Kenneth A. Farley's research while affiliated with Planetary Science Institute and other places
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Publications (379)
The observation that many lavas associated with mantle plumes have higher ³He/⁴He ratios than the upper convecting mantle underpins geophysical, geodynamic and geochemical models of Earth’s deep interior. High ³He/⁴He ratios are thought to derive from the solar nebula or from solar-wind-irradiated material that became incorporated into Earth during...
Lithology plays a fundamental role in rock weathering and erosion, and in landscape evolution. When weathering‐ and erosion‐prone lithologies are protected from erosion by more resilient rock types (e.g., quartzites and banded iron formations) unusual weathering products result. At the Southern Espinhaço Range, Minas Gerais, Brazil, bauxitic weathe...
The presence and distribution of preserved organic matter on the surface of Mars can provide key information about the Martian carbon cycle and the potential of the planet to host life throughout its history. Several types of organic molecules have been previously detected in Martian meteorites¹ and at Gale crater, Mars2–4. Evaluating the diversity...
The first samples collected by the Mars 2020 mission represent units exposed on the Jezero Crater floor, from the potentially oldest Séítah formation outcrops to the potentially youngest rocks of the heavily cratered Máaz formation. Surface investigations reveal landscape‐to‐microscopic textural, mineralogical, and geochemical evidence for igneous...
The Mars 2020/Mars Sample Return (MSR) Sample Depot Science Community Workshop was held on September 28 and 30, 2022, to assess the Scientifically‐Return Worthy (SRW) value of the full collection of samples acquired by the rover Perseverance at Jezero Crater, and of a proposed subset of samples to be left as a First Depot at a location within Jezer...
The Perseverance rover landed in Jezero crater on February 18, 2021, with the mission goals to explore the geology, astrobiological potential, and modern environment of the crater floor and delta, and to collect and cache well-documented samples for Mars Sample Return. After completion of the “Crater Floor” science campaign [1], the rover conducted...
Orbital and rover observations of
relict geomorphic features and stratigraphic
architectures indicate Mars once had a warmer, wetter
climate. Constraining the character, relative timing and
persistence of ancient aqueous activity on Mars is
possible through detailed interrogation of the stratal
geometry of aqueously deposited sedimentary bodies.
Su...
The Perseverance rover landed in Jezero crater, Mars in February 2021. We used the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument to perform deep ultraviolet Raman and fluorescence spectroscopy of three rocks within the crater. We identify evidence for two distinct ancient aqueous environ...
jats:p>The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater’s sedimentary delta, finding that the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Séítah, is a coarsely crystalline olivine-rich roc...
Before Perseverance, Jezero crater's floor was variably hypothesized to have a lacustrine, lava, volcanic airfall, or aeolian origin. SuperCam observations in the first 286 Mars days on Mars revealed a volcanic and intrusive terrain with compositional and density stratification. The dominant lithology along the traverse is basaltic, with plagioclas...
The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater’s sedimentary delta, finding the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Séítah, is a coarsely crystalline olivine-rich rock, which acc...
The geological units on the floor of Jezero crater, Mars, are part of a wider regional stratigraphy of olivine-rich rocks, which extends well beyond the crater. We investigate the petrology of olivine and carbonate-bearing rocks of the Séítah formation in the floor of Jezero. Using multispectral images and x-ray fluorescence data, acquired by the P...
A pervasive challenge in noble gas geochemistry is to ensure that analytical techniques do not modify the composition of the noble gases in the samples. Noble gases are present in the atmosphere and are used in a number of manufacturing procedures and by laboratory equipment. Of particular concern is the introduction of atmospheric or laboratory no...
Distinctive sediments containing mostly quartz, kaolinite, and both detrital and authigenic hematite and goethite blanket ~5000 km of the Atlantic coast of Brazil from Rio de Janeiro all the way to the mouth of the Amazon River. The sediments represent a significant period of continental erosion followed by renewed weathering. Here we present (UTh)...
Prior to the Perseverance rover landing, the acoustic environment of Mars was unknown. Models predicted that: (i) atmospheric turbulence changes at centimeter scales or smaller at the point where molecular viscosity converts kinetic energy into heat1, (ii) the speed of sound varies at the surface with frequency2,3, and (iii) high frequency waves ar...
