ASTID

A CRDS for Isotopic Measurement of Martian CH4

PI: Tullis Onstott

To determine the sources and sinks of Martian atmospheric CH4 and whether it is biologically generated or consumed, this project will design, fabricate and test a near-IR, Cavity Ring-down Spectrometer (CRDS) that will satisfy TRL6 requirements for a Mars mission, such as AFL, MSR or mid-size rover. This CRDS will be based upon our currently existing high sensitivity CRDS modified to produce high precision, stable isotope measurements of both 13CH4 and CH3D. The project will also extend the capabilities of this CRDS to enable the isotopic measurements of other Martian atmospheric constituents or gases produced during solid phase analysis by a system like SAM.
Princeton University will fabricate, assemble and test the isotopic capability of this unit in year 1 and 2. GSFC will then perform component and cavity testing including: radiation testing of key components, thermal-vacuum-vibrational testing to assess affects on cavity alignment and testing of the CRDS in the B33 Mars environmental chamber in year 2. Based upon faults identified in the testing stage the instrument will be modified until TRL6 is achieved in year 3. The University of Virginia will modify the current design in year 1 and 2 to increase measurement rates by 500x, thereby increasing precision and sensitivity.
Different CH4 sources do not necessarily produce unique values of 13CH4 OR CH3D, but they do produce unique patterns of 13CH4 AND CH3D. Both must be measured with a precision approaching that of IRMS. Our CRDS has four advantages over the TLS being flown on MSL. First, it is 1000x more sensitive than the TLS. Second, it will provide IRMS quality precision measurements of both 13CH4 and CH3D. Third, it can potentially measure the concentration and isotopic composition of other relevant gases. Fourth, it will do this more rapidly than the TLS and potentially with only one laser.