My notes. I did not see the Faint Young Sun problem discussed for Precambrian Earth in this report. From the 9-page PDF report: “The two global Snowball Earth events (i.e., the Sturtian and Marinoan ice ages) during the Cryogenian Period (720–635Ma) played a key role in the evolution of the Earth-life system1–5. During Cryogenian Period, the oceanic redox landscape was restructured6,7, and animals probably emerged3, highlighting the possible impact of this climatic event on the Earth’s biosphere8,9. The surface ocean is hypothesized to have been mostly or completely frozen during this glacial event1,10, but alternative climate models and sedimentary evidence indicate the presence of open marine waters in low-latitude regions during the Snowball glaciations11–16."
The Faint Young Sun problem remains to be solved for the Precambrian timescale in geology. Mars should experience an even colder climate. The Earth 4 Gyr, 3 Gyr, 2 Gyr ago should be frozen completely, not just Cryogenian Period with the Marinoan Ice Age or another. This should raise real concerns about how Precambrian tiny life evolved into the Cambrian explosion fossils documented. A problem for Charles Darwin in the fossil record, a bigger problem now because of the Faint Young Sun (now snowball Earth), something Charles Darwin did not know about.
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