IT’S A TRAP!!!

I take it that’s elemental hydrogen not just the hydrogen part on the water molecules you’re meaning with that last sentence right?

BTW. Good article on GJ1214b here :

http://scienceblogs.com/startswithabang/2012/02/the_planet_with_nowhere_to_lan.php

on Ethan Siegel’s Starts With A Bang blog.

(Hope that’s okay to note here netiquette~wise, my apologies & please let me know if not. )

GJ1214b also has a wiki-page already :

http://en.wikipedia.org/wiki/GJ1214b

which has a size comparison with this new “waterworld”, Neptune & Earth which makes it seem much more Neptune-y in my view.

Off topic sorry but there’s a good article here :

http://freethoughtblogs.com/zingularity/2012/02/23/the-mysteries-of-titan/

by Stephen “DarkSyde” Andrew on the Zingularity blog about Titan which makes interesting reading. Again hope its okay to mention that here & pleaes let me know & accept my apologies if not.

Even exotic hot ices at high pressures in the deeper layers?

As you go deep into the interior of Uranus and Neptune you end up with weird superionic phases which essentially behave as plasma. There might be a “solid” core at the centre but the bulk of the planet is fluid. Gliese 436b is predicted to behave in a similar way.

Planets which do not have a significant amount of hydrogen would probably end up forming high-pressure ices though.

“Given the 14X earth irradiation and the effectiveness of water vapor as a greenhouse gas, the interior of this world could be quite a bit higher than 230C in reality….” [Quoting #45. amphiox -ed.]
This is what irks me about these temperatures that are quoted regarding exoplanets. If you give someone a temperature value they’ll probably think that it means the number you get if you put a thermometer there. In fact these temperatures represent the energy balance of the planet: you work out how much energy the planet absorbs from the star, assume the planet is a uniform-temperature blackbody and work out how hot this uniform-temperature blackbody would have to be to balance the incoming radiation. This gives a decent approximation of the temperature for planets with no atmosphere (provided you restrict the region of the planet which is re-emitting the radiation to the daylight hemisphere), but once you have an atmosphere you’re going to get wildly different answers.

Very good point & comment.

I think we need to be careful of getting ahead of ourselves on things like temperature unless we have direct measures. We can say that the range is likely to be so & so but saying as certainty that temperaures are X when the calculations could well be wrong is a misleading thing that we’re better off not doing.

@39. Torbjörn Larsson, OM : Thanks for that informative comment on extremophiles too.

@42. andy :

However we know from spacecraft observations of their gravitational fields that they have fluid interiors: the mixing between the various components of the planet prevents the ice from solidifying. This also applies to Gliese 436b which was announced as a “hot ice” planet in the media: it appears to have a composition similar to that of our ice giants but more strongly-irradiated, it likely does not have a solid ice mantle either.

Even exotic hot ices at high pressures in the deeper layers?

Also, is anyone naming these planets? Or is that only reserved for our own solar system? My vote’s for Humidia.

At least when we exchange embassadors there are places here on Earth that they can stay.

Given the 14X earth irradiation and the effectiveness of water vapor as a greenhouse gas, the interior of this world could be quite a bit higher than 230C in reality….

This is what irks me about these temperatures that are quoted regarding exoplanets. If you give someone a temperature value they’ll probably think that it means the number you get if you put a thermometer there.

In fact these temperatures represent the energy balance of the planet: you work out how much energy the planet absorbs from the star, assume the planet is a uniform-temperature blackbody and work out how hot this uniform-temperature blackbody would have to be to balance the incoming radiation. This gives a decent approximation of the temperature for planets with no atmosphere (provided you restrict the region of the planet which is re-emitting the radiation to the daylight hemisphere), but once you have an atmosphere you’re going to get wildly different answers.

For example the equilibrium temperature of Venus calculated this way is 184 K (-89°C), versus the actual temperature at the surface of 737 K (464°C).

The discrepancy for Earth is less but still significant: equilibrium temperature 254 K (-19°C) versus the average temperature of 288 K (15°C). One suggests an iceball, one does not.

(Values above from the NASA planet fact sheets.)

We know that GJ 1214b has an atmosphere, so we shouldn’t expect the equilibrium temperature value to reflect the true conditions there either.

