Water Vapor On The Habitable-Zone Exoplanet K2-18b

[Topper]

http://astrobiology.com/2019/09/water-vapor-on-the-habitable-zone-exoplanet-k2-18b.html
https://arxiv.org/abs/1909.04642

I gues this is the first time we found water on an exoplanet?

 

[Urwumpe]

Yes, it is the first time we have strong evidence of water on a exoplanet. BUT: It is not a sign of liquid water.

 

[Topper]

When I was a child (I'm was born in 81), I remember that my teacher was saying us that it is unknown if other stars have planets and that we will never be able to proof such planets... And today, we are able to proof water in an atmothphere of a world which is 110 light years away from us. I know that the idea of this method is not new, but it is really strange to me that it works...

 

[Linguofreak]

Yes, it is the first time we have strong evidence of water on a exoplanet. BUT: It is not a sign of liquid water.

The direct spectroscopic signature only indicates vapor, but if I read the Arxiv paper correctly, there is evidence in the general transit light curve for a cloud layer, which would indicate condensation, and in any case the orbit of the planet is such that the existence of liquid water is a very good bet.

Now, what's more questionable, given the size of the planet, is the existence of liquid water as anything more than clouds and precipitation. It's quite likely that any "ocean" surface is deep enough in to be in the supercritical, not liquid regime.