How Earth’s Early Atmosphere Cooked Up the Ingredients for Life

From simple gases to complex organics: A story of Earth’s first atmosphere

I have talked extensively about my life as a parent of scientists. Indeed, I have two amazing kids aged two and a half and four and a half years old. And you know what kids at these ages are well known for? Questions. Lots of them.

In a way, though, I feel sorry for these little kiddos, exposed to all sorts of scientific explanations for everything they ask. They rarely get a simple straight answer. That said though, we can tell that their minds are expanding in a way we never imagined possible.

Among the topics they most ask about are Astronomy. I mean, it’s not like we aren’t to blame. After all, we bought them multiple books on the topic, and we read them every night before bed.

If you have kids, you know how this works. You start talking about a topic, and they start asking why every single thing you say. They can insist so much on the process that sometimes they go to a point we don’t have answers to.

“Why did life on Earth form?” “Well, the organic compounds on Earth made it possible.” “And what made the organic compounds possible?”

I promise they don’t really understand the full picture of what’s going on at this point, but we give the full explanation regardless and then address whatever we think they can understand.

However, this question got us thinking. What was it? Well, recent research tells us a bit more about the story!

Oh, and before you proceed. If you are curious about the ins and outs of a Science-based education, Silvia just started a new publication on the topic. Makes sure you check it out!

STEM Parenting – Medium

A science-based approach for an education and parenting that nurture kid’s bodies and minds.

When we think about Earth’s past from when life first appeared, images of volcanoes, meteors, and roiling oceans might come to mind. However, the sky above was also busy brewing the building blocks of life. In fact, it may have been crucial for life to happen in the first place.

Researchers from Tohoku University, University of Tokyo, and Hokkaido University recently modeled Earth’s ancient atmosphere to understand just how our planet went from barren rock to a world brimming with life’s ingredients. Something that many have a hard time visualizing.

Their study, published in the journal Astrobiology, suggests that Earth’s early skies held a fascinating secret: an environment enriched with organic compounds, all set to nurture life.

“Ancient Earth was nothing like our current home,” said Dr. Shungo Koyama from Tohoku University. Instead of the oxygen we’re used to, it was a “much more hostile place” with an atmosphere loaded with hydrogen and methane.

If you want to better understand what we know about this time in Earth’s past, see Neil deGrasse Tyson’s video below. Neil’s videos never fail to deliver!

In fact, according to Dr. Koyama, it’s precisely these gases that held the clues for how life was able to take off on this planet. By understanding what was happening in these early conditions, researchers are now piecing together how Earth could have sparked life — and what that could mean for other planets with similar chemical makeups.

To get a closer look at this primordial atmosphere, the research team developed a one-dimensional (1D) photochemical model. This approach allowed them to simulate interactions among different gases and the effects of ultraviolet (UV) radiation, using the chemistry of hydrogen and methane as the base. I know, it sounds complicated, but I made it easy to digest for you.

While other studies have highlighted these gases’ role in forming early organic molecules, the researchers’ model added a new layer: the role of hydrocarbon gases, like acetylene, that shield UV radiation and, as a result, reduce oxidation.

This reduction slowed down how fast hydrogen was lost to space, allowing more complex organics to form over time. In a way, having more ingredients available.

By simulating these interactions over a lengthy timescale, the team recreated conditions that could have allowed prebiotic molecules to build up in Earth’s oceans for millions of years. Tell me this isn’t one of the coolest methods you have ever heard of!

But, what did they find?

The results were intriguing. As Dr. Tatsuya Yoshida, one of the study’s authors, explained, their calculations suggest that hydrocarbons acted as a protective UV shield, keeping certain destructive reactions at bay. This meant that the breakdown of methane into simpler molecules, which would otherwise react with water and oxidize, was limited.

Instead, as Dr. Yoshida explains, “there may have been an accumulation of organics that created what was like an enriched soup of important building blocks. That could have been the source from which living things first emerged on Earth.”

But what kind of “soup” are we talking about here?

The model showed that with enough methane — comparable to the carbon in Earth’s crust today — Earth’s atmosphere could have generated thick layers of organic material, building up in oceans and creating a mix that scientists often describe as a “prebiotic soup.” I know, it sounds like something your dietician may prescribe to you.

Within this organic-rich stew, essential molecules like amino acids and nucleic acids could begin to emerge. These are the same molecular building blocks that makeup DNA and proteins, molecules essential for life as we know it. So when we talk about essential, we truly mean it.

What’s particularly exciting about this research is the idea that Earth’s conditions weren’t all that unique. In fact, this type of early atmosphere, filled with hydrogen and methane, closely resembles the atmospheres on our planetary neighbors Venus and Mars.

The difference, of course, is that Earth somehow developed life, while our neighboring planets didn’t (as far as we know). Researchers are still investigating what set Earth on a different path, but this model helps us understand how specific chemical processes on our planet might be one piece of that puzzle. A puzzle we may be getting closer to solve.

This research brings a dash of optimism to those hoping to find life elsewhere in the cosmos. By understanding how Earth’s atmosphere builds up organics, scientists can apply this knowledge to studying planets around other stars with similar conditions.

Even if these planets don’t end up teeming with life, they might still hold reservoirs of organic material just waiting to be explored.

In the end, this research shows how Earth’s early atmosphere may have transformed itself into a veritable incubator for life. Through the interaction of methane, hydrogen, and solar UV radiation, our ancient atmosphere may have brewed up a rich cocktail of organic compounds, ultimately setting the stage for life to emerge.

The study highlights not just the delicate chemistry of our own planet’s past but also what might be possible in other worlds, suggesting that the conditions for life could be more common than we’ve imagined.

I can’t wait to see what else we can tell the kids soon!