  We have searched for the presence of simple P and S-bearing molecules in
Titan's atmosphere, by looking for the characteristic signatures of phosphine
and hydrogen sulfide in infrared spectra obtained by Cassini CIRS. As a result
we have placed the first upper limits on the stratospheric abundances, which
are 1 ppb (PH3) and 330 ppb (H2S), at the 2-sigma significance level.
