Would You Bet Your Species on "Earth-Like"?

Otis writes:

Here is an excerpt from the article in Science Daily that I think explains what is thought to happen when planets form:

 

 

"Planetary systems, including our own Solar system, are thought to form from hydrogen, helium and heavier elements that orbit their parent stars in a so-called protoplanetary disk. Dust and rocky material is thought to clump together over time, eventually forming rocky cores that go on to be planets. The gravity of these cores attracts hydrogen from the disk around them, some of which is stripped away by the ultraviolet light of the young star they orbit."

 

So as the protoplanetary rocky core forms it attracts hydrogen, methane and other gasses.  If the core is not too big, the hydrogen is stripped away by the host star's ultraviolet light.  For Earth, the hydrogen was stripped away long before the Moon-forming impact that further removed some of the Earth's atmosphere.  According to the recent work reported in Science Daily, if the rocky core is larger than about 1.15 Earth radius then the hydrogen sticks around on the planet and it turns into a "mini-Neptune."  The researchers do acknowledge that some unusual event (like the impact that formed the Earth-Moon) could remove the hydrogen from those 'super-Earths'.  

 

I think that the takeaway message is that Super Earths are not likely to be habitable.

Terms such as "Earth-like" and "Earth Cousins" are misnomers.  If you are not willing to go live there, then the exoplanet is NOT Earth-like.

 

Astrobiologist Caleb Scharf agrees with that assessment. (click for link)

 

Otis