2D XRF for Planetary Exploration
- the identification of environments that have or once had the potential to harbor life (habitability); and
- the detection of morphological or chemical features suggestive of extinct or extant life (biosignatures).
MapX is a first-of-its-kind imaging Alpha Particle X-ray Spectrometer (iAPXS), a full-frame elemental imager capable of analyzing surface regolith in situ without sample preparation. MapX has no moving parts and will utilize 244Cm radioisotope sources, eliminating the complexity and risk of High Voltage Power Supplies and X-ray tubes. Figure 1 shows a schematic of the instrument, which consists of X-ray / γ-ray / α-particle sources, a Micro-Pore Optic (MPO) focusing lens and CCD imager.
Example MapX datasets
Samples were imaged first on an EDAX commercial laboratory instrument (~50 µm resolution), then on MapX-III, a third-generation prototype of MapX (~150 µm resolution). Note: in all figures, X-ray tube sources are used in place of 244Cm. Figure 2 shows a partial MapX-III dataset collected from a quartz sandstone decorated with hematite crystals. Figure 3 shows a partial MapX-III dataset collected from a polished stub of 1.9 Gyr old Gunflint Chert Stromatolite. ROI and XRF spectra returned by MapX-III are sufficient to identify this rock as a chert with preserved carbonates displaying stromatolitic features.
Figure 2. Hematite crystals on quartz sandstone. a). image of sandstone fragment, scale bar = 1 cm; b). RGB elemental image from EDAX commercial instrument, Fe=Red, Si=Green, K=Blue; c). RGB elemental image from MapX prototype, same color scheme as b); d). instrument selected ROI, H = hematite, QS = quartz sandstone; e). XRF spectra from yellow (hematite) and purple (quartz sandstone) ROI.
Figure 3. Precambrian Gunflint Stromatolitic Chert. a). image of thin section, scale bar = 1 cm; b). RGB elemental image from EDAX commercial instrument, Fe=Red, Ca=Green, Si=Blue; c). RGB elemental image from MapX prototype, same color scheme as b); d). instrument selected ROI, C = Chert, FC = Ferroan Carbonate; e). XRF spectra from ROI.
MapX Flight Instrument
Figure 4 shows cut-away and solid 3D views of the MapX camera head, containing the sources, imaging optics, CCD and camera electronics (“Arm Unit”). A second processing unit (“RAMP Unit”) is located in the body of the rover and contains the computer processor, communications and instrument control software. Table 1 shows the proposed mass, volume and power requirements of the instrument as well as survival and operating temperatures.
- . Walroth, R.C. et al. (2019). “MapX: A Full-field X-ray Fluorescence Imager for In-Situ Habitability and Biosignature Investigations.” 9th Intl. Conf. on Mars, abstr. #6329.
- . Fraser, G., et al. (2010). “The mercury imaging X-ray spectrometer (MIXS) on bepicolombo.” Planet. Space Sci. 58 (1-2), 79–95, 2010. https://doi.org/10.1016/j.pss.2009.05.004
- . Walroth, R.C. et al. (2019). “Machine Learning Approaches to Data Reduction from the MapX X-ray Fluorescence Instrument for Detection of Biosignatures and Habitable Planetary Environments.” AbSciCon abstr. #142-177.
- . Lafuente B, et al. (2015). “The power of databases: the RRUFF project.” In: Highlights in Mineralogical Crystallography, T Armbruster and R M Danisi, eds. Berlin, Germany, W. De Gruyter, pp 1-30