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Project Progress

NAI support has contributed to the development of a center for mass spectrometer development at UH, with systems under development for chemical measurements using electron impact (for gases), electrospray (liquids), laser ablation resonance ionization (isotope and elemental abundance in solids), and secondary ionization (a standard for geochemical assays). These instruments will allow us to assess the potential of a habitat to support life and search directly for biomarkers, as well as determine the age of materials these compounds are found in. In addition, we are preparing to propose a new cycloidal mass spectrometer to PIDDP, in combination with an ASTEP proposal, in order to study the fractionation of hydrogen and deuterium, as well as ¹⁶O and ¹⁸O, in water. This system will be used in deep drill holes and contribute to constraining the true isotopic composition of primitive water on Earth and in the solar system.

Work to date has focused on the development of a nano-electrospray rotating field mass spectrometer (ESI-RFMS) to study heavy compounds commonly associated with life in water directly. The mass spectrometer is <5' in size, is optimized for detecting heavy organic molecules (50-500K Da), can withstand ballistic emplacement (currently demonstrated to 1200g), operates at pressures as high as several milliTorr, and has simple electronics. These traits make the instrument uniquely relevant for astrobiology applications such as the detection of key organic biomarkers derived from cellular components as well as geochemical environmental characterization on wet or icy bodies throughout the solar system. The ionizer uses a modified electrospray introduced directly to vacuum, and the spectrometer operates as a momentum filter using rotating RF fields applied to four poles.

The ESI ion source has now been extensively tested in a wide variety of vacuum conditions and with a wide variety of sample delivery pressures, as well as under a range of electrical conditions and sample chemistries. We have also tested the RFMS mass filter using an off-the-shelf electron impact (EI) gas ionizer (Fig. 1), which demonstrated the new concepts of RFMS mass filtering (Fig. 2) and ion beam control, as well as significant advances in noise reduction. Finally, all of the hardware has evolved significantly from the initial designs (Fig. 3). A critical issue that evolved from this work is the importance of a well focused beam of ions in this type of spectrometer versus other similar but less capable spectrometers like the standard quadrupole. Our initial tests show that both the ESI and EI ionizers significantly deviate from a beam (Fig. 4), which we have begun to address using Einzel lenses (Fig. 5, 6) and mesh apertures.

ESI-RFMS characteristics are currently undergoing extensive characterization in our laboratory test stand developed in part through support of the NAI. The other mass spectrometers mentioned here will be installed in a second new laboratory being built at UH to support this program. We have leveraged NAI funding with both NASA Mars Instrument Development (MIDP), Planetary Instrument Design and Development (PIDDP), NSF Information & Intelligent Systems (IIS), ONR, & DIA Measurement and Signals Intelligence (MASINT) funds. We have presented our results at numerous conferences, including the American Geophysical Union Fall Conference, and the BioAstronomy Conference. We have nearly completed characterization the electrospray ionizer during the first year of effort, and that in year two we will begin calibration efforts. In later years we plan to test this system in lacustrine and icy environments.

In summary, we anticipate using the ESI-RFMS, as well as the other mass spectrometers spawned by this effort, to aid in searching for and identifying the signatures of life, both on Earth, and potentially on future robotic missions throughout the solar system.

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