How hot were the oceans when life first evolved?

[Binary_Bark]

We know little about Earth's surface temperatures for the first 4 billion years or so of its history. This presents a limitation into research of life's origins on Earth and also how it might arise on distant worlds as well.
Now researchers suggest that by resurrecting ancient enzymes they could estimate the temperatures in which these organisms likely evolved billions of years ago. The scientists recently published their findings in the journal, Proceedings of the National Academy of Sciences.
"We need a better understanding of not only how life first evolved on Earth, but how life and the Earth's environment co-evolved over billions of years of geological history," said lead author Amanda Garcia, a paleogeobiologist at the University of California, Los Angeles. "A similar co-evolution seems certain to be the case for any life elsewhere in the Universe."
Garcia and her colleagues focused on the history of Earth's surface temperatures. Rocks offer many clues to deduce temperatures over the last 550 million years in the Phanerozoic Era, when complex, multicellular life took off, including that of humans. However, few such "paleothermometers" exist for the earlier Precambrian Era, spanning the Earth's formation 4.6 billion years ago and the rise of life.
Earlier geological evidence has suggested that 3.5 billion years ago, during the Archean Eon, the oceans were 131º to 185º F (55º to 85º C). They cooled dramatically to current average temperatures of 59º F (15º C). Scientists made these estimates by examining oxygen and silicon isotopes in marine rocks.Quartz-rich rocks in the seabed, known as cherts, have higher levels of the heavier oxygen-18 and silicon-30 isotopes as the seawater gets colder. In principle, the ratio of heavier to lighter oxygen and silicon isotopes can shed light on ancient temperatures.

Read more at: https://phys.org/news/2017-06-hot-oceans-life-evolved.html#jCp

 

[Clive2]

...which widens the possibility of even primitive life evolving on other planets, even 'hostile' ones.

 

[Zophos]

Fascinating stuff.

I would love to see more research on how to planet changed after each extinction event. This is a huge step in understanding why life here (and possibly somewhere else) takes on the forms that we see.