It is hard to believe but it was almost 10 years ago that Yuichiro Ueno, now PI at ELSI and professor of Tokyo Tech, presented his work for the first time at Yoshida lab. Back then I was a PhD. student and he was a COE project researcher. (Global COE Program was a Japanese government funded program for establishing "Centers of Excellence" that could be internationally competitive in the fields of education and research.) My masters work was on the field of computational chemistry so I was still struggling to keep up with the stable isotopes jargon and definitions. It was already quite complicated for me to understand the meaning of all these δ values, the notion of enriched and depleted samples and why on earth they just keep using that annoying per mil units? Then the mass independent fractionation (MIF) effect made its appearance, and I was instantly knocked out; I didn't have the slightest clue what this Ueno guy was talking about. Capital delta? And what the Diablo has this to do with this sulfur MIF? Sulfur and its 4 isotopes are already devilish enough to use a Cañon Diablo troilite (CDT) as the standard for sulfur measurements. The situation was not improved by the fact that these stable isotopes were applied to geological records with their fair share of technical names and concepts.

Despite all the difficulties and complexities of trying to follow a talk that was out of one's field, the idea that these isotopes could be used to decipher the atmospheric composition of --I didn't even know then the name of the geological age-- the Archean was simply fascinating to me. In retrospect, I now realize that I was fascinated by something that I had no clue about. Well, I suppose that is how things go for PhD students; we follow our curiosity.

Destiny somehow decided to tie me to the Archean. I started working on the isotopic effects of OCS photodissociation with a theoretical-experimental mix approach when another molecule showed up in the horizon as a great candidate for photodissociation induced isotopic effects; and that was how SO2 made its appearance. It turned out that this molecule was thought to be the source of the isotopic anomaly observed in the geological record and measurements of isotopically enriched SO2 ultraviolet absorption cross section would be key to prove this mechanism. We started doing measurements at the cyclotron at Lund University, and later we continued the measurements at Copenhagen University. It took several years until we managed to get all the samples and the measurements to a level where publishable data was produced. Eventually we succeeded to do the measurements and we were able to show that a single chemical reaction was capable to set an upper limit to the plausible O2 levels in the Archean atmosphere. Further applications of these stable isotopes open up the possibility to solve the faint young sun paradox and find the green-house gas that would solve the puzzle was none other than OCS(!). Our most recent measurements may point in a different direction but the possibility was really entertaining. Regardless of whether a specific isotopic imprint is capable or not of explaining the atmospheric composition of the Archean, we managed to connect geological records to a trace mechanism in the atmosphere.

The question now is: how can we use these techniques to unravel the origin of life? The mechanisms that originated the first forms of life in the planet certainly were adapted to their local environment so by providing information on what sort of atmosphere or what kind of ocean was around when these event took place would be our sand-grain size contribution to ELSI final goal.

Sebastian Danielache's webpage: http://www.seba-ken.com