Mössbauer studies have been made to evaluate the temperature dependence of lattice distortion in two aerogel-synthesized iron-molybdenum oxides having different atomic ratios Fe:Mo=1:1 and 2:3, but both with a ß-FeMoO4 structure. The experimentally obtained spectra discern three distinctive iron ions, OFe2+, PTFe2+, and O/TFe3+. The subscripts refer to octahedral, pseudotetrahedral, and unresolved octahedral and tetrahedral lattice sites, respectively. As anticipated, only the quadrupole splitting (QS) of both ferrous ions shows a measurable dependence on temperature. However, the remarkable sensitivity of the PTFe2+ QS indicates a temperature induced asymmetric lattice distortion on the pseudotetrahedral sites.