In situ resource utilization (ISRU) is essential for several of NASA's future flagship missions. Currently envisioned ISRU plants include production of oxygen from hydrogen reduction of lunar regolith and extraction of water from Martian regolith or asteroid material. These ISRU processes require heating of the regolith to high reaction temperatures. To support ISRU activities, NASA requires the development of a compact, lightweight gas chromatograph mass spectrometer (GC-MS) instrument that can quantify volatile gases released by sample heating below atomic number 70. The instrument must also be designed to withstand exposure to the release of HF, HCl, or Hg that may result from heating regolith samples to high temperatures. Creare proposes to design, build, and test a compact, lightweight gas chromatograph - mass spectrometer (GC-MS) system, capable of detecting, identifying, and quantifying ppm to 100%-level concentrations of relevant compounds having mass less than 100 amu. Our GC-MS design is based on components that have been previously or can easily be space-qualified using techniques proven on numerous past space hardware development projects. During the Phase I project, we will prove our design with benchtop testing, and in Phase II, we plan to build engineering model versions of our GC-MS.