The results of NASA flight tests have verified the suitability of mid-infrared quantum cascade lasers for atmospheric gas measurements. Reporting in the Jan. 20 issue of Applied Optics, project researchers from the Jet Propulsion Laboratory in Pasadena, Calif., and Lucent Technologies' Bell Labs of Murray Hill, N.J., suggest that the lasers will find applications in miniature spectrometers for missions to Mars. In a series of test flights aboard a modified U-2 aircraft in 1999 and 2000, a spectrometer incorporating a cryogenically cooled, 8-µm quantum cascade laser measured atmospheric levels of methane and nitrous oxide. The 10-mW laser enabled the system to detect methane levels as low as two parts per billion.