Halite Air Inclusions as Deep‑Time Atmosphere

Fluid and gas pockets trapped in ancient halite crystals can be directly analyzed to reconstruct atmospheric composition at billion‑year timescales. The RPI/Lakehead PNAS study using 1.4‑billion‑year halite reports unexpectedly high O2 and elevated CO2 during the Mesoproterozoic, providing a new, precise proxy for models of early Earth climate and evolution. — This creates a new empirical lever for debates about when and why oxygen rose, how climate stayed warm under a faint young sun, and what environmental conditions made animal evolution possible.