The aim, essentially, is to start from oxygen gas and split its nucleus into its starting ingredients: an alpha particle and a carbon-12
"So when the ratio of carbon-12
to carbon-13 decreases, it indicates the presence of the kind of bacteria we are looking for," said Haggblom.
* By comparing the ratio of carbon-12
to carbon-13, "We can conclude that there is no active biota on Titan," says Bruno Bezard (University of Paris).
Carbon-14 (which chemically reacts like the much more common and stable carbon-12
and carbon-13) combines with oxygen to form carbon dioxide, and is taken up by plants in photosynthesis.
Living things tend to have a preference for the carbon-12
isotope in their make-up.
Also, the reaction of atmospheric methane with hydroxyl favours the lighter isotope (carbon-12
Eventually, the commonest isotope of carbon, carbon-12
, was accepted as standard, since this would entail less change in the value of atomic weights generally.
General Electric researchers have synthesized isotopically pure diamonds composed almost entirely of carbon-12
atoms that conduct heat 50 percent better than their natural counterparts.
SIMS analyzes the ratio of carbon-13 to carbon-12
isotopes, comparing samples from the alleged fossils with those from empty sections of rock.
Life-forms preferentially stockpile carbon-12
in their cells, so any ancient substance enriched with carbon-12
could have a biological origin.
, an essential element we're all made of, can only form when three alpha particles, or helium-4 nuclei, combine in a very specific way.