Sciency Words: The Oxygen Catastrophe

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Every Friday, we take a look at a new and interesting scientific term to help us all expand our scientific vocabularies together. Today’s word is:

OXYGEN CATASTROPHE

If an extraterrestrial intelligence were to examine Earth from a distance, perhaps analyzing the spectral lines of Earth’s atmosphere, Earth might not seem like the most hospitable of planets. The atmosphere contains one of the most dangerous substances in the known universe: oxygen.

Ap05 Professor Xiggoloplod

 

Earth Before Oxygen

In the beginning, Earth had an atmosphere composed mainly of carbon dioxide. Life thrived in this environment until someone (I’m looking at you, cyanobacteria) discovered the secret to photosynthesis: the ability to draw energy from sunlight.

Unfortunately, photosynthesis produces oxygen as a byproduct. As the cyanobacteria population boomed, so too did the oxygen content of both the oceans and the atmosphere. This led to Earth’s first mass extinction event: the oxygen catastrophe.

That’s Too Much Oxygen!

Oxygen is a highly reactive gas. It’s so reactive that one of the most common types of chemical reactions—oxidation—is named after it. Oxygen will do just about anything to react with other substances, and it doesn’t care who gets hurt in the process.

Here are some of the ways oxygen harmed Earth’s earliest organisms:

  • Oxygen oxidized minerals in the oceans, robbing microbial life forms of vital nutrients, causing many microbes to starve to death.
  • Oxygen attacked microbes directly, essentially oxidizing them to death.
  • Oxygen sucks at trapping heat, so as atmospheric oxygen levels climbed, global temperatures plummeted. In fact, Earth may have briefly looked a little like the planet Hoth from Star Wars. End result: many microbes froze to death.

And that was the end of life on Earth, or at least it should have been.

Breath Easier Thanks to Aerobic Respiration

Aerobic respiration is a biological process that puts oxygen’s oxidizing tendencies to good use. Through aerobic respiration, glucose molecules (a.k.a. sugar) are disassembled, releasing enormous quantities of energy stored within glucose’s chemical bonds—far more energy than we could get without oxygen’s help.

During the height of the oxygen catastrophe, a handful of clever microbes figured out this aerobic respiration thing. They also developed special enzymes to protect themselves from the ravages of prolonged oxygen exposure. Atmospheric oxygen levels dropped to safer levels, the planet thawed, and a new balance was achieved between respirating and photosynthesizing organisms.

In fact, aerobic respiration has been so successful that it’s hard for us to think of oxygen as a deadly poison. Rather, it’s become a source of life. As for the cyanobacteria that started this whole mess, they’re still here, unrepentant, continuing to spew their oxygen waste all over the place.

 

So if an extraterrestrial intelligence were to examine Earth from a distance and notice the high oxygen content of the atmosphere, this might not be an obvious sign of life. But oxygen atmospheres don’t just happen. Something has to make them happen, and something has to maintain them over time. That should be enough to at least leave our E.T. friends scratching their heads.

Links

Bacteriapocalypse from Damn Interesting.

Evolution of Aerobic Respiration from the Astrobiology Conference of 2010.

Evolution and Oxygen from Science Online.

How Did Early Bacteria Survive Poisonous Oxygen? from Universe Today.

3 Responses to Sciency Words: The Oxygen Catastrophe

  1. Spacerguy says:

    I love that scene in Galaxy Quest when Guy says ” HEY! Don’t open that! It’s an alien planet! Is there air? You don’t know!” Hilarious but so true!

    Liked by 2 people

  2. […] Long ago, life on Earth was nearly wiped out by a certain oxidizing agent called oxygen. This event is known as the oxygen catastrophe. […]

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: