A team from NASA's Goddard Space Flight Center in Greenbelt, Maryland, is developing a new, third-generation facility science instrument for the Stratospheric Observatory for Infrared Astronomy, SOFIA. The High Resolution Mid-InfrarEd Spectrometer (HIRMES), is a spectrometer optimized to detect neutral atomic oxygen, water, as well as normal and deuterated (or "heavy") hydrogen molecules at infrared wavelengths between 25 and 122 microns (a micron is one-millionth of a meter). These wavelengths are key to determining how water vapor, ice, and oxygen combine at different times during planet formation, and will enable new observations of how these elements combine with dust to form the mass that may one day become a planet. HIRMES will provide scientists with a unique opportunity to study this aspect of planetary formation, as SOFIA is currently the only NASA observatory capable of accessing these mid-infrared wavelengths. Infrared wavelengths between 28 and 112 microns do not reach ground-based telescopes because water vapor and carbon dioxide in the Earth's atmosphere block this energy. SOFIA is able to access this part of the electromagnetic spectrum by flying between 39,000 feet and 45,000 feet, above more than 99 percent of this water vapor.