Orbital and rover observations of relict
geomorphic features and stratigraphic architectures
indicate Mars once had a warmer, wetter climate.
Constraining the character, relative timing and
persistence of ancient aqueous activity on Mars is
possible through detailed interrogation of the stratal
geometry of aqueously deposited sedimentary bodies.
Su...
The Perseverance rover landed on the floor of Jezero crater on 18 February 2021. The landing site, named “Octavia E. Butler” is located ~2.2 km from the SE-facing erosional scarp of the western fan deposits, which are of strong interest for the mission [1-2]. Images obtained using the Mastcam-Z camera and the Remote Micro-Imager (RMI) of the SuperC...
A pervasive challenge in noble gas geochemistry is to ensure that analytical techniques do not modify the composition of the noble gases in the samples. Noble gases are present in the atmosphere and are used in a number of manufacturing procedures and by laboratory equipment. Of particular concern is the introduction of atmospheric or laboratory no...
Rio Grande Rise (RGR) is an intraplate oceanic elevation in the South Atlantic Ocean that formed at a hotspot on the Mid-Atlantic Ridge during the Cretaceous. In spreading center and hotspot environments, ironstones form mainly by biomineralization of reduced Fe from hydrothermal fluids or oxidation of sulfide deposits. However, RGR has been consid...
Researchers have characterized extraterrestrial (ET) helium, likely carried by interplanetary dust particles (IDPs), in deep-sea sediments spanning more than the last 100 Myr. Here we complement those low resolution and deep time studies by measuring He in modern Antarctic air and recent ice. We analyzed 180 air filter samples collected in 2017 and...
Perseverance images of a delta on Mars
The Perseverance rover landed in Jezero crater, Mars, in February 2021. Earlier orbital images showed that the crater contains an ancient river delta that was deposited by water flowing into a lake billions of years ago. Mangold et al . analyzed rover images taken shortly after landing that show distant cliff...
The Atacama Desert, on the western margin of the Central Andes, hosts some of the world's largest porphyry copper deposits (PCDs). Despite a hyperarid climate, many of these PCDs have undergone secondary “supergene” enrichment, whereby copper has been concentrated via groundwater-driven leaching and reprecipitation, yielding supergene profiles cont...
Geochronology is an indispensable tool for reconstructing the geologic history of planets, essential to understanding the formation and evolution of our solar system. Bombardment chronology bounds models of solar system dynamics, as well as the timing of volatile, organic, and siderophile element delivery. Absolute ages of magmatic products provide...
We test whether X-ray micro-computed tomography (microCT)
imaging can be used as a tool for screening magnetite grains to improve the
accuracy and precision of cosmogenic 3He exposure dating. We extracted
detrital magnetite from a soil developed on a fanglomerate at Whitewater,
California, which was offset by the Banning strand of the San Andreas F...
We test whether X-ray micro computed tomography (microCT) imaging can be used as a tool for screening magnetite grains to improve the accuracy and precision of cosmogenic 3He exposure dating. We extracted magnetite from a soil developed on a fanglomerate at Whitewater, California, which was offset by the Banning Strand of the San Andreas Fault. Thi...
Paleocene basaltic lavas exposed on Baffin Island have the highest ³He/⁴He found in any terrestrial igneous rocks and potentially contain the most pristine primordial mantle material exposed on Earth's surface. By vacuum-crushing large (1–3 g) olivine mineral separates, we extracted enough magmatic gas to obtain the first coupled helium, neon, and...
Cosmic ray muons penetrate deeply into rock where they interact with atoms to produce cosmogenic nuclides. Incorporation of the muon contribution to the production rates of cosmogenic nuclides increases the accuracy of exposure dates, burial ages, and erosion rates inferred from measured nuclide concentrations. In the absence of empirical evidence,...
The erosion rates and mechanisms operating on Mount Sharp in Gale crater, Mars were assessed via experiments performed by the SAM instrument to determine the cosmogenic noble gas contents of Murray mudstone formation samples Mojave 2 and Quela. Previous measurements of samples from the Aeolis Palus depression between Mount Sharp and the north rim o...
Geochronology, or determination of absolute ages for geologic events, underpins many inquiries into the formation and evolution of planets and our Solar System. Absolute ages of ancient and recent magmatic products provide strong constraints on the dynamics of magma oceans and crustal formation, as well as the longevity and evolution of interior he...
