SEAL will begin taking measurements as the lander enters orbit about the Moon and throughout its descent to the surface. The spectrometer will measure the gas that gets released by the lander’s propulsion system into the Moon’s atmosphere, which is called an exosphere.After touching down, SEAL will sniff out the engine exhaust molecules that will have made it to the Moon’s surface. Among the molecules of interest for SEAL are water and carbon dioxide, which the team expects will diffuse into the atmosphere as the surface gets heated by the Sun. The team will pay special attention to which molecules get stuck in the lunar soil and which break free and drift above the surface, possibly to different parts of the Moon, such as the poles. This will help scientists determine how temperature affects molecules on the Moon that can easily evaporate, known as volatile molecules. Ultimately, this will provide insight into the stability of water, a critical resource for exploration.