This project will lead to a small portable sensor for use in isotope hydrology. Water isotope data provide information about past and present global climate and the global water cycle on Earth. They allow mapping of aquifers, conserving water supplies and trace transport and dispersion of contaminants in the subsurface. The fully-developed prototype instruments shall offer a compelling and desirable blend of compactness, performance, affordability, simplicity and ease-of-use relative to present commercial product offerings in these applications. Beyond these applications, the developed sensor platform will be broadly deployable for trace gas detection of a variety of molecules with a cost-effective, small device. Examples include contaminant monitoring in process gas streams in the chemical and microelectronics industries, medical diagnosis through detection of biogenic gases in human breath that correlate to specific pathologies, and environmental monitoring and regulatory compliance in agriculture, power production, and occupational safety. The targeted NASA applications are analyzing water samples on the Moon as well as on other planets. The emerging technology is adaptable to changing pressure conditions and suitable to operate in diverse environments, including corrosive atmospheres. The developed technology can be extended to selectively detect trace gas species for NASA relevant applications such as contaminant sensing in air revitalization and water recovery processes, and atmospheric composition monitoring.