The Carajás Mountains, located in the southeastern part of the Amazon craton, Brazil, host some of the deepest and most ancient continuously exposed weathering profiles on earth. Palaeodrainage systems, now inactive, filled with rounded hematite cobbles and pebbles are preserved on the Carajás Surface. These now fossilized rivers carved the landsca...
Measuring the abundance and isotopic composition of noble gases in planetary atmospheres can answer fundamental questions in cosmochemistry and comparative planetology. However, noble gases are rare elements, a feature making their measurement challenging even on Earth. Furthermore, in space applications, power consumption, volume and mass constrai...
![Figure 4. (U-Th)/He date for sample B−5 plotted vs. grain size [12]....](profile/Francis-Sousa/publication/346931184/figure/fig3/AS:967310600851456@1607636227175/U-Th-He-date-for-sample-B-5-plotted-vs-grain-size-12-The-biggest-grain-with-the_Q320.jpg)
This paper presents a framework for evaluating variation in (U-Th)/He datasets. The framework is objective, repeatable, and based on compatibility of thermal histories derived from individual (U-Th)/He dates. The structure of this new method includes three fundamental steps. First, the allowable thermal history of each individual grain is quantitat...
The Mars 2020 Perseverance rover landing site is located within Jezero crater, a ∼50km\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\sim50~\mbox{km}$\end{document} dia...
SuperCam is a highly integrated remote-sensing instrumental suite for NASA’s Mars 2020 mission. It consists of a co-aligned combination of Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), Visible and Infrared Spectroscopy (VISIR), together with sound recording (MIC) and high-magnification imaging techniques...
The Mars 2020 mission will seek the signs of ancient life on Mars and will identify, prepare, document, and cache a set of samples for possible return to Earth by a follow-on mission. Mars 2020 and its Perseverance rover thus link and further two long-held goals in planetary science: a deep search for evidence of life in a habitable extraterrestria...
An expanded sedimentary section provides an opportunity to elucidate conditions in the nascent Chicxulub crater during the hours to millennia after the Cretaceous‐Paleogene (K‐Pg) boundary impact. The sediments were deposited by tsunami followed by seiche waves as energy in the crater declined, culminating in a thin hemipelagic marlstone unit that...
The crystal structure of goethite, FeO(OH), has two distinct oxygen sites, one with exclusively Fe-O bonds, the other with bonds to both iron and hydrogen. We developed a method to assess the oxygen isotope contrast between these sites by measuring both the bulk goethite and the oxygen released in the conversion of goethite to hematite. The method...
We built a collector to filter interplanetary dust particles (IDPs) larger than 5 μm from the clean air at the Amundsen Scott South Pole station. Our sampling strategy used long duration, continuous dry filtering of near‐surface air in place of short duration, high‐speed impact collection on flags flown in the stratosphere. We filtered ~10⁷ m³ of c...
Perchlorate (ClO₄⁻) was discovered in Martian soil by the Phoenix lander, with important implications for potential Martian biology, photochemistry, aqueous chemistry, and the chlorine cycle on Mars. Perchlorate was subsequently reported in both loose sediment and bedrock samples analyzed by the Sample Analysis at Mars instrument onboard the Curios...
This work presents new analytical techniques for extraction and analysis of neon from a suite of different mineral phases, including quartz, pyroxene, hematite, apatite, zircon, topaz, and fluorite. Neon was quantitatively extracted at 1100 °C from all of these minerals using an in-vacuum lithium borate-flux fusion technique. Evolved neon was purif...
We present protocols for high-spatial resolution measurement of oxygen isotope ratios of goethite (α-FeOOH) with the Sensitive High Mass Resolution Ion Microprobe – Stable Isotopes (SHRIMP-SI) and propose a natural sample as a potential goethite reference material (RM) for ion microprobe analysis. We assess the effects of goethite chemical composit...
Single-aliquot (U-Th)/He dating of hematite has been used to study iron-oxide precipitation in various environments, but we show there is an important challenge to the method: highly retentive hematite samples require temperatures of > 1000° C to be completely degassed, whereas the temperature for major U-loss is ∼980° C. This leads to erroneously...
The breakup of the L-chondrite parent body in the asteroid belt 466 million years (Ma) ago still delivers almost a third of all meteorites falling on Earth. Our new extraterrestrial chromite and ³ He data for Ordovician sediments show that the breakup took place just at the onset of a major, eustatic sea level fall previously attributed to an Ordov...
