Recent lunar magnetism

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2011.Cataloged from PDF version of thesis. Page 37 blank.Includes bibliographical references (p. 36).The magnetization of young lunar samples (<1.5 Ga) is a mystery because common sources of magnetic fields (e.g. core dynamo and long-lived impact plasma fields) have not been present within the last 1.5 Ga. To better characterize the source of magnetization in young lunar samples, we conducted paleomagnetic measurements on several subsamples of lunar glass 12017, which has a formation age of -9 ka, as well as on the underlying basalt from the same sample. Various methods of magnetization were tested, including possible contamination from Earth's magnetic field, exposure to transient magnetic fields such as on the Apollo module, and interaction fields from underlying magnetized rocks. The magnetic field emanated by the rock underlying the 12017 glass was determined to be -150 nT, comparable with the noise associated with paleomagnetic techniques. This opens up a new possible source of magnetization for samples- the laboratory. It is likely that other young lunar samples' paleointensities are overestimates, and that the strengths of magnetic fields on the Moon in the last 1.5 Ga are more similar to the strengths we observed from the 12017 glass. Underlying rocks and laboratory techniques are viable sources of magnetic fields, therefore, young lunar sample magnetization can no longer be used as evidence against an ancient core dynamo. Furthermore, the basalt portion of the 12017 is unidirectionally magnetized, suggesting an ancient core dynamo on the Moon when it formed at 3.2 Ga.by Jennifer Buz.S.M

Mineralogy and fluvial history of the watersheds of Gale, Knobel, and Sharp craters: A regional context for the Mars Science Laboratory Curiosity's exploration

A 500 km long network of valleys extends from Herschel crater to Gale, Knobel, and Sharp craters. The mineralogy and timing of fluvial activity in these watersheds provide a regional framework for deciphering the origin of sediments of Gale crater's Mount Sharp, an exploration target for the Curiosity rover. Olivine-bearing bedrock is exposed throughout the region, and its erosion contributed to widespread olivine-bearing sand dunes. Fe/Mg phyllosilicates are found in both bedrock and sediments, implying that materials deposited in Gale crater may have inherited clay minerals, transported from the watershed. While some topographic lows of the Sharp-Knobel watershed host chloride salts, the only salts detected in the Gale watershed are sulfates within Mount Sharp, implying regional or temporal differences in water chemistry. Crater counts indicate progressively more spatially localized aqueous activity: large-scale valley network activity ceased by the early Hesperian, though later Hesperian/Amazonian fluvial activity continued near Gale and Sharp craters

Macro Mars to Micro Mars: Mapping Minerals and Magnetization

Combination of remote sensing data with in-situ measurements provides a fuller understanding of Mars phenomena. This dissertation focuses on integrating macroscopic and microscopic scales of measurement with regard to spectroscopy and magnetization. In the first chapter high resolution orbital spectroscopy (~18 m/px) and imagery (~30 cm/px) are used to identify potential sources for some of the sedimentary rocks investigated by the Curiosity rover and expand the accessible stratigraphy. While we find mineralogies in common outside and inside the crater as well as transport mechanisms, we conclude that additional sedimentary sources and/or modification after transport are required to explain chemical differences and that strata point to multiple episodes of a lake in Gale crater. In the third chapter we conducted a laboratory photometric study on candidate calibration target materials for the Mars-2020 rover. We characterized these target materials for proper calibration and monitoring of the Mastcam-Z instrument to enable mineral identification through reflectance spectroscopy. The fourth and fifth chapters focus on the microscopic magnetizations found within Martian meteorite ALH84001. Chapter four reports on paleomagnetic experiments conducted on isolated carbonate crystals which contain magnetite previously reported to be biogenic. We compare paleomagnetic test results which distinguish between biogenic and abiogenic origin hypotheses and find that the magnetization within the carbonates is most consistent with a shock processes. In chapter five we analyzed the distribution of dipoles within slices of ALH84001 and determined that they lie in a girdle distribution which could be interpreted as resulting from a true polar wander event on Mars. Looking at kilometer scale observations outside of Gale enlightened observations made along the rover transverse path. A high resolution laboratory analysis of calibration materials will enable future multispectral mineralogical explorations. Microscopic analyses of magnetization inform ancient surface processes on Mars and hint at large-scale global change. In each of these chapters our results were only made possible or greatly enhanced by the combination of data sources and scales.</p

