A Breath of Fresh Hydrogen

Hello, friends!

So let’s imagine that extraterrestrials don’t breathe oxygen.  Oxygen is a pretty dangerous chemical, after all, so there’s good reason why alien organisms might want to avoid it.  But what would these aliens breathe instead?

A few years back, I came across an interesting “fact” on a conspiracy theory website.  The government doesn’t want you to know this, but apparently a lot of alien species breathe hydrogen.  That conspiracy theory website said a lot of weird and wacky things, but this hydrogen-breathing alien idea… based on what I know about chemistry, that idea kind of made sense to me.

You see we Earthlings use oxygen to oxidize our food.  This oxidation reaction generates the energy we need to stay alive.  But oxidation reactions are sort of equal-and-opposite to reduction reactions.  Oxygen is a powerful oxidizing agent, obviously, but hydrogen?  Hydrogen is a pretty effective reducing agent.

A paper published earlier this year examined the possibility of Earth-like planets with hydrogen-rich atmospheres.  Such planets could, in theory, exist, but they’d have to meet one or more of the following criteria:

  • The planet would have to be much colder than Earth (think Titan or Pluto-like temperatures).
  • The planet would have to have much higher surface gravity than Earth.
  • The planet would have to continuously outgas hydrogen from some underground source (subsurface reservoirs of water ice mixed with methane ice might do the trick).

If one or more of these conditions are not met, then a hydrogen-rich atmosphere would quickly fizzle out into space through a process called Jeans escape.

Now, could life exist in that sort of hydrogen-rich environment?  The answer is yes.  Absolutely yes.  Even here on Earth, there are organisms that “breathe” hydrogen and use it to generate energy through reduction reactions.  These organisms can be found deep underground, or clustered around deep-sea hydrothermal vents, or in other exotic niche environments where hydrogen is plentiful and oxygen is rare.

The real question is: could hydrogen-breathers evolve into complex, multicellular life forms?  Earth’s hydrogen-breathers are mere microorganisms.  Their version of respiration is nowhere near as efficient as the oxygen-based system we humans and our animal friends use.  The inefficiency of hydrogen-based respiration has stunted the evolutionary development of Earthly hydrogen-breathers.

But maybe on another planet—a planet with a hydrogen-rich atmosphere unlike anything Earth has ever seen—maybe complex multicellular life could evolve on a planet like that.  Maybe.

It’s plausible enough for science fiction, at least.

Sciency Words: Oxidation

Hello, friends, and welcome back to Sciency Words, a special series here on Planet Pailly where we talk about the definitions and etymologies of scientific terms.  Today on Sciency Words, we’re talking about:


You may think of oxygen as something good and wholesome.  It’s what we breathe.  It gives us life.  How easily you forget all the other things oxygen can do.  It corrodes metals.  It degrades organic materials.  And under the right conditions, oxygen supports and perpetuates combustion reactions (a.k.a. fire).

French chemist Antoine Lavoisier usually gets credit for coining the words oxygen and oxidation.  He was the first to write about the principe oxygine (French for the acidifying principle).  The words oxygen and oxidation appeared soon afterwards in English translations of Lavoisier’s work, so maybe the English translators should get some of the credit too.

Anyway, oxidation originally referred to chemical reactions involving oxygen, specifically.  But then through a process of semantic generalization, the word oxidation came to refer to any chemical reaction similar to the kind of chemical reaction oxygen could cause.  Oxygen is no longer considered a necessary ingredient for oxidation, and some chemicals (i.e.: chlorine and fluorine) have turned out to be better oxidizers than oxygen.

So what actually happens when one chemical substance oxidizes another?  Well, oxygen and other strong oxidizing agents are greedy for electrons.  Oxidation is the act of stealing electrons from another chemical substance.  Or, if outright stealing doesn’t work, then oxidizing agents will try to form chemical bonds that allow them to “share” electrons—but it will be a highly unequal kind of sharing, one that does not favor the atoms that originally owned those electrons.

A whole lot of energy can be released in oxidation reactions.  That’s what makes them so destructive.  However, life on Earth has found ways to control the energy released by oxygen oxidation and put that energy to good use.  That’s why oxygen is generally thought of as something good and wholesome, even though it’s really one of the most dangerous and destructive chemicals in the world.

P.S.: It’s important to remember that whenever an oxidation reaction occurs, a reduction reaction also occurs.  And reduction is another Sciency Word with an interesting history.

