The Potassium-Argon Laser Experiment (KArLE): In Situ Geochronology for Planetary Robotic Missions
No abstract available
instrument↗
Engineering topics
Miller, J. S.
Publications and source records attributed to Miller, J. S..
The Potassium-Argon Laser Experiment (KArLE): In Situ Geochronology for Planetary Robotic Missions
No abstract available
KArLE↗
The Potassium-Argon Laser Experiment (KARLE): In Situ Geochronology for Planetary Robotic Missions
Isotopic dating is an essential tool to establish an absolute chronology for geological events, including crystallization history, magmatic evolution, and alteration events. The capability for in situ geochronology will open up the ability for geochronology to be accomplished as part of lander or rover complement, on multiple samples rather than just those returned. An in situ geochronology package can also complement sample return missions by identifying the most interesting rocks to cache or return to Earth. The K-Ar Laser Experiment (KArLE) brings together a novel combination of several flight-proven components to provide precise measurements of potassium (K) and argon (Ar) that will enable accurate isochron dating of planetary rocks. KArLE will ablate a rock sample, measure the K in the plasma state using laser-induced breakdown spectroscopy (LIBS), measure the liberated Ar using mass spectrometry (MS), and relate the two by measuring the volume of the ablated pit by optical imaging. Our work indicates that the KArLE instrument is capable of determining the age of planetary samples with sufficient accuracy to address a wide range of geochronology problems in planetary science. Additional benefits derive from the fact that each KArLE component achieves analyses useful for most planetary surface missions.
Cohen, B. A.↗
Updates of the KArLE Experiment: New Libs Calibration Under High Vacuum for the Quantification of Potassium in Basalt for In Situ Geochronology
In planetary exploration, in situ absolute geochronology is one of the main important measurements that needs to be accomplished. Until now, on Mars, the age of the surface is only determined by crater density counting, which gives relative ages. These ages can have a lot of uncertainty as they depend on many parameters. More than that, the curves must be ties to absolute ages. Thus far, only the lost lander Beagle 2 was designed to conduct absolute geochronology measurements, though some recent attempts using MSL Curiosity show that this investigation is feasible and should be strongly encouraged for future flight. Experimental: The Potassium (K)-Argon Laser Experiment (KArLE) is being developed at MSFC through the NASA Planetary Instrument Definition and Development Program (PIDDP). The goal of this experiment is to provide in situ geochronology based on the K-Ar method. A laser ablates a rock under high vacuum, creating a plasma which is sensed by an optical spectrometer to do Laser Induced Breakdown Spectroscopy (LIBS). The ablated material frees gases, including radiogenic 40Ar,which is measured by a mass spectrometer (MS). As the potassium is a content and the 40Ar is a quantity, the ablated mass needed in order to relate them. The mass is given by the product of the ablated volume by the density of this material. So we determine the mineralogy of the ablated material with the LIBS spectra and images and calculate its density. The volume of the pit is measured by using microscopy. LIBS measurement of K under high vacuum: Three independant projects [1, 2, 3] including KArLE, are developing geochronological instruments based on this LA-LIBS-MS method. Despite several differences in their setup, all of them have validated the methods with analyses and ages. However, they all described difficulties with the LIBS measurements of K [3,4]. At ambient pressure, the quantification of K by LIBS on geological materials can be accurate [5]. However the protocol of the LA-LIBS-MS experiment required hundreds of shots under high vacuum in order to free enough 40Ar* to be measured by the QMS. This long duration of ablation may induces significant changes in the LIBS spectra. The pressure may increases by orders of magnitudewithin the chamber and the laser pit geometry can change the effectiveness of ablation and intensity of plasma light received. These effects introduce variation between the first and last spectra and so the quantification of K is more complex. The ablation of one crater can give, depending on the protocol of acquisition, from tens to hundreds of spectra. Protocol and results: We are in the process of further characterizing the variation introduced into LIBS spectra by the use of hundreds of laser shots, and definining a protocol that can be used to ensure accuracy and reporoducibility in the results.We are using natural rock powder standards fused in a furnace, as well as mars analog samples with known K content. We will show the result of the calibration and some new statistical approaches in order to apprehend the effects of the long time ablation on rocks under high vacuum.
