A parameter of importance in various industrial and commercial applications is sensitivity to moisture. A new class of molecular sensors which enable the qualitative and quantitative determination of air moisture (high selectivity and sensitivity) by application of Mössbauer spectroscopy as the probe technique has been investigated. The electronic properties of the iron-containing sensor depend upon the presence of moisture which is taken up by it and this process is accompanied by a change in electronic spin ground state which can be detected by Mössbauer spectroscopy. The sensor is suitable for in-field and industrial application using the recently developed Mössbauer spectrometer MIMOS II. Possible suitability for the detection of moisture in extraterrestrial environments is considered.