Developing a JPL Planetary Mass Spectrometer

The overarching objectives of the strategic research and technology development (SRTD) initiative are to: mature the Technology Readiness Level (TRL) of the JPL quadrupole ion trap mass spectrometer (QITMS) and supporting sub-assemblies to TRL 6 by the end of FY17; submit competitive proposals to the NASA ROSES Maturation of Instruments for Solar System Exploration (MatISSE) Announcement of Opportunities (AOs); and win a JPL MS on a planetary mission within the next decade.

Maturation of a MS for In-Situ Venus Atmospheric Descent Probe Mission Concept:  Under SRTD funding, the JPL QITMS met its goal of being packaged and validated through testing, into a prototype TRL 5 instrument for future Venus atmospheric probe mission concepts.  We’ve demonstrated the MS operational capability to selectively trap species, enabling trace species abundance measurements by excluding the major constituent species of terrestrial atmosphere.  This ability would be used in a Venus experiment to exclude the CO₂ and N₂ species, enabling measurements of trace sulfur-cycle species (e.g. SO₂ and H₂S).  We have also demonstrated the ability to measure the light elemental isotopes of ³²S and ³⁴S from SO₂ in a Venus atmospheric sample. 

Maturation of a MS for Cupid’s Arrow-type Atmospheric Probe Mission Concept:  The Cupid’s Arrow (CA) concept has been developed as a novel low-cost atmospheric probe for orbiter/flyby missions.  CA is a small cubesat-sized spacecraft, containing the JPL MS, that is assumed to be deployed by the main spacecraft, coasts to the planet, dips into the atmosphere, and acquires a trapped volume of atmospheric gases which are then analyzed by the MS.  For Venus, the simple low-cost CA concept would measure the noble gas abundances and isotopic ratios, answering the top four Venus decadal survey questions.  We have demonstrated the ability to measure very small (<10^-8 torr) quantities of noble gases without consumption.  The non-consumption of species is important as this enables a very small quantity of atmospheric gas to be acquired and simply perform measurements until the required statistical accuracies are achieved.

Maturation of a MS-based Instrument for a Europa Lander Mission Concept:  The liquid-based separation technique of capillary electrophoresis (CE), coupled with the most powerful organic detection and characterization technique, mass spectrometry (MS), overcomes the limitations of gas-phase techniques and holds unique promise in the search for signatures of life on ocean worlds such as Europa.  As such, JPL has targeted a CE-MS system for the Europa Lander instrument AO expected in 2018.   Under STRD funding the primary subsystems for the CE-MS system (Sample Handling (SH), CE, and MS) started the design and maturation necessary to meet this opportunity.  During the 2016 SRTD effort the technology readiness level (TRL) of the SH, CE, and MS subsystems advanced from 2/3 to 3/4.   Significant advancements were made in the SH and MS subsystems, where prototype TRL 4/5 hardware devices were designed and are currently under integrated and test. An upgraded TRL 5 Revision 2 of the MS electronics were fabricated for CEMS, sufficient for thermal-vac testing which will occur in FY17. A TRL 4 benchtop MS system was also integrated to start work on interfacing the CE electrospray ionization source to the ion trap MS.   For the CE subsystem, primary proof-of-concept measurements were performed to validate a CE system could be employed for the Europa mission concept.  Specifically, under SRTD funding it was successfully demonstrated that: 1) The required analysis of amino acids in the presence of high salt concentrations can be performed by the CE.  2) That a candidate CE + electrospray ionization source, from SCIEX Inc., meets the analytical requirements for amino acid analysis. 3)  Initial designs of an integrated CEMS instrument were completed. At the lowest salt concentration studied (0.3 M), it was possible to analyze the amino acid mixture with both types of injection. It is important to mention that the concentration of amino acids was only 5 nM, so the sample contained 6x10⁴ times the concentration of salt in the sample compared to the amino acids and still it didn’t hinder their detection. In both cases there are changes in peak shape due to difference in ionic strength between the sample plug and the separation buffer.  For electrokinetic injection we observe an increase in response for some amino acids. This is most likely due to a stacking effect. Even with the highest concentration of sodium chloride we studied (3 M) which corresponds to five times the concentration on Earth oceans we were able to detect all the amino acids in the mixture. We observed that peak shape is better when using pressure injection and it is easier to identify the peaks. These results demonstrate that CE-LIF is not only tolerant to salts, but also, that salts can actually enhance the response of amino acids.