Early Earth Key To Finding Life In Space

Life emerged during the Archean Era, and Universe Today reports that life might be easiest to find on planets that match early Earth, or at least some version of it.

The truth is that we’re inching closer and closer to reliably detecting biosignatures on distant planets, and the focus is primarily placed on celestial bodies that have life-supporting chemicals—mostly water and carbon.

However, the presence of chemicals could indicate life, which could potentially create free energy in a system as a whole.

That access to energy could potentially create a chemical disequilibrium, which is precisely what happened on Earth when life first emerged.

It’s lead scientists to wonder whether a chemical disequilibrium can be characterized as a biosignature.

Well, the new research tackles this question, suggesting that chemical disequilibrium might be a potential indicator of life. A good example of this is the Great Oxidation Event on early Earth, which, at the time, had no oxygen in its atmosphere.

The cyanobacteria, known as blue-green algae, evolved with the ability to perform oxygenic photosynthesis, which basically splits water molecules and releases oxygen as a byproduct.

As cyanobacteria thrived in the world’s oceans, the oxygen was initially captured by the oceans, resulting in the formation of banded iron form. Once the oceans became saturated with oxygen, it started to be released into the atmosphere.

This is a really important part because the oxygenation of the atmosphere led to a massive extinction event of all anaerobic organisms, the formation of the ozone layer, and the subsequent evolution of complex aerobic life forms and multicellular organisms.

All because the algae on early Earth was hungry. Now, the new research suggests something similar with methane and oxygen, stating that their presence is an indication of life at work.

Namely, methane only lasts about ten years in an oxygen environment, as it’s slowly converted into water and carbon dioxide as a result of its oxidation.

Continuous (or slightly varying) levels of methane in an oxygenic atmosphere indicate that the gas is being replenished in amounts only life can produce.

So, while the research is founded on early Earth’s history, it’s actually pretty sound if you’re looking for life on Earth-like planets—ones that are similar in size, have an atmosphere, trace amounts of methane, and varying levels of oxygen.

This research could potentially allow us to search for chemical disequilibrium as an indicator of life within distant planets’ atmospheres.

The observation would mostly be done in the light spectrum, which would allow us to “color code” the atmospheric content and thus determine whether the planet contains proto-life forms analogous to cyanobacteria.

And if we’re even fortunate enough to discover life on other planets, those exoplanets are more likely to look like early Earth rather than a modern-day version of our planet.