The stepped combustion experiment which converts organic carbon
to carbon dioxide can reveal differences in isotopic composition
between biotic and abiotic forms of the element. Biological
processes preferentially use the lighter of the two stable isotopes
of carbon 12C and 13C. The ratio of the
two stable isotopes (isotope scientists use the term "delta
13C" to describe differences in the ratio) can give a clue
to the type of life processes (eg. photosynthesis, methanogenesis)
which have resulted in the fractionation.
Stepped combustion data from ALH 84001,106 with corresponding isotope measurements
The diagram shows a stepped combustion plot and the values of the stable isotope ratios measured at the temperature step added (solid line).