Devismes, D.↗
KArLE: In-Situ Geochronology on the Mars 2020 Rover with KArLE (The Potassium-Argon Laser Experiment)
No abstract available
Cohen, Barbara A.↗
Volume Measurements of Laser-generated Pits for in Situ Geochronology Using KArLE (Potassium-Argon Laser Experiment)
KArLE (Potassium-‐Argon Laser Experiment) has been developed for in situ planetary geochronology using the K - Ar (potassium-‐argon) isotope system, where material ablated by LIBS (Laser-‐Induced Breakdown Spectroscopy) is used to calculate isotope abundances. We are determining the accuracy and precision of volume measurements of these pits using stereo and laser microscope data to better understand the ablation process for isotope abundance calculations. If a characteristic volume can be determined with sufficient accuracy and precision for specific rock types, KArLE will prove to be a useful instrument for future planetary rover missions.
French, R. A.↗
In-situ Geochronology on the Mars 2020 Rover with KArLE (The Potassium-Argon Laser Experiment)
A successful Mars exploration program has revealed chapters of Mars history, but in this book, the pages are ripped out of the binding and scattered across the surface. An examination of each page reveals interesting information, but there is no way to read the book in a logical order. Geochronology is the tool that puts page number onto the individual pages, and allows the book of Martian history to be read in its proper order. The KArLE experiment performs the first dedicated in situ geochronology investigation on Mars, bringing clarity to Mars 2020 samples and context to its landing site.
Cohen, Barbara A.↗
Volume Measurements of Laser-generated Pits for In Situ Geochronology using KArLE (Potassium-Argon Laser Experiment)
The Potassium-Argon Laser Experiment( KArLE), is composed of two main instruments: a spectrometer as part of the Laser-Induced Breakdown Spectroscopy (LIBS) method and a Mass Spectrometer (MS). The LIBS laser ablates a sample and creates a plasma cloud, generating a pit in the sample. The LIBS plasma is measured for K abundance in weight percent and the released gas is measured using the MS, which calculates Ar abundance in mols. To relate the K and Ar measurements, total mass of the ablated sample is needed but can be difficult to directly measure. Instead, density and volume are used to calculate mass, where density is calculated based on the elemental composition of the rock (from the emission spectrum) and volume is determined by pit morphology. This study aims to reduce the uncertainty for KArLE by analyzing pit volume relationships in several analog materials and comparing methods of pit volume measurements and their associated uncertainties.
French, R. A.↗
Update on Development of the Potassium-Argon Laser Experiment (KArLE) Instrument for In Situ Geochronology
Absolute dating of planetary samples is an essential tool to establish the chronology of geological events, including crystallization history, magmatic evolution, and alteration. We are addressing this challenge by developing the Potassium (K) -- Argon Laser Experiment (KArLE), building on previous work to develop a K-Ar in situ instrument. KArLE ablates a rock sample, determines the K in the plasma state using laser-induced breakdown spectroscopy (LIBS), measures the liberated Ar using quadrupole mass spectrometry (QMS), and relates the two by the volume of the ablated pit using laser confocal microscopy (LCM). Our goal is for the KArLE instrument to be capable of determining the age of several kinds of planetary samples to address a wide range of geochronolgy problems in planetary science.
