Abstract. Trace gases and their isotopic ratios in planetary atmospheres offer important but subtle clues as to the origins of a planet's atmosphere, hydrology, geology, and potential for biology. Calculations show that an orbiting laser remote sensing instrument is capable of measuring trace gases on a global scale with unprecedented accuracy, and higher spatial resolution that can be obtained by passive instruments. Our proposed lidar uses Integrated Path Differential Absorption technique, Optical Parametric Amplifiers, and a receiver with high sensitivity detector at 1.65 μm to map methane concentrations, a strong greenhouse gas. For Mars we can use the same technique in the 3–4 μm spectral range to map various biogenic gas concentrations and search for the existence of life. Preliminary results demonstrating methane and water vapour detection using a laboratory prototype illustrate the viability of the technique.