Groundbreaking research suggests that the complex life on Earth could persist for nearly twice as long as previously estimated, offering new insights into the longevity of our planet’s biosphere and the potential for life on exoplanets.
Rethinking the Sun’s Impact
The ancient…. argument went that over a billion years from now as the Sun brightens, it at some point pushes this homeostasis too far with devastating results: atmospheric CO2 levels plummet to zero and whatever might be left of humanity or Earthly life is left without an energy source. This in turn would lead to the near extinction of all life on land due to a lack of plant diversification.
But a team of scientists from the University of Chicago has found that this dire scenario may not play out after all. The resulting analysis shows that the carbonate–silicate cycle, which serves as a thermostat for nature in this scenario, may not be as sensitive to temperature changes as it was believed before. Instead the primary influence is by levels of CO2 in the air.
That escapement of CO2 will therefore operate on timescales longer than expected for the silicate weathering that is taking place in response to a better-lit Sun. As a result of this interplay between climate, plant productivity, and weathering the slowdown in future CO2 decrease due to the microbial thermostats will actually be slowed down and reversed temporarily saving the plants from starvation as themselves decline.
Longer lifetimes for complex life
These results imply that the planet could host life rather longer: 600–860 million years into the future, instead of 1 billion as was estimated before. As a result, the planet’s molecular sea is unlikely to lead to certain death by CO2 starvation and will instead doom its inhabitants to roast because of what could be described as a ‘moist greenhouse transition’ — at some point the atmosphere will grab so much water vapor that it tips into a runaway heating state in which temperatures spiral up into regime where even plants cannot grow.
This longer period of time has great consequences when we try to figure out our past, current and future (here or on other planets). We need to call into question the hard steps model, which argues that many critical evolutionary transitions were rare events that would not have occurred again. If the biosphere on Earth is much older than previously thought, it might mean that there were numerous opportunities for life to arise and complex organisms like us emerge long before the Cambrian explosion.
This, in turn, might mean that habitable exoplanets are less rare than thought by some — a tantalizing prospect to increase the probability of finding extraterrestrial life one day.
Conclusion
The newest questioning of these assumptions on the outlook for Earth’sss biosphere seriously flips the script. Not only does this change our view of the Earth’s distant future, and the likelihood that at least complex life on our own world has billions of years left until it becomes uninhabitable, but it also has major consequences for the search for alien habitable worlds and even the evolution and lifetime of extraterrestrial life. This study, which is the first of it’s kind, inspires exciting new questions that can be addressed ecosystem by ecosystem and ultimately reinforces the idea that there are always learning to do when analyzing our Earth.
