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In the absence of an ozone layer during Earth's early days, this process, known as photolysis, would have quickly purged sulfur compounds from the atmosphere and the water, albeit not quite as efficiently as the abundant oxygen in today's world.

While it's plausible that slow disproportionation could have allowed sulfites to accumulate, photolysis would have made that very unlikely except in certain environments such as shallow water pools, shaded from UV radiation, particularly if fed by surface runoff to provide mineral shields.

"Even otherwise very stable solvents can be attacked by the superphotooxidant when excited by LED light," emphasized Dr. Nathan East, who prepared the new complex and performed all photolysis experiments during his PhD in the group of Professor Katja Heinze.

This process would have been self- limiting, as Urey showed, since the wave lengths needed for photolysis are the very ones screened out selectively by oxygen; the production of oxygen would have been cut off almost as soon as it occurred.

As a result, he says, the clouds inside are more susceptible to UV photolysis.