Cohen, Barbara A.↗
Development of the Potassium-Argon Laser Experiment (KArLE) Instrument for In Situ Geochronology
Absolute dating of planetary samples is an essential tool to establish the chronology of geological events, including crystallization history, magmatic evolution, and alteration. Traditionally, geochronology has only been accomplishable on samples from dedicated sample return missions or meteorites. The capability for in situ geochronology is highly desired, because it will allow one-way planetary missions to perform dating of large numbers of samples. The success of an in situ geochronology package will not only yield data on absolute ages, but can also complement sample return missions by identifying the most interesting rocks to cache and/or return to Earth. In situ dating instruments have been proposed, but none have yet reached TRL 6 because the required high-resolution isotopic measurements are very challenging. Our team is now addressing this challenge by developing the Potassium (K) - Argon Laser Experiment (KArLE) under the NASA Planetary Instrument Definition and Development Program (PIDDP), building on previous work to develop a K-Ar in situ instrument [1]. KArLE uses a combination of several flight-proven components that enable accurate K-Ar isochron dating of planetary rocks. KArLE will ablate a rock sample, determine the K in the plasma state using laser-induced breakdown spectroscopy (LIBS), measure the liberated Ar using quadrupole mass spectrometry (QMS), and relate the two by the volume of the ablated pit using an optical method such as a vertical scanning interferometer (VSI). Our preliminary work indicates that the KArLE instrument will be capable of determining the age of several kinds of planetary samples to +/-100 Myr, sufficient to address a wide range of geochronology problems in planetary science.
Cohen, Barbara A.↗
A One-Piece Lunar Regolith Bag Garage Prototype
Shelter structures on the moon, even in early phases of exploration, should incorporate lunar materials as much as possible. This Technical Memorandum details the design and construction of a prototype for a one-piece regolith bag unpressurized garage concept and a materials testing program to investigate six candidate fabrics to learn how they might perform in the lunar environment. The conceptualization was that a lightweight fabric form be launched from Earth and landed on the lunar surface to be robotically filled with raw lunar regolith. Regolith bag fabric candidates included: Vectran(TM), Nextel(TM), Gore PTFE Fabric(TM), Zylon(TM), Twaron(TM), and Nomex(TM). Tensile (including post radiation exposure), fold, abrasion, and hypervelocity impact testing were performed under ambient conditions, and also performed under cold and elevated temperatures. In some cases, Johnson Space Center lunar simulant (JSC-1) was used in conjunction with testing. A series of preliminary structures was constructed during final prototype design based on the principles of the classic masonry arch. The prototype was constructed of Kevlar(TM) and filled with vermiculite. The structure is free-standing, but has not yet been load tested. Future plans would be to construct higher fidelity prototypes and to conduct appropriate tests of the structure.
Smithers, G. A.↗
Analysis of pyroxene absorptions observed in Martian dark regions
We have investigated the mineralogy of the Martian dark regions by analysis of the pyroxene Fe(2+) absorption band near 1.0 micron in a set of VIS/NIR reflectance spectral images. The data used for these analyses were selected from a larger set, extending from 0.44 to 1.02 microns, obtained during the close 1988 opposition and covering substantially all of Mars south of 40 degrees N. This data set is being used in regional mapping of spectral parameters related to surface mineralogy. Martian dark regions are of interest in reconstructing the geologic history because they contain exposures of unaltered or little-altered basaltic crustal material; mapping differences in composition among dark regions could reveal regional or temporal variation in magmatic activity or mantle source composition. Two types of dark regions are seen, with the pyroxene band present and absent; where present, the inferred composition is in the range pigeonite-augite to very high-Fe, low-Ca pyroxene, with a two-pyroxene mixture possible.
Miller, J. S.↗
Exploring compositional variations on the surface of Mars applying mixing modeling to a telescopic spectral image
The linear mixing model approach was successfully applied to data sets of various natures. In these sets, the measured radiance could be assumed to be a linear combination of radiance contributions. The present work is an attempt to analyze a spectral image of Mars with linear mixing modeling.
