Earth’s air pressure 2.7 billion years ago constrained to less than half of modern levels (Nature Geoscience, 2016)
VPL Authors
Full Citation:
Som, S., Buick, R., Hagadorn, J. et al. Earth's air pressure 2.7 billion years ago constrained to less than half of modern levels. Nature Geosci 9, 448–451 (2016). https://doi.org/10.1038/ngeo2713
Abstract:
How the Earth stayed warm several billion years ago when the Sun was considerably fainter is the long-standing problem of the ‘faint young Sun paradox’. Because of negligible1 O2 and only moderate CO2 levels2 in the Archaean atmosphere, methane has been invoked as an auxiliary greenhouse gas3. Alternatively, pressure broadening in a thicker atmosphere with a N2 partial pressure around 1.6–2.4 bar could have enhanced the greenhouse effect4. But fossilized raindrop imprints indicate that air pressure 2.7 billion years ago (Gyr) was below twice modern levels and probably below 1.1 bar, precluding such pressure enhancement5. This result is supported by nitrogen and argon isotope studies of fluid inclusions in 3.0–3.5 Gyr rocks6. Here, we calculate absolute Archaean barometric pressure using the size distribution of gas bubbles in basaltic lava flows that solidified at sea level ∼2.7 Gyr in the Pilbara Craton, Australia. Our data indicate a surprisingly low surface atmospheric pressure of Patm = 0.23 ± 0.23 (2σ) bar, and combined with previous studies suggests ∼0.5 bar as an upper limit to late Archaean Patm. The result implies that the thin atmosphere was rich in auxiliary greenhouse gases and that Patm fluctuated over geologic time to a previously unrecognized extent.
URL:
https://www.nature.com/articles/ngeo2713
VPL Research Tasks:
Task B: The Earth Through Time