Don't pack your bags

LHS 1140 b has been mooted as potentially habitable over on ScienceDaily. If it has nitrogen, the researchers moot an iceworld with a 4000 km diameter "eyeball" sea facing the star. I don't think this is habitable.

First up, no oxygen has been detected. At 10-20% water composition and at overall mass, I'm thinking the ocean is too deep and dense to allow for nonbacterial life. Certainly there are no tectonics. Also superterrans from 2.5+ might not have cores.

I actually think that oxygen is being formed from this waterworld. The star is M4.5 on mainseq a little longer than our Sun; surface temperature in the 3100s K. But unlike boring ol' Gliese 12, LHS 1140 might still be flaring. Proxima is a little smaller in mass and more Sol-ar in age, temperature a little less: for "M5.5Ve". Have we been watching LHS 1140 long-enough to rule out flares? A good flare will ionize the hydrogen from the oxygen. Oxygen and even ozone gasses will result. Ozone will react with the nitrogen for nitrous oxides. Oxygen too eventually, I think.

I think we're looking at an atmosphere of nitrogen... and of laughing gas, hydrogen-cyanide, carbon-dioxide, and trace carbon-monoxide. The ocean will in turn have the composition of soda water.