The problem of age determination of fire based on wood charcoal has been mentioned earlier (Payette & Lajeunesse 1980) and described in more detail recently (Gavin 2001). (rstb.royalsocietypublishing.org)
Using the naturally occurring uranium - lead isotope decay system, which is used for age determinations on geological time - scales, the authors deduced that these events took place at least 3.02 billion years ago. (sciencedaily.com)
Findings from the first such experiment on the Red Planet — published by Farley and coworkers this week in a collection of Curiosity papers in the journal Science Express — provide the first age determinations performed on another planet. (sciencedaily.com)