Sciency Words: Oxygen

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we take a closer look at the definitions and etymologies of scientific terms.  Today on Sciency Words, we’re talking about:


Earth.  Fire.  Air.  Water.  Only the Avatar can master all four elements.  Only the Avatar… or Antione-Laurent Lavoisier, the 18th Century French chemist.  As described in this article, Lavoisier originally intended to study each of the four elements in turn, starting with air.  But Lavoisier’s air research quickly “bent” the concept of the four elements so hard that the whole concept broke. And thus…

Lavoisier did not discover oxygen, but he did name it.  You see, when oxygen was first discovered in the early 1770’s, it was called “dephlogisticated air.”  That’s a mouthful of a name, but it made perfect sense to anyone who was familiar with the phlogiston theory of combustion.

Now I’m not going to waste your time explaining what phlogiston theory was, except to tell you that it was an updated-for-the-18th-Century version of the theory that fire is an element.  The important thing to know is that Lavoisier’s experiments on dephlogisticated air poked some pretty big holes in phlogiston theory, and so that theory had to be abandoned in favor of “oxygen theory.”

So where did the word oxygen come from?  Let me try to reconstruct Lavoisier’s thought process.  Among other things, Lavoisier found that burning stuff in “dephlogisticated air” tended to produce substances that were more acidic than the original reactants.  “Oxy” is Greek for acid.  So some sort of acid-generating process was occurring… an “oxy-genesis,” if you will.  Or “oxy-gen” for short!

The term Lavoisier actually used was principe oxygéne, meaning “the acidifying principle.”  The words oxygen and oxidation start appearing in English shortly thereafter, thanks mainly to translations of Lavoisier’s work.  But by that point, it was clear that oxygen was more than merely an acid-generating gas.  It had other properties too. Lavoisier demonstrated that oxygen played an important role in both combustion and animal respiration, as well as other natural processes like the rusting of iron.

But we’ll talk more about oxygen’s many abilities in next week’s episode of Sciency Words.

P.S.: Lavoisier also named hydrogen.  Burning “inflammable air” and “dephlogisticated air” together produced water.  “Hydro” is Greek for water.  So some sort of water-generating process was occurring… a “hydro-genesis,” if you will.  Or “hydro-gen” for short!

P.P.S.: And since you can make water by mixing two different kinds of air, water must not be an element.  Also, how can air truly be an element if there are different kinds of air? This whole four elements thing fell apart pretty quickly as Lavoisier continued his research.

Sciency Words A to Z: Oxygen Catastrophe

Welcome to a special A to Z Challenge edition of Sciency Words!  Sciency Words is an ongoing series here on Planet Pailly about the definitions and etymologies of science or science-related terms.  In today’s post, O is for:


Oxygen.  What could be more healthy or more wholesome to life than oxygen?  But oxygen is, in fact, one of the most dangerous and deadly chemicals on Earth.  It is, as you might easily guess, a powerful oxidizer, and it reacts with just about everything—especially organic matter!

True, life on Earth as we currently know it would not be possible without oxygen, but left to its own devices oxygen would eagerly burn us all up.

It started with cyanobacteria (also known as blue-green algae).  Cyanobacteria were the first organisms on this planet to develop photosynthesis, a process that uses sunlight to convert water and carbon dioxide into biomolecules.  But photosynthesis also produces hazardous oxygen as a waste product.

Things were okay for Earth’s biosphere for a while, but eventually the oxygen situation turned deadly.  As David Grinspoon explains in his book Earth in Human Hands:

For hundreds of millions of years, the cyanobacteria kept spitting out oxygen, but all the excess was hungrily snapped up by the abundant iron in Earth’s crust and interior.  Yet eventually, around 2.4 billion years ago, the crust was thoroughly oxidized and there was no more available iron lying around.

Grinspoon goes on to explain how life would eventually learn to protect itself from the harmful effects of oxygen exposure and even learn to control oxygen, transforming what was (and still is, in some respects) a deadly poison into a valuable and powerful new fuel.

Before we evolved that ability, however, the buildup of corrosive oxygen in the atmosphere was massively fatal for most of the species that existed on Earth at the time.

This event, approximately 2.4 billion years ago, is generally known as the Great Oxidation Event, but it’s also sometimes called the Oxygen Catastrophe.  I prefer calling it the Oxygen Catastrophe, because the consequences were truly catastrophic for almost everyone who was not a cyanobacteria. This was, in fact, Earth’s first mass extinction event.

As we continue our search for alien life, I think it’s important to keep oxygen’s true nature in mind.  To us, oxygen means life, but it could just as easily be seen as a deadly poison.  There may be other worlds out there with “poisonous” atmospheres, and those worlds may turn out to be the ones we should pay the most attention to.

Next time on Sciency Words A to Z, what if life on Earth started somewhere else?