Back in 2024, on a drizzly summer day, an email landed in my inbox.
It was a tip-off about a new study that was about to be published in a big journal.
I'm a science journalist.
I get sent lots of new research every week.
But the subject line grabbed me.
It said, evidence of dark oxygen production at the abyssal sea floor.
So I opened it and read an extraordinary claim.
Oxygen had been discovered two and a half miles down, produced at the bottom of the Pacific Ocean, in complete darkness.
In a place where it couldn't possibly be made.
School science textbooks tell us that oxygen's made by plants in sunlight,
and there 's no sunlight at the seabed 4,000 metres down.
So this was a tantalising claim.
If true, it could upend hundreds of years of scientific knowledge,
everything we know about how oxygen, that vital ingredient for life, is made.
So I reported on it, as did much of the world's media.
Scientists say they've discovered a source of oxygen deep in the Pacific Ocean that they never knew existed.
About half of the oxygen in the air we breathe comes from the seas,
and until now is thought to be made exclusively by marine plants using sunlight.
But a year and a half on, some scientists have serious doubts, and I still have so many questions.
Top of that list?