Water detected in atmosphere of habitable exoplanet for the first time

[Subduction Zone]

I predict the inhabitants won't be very tall.

Shorter, but not that much shorter. Only 30% more g force than on Earth.

A 150 pound man on Earth would weigh 195 there, actually a hair less if the figures that I got were right.

 

[chevyontheriver]

Not really all that much greater. The planet is 8 times the mass of the Earth but its diameter is about 2.5 times the Earth's. To convert gravity you would take 8/(2.5)^2 times Earth's gravity. You would only be about thirty percent heavier there.

OK then, no worse than a downward elevator stopping at your floor. Let's go.

 

[Ophiolite]

I get the curiosity of wanting to know how things work as well as the practical benefits of such knowledge. It's part of why I'm an engineer. But I do wonder: what is it that drives people to search for life "out there"?

You have answered your own question. It is just another expression of curiosity.

You would only be about thirty percent heavier there.

Due to my unhealthy diet I already am.

 

[Nithavela]

OK then, no worse than a downward elevator stopping at your floor. Let's go.

Having to deal with that 24/7 would still have a noticeable impact. Especially if you're younger, and for old people, falls would be that much more deadly. People would propably use some sort of exo-skeleton and natives would develop higher bone-density.

 

[Resha Caner]

You have answered your own question. It is just another expression of curiosity.

Maybe for some. I doubt the answer is the same for everyone.

 

[Nithavela]

After reading a bit more about this, the planet seems to be uninhabitable after all. Not because of gravitation or temperature, but because of the high radiation the star it orbits emits.

 

[Ophiolite]

Having to deal with that 24/7 would still have a noticeable impact. Especially if you're younger, and for old people, falls would be that much more deadly. People would propably use some sort of exo-skeleton and natives would develop higher bone-density.

I have been in touch, via FTL courier, with Grinxhchpuyalc, a native of K2-18b and he wished me to relay the following message in response to your post.

Well, that's just silly. Obviously our young people spend their developing years in the oceans, where skeletal support is of secondary importance. They do not develop the adult bone fabric until the Emergence, in parallel with the loss of functional gills and the transition to the full air processing system. (The system is of course the Life Utilising Normal Gases, or LUNG).

Our own acrobats spend many years of dedicated effort to overcome the enormous challenge of actually falling. The low centre of gravity, conical shape and ten legs make make it so difficult that it is astounding to see these dedicated practitioners actually fall. (We were also amused by the notion that a supposedly intelligent species that can fall relatively easily would undertake actions that had a significant and calculable possibility of causing such a fall.)

Without wishing to be patronising we do regret the enormous restrictions you must experience from living on a planet with such a small surface area and such a limited range of natural regions. Perhaps falling down and killing yourselves is a way of escaping the boredom. We suppose this has also inspired your species to implement their latest venture: turning the planet into a hothouse like your neighbour, Venus. It should relieve the monotony, if only briefly.

After reading a bit more about this, the planet seems to be uninhabitable after all. Not because of gravitation or temperature, but because of the high radiation the star it orbits emits.

No! No! The radiation is what facilitates the necessary genetic changes to enable the Emergence. The control genetics, protected in the inner core, supervise the filtering of radiation induced mutation in the exo-body. Don't you sapients know anything?

 

[Nithavela]

I have been in touch, via FTL courier, with Grinxhchpuyalc, a native of K2-18b and he wished me to relay the following message in response to your post.

Well, that's just silly. Obviously our young people spend their developing years in the oceans, where skeletal support is of secondary importance. They do not develop the adult bone fabric until the Emergence, in parallel with the loss of functional gills and the transition to the full air processing system. (The system is of course the Life Utilising Normal Gases, or LUNG).

Our own acrobats spend many years of dedicated effort to overcome the enormous challenge of actually falling. The low centre of gravity, conical shape and ten legs make make it so difficult that it is astounding to see these dedicated practitioners actually fall. (We were also amused by the notion that a supposedly intelligent species that can fall relatively easily would undertake actions that had a significant and calculable possibility of causing such a fall.)

