Billion-year-old air reveals surprise about oxygen on ancient Earth
Here's what worries me about this type of extrapolation:<p>"The researchers also compared salt samples from other halite deposits of different ages — including the modern day — when oxygen concentrations were known and found their results matched up with known concentrations. That gave them confidence in their result, they said."<p>OK, so you take a recent sample and it matches up.  Great.<p>But this seems to assume there is some sort of barrier at the atomic level that "traps" the atmosphere at the time the salt crystals were formed and that time and pressure will never have an impact on what components of the atmosphere remain in the salt crystal.