Friday was the fifth and last day of the gigantic Fall Meeting of the American Geophysical Union, which once again broke last year's record with 23,000 geoscientists attending. It always sort of peters out at the end of the last day, with no closing ceremony (of course there's no opening ceremony either). But when I left at 4:04 p.m. the poster sessions were still going strong. When things are really busy, the room starts sounding like the crowd at a big football game, and maybe that's just the sound that several thousand excited people make wherever they are.
I enjoyed the session I attended in the morning, which surveyed the state of the science around the rise of oxygen in Earth's atmosphere during Archean time, before 2.5 billion years ago. I seek these sessions out to be informed of the current frontier. But this was one of those "everything you know is wrong" sessions instead, with the eminent speakers casting doubt on some of the basic things we thought we knew about the period. We can't definitively say that the planet was totally oxygen-free. We can't tell when the oldest, most primitive form of bacterial photosynthesis (which does not generate oxygen) was joined by the oxygen-generating photosynthesis of the cyanobacteria. Most of us now assume that the whole mantle is convecting, but that's not definitively known either. The story that uranium geochemistry tells is still confusing. We just have to keep gnawing at the problem. When scientists are baffled, in that newspaper cliché, they really are happy. And after approximately 30 years of attending this event, I'm still eager to come back next year.