Faint Young Sun Paradox Explained by Microbes?

The faint young sun paradox asks why the early Earth had liquid oceans when the young sun was much fainter than it is today. Scientists from the University of British Columbia think they have an answer. Find out more.

We’re a bit concerned about delving into this topic. It involves greenhouse gases. Climate contrarians might use this story to claim that “the climate always changes, so we have nothing to worry about.” Let’s get that out of the way first.  

The climate change we’re experiencing due to greenhouse effects today is unprecedented. Virtually all climate scientists agree that the current climate crisis is real, caused by humans and an emergency.

With that out of the way, we can get on with today’s story. In an earlier post, we talked about the legacy of Carl Sagan. He’s known today mainly as a science communicator. However, he also made significant contributions to the study of our solar system.


In 1972, he and fellow astronomer George Mullen noticed a problem. It arose from the discovery that there were liquid oceans on the early Earth billions of years ago. At the same time, the young sun was faint by today’s standards. David Whitehouse provides a complete history of the Sun’s origins in his book The Sun: A Biography.

Our sun had more hydrogen and less helium in its core than today. Because of that, it only emitted about 70% of the energy we currently enjoy. At that output, the Earth should have been too cold for liquid oceans. It should have been covered in ice instead. This poses a climate paradox.

Scientists call it the faint young sun paradox. Various researchers have tried to come up with explanations for it. These have included attributing it to atmospheric carbon dioxide or ammonia levels in the early atmosphere.  


Other theories have pointed to cosmic rays, solar wind or to different cloud patterns. There is also the idea that the Earth is somehow self-regulating with its own built-in feedback mechanisms.  

None of these ideas has really caught on. They don’t provide robust solutions to the paradox of the faint young sun. This puzzle concerns scientists because it the early Earth was frozen, that would mean very little life on Earth should have arisen. The paradox leaves a gap in our origin story.

Earlier this month, researchers from the University of British Columbia (UBC) and other institutions announced a possible solution to the faint early sun paradox. They published their findings in the journal Science Advances.


Their research focused on a body of water called Kabuno Bay, a sub-basin in Lake Kivu. This iron-rich lake is in the Democratic Republic of Congo. The team found that the iron deposits in Kabuno Bay come from a distinctive kind of ancient bacteria.

These bacteria can expel iron minerals through their surfaces and deposit them on the lake bed. Over time, this created the world’s largest iron ore deposit. Once they’ve released their iron, the bacteria become prey to other microbes that produce methane.

As we know, methane is a potent greenhouse gas. In the young Earth, when the methane entered the atmosphere and surface of the Earth, it would have raised the Earth’s surface temperature, just as it does today. This seems to explain why there was liquid water on the early Earth despite the faint young sun that existed in those primordial times.


This isn’t an entirely new idea. Professor James Walker of the University of Michigan first put it forward in 1987. Until now, empirical evidence to support the hypothesis has been limited.

This discovery changes that. It provides solid evidence that microscopic interplays between bacteria and minerals could have caused the moderate temperatures needed to sustain liquid oceans even with the faint young sun.

The techniques used to make this discovery have other applications as well. As senior author of the study, Sean Crowe put it, “The fundamental knowledge we’re gaining from studies using modern geomicrobiological tools and techniques is transforming our view of Earth’s early history and the processes that led to a planet habitable by complex life including humans.”


There are also more practical implications for today’s world. These could include new ways to recover resources, innovative construction materials, and new medical treatments.

In terms of our current climate crisis, it may be possible to reverse engineer the processes the microbes used to mitigate the effects of the faint young sun. Applying that process in reverse could play a role in the kinds of carbon capture and storage projects we discussed in an earlier story.

We tend to think of the origin of life in terms of biology alone. As we see with this new research, it’s actually a more complex interplay. It involves astronomy, geology and biology interacting as a team.  


Explaining the faint young sun paradox required an interdisciplinary approach. In the 20th century, expertise became highly specialized. This could lead to silos where complex phenomena were hard to understand if they happened to fall into the cracks between disciplines.  

In today’s post-modern academic world, we see a return to more collaborative and generalized approaches to science. We’re moving away from highly mechanistic world views to more holistic perspectives.

There’s a humourous paragraph that has been circulating for decades. It used to be distributed using photocopiers, and now it pops up on social media.  


It goes like this, “We have not succeeded in answering all our problems. The answers we have found only serve to raise a whole set of new questions. In some ways we feel we are as confused as ever, but we believe we are confused on a higher level and about more important things.”

Problems like the faint young sun paradox seem to fall under this category. Interdisciplinary techniques like those used by the UBC research team seem to be fruitful in dealing with this higher level of confusion about more important things.

We always have more to learn if we dare to know.

University of British Columbia
Photoferrotrophy, deposition of banded iron formations, and methane production in Archean oceans
The Sun: A Biography
Can Carbon Capture Solve the Climate Crisis?
Origin of Life Before Origin of Species – 4 Theories
Life Began Even Earlier Than Thought
Plasma: Exotic Fourth State of Matter on the Sun
Meteorites Brought Space Sugar to Earth
Carl Sagan Day: Let’s Make It Official


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