Scientists have long thought that about 3.5 billion years ago, Earth’s oceans and atmosphere rose to temperatures as high as 185 degrees Fahrenheit (85 degrees Celsius), but a new study on hydrothermal fields and glacial deposits at the bottom of the ocean suggests that our planet’s climate was actually quite cool – not very different from today.
The new study – published Friday (Feb. 26) in the journal Science Advances – sheds some light on the Archean climate – the Archean is one of the four principal geologic eons, during which Earth’s crust and layers had just formed.
Harald Furnes of the University of Bergen and Maarten de Wit of Nelson Mandela Metropolitan University (both authors of the study) looked at chemical data collected from some of our planet’s oldest sedimentary volcanic materials and rocks – those were taken from the Makhonjwa Mountains also known as the Barberton Greenstone Belt (BGB) or Barberton Mountain Land in South Africa.
The researchers found that the estimates of temperatures in marine environments – that were between 79 and 185 degrees Fahrenheit – might not have been as high as previously thought.
Pieter Visscher, a geomicrobiology professor at the University of Connecticut, said that the new study focuses on showing the early ocean temperatures to help scientists better understand how life on Earth evolved.
In previous studies, researchers have said that the warmer temperatures were due to fissures in the planet’s surface, or hydrothermal fields. However, the new study states that those fluids were mixed with cool water from the ocean – just like it happens today our deep oceans and shallow seas. According to Dr. de Wit, the new findings show that temperatures of the oceans at that time were not that hot.
For the study, Dr. Furnes and de Wit focused on fields of the hydrothermal, pipe-like structures. They also looked at sulphur minerals in the same environment as the hydrothermal fields, and at glacial deposits, also referred to as diamictites, de Wit stated. Nowadays, sulphur minerals and diamictites can only be found in the extremely cool temperatures of the deep sea.
Dr. Visscher noted that further research need to be conducted to figure out whether the same conditions could be found all across Earth. To do so, the researchers will need to conduct the same analysis on rocks at different located in different areas on our planet. Visscher and his colleagues may be able to at rock records of similar ages at different places of the world to find whether the same finding hold true in other locations as well.
Overall, the new observations challenge scientists’ understanding of life on Earth billions of years ago, as well as of the Archean climate, the researchers said. Since the atmospheric and marine temperatures back then might not have been very different from today, which means that they could have created an ideal environment for life to flourish.
The set of rock records found in South Africa suggest that ever since we have had records of life on Earth, the planet has been predominantly not too cool and not too hot to eliminate life, according to the researchers.
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