Cosmogenic nuclide surface exposure dating and erosion rate measurements in basaltic landscapes rely primarily on measurement of ^3He in olivine or pyroxene. However, geochemical investigations using ^3He have been impossible in the substantial fraction of basalts that lack separable olivine or pyroxene crystals, or where such crystals were present...
The Atacama Desert of northern Chile hosts many of the world's largest porphyry copper deposits (PCDs), many of which have been upgraded through supergene enrichment (Sillitoe and McKee 1996). Enrichment of exhumed PCDs occurs in the near-surface weathering environment, when copper is leached from primary sulphides and reprecipitated beneath the wa...
Defying common expectations, some of the oldest landscapes on Earth are found in the humid tropics. ⁴⁰ Ar/ ³⁹ Ar dating shows that Fe-rich regolith that armors the ∼700–1000 m elevation banded iron-formation plateaus at Urucum, Mato Grosso do Sul, Brazil, results from chemical weathering that began at least 70 million years ago. Cosmogenic ³ He con...
We review the in situ geochronology experiments conducted by the Mars Science Laboratory mission's Curiosity rover to understand when the Gale Crater rocks formed, underwent alteration, and became exposed to cosmogenic radiation. These experiments determined that the detrital minerals in the sedimentary rocks of Gale are ∼4 Ga, consistent with thei...
Thorium-230 (²³⁰Th) is a fundamental tool for estimating sediment fluxes in the open ocean. Because ²³⁰Th is rapidly scavenged by particles falling through the water column, the flux of ²³⁰Th to underlying sediments is typically equal to its water column production rate. However, recent surveys suggest hydrothermal plumes are unusually efficient sc...
We measured U/Ca ratios, ^4He concentrations, ^(234)U/^(238)U, and ^(238)U/^(235)U in a subset of well-preserved aragonitic scleractinian fossil corals previously described by Gothmann et al. (2015). Comparisons of measured fossil coral He/U ages with the stratigraphic age demonstrate that well-preserved coral aragonite retains most or all of its r...
X-ray computed tomography of individual olivine crystals in basalts from Ofu and Olosega islands, American Samoa, reveals that a small fraction of the olivines contain the vast majority of the fluid inclusions. Single-grain crushing experiments demonstrate that He and CO_2 reside primarily in these inclusions. Low CO_2 pressures in most grains, cor...
Measuring the abundance and isotopic composition of noble gases in planetary atmospheres can answer fundamental questions in cosmochemistry and comparative planetology. However, noble gases are rare elements, a feature making their measurement challenging even on Earth. Furthermore, in space applications, power consumption, volume and mass constrai...
Elemental Composition of Analogs to Mars Return Samples Studied with X-Ray Fluorescence Imaging at NSLS-II - Volume 24 Supplement - Juergen Thieme, Joel Hurowitz, Martin Schoonen, K. A. Farley, S. Sherman, John Hill
The process of identifying the landing site for NASA's Mars 2020 rover began in 2013 by defining threshold mission science criteria related to seeking signs of ancient habitable conditions, searching for biosignatures of past microbial life, assembling a returnable cache of samples for possible future return to Earth, and collecting data for planni...
The Cretaceous/Palaeogene mass extinction eradicated 76% of species on Earth1,2. It was caused by the impact of an asteroid3,4 on the Yucatán carbonate platform in the southern Gulf of Mexico 66 million years ago 5 , forming the Chicxulub impact crater6,7. After the mass extinction, the recovery of the global marine ecosystem-measured as primary pr...
This contribution reports new parameters for helium diffusion in hematite useful for interpretation of cosmogenic ^3He and radiogenic ^4He chronometry. Fragments of a coarse, euhedral single crystal of hematite from Minas Gerais, Brazil were subjected to bulk step-heating helium diffusion experiments after proton irradiation to make a uniform distr...
(U-Th)/He geochronology of two weathered plateaus in the Carajás Mountains, Pará, Brazil, reveals a history of weathering spanning from ca. 80 Ma to the present for this high elevation (∼720 m) land surface. Cosmogenic ^3He measurements of hematite pebbles and blocks cemented onto the plateaus at two sites, N1 and S11D, yield erosion rates as low a...
U