Without wishing to be patronising we do regret the enormous restrictions you must experience from living on a planet with such a small surface area and such a limited range of natural regions. Perhaps falling down and killing yourselves is a way of escaping the boredom. We suppose this has also inspired your species to implement their latest venture: turning the planet into a hothouse like your neighbour, Venus. It should relieve the monotony, if only briefly.

No! No! The radiation is what facilitates the necessary genetic changes to enable the Emergence. The control genetics, protected in the inner core, supervise the filtering of radiation induced mutation in the exo-body. Don't you sapients know anything?

Tell your buddy to not visit. It's a silly place.

 

[Subduction Zone]

After reading a bit more about this, the planet seems to be uninhabitable after all. Not because of gravitation or temperature, but because of the high radiation the star it orbits emits.

But that appears to make little sense. No reason is given for the radiation. At least not directly. The hydrogen in the atmosphere indicates that there is little to no oxygen, and going without oxygen might be a little bit of a hardship. At any rate the lack of O2 would mean no ozone layer. And the surface could get some UV, though how much UV is put out by a red dwarf is hard to say.

 

[Nithavela]

But that appears to make little sense. No reason is given for the radiation.

AFAIK the star it is orbiting is emitting far more radiation than our sun.

Of course, the planet might have a really powerfull magnetic field that we can't detect yet and that protects the planet as well as ours protects us.

 

[Ophiolite]

AFAIK the star it is orbiting is emitting far more radiation than our sun.

It is a Red dwarf - it omits considerably less radiation than the sun. The potential issue is that it also a moderately active flare star. Such flares incorporate a significant amount of UV radiation which would be potentially damaging to Earth-like life and probably to any carbon based life form.

However, this may not be a problem. See, for example, Section 7. Biological Tolerances to UV and Special Adaptations in Heath el 1998 Habitability of Planets Around Red Dwarf Stars. The authors note that:

. . . .microbes in an aquatic environment can be protected by inorganic ions, such as nitrates and nitrites and some organics, such as purines and pyrimidines, absorb UV strongly at 2500 Å. A surface microlayer composed of complex organics and enriched in metallic elements, may also be UV protective. Towards a planet’s terminator, we point out, there is a substantial reduction in direct UV radiation (to 0.2% subsolar value for a Sun altitude of 5◦ at 3400 Å), due to the greater air mass traversed.
​

They continue with further examples of UV tolerance of terrestrial organisms, including repair mechanisms. I conclude that while the UV radiation may be an issue, it is not definitely one. A more thorough literature search would provide greater insight, but - at this point - is unlikely to provide a definitive answer.

Of course, the planet might have a really powerfull magnetic field that we can't detect yet and that protects the planet as well as ours protects us.

Magnetic fields do not shield against UV radiation, though they would reduce/eliminate bombardment by H+, or heavier ions. That said if K2-18b has a thick atmosphere, as seems likely, that would also be an effective shield for these.

 

[essentialsaltes]

 

[Astrophile]

Not really all that much greater. The planet is 8 times the mass of the Earth but its diameter is about 2.5 times the Earth's. To convert gravity you would take 8/(2.5)^2 times Earth's gravity. You would only be about thirty percent heavier there.

According to https://en.wikipedia.org/K2-18b , the planet's radius is 2.71±0.07 Earth radii and its mass is 8.63±1.35 Earth masses. This gives it a density of about 2390 kg/m³, and a surface gravity about 18% larger than the Earth's.

A planet with such a low density is clearly not a terrestrial (silicate+iron) planet with surface oceans and a thin atmosphere; it is more likely to be a gas giant or ice giant (a sort of warm mini-Neptune), with an envelope of ice or water and a thick hydrogen+helium atmosphere, with small quantities of water vapour. Such a planet cannot support life as we know it.