Wife not in the mood? Then read her this tonight:
http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=1&ved=0CC4QFjAA&url=http%3A%2F%2Fwww.ajol.info%2Findex.php%2Ftjs%2Farticle%2Fdownload%2F18344%2F17273&ei=1TOrUqaSC6rxiAeolIGADg&usg=AFQjCNGatD1RB8mKFVrClj1fpAwrpsQ5DQ
A bit of Fission Track Thermochronology should spark her Apatite!