Laser Ablation-electrodynamic Ion Funnel for in Situ Mass Spectrometry on Mars

NASA has invested a great deal of resources into the development of various instruments for in situ analysis of extraterrestrial bodies. As a result, there currently exists a wealth of instrumentation suitable for detailed in situ analytical investigation. One common characteristic among many of these instruments is that they require extensive sample handling in order to extract and ionize atoms and/or molecules, before interrogation by the instrument in question can take place. Instruments falling within this class of analytical technique include time-of-flight and quadrupole ion trap mass spectrometers, quadrupole mass filters, and ion mobility spectrometers. Despite the relative maturity of the fundamental analytical techniques and instrumenta-tion, there exists a conspicuous lack of investigation into the details surrounding the sample manipulation and preparation required by such instruments. This situation is particularly troubling given that applicable practices, used commonly in terrestrial laboratories, do not readily lend themselves to robotic execution. We will address this issue by developing a front-end instrument to extract, ionize and inject samples into a mass spectrometer with no prior sample preparation. A promising means of reducing the complexity of the sample handling required by instruments such as those discussed above is to employ laser ablation ioni-zation. Laser ablation is a very attractive technique for in situ ionization of rock and soil samples since a laser is able to sample the surface of a rock or soil with minimal manipulation of the sample and no sample preparation. As such, the utility of laser ablation ioni-zation for space applications has been considered previously [1,2]. However, despite the potential benefits of laser ablation ionization, there are major issues with the two scenarios for its implementation in an in situ Martian experiment that are possible with existing in-strumentation. One possible scenario is to perform the ablation on a sample in Martian atmosphere and then transport the ions into the high vacuum of a mass spectrometer. The problem with this scenario is that traditional ion transportation and focusing devices do not function in this pressure regime (~ 5 Torr) due to collisions between the ions and the ambient gas. As a case in point, terrestrial instruments using atmospheric ioni-zation techniques typically suffer ion losses as high as three orders of magnitude over the 0.1-10 Torr region of a primary pumping stage. The second scenario is to bring the sample within the high vacuum chamber, and evacuate the chamber before ablation and analysis. When …