Merenyi, E.↗
Evidence for crystalline hematite as an accessory phase in Martian soils
Based on visible and near-IR spectral images of Mars obtained by us in 1988, we have confirmed the occurrence of bulk crystalline hematite as a minor or accessory phase on the surface. This hematite is not uniformly distributed, being less abundant or absent in certain northern low-albedo regions. Even where most abundant, bulk hematite is not the primary coloring agent of heavily weathered materials on Mars. The primary coloring agent is apparently an amorphous or nanophase Fe3(+) phase, analogous to the coloring agent in certain Hawaiian palagonites (e.g. Adams and Evans, 1980; Singer, 1982; Morris et al, 1989). Based on these results, we can say with considerable certainty that bulk crystalline hematite exists on Mars in small amounts, in addition to the more ubiquitous nanophase or poorly crystalline ferric oxide phase(s). We conclude that Type 2 low-albedo regions (typified by Acidalia Planitia) contain less of this hematite than Type 1 regions (typified by Meridiani Sinus). Oxia Palus shows indication of slightly more oxidation and bulk hematite than Acidalia. This may be a real compositional difference, indicating that Oxia is in some sense transitional between Type 2 and Type 1 regions, but we cannot rule out the possibility of some optical mixing with surrounding higher-albedo regions. We are currently investigating the relationship of ferric-oxides in high-albedo regions to both types of low-albedo regions. As expected, spectral ratios of data from western Arabia to dark regions show considerably greater Fe3(+) in Arabia. There are not obvious spectral indications of a difference in ferric-oxide composition between Arabia and Type 1 low-albedo regions, implying that Arabia also contains minor bulk hematite.
Singer, R. B.↗
Lick Observatory charge-coupled-device data acquisition system
The Lick Observatory CCD data acquisition system is described, with some observational results to illustrate the system capability. The electronics for the CCD are subdivided into those attached to the dewar, a 'smart' controller near the dewar, and a computer connected by serial link to the smart controller. Software for the controller is in assembler code, while the software for data acquisition and on-line analysis is written in C and uses the UNIX operating system. The computers and controllers are programmed to recognize and operate several different types of CCD. Three separate instruments that use the CCDs are described briefly, together with examples of the data they produce.
Robinson, L. B.↗
Wind ripples in low density atmospheres
The effect of varying fluid density (rho) on particle transport was examined by conducting tests at atmospheric pressures between 1 and 0.004 bar in the Martian Surface Wind Tunnel (MARSWIT). This study specifically concerns the effect of varying rho on the character of wind ripples, and elicits information concerning generalized ripple models as well as specific geological circumstances for ripple formation such as those prevailing on Mars. Tests were conducted primarily with 95 micron quartz sand, and for each atmospheric pressure chosen, tests were conducted at two freestream wind speeds: 1.1 U*(t) and 1.5 U*(t), where U*(t) is saltation threshold. Preliminary analysis of the data suggests: (1) ballistic ripple wavelength is not at variance with model predictions; (2) an atmospheric pressure of approximately 0.2 bar could represent a discontinuity in ripple behavior; and (4) ripple formation on Mars may not be readily predicted by extrapolation of terrestrial observations.
Miller, J. S.↗
CCD use at Lick Observatory
The CCD detector and data handling system in regular use at Lick Observatory are described. A grism system has been installed on the automated Cassegrain spectrograph at the Shane 3-meter telescope. A very compact CCD cooling system has been developed using a commercial gas expansion refrigerator; the dewar is a cylinder 15 cm in diameter and 6 cm high. The data acquisition computer, an LSI 11/23 with 256 kbyte RAM, 160 Mbyte Winchester disk, and color video display, provides for FITS format magnetic tape storage as well as preliminary analysis of images and spectra. The 3-meter telescope spectrographic system uses a 500 x 500 pixel thinned CCD. Design information and operational experience for these detector systems are presented along with some results to illustrate the quality of the data being obtained and the current limitations of the CCD detectors and data system.
Lauer, T. R.↗
X-ray, optical, and radio properties of quasars
A sample of 26 low-redshift quasars was examined for relationships between X-ray luminosity and optical spectroscopic features; all quasars were observed with the Einstein Observatory and with the IDS on the Lick 3 meter telescope. Evidence is found for correlations between quasar X-ray luminosity and both optical continuum luminosity and H-beta luminosity. In the latter case, there is a smooth relationship connecting quasars, Seyfert 1, and Seyfert 2 galaxies. For the quasars in this sample, there is also a strong correlation between optical continuum luminosity and both the H-beta luminosity and equivalent width. Evidence is also found for a weak correlation between alpha-prime (ox), the mean continuum spectral index between 5000 A and 2 keV, and Fe II equivalent width, H-beta equivalent width, H-beta line width at zero intensity, and the ratio of H-beta equivalent width to its line width at zero intensity.
Blumenthal, G. R.↗