Scientists question possible signs of life on exoplanet K2-18b in new study: 'We never saw more than insignificant hints

[Admin]

The skepticism continues over recent claims of possible hints of alien life on exoplanet K2-18b.

Scientists question possible signs of life on exoplanet K2-18b in new study: 'We never saw more than insignificant hints : Read more

 

[Helio]

This comes with little surprise to those who, like me, are pessimistic for life on exoplanets hosted by red dwarf stars.

It is in the calculated HZ (Habitable Zone) but it's only 0.14 AU from its star. It's a little large at over 2x the Earth's radius and has a surface gravity of about 3g (1.66g). The size, however, doesn't disqualify it.

There are several other concerns I have for this exo:
1) It is so close to the star, thus it is likely in a tidal lock -- one side always sees the light of day, the other side only sees the light of night.
2) Red dwarfs are notorious at spewing flares and CMEs, including monster versions of both. The planets proximity to the star only makes their impact even worse.
3) Red dwarfs are called red for a reason. The emissions of higher energy photons of violet and blue, and ultraviolet are greatly diminished which may, or may not, impact the chance for the emergence of sustained life.

As a result, FWIW, K2-18 b isn't in my Top 10 list. My favorite is KOI-4878 b.

 

[rod]

Others are reporting a bit more skeptical thinking about life on K2-18 b now. Hopes for alien life dim as doubts emerge over exoplanet K2-18b chemical signals, https://phys.org/news/2025-05-alien-life-dim-emerge-exoplanet.html

My note, exoplanet properties for K2-18 b can be seen here, https://exoplanet.eu/catalog/k2_18_b--3953/

The mass is about 8.921 earth mass and radius about 2.365 earth radii. The surface gravity would be some 1.59 g. I have seen no reports that show abiogenesis creates life from non-living matter in higher surface gravity than Earth's surface gravity. This is an assumption introduced into astrobiology *science* it appears. Higher gravity suggests more bombardments too when the exoplanet formed from a solar nebula type model.

 

[Helio]

The mass is about 8.921 earth mass and radius about 2.365 earth radii. The surface gravity would be some 1.59 g.

Oops, I see my revised program ignored the given radius of the exoplanet, thus it calculated its radius based on a rough density table. I'm further off than I would like to see. But, I did correct my code hiccup. Thanks!

We are in agreement, but we are off only a little on the radius. I use 10.937x as the size difference, in lieu of 11.2. The 10.937 is the radius based on the volumetric mean, so it's a little more accurate.

I have seen no reports that show abiogenesis creates life from non-living matter in higher surface gravity than Earth's surface gravity. This is an assumption introduced into astrobiology *science* it appears.

Where do you see such assumptions that favor higher surface gravities are more favorable for abiogenesis? I haven't seen that idea, though it wouldn't surprise me.

Higher gravity suggests more bombardments too when the exoplanet formed from a solar nebula type model.

That's a good point. This might, however, have the advantage of a faster rotating iron core, thus granting far greater protection from the heavy hits likely from a fisty red dwarf.

 

[Helio]

One other thing worth noting, the original public presentation for DMS came with the optimistic statement of "I kid you not."