Okay, I Googled organic molecules to see if I could identify one that might really excite a NASA scientist. Obviously, it would have to be one that is associated with living organisms, and not just any old compound that happened to contain carbon.
Maybe I'm wrong about that and maybe they would flip out if they found a carbon compound on the surface, but it sure would be an anticlimactic announcement for the rest of us. Besides, they already know carbon is there; for instance, carbon dioxide makes up most of the Martian atmosphere and does not have to originate with life. No, it has to have something to do with life, imho.
Organic molecules found in living organisms fall into one of four major categories: carbohydrates, lipids, proteins and nucleic acids. Astronomers long ago identified carbohydrates and proteins in interstellar clouds of gas and dust, so it seems that's not too likely to excite them if they also find them on Mars. OTOH, nucleic acids (DNA and RNA)seem almost too good of a discovery to be true as I think that would point directly to life on Mars. So... I'm guessing they've found some kind of fat molecule.
That is a good analysis, but also consider that the instrument in question bakes the samples at 1800F before measuring. Molecules like methane are broken up at that temperature, and I doubt anything like DNA would survive intact. On earth, that temperature is used for dissociation on methane as a feedstock chemical for manufacturing other chemicals, like ammonia. So, they are only going to detect some base molecules and atomic signatures, but those signatures may be in the proportions that point to things like methane or other organics.