‘What oxygen is to the lungs, such is the hope to the meaning of life.’
This is what Emil Brunner, a Swiss theologian, once wrote in his book Eternal Hope.
What the guy really meant to say is that oxygen is the hope to finding life beyond Earth.
Oxygen is seen as one of the key ingredients to life on the blue marble as most oxygen is produced by living organisms.
But scientists have discovered a new way for oxygen to form on planets with atmospheres thick with carbon dioxide without the need for critters.
Researchers told Space.com how they looked for novel ways for molecular oxygen to form by smashing CO2 with helium.
This way of making oxygen is called an ‘abiotic’ process, or one that doesn’t involve living creatures.
The filling of Earth’s skies with oxygen, roughly 2.1 to 2.4 billion years ago, has long been one of history’s biggest mysteries. Before what geologists call the Great Oxidation Event, most of Earth was filled with that stinky greenhouse gas CO2.
There was a whiff of oxygen in the air after ancient microbes floating in the ocean evolved the ability to carry out photosynthesis, however. After nibbling on sunlight, they gave off oxygen.
Most of this oxygen didn’t last that long. With all the volcanoes bubbling at the time, hydrogen would gobble most of it up.
But after a few hundred million years, the Earth began to cool, giving a chance for our weirdly oxygen-rich atmosphere to form.
Shan Xi Tian and and Jie Hu at the University of Science and Technology of China decided to look at how the helium made by solar wind interacting with a planet’s atmosphere could make oxygen.
During this interaction, the helium makes ions – charged particles that act like wrecking balls to CO2, smashing it into other molecules.
‘This reaction should be observed in the upper atmosphere of Mars because lots of He+ ions (due to solar winds) and CO2 exist there,’ said Hu.
But while O+, O2+, and CO2+ are made, O2 isn’t, at least on the red planet.
So Tian and Hu used three techniques in their tool belt to test their idea.
The first is time-of-flight (TOF) mass spectrometry, where particles are ionised and sped up to have the same kinetic energy. How long it takes for them to travel the same distance is used to find their mass.
The pair then used a ‘crossed-beam apparatus’, which can smash two molecules together, and ‘ion velocity maps’ to record the trajectories and velocities of ions.
‘We found a distinctly different pathway to produce O2 from molecular CO2,’ Tian said. ‘Namely, through the reaction of helium ions [He+] with CO2.’
In other, far less complicated terms, Tian and Hu’s study found that there’s a chance life-sustaining oxygen can form on planets with CO2-rich atmospheres where living beings haven’t formed yet.
David Benoit, a senior lecturer in Molecular Physics and Astrochemistry at the University of Hull’s EA Milne Centre for Astrophysics, now says the search is on for planets where this could realistically be happening.
‘This new mechanism will likely be incorporated into future models used to predict the atmospheres of other planets,’ Benoit told Space.com, ‘and will help us better explain the quantities of oxygen we might find there.’
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