #89
at_a_remove wrote: post #48

Earlier quoted context omitted.

Numerous other ideas exist for alien life, but most of them have their shortcomings. It all boils down to chemical reactions and physics. Imagine a universe of only helium. No valence electrons would be readily available, so chances are you are not going to see helium molecules. Lithium, sure, as a metal. Continue examining various smaller (and more plentiful elements). Fluorine? Well, only one slot available, so you…

You only considered chemistry-based life. Cannot hold it against you of course. But some hard SF writers like Baxter also imagined life based on electromagnetic interactions, nuclear reactions (life in the mantle of a neutron star), fluid vortices and turbulences (life in liquid or gaseous planets), etc. Basically he included a lot of substrates that could be used to implement complexity. Also, a big drawback of sear…

Where I think most of the proposed alternate forms of life in SF fail is they focus on complexity but disregard the need to maintain order. Vortices are a good example, theres plenty of complexity there, but also a huge amount of entropy and no real way to maintain ordered, purposeful changes in structure, or isolation of function. Complexity just isn't enough, so until some of those ideas get a lot more clearly developed, and solve some fundamental issues I just don't find them compelling. Great for fiction and speculation, but not really relevant in real world investigations.

Yes, I know that makes me sound like the boring, hide bound characters in such novels that are incapable of understanding this new amazing form of life, but frankly in the real world those guys would be absolutely right. The protagonists who contact the amazing new life forms just make far too many fundamental errors and intellectual shortcuts to really be credible.

Re: Planet Ceres is an 'ocean world' with sea water beneath surface, mission finds

#174

Post by dmurray »

dc443 wrote: post #81
dmurray wrote: post #52

Earlier quoted context omitted.

Faster is normally not all that important: it's much better to save fuel and send more stuff than to get there a few months earlier. Fuel costs vary roughly with delta-V, the total amount you have to accelerate or decelerate your spaceship. Because of the tyranny of the rocket equation, they aren't linearly proportionate to delta-V, but in general, if it takes more delta-V it's going to be harder and more expensive t…

Based on the linked (very cool) map, I don’t think what you say is accurate? A flyby of Ceres would be slightly harder than entering Mars orbit, and entering Ceres orbit would be harder than entering Neptune orbit.

Yes for a flyby or orbital mission. I was thinking of a landing mission which costs more delta-V. In practice, you can get that delta-V by aerobraking when going to Mars but not to Ceres, though on the other hand you need to build the spacecraft to withstand the Mars atmosphere. So maybe the answer is "it's complicated" but either way it's reasonably close, not the 5x further you might think from looking at the closest approaches of the orbits of Earth, Mars and Ceres.

Re: Planet Ceres is an 'ocean world' with sea water beneath surface, mission finds

#175

Post by lopmotr »

f_allwein wrote: post #151
QuadrupleA wrote: post #114

Earlier quoted context omitted.

Hmm... according to wikipedia Ceres' surface is 110 - 155 Kelvin, or a toasty -262 to -181°F. https://en.m.wikipedia.org/wiki/Ceres_(dwarf_planet) Which makes sense, with little to no atmosphere. If that's correct I'm a little surprised this got voted up to top comment.

in case you’re wondering: That’s between -163,15 and -118,15 °C.

You really shouldn't put that 0.15 on the end. The numbers weren't that accurate to begin with so it gives the false impression that those digits mean something.

I hope it doesn't feel like I'm picking on you but I can't help myself saying something because this is a pet peeve of mine. Rounding appropriately is taught in physics class at school but I think most people don't learn that or think it doesn't apply outside of class.

Re: Planet Ceres is an 'ocean world' with sea water beneath surface, mission finds

#176

Post by thom »

Balgair wrote: post #102
henearkr wrote: post #89

Earlier quoted context omitted.

You only considered chemistry-based life. Cannot hold it against you of course. But some hard SF writers like Baxter also imagined life based on electromagnetic interactions, nuclear reactions (life in the mantle of a neutron star), fluid vortices and turbulences (life in liquid or gaseous planets), etc. Basically he included a lot of substrates that could be used to implement complexity. Also, a big drawback of sear…

That neutron star story is wild . Hard recommendation to read. One point I have with Baxter is that his premises are just bananas, but the people acting in them are pretty recognizable. To be fair, if the characters were also nutter-butter, no one would read it, as it wouldn't be a story anymore, just a strangely formatted research paper. https://en.wikipedia.org/wiki/Flux_(novel)

I can never forget reading Titan for the first time. Extremely bleak in many ways but worryingly plausible.

Re: Planet Ceres is an 'ocean world' with sea water beneath surface, mission finds

#177

Post by alex_duf »

bjo590 wrote: post #46
outworlder wrote: post #17

There goes the water rationing narrative in The Expanse...

No, it doesn't create a plot loop. The book explains that all of the H2O on Ceres was used to apply spin to Ceres to create artificial gravity. This is a symbol of Inner Planet's dominance over the Beleter's, because a _real_ Belter would never trade precious water for artificial gravity. This is mentioned fairly subtly in the first book, and is easy to miss while taking in the rest of the world. In addition the spin…

I had missed that Ceres' gravity is due to its spin.

Does that mean humans are living upside down in their tunnels compared to Earth?

And if that's the case, surely a spin that's greater than the local gravity should shatter the planet itself as the matter has no reason to stay concentrated around its core right?

Am I missing something?

Re: Planet Ceres is an 'ocean world' with sea water beneath surface, mission finds

#178

Post by alexgmcm »

QuadrupleA wrote: post #114
gaukes wrote: post #2

Ceres is one of the more interesting candidates for life in our solar system. Ceres is in the habitable zone for our solar system (although just barely), it's surface temperature is -30 F (eq. to winter in Greenland), and it's detected that the water on the surface is 20% carbon by mass (though that can mean a lot of things).

Hmm... according to wikipedia Ceres' surface is 110 - 155 Kelvin, or a toasty -262 to -181°F. https://en.m.wikipedia.org/wiki/Ceres_(dwarf_planet) Which makes sense, with little to no atmosphere. If that's correct I'm a little surprised this got voted up to top comment.

Is it possible that the conditions in the deep oceans of that world might still be amenable to life - far below the harsh surface conditions?

Re: Planet Ceres is an 'ocean world' with sea water beneath surface, mission finds

#179

Post by Symmetry »

bitreality wrote: post #161
eru wrote: post #117

Earlier quoted context omitted.

Though, of course, you might expect to see that, even if life can arise in extreme environments: It's uncontroversial that life is much denser in more hospitable environments. If the extreme environments are in regular contact with the hospitable environments, and if evolution is sufficiently random, you would expect over time that most organisms anywhere have an ancestor in the hospitable environment. Even if life c…

What is the most hospitable environment? A tide pool? Also the most hospitable environment for genesis is likely different from the most hospitable environment for a complex ecosystem.

For life without photosynthesis, which takes a while to develop, some place with a lot of free chemical energy because the first replicators will be very inefficient. White and black smokers under the sea are usually put forward as candidates.
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