Mineralogy and stratigraphy of the Gale crater rim, wall, and floor units

The Curiosity rover has detected diverse lithologies in float rocks and sedimentary units on the Gale crater floor, interpreted to have been transported from the rim. To understand their provenance, we examine the mineralogy and geology of Gale's rim, walls, and floor, using high-resolution imagery and infrared spectra. While no significant differences in bedrock spectral properties were observed within most Thermal Emission Imaging System and Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) scenes, some CRISM scenes of rim and wall rocks showed olivine-bearing bedrock accompanied by Fe/Mg phyllosilicates. Hydrated materials with 2.48 μm absorptions in Gale's eastern walls are spectrally similar to the sulfate unit in Mount Sharp (Aeolis Mons). Sedimentary strata on the Gale floor southwest of the landing site, likely coeval with the Bradbury units explored by Curiosity, also are hydrated and/or have Fe/Mg phyllosilicates. Spectral properties of these phyllosilicates differ from the Al-substituted nontronite detected by CRISM in Mount Sharp, suggesting formation by fluids of different composition. Geologic mapping of the crater floor shows that the hydrated or hydroxylated materials are typically overlain by spectrally undistinctive, erosionally resistant, cliff-forming units. Additionally, a 4 km impact crater exposes >250 m of the Gale floor, including finely layered units. No basement rocks are exposed, thus indicating sedimentary deposits ≥250 m beneath strata studied by Curiosity. Collectively, the data indicate substantial sedimentary infill of Gale crater, including some materials derived from the crater rim. Lowermost thin layers are consistent with deposition in a lacustrine environment; interbedded hydrated/hydroxylated units may signify changing environmental conditions, perhaps in a drying or episodically dry lake bed

Photometric characterization of Lucideon and Avian Technologies color standards including application for calibration of the Mastcam-Z instrument on the Mars 2020 rover

Several commercially available color standards exist, generated by a variety of manufacturers including LabSphere, Lucideon, and Avian Technologies. Previous work has characterized the photometric properties of LabSphere Spectralon targets. Here, we measure the visible and shortwave infrared (VSWIR; 0.4 to 2.5  μm) reflectance at multiple angles and determine the photometric properties of materials manufactured by Lucideon and Avian Technologies for potential use as calibration target materials for the Mars 2020 Mastcam-Z instrument. The Lucideon black, gray 33, green, and cyan samples are found to be significantly forward scattering. The yellow, red, and gray 70 samples are found to be weakly forward scattering. The Avian Technologies AluWhite98 sample was found to be weakly backward scattering. We characterize the absorptions observable and note the occurrence of wavelength-dependent photometric properties. The reflectance and photometric data collected and released here enable the use of these color standards for calibration of data from Mastcam-Z and other Mars-2020 rover instruments as well as provide key information for many other imaging and spectroscopy applications that require the calibration of data from multiple lighting or viewing geometries

Photometric characterization of Lucideon and Avian Technologies color standards including application for calibration of the Mastcam-Z instrument on the Mars 2020 rover

Several commercially available color standards exist, generated by a variety of manufacturers including LabSphere, Lucideon, and Avian Technologies. Previous work has characterized the photometric properties of LabSphere Spectralon targets. Here, we measure the visible and shortwave infrared (VSWIR; 0.4 to 2.5  μm) reflectance at multiple angles and determine the photometric properties of materials manufactured by Lucideon and Avian Technologies for potential use as calibration target materials for the Mars 2020 Mastcam-Z instrument. The Lucideon black, gray 33, green, and cyan samples are found to be significantly forward scattering. The yellow, red, and gray 70 samples are found to be weakly forward scattering. The Avian Technologies AluWhite98 sample was found to be weakly backward scattering. We characterize the absorptions observable and note the occurrence of wavelength-dependent photometric properties. The reflectance and photometric data collected and released here enable the use of these color standards for calibration of data from Mastcam-Z and other Mars-2020 rover instruments as well as provide key information for many other imaging and spectroscopy applications that require the calibration of data from multiple lighting or viewing geometries

Dataset accompanying "Photometric characterization of Lucideon and Avian Technologies color standards including application for calibration of the Mastcam-Z instrument on the Mars 2020 rover"

This data packet contains supplementary figures which are useful for visualization of the photometric properties of the studied materials. These figures augment those presented in the manuscript but consist of the same data. Figures related to the properties of the detector and white reference used are also included. The raw data from measurements is provided in a spreadsheet for further analysis.Related Publication: Photometric characterization of Lucideon and Avian Technologies color standards including application for calibration of the Mastcam-Z instrument on the Mars 2020 rover Jennifer Buz California Institute of Technology Optical Engineering 2019-02-12 https://doi.org/10.1117/1.OE.58.2.027108 en

Widespread Shallow Water Ice on Mars at High and Mid Latitudes

The auxiliary information associated with "Widespread Shallow Water Ice on Mars at High and Mid Latitudes" by Piqueux et al. consists of a set of 2 maps (d_m.ascii and TI_SI.ascii) and 2 coordinate files (Lon.ascii and Lat.ascii). - d_m.ascii (720 x 360): Depth to the top of the water ice table, in meter - TI_SI.ascii (720 x 360): Upper (dry) regolith thermal inertia, in J m^2 K-1 s^-1/2 These maps are projected on a simple cylindrical canevas; the coordinates can be using these two files: - Lon.ascii (720 x 1) - Lat.ascii (1 x 360) Resolution is 2ppd. Empty bin are assigned -32768. These files were created from work performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Government Support Acknowledged