APXS and MIMOS IIA: Planetary and terrestrial applications

Alpha particle X-ray spectrometer (APXS) is one of the payloads of Chang'E-3 lunar rover of China's Lunar Exploration Project. The present paper introduces briefly the components of APXS, how it works and its working environment on the lunar surface. The environmental temperature effect has been studied with simulations and experiments, and the results show that the temperature of the APXS sensor will be varying during the measuring on the lunar surface. And another experiment reveals that the energy resolution becomes worse if the sensor's temperature is varying. In this paper, a correction method based on Pearson's chi-squared test is presented. The method can improve the energy resolution when the sensor's temperature is varying. We have tested the method with the spectra acquired by APXS in the temperature varying period of Temperature Cycling Test, and the results show that the method is efficient and reliable.

Ground calibration of Alpha Particle X-ray Spectrometer (APXS) on-board Chandrayaan-2 Pragyaan rover: An empirical approach

Mars Pathfinder project progress report

Alpha Particle X‐ray spectrometer (APXS) analyses of the distinct Amapari Marker Band (AMB), Gale crater, Mars reveal the highest, in situ, FeO and Zn abundances (47.51, 2.23 wt%), and elevated MnO associated with a lower rippled unit. APXS analyses also reveal a marked shift in provenance, to a generally basaltic composition, compared to the underlying Mg‐sulfate‐bearing strata, which persists into the overlying stratigraphy. The AMB also records perturbation in the MgSO 4 ‐forming conditions present above and below. AMB chemistry could be consistent with a volcanic ash source; high metal concentrations resulting from volatile reactions within an ash cloud. Alternatively, syn‐ and/or post‐depositional precipitation processes within a primary lake setting and/or a later diagenetic event or events may have played a role. Ongoing and future work will aim to further constrain processes responsible for deposition of the AMB, the high metal concentrations and its regional and global implications.

X-ray fluorescence (XRF) spectroscopy has long served as a cornerstone analytical technique in planetary surface exploration, enabling high-precision compositional analyses of planetary materials in situ. On Mars, two prominent XRF instruments — the Alpha Particle X-ray Spectrometer (APXS) aboard Curiosity and the Planetary Instrument for X-ray Lithochemistry (PIXL) aboard Perseverance — have demonstrated that the capabilities of landed XRF instruments extend beyond the quantification of bulk chemistry. Native Sulfur on MarsAPXS has performed ~1700 compositional analyses since Curiosity landed in Gale crater in 2012. While APXS traditionally derives bulk rock and soil compositions, systematic advancements have been made that enable the assessment of distinct features on the sub-cm scale, smaller than the APXS field of view (e.g., [1]). This advancement, combined with the capability to characterize light‑element (i.e., Z

The Alpha Particle X-ray Spectrometer on the Opportunity rover determined major and minor elements of soils and rocks in Meridiani Planum. Chemical compositions differentiate between basaltic rocks, evaporite-rich rocks, basaltic soils, and hematite-rich soils. Although soils are compositionally similar to those at previous landing sites, differences in iron and some minor element concentrations signify the addition of local components. Rocky outcrops are rich in sulfur and variably enriched in bromine relative to chlorine. The interaction with water in the past is indicated by the chemical features in rocks and soils at this site.

Calibration of the Curiosity Rover's alpha particle X‐ray spectrometer (APXS) was accomplished using geochemical reference materials and a fundamental parameters treatment of the X‐ray fluorescence and particle‐induced X‐ray emission (PIXE) excitation processes. For most major and minor elements the influence of different rock types was not significant. For the three light elements, Na, Mg, and Al, which are excited almost entirely by PIXE, systematic differences among felsic and mafic rocks were observed. A qualitative explanation is found in the very shallow interrogation depth (a few microns), which suggests that the X‐rays of these elements must emerge from a single mineral rather than an assumed average over the various minerals present. A quantitative explanation was sought by determining the mineralogy of several reference materials and computing their expected PIXE X‐ray yields with an adaptation of the yield prediction sub‐routine GUYLS in the Guelph PIXE software package GUPIX. The complexity of assigning the certified overall element mass fractions to specific minerals limited this exercise to cases with only a few minerals present. Good agreement was found between the X‐ray yields determined in the calibration exercise and those predicted in this new approach. It is expected that automation of the computational approach may enable examination of mineralogically more complex reference materials. This might also offer a means of coupling results from the X‐ray diffraction and APXS instruments on Mars. Copyright © 2014 John Wiley & Sons, Ltd.

The subsurface chlorine depth distribution at Gale crater has been studied using measurements from the Alpha Particle X‐ray Spectrometer (APXS) and Dynamic Albedo of Neutrons (DAN) instruments onboard NASA's Curiosity Mars rover. These measurements have been acquired at or near ∼30 drill holes made by Curiosity along its 30 km drive. APXS measured a ∼15 micron surface layer of bedrock and shallow depth of ∼5 cm of drill tailings. DAN is sensitive to the bulk (∼50 cm depth) chlorine abundance and that of other neutron absorbing elements. Joint analysis of APXS and DAN data shows that the chlorine distribution at Gale crater consists of two components: surficial chlorine with concentrations >1 wt.%, possibly controlled by aeolian deposition of Cl‐rich dust and surface alteration, and subsurface chlorine with concentrations <1 wt.%, likely a result of groundwater activity in the past.