(Incidentally the equilibrium temperature for Venus is lower than that of the Earth: this is because the reflective cloud layer on Venus more than compensates for it being closer to the Sun, the high temperatures there cannot be explained by the increased insolation. The really nasty surface conditions are powered using a lower energy budget per unit area than Earth: with Venus we have an energy-efficient hellworld. Nevertheless I have seen it argued that the carbon dioxide warming in the Earth’s atmosphere is “saturated” and adding more would not warm the planet. Hmmmm.)

Nope, you are thinking of the <= 130 degC surviving extremophiles, and they can't procreate above 121 deg C (IIRC).

Thanks for the reply!

I always thought, though that this 130 C temperature was for 1 atmosphere pressure, while the effective temperature at higher pressures would be significantly higher. But then of course the extremophiles don’t actually live in the very hottest places in the deep ocean vents, but around them, where the temperature gradient falls off.

Given the 14X earth irradiation and the effectiveness of water vapor as a greenhouse gas, the interior of this world could be quite a bit higher than 230C in reality….

From Kundurthy et al. (2011), the luminosity of the star is 0.0028 times solar (this is a bolometric value: red dwarfs radiate most of their energy in the infrared, so the visual luminosity computed from V magnitudes will be lower than this). The orbital distance of the planet is 0.014 AU. Apply the inverse square law: 0.0028 / (0.014^2) = 14 times the irradiation that Earth receives (to 2 significant figures), somewhat greater than the irradiation received by Mercury at perihelion.

I’d also be careful about the assumption that there would be solid “hot ice” in the planet. A naïve three-layer model for the ice giant planets Uranus and Neptune would have them with a hydrogen atmosphere surrounding a “hot ice” shell surrounding a rocky core. However we know from spacecraft observations of their gravitational fields that they have fluid interiors: the mixing between the various components of the planet prevents the ice from solidifying. This also applies to Gliese 436b which was announced as a “hot ice” planet in the media: it appears to have a composition similar to that of our ice giants but more strongly-irradiated, it likely does not have a solid ice mantle either.

To quote the Bard: “Hot ice and wondrous strange snow”.

Isn’t 230 celsius within the range of habitability for known extremophiles on earth? Especially in high pressure environments under deep layers of water?

Nope, you are thinking of the <= 130 degC surviving extremophiles, and they can't procreate above 121 deg C (IIRC).

Yes, the pressure keeps the water from boiling. Presumably you can still steam boil the cell content of these critters. Or more likely their membranes can’t take the expansion, a cell wall can withstand a 40 atmosphere differential before it pops. (Which is still a lot. I assume it evolved in an early UCA as a passive means to handle sudden osmotic differentials before cell membrane pumps evolved.)

Or would we see clouds if there’s only water vapour and no particulate matter to form the condensation “cores” of raindrops?

There is always particulate matter available. If not in the form of grains of dust, then at least cosmic rays will do. Think of this as an enormous cloud chamber.
Also there is the solar wind. No idea how strong it will be from a red dwarf in 2Gm distance, but for sure it exists.
So yes, there will be condensation if the atmosphere is prepared for rain.

Pressurized Cooker (http://en.wikipedia.org/wiki/Denis_Papin) and therefore “enough to boil” a chicken is much more appropriate:=)
Georg

Purely hypothetical here. Could an Earth-sized or larger world be composed of nothing but water? Literally, does an Earth-sized drop of water boil away if all other variables remain the same – sunlight, near-circular orbit etc? 10x Earth-sized drop of water? Up high the low pressure freezes the water, down low it’s liquid, and even lower it starts to boil or do some crazy super-fluid thing right?

Yup – I think so – Hot ice forms or so I understand it – different exotic types of ice that remain solid despite extreme temperatures and pressures.

EDIT : Wikipage now linked to my name here – apparently 15 forms of ice with it becoming a metal at the very highest pressures of all akin, I guess, to metallic hydrogen.

Not an expert astrophysicists /astrochemist but I’d speculate that you could have a planet composed of all these cold ‘n’hot ice forms – & later water phases eg. liquid, vapour, clouds* – at various temperature / pressure levels. Finding a purely water planet with no impurities (eg. the odd ingested asteroid or cometary carbon dust & chemical spices) at all strikes me as very unlikely but not entirely out of the question.

Interesting idea if a bit wet!

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* Or would we see clouds if there’s only water vapour and no particulate matter to form the condensation “cores” of raindrops?