Environment

Scientists calculate life expectancy of Earth's atmospheric oxygen

Scientists calculate life expe...
An artist's interpretation of the atmosphere of Archean Earth, prior to 2.4 billion years ago. A new study suggests it may return to this oxygen-poor, methane-rich atmosphere in about 1 billion years' time
An artist's interpretation of the atmosphere of Archean Earth, prior to 2.4 billion years ago. A new study suggests it may return to this oxygen-poor, methane-rich atmosphere in about 1 billion years' time
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An artist's interpretation of the atmosphere of Archean Earth, prior to 2.4 billion years ago. A new study suggests it may return to this oxygen-poor, methane-rich atmosphere in about 1 billion years' time
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An artist's interpretation of the atmosphere of Archean Earth, prior to 2.4 billion years ago. A new study suggests it may return to this oxygen-poor, methane-rich atmosphere in about 1 billion years' time

The Earth has an expiry date – in about five billion years, the Sun will expand and swallow up our home world. But it turns out life on Earth could have a much earlier end point. A new study has found that in about a billion years’ time, the atmosphere will lose most of its oxygen rapidly, which may have important implications in the search for life on other planets.

An oxygen-rich atmosphere is one of the defining features of Earth, with the vital gas making up around 20 percent of the air. That of course is good news for humans and most other animals that call this planet home, and we have plants to thank for it.

But how long can an oxygen-rich atmosphere stick around? For the new study, researchers from Georgia Tech and Toho University set out to investigate the long-term stability of Earth’s atmospheric oxygen.

The team conducted simulations of the Earth’s systems, including its climate, biological and geological processes, and even the brightness of the Sun, and observed how the oxygen levels changed as it was shuttled between the air, water and rock. While other studies have simulated some of these systems in the past, these new models were more complex than usual.

The researchers found that Earth’s oxygenated atmosphere will most likely last another billion years, before it plummets relatively rapidly. By about 1.1 billion years from now, the team says, oxygen levels will likely drop to just one percent of the present atmospheric level.

The leading cause of this deoxygenation, according to the models, is the Sun. As it ages, our parent star is expected to brighten and heat up, which will increase Earth’s surface temperature and break down carbon dioxide in the atmosphere. These two factors would kill off plant life, depriving the planet of its main oxygen source.

This future atmosphere would end up bearing a striking similarity to that of the ancient past – after all, even Earth wasn’t always this pleasant a place. It only began around 2.4 billion years ago, when photosynthesizing microbes and later plants began pumping out oxygen in high amounts. That paved the way for multicellular life to arise.

While this find may not seem to have a direct impact on our lives today – humans will no doubt be long gone in a billion years anyway – it does complicate the search for signs of alien life. Since oxygen is tied so inextricably to life on Earth, astronomers have long considered it a useful signature to look for in the atmospheres of exoplanets, where it could indicate the existence of extraterrestrial life.

Now, it’s becoming clearer that it’s not enough to look for worlds that are in the right point in space to be habitable – the right point in time will be key too. The team calculated that oxygen might only be detectable in an atmosphere for about 20 to 30 percent of the planet’s overall lifetime.

It’s still worth looking for, of course, but the team suggests that there are other potential biosignatures that we should keep an eye out for too. One of those might be a methane-rich, organic haze that they predict will hang in the air of far-future Earth, post-oxygen. And most intriguingly, that sounds an awful lot like the atmosphere of modern-day Titan.

The research was published in the journal Nature Geoscience.

Source: Springer Nature

14 comments
14 comments
Ron
Studies like this drive me crazy, travel to distant planets is a joke. Unless you have some magical new physics discovery in your back pocket Einstein's work puts the cabbash on travel past our own solar system. Besides wherever man goes destruction follows, why screw up some other poor planet.
Nobody
We don't just need oxygen. We need 20% oxygen. 5% more and you would have extreme difficulty putting fires out and with 5% less we would have trouble getting a fire started. Our industrial system depends on this nearly exact percentage. Vary much from it and life gets much more difficult very quickly.
Tyler
A simulation? Extrapolating out 5 billion years? Bwahahahaha...
piperTom
NEAR TERM travel to distant planets is a joke, but we have hundreds of millions of years to get ready for this (supposed) oxygen event. NOTHING is beyond us on that time scale. A mere eye-blink of just three hundred years ago, you could not explain to most people what oxygen was.
MontanaTrace
This will surely be addressed in the Paris Accord.
Capt_Ahab84
One thing that this article fails to consider is human ingenuity. I find it hard to believe that we will simply let the Earth cook as the sun grows hotter. I can see in a billion years time, we'll have the technology to create a solar shade in space with a vast array of mirrors or some other type of material. Scientists have already proposed this sort of solution for climate change.
drBill
Before we throw in the towel, we have time to figure a lot out. The abstract one can read for free at the Nature Geoscience link (qv) did not provide nearly enough detail for me to guess/critique the idea, logic or methodology. The wiki article on the carbonate-silicate cycle was informative but overall unsatisfying https://en.wikipedia.org/wiki/Carbonate%E2%80%93silicate_cycle
I agree with Ron that such articles can seem to be warning about stuff with no way out (Sartre), but if humans keep poking their nose into science and don't throw in the towel, we'll find a way (Huh. Imagine science as a faith-based philosophy/religion ;). Even if the first 20,000 person leviathon space ship to Fomalhaut XII is passed by the FTL ship in 3854 CE (a regular meme for sci-fi).
ScottBaker
Or, we can just move the Earth to a farther orbit: https://arxiv.org/abs/astro-ph/0102126
I proposed something similar but apparently more difficult, using the Moon in a bola fashion, here: https://www.quora.com/Before-the-Sun-goes-nova-could-we-use-the-Moon-in-a-bola-fashion-with-rockets-on-the-Moon-to-swing-the-Earth-to-a-farther-orbit-gain-a-few-billion-years-of-habitable-existence
madsci
Unfortunately, I doubt we will have to worry about running out of oxygen in several million years. Currently I don't see us lasting that long with oxygen the way things are going.
christopher
ROFL - what Tyler said.
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