This paper presents the work carrie dout in support of Silicon Drift Detector (SDD) characterization for the Chandrayaan-2 instruments namely Solar X-ray Monitor (XSM) and Alpha Particle X-ray Spectrometer (APXS). The XSM and APXS instruments use SDD to detect X-rays from the Sun and fluorescent X-rays from the lunar surface respectively. The aim of this study is to understand and quantify any spectroscopic performance degradation of these X-ray spectrometers due to space radiation in the SDD during its operational period. Any radiation damage to the SDD leads to increase in the detector leakage current and thus degrades the spectroscopic performance, mainly the energy resolution. The expected end-of-life (EOL) 10 MeV equivalent proton fluence was modeled using SPENVIS simulation software. The Silicon Drift Detector was irradiated with 10 MeV protons for the doses up to 24 krad in logarithmic steps and measured the energy resolution and the leakage current at each dose. The spectrometer energy resolution degraded from ∼ 142 eV at 5.9 keV to ∼ 250 eV for the cumulative proton dose of ∼ 11 krad for the mission life of one year. This satisfies the performance requirement of the SDD based X-ray spectrometers onboard Chandrayaan-2 mission.

Curiosity has four instruments that study the chemistry of Martian materials. Two of them focus on elemental abundances. ChemCam is a remote sensing instrument, able to detect the elemental composition of a rock or soil from a distance of up to 7 meters by shooting it with a laser, a technique deployed in space for the first time on Curiosity. The Alpha Particle X-Ray Spectrometer (APXS) is a contact science instrument to examine the compositions of rocks and soils reached by the arm, and has a long Martian heritage.

The Mars Surveyor 2001 Lander will carry with it both a Robotic Arm and Rover to support various science and technology experiments. The Marie Curie Rover, the twin sister to Sojourner Truth, is expected to explore the surface of Mars in early 2002. Scientific investigations to determine the elemental composition of surface rocks and soil using the Alpha Proton X-Ray Spectrometer (APXS) will be conducted along with several technology experiments including the Mars Experiment on Electrostatic Charging (MEEC) and the Wheel Abrasion Experiment (WAE). The Rover will follow uplinked operational sequences each day, but will be capable of autonomous reactions to the unpredictable features of the Martian environment. The Mars Surveyor 2001 Robotic Arm will perform rover deployment, and support various positioning digging, and sample acquiring functions for MECA (Mars Environmental Compatibility Assessment) and Mossbauer Spectrometer experiments. The Robotic Arm will also collect its own sensor data for engineering data analysis. The Robotic Arm Camera (RAC) mounted on the forearm of the Robotic Arm will capture various images with a wide range of focal length adjustment during scientific experiments and rover deployment.

The resistant ~50 m thick Vera Rubin ridge (VRR) situated near the base of Mount Sharp, Gale crater, Mars, has been deemed a high priority science target for the Mars Science Laboratory mission. This is because of (1) its position at the base of the 5 km layered strata of Mount Sharp and (2) the detection of hematite from orbit, indicating that it could be the site of enhanced oxidation. The compositional data acquired by the Alpha Particle X‐ray Spectrometer (APXS) during Curiosity's exploration of VRR help to elucidate questions pertaining to the formation of the ridge. APXS analyses indicate that VRR falls within the compositional range of underlying lacustrine mudstones, consistent with a continuation of that depositional environment and derivation from a similar provenance. Lower Fe concentrations for VRR compared to the underlying strata discounts the addition of large amounts of hematite to the strata, either as cement or as detrital input. Compositional trends are associated with VRR cross‐cut stratigraphy, indicating postdepositional processes. Higher Si and Al and lower Ti, Fe, and Mn than the underlying mudstone, particularly within distinct patches of gray/blue bedrock, are consistent with the addition of Si and Al. Lateral and vertical compositional variations suggest enhanced element mobility and fluid flow (possibly via multiple events) through VRR, increasing toward the top of the ridge, consistent with the action of warm (~50–100°C), locally acidic saline fluids as inferred from the mineralogy of drilled samples.

A major mission goal for the Mars Science Laboratory’s rover, Curiosity , is to investigate the transition from clay‐bearing to hydrated‐Mg‐sulfate‐bearing sedimentary strata hypothesized to record a transition from a wet to a dry paleoclimate. Alpha Particle X‐ray Spectrometer (APXS) results from this region, named the Clay‐Sulfate Transition (CST), indicate an overall ∼5% increase in Ca‐sulfate, but Mg‐sulfate enrichment is limited to diagenetic nodules. Sulfates in the CST change sharply at the contact with the overlying Mg‐sulfate unit, which has ∼5% Ca‐sulfate and ∼10% Mg‐sulfate in the bedrock matrix. Despite this change in sulfate assemblage, and the transition from fluvial‐lacustrine to drier aeolian sedimentary deposits, the bulk chemical composition of the aeolian sandstone (sulfate‐free basis) effectively has the same altered basalt chemical fingerprint as the underlying fluvial‐lacustrine mudstone. That is, the composition of rocks that record the transition from a wet to a dry paleoclimate is isochemical. It is remarkable that the aeolian sandstone has the same altered bulk chemical characteristics as the fluvial‐lacustrine mudstone, notwithstanding very different inferred geochemical regimes. We propose a simplified model wherein older basaltic sediment was aqueously altered in a fluvial‐lacustrine regime and reworked, likely during cycles of alteration, salt formation, and reworking. This process led to an averaging of the bulk chemical composition of the Mt. Sharp group sediment, resulting in the isochemical characteristics of the paleoenvironment change.

The alpha proton x-ray spectrometer (APXS) on board the rover of the Mars Pathfinder mission measured the chemical composition of six soils and five rocks at the Ares Vallis landing site. The soil analyses show similarity to those determined by the Viking missions. The analyzed rocks were partially covered by dust but otherwise compositionally similar to each other. They are unexpectedly high in silica and potassium, but low in magnesium compared to martian soils and martian meteorites. The analyzed rocks are similar in composition to terrestrial andesites and close to the mean composition of Earth's crust. Addition of a mafic component and reaction products of volcanic gases to the local rock material is necessary to explain the soil composition.

Low cost approach to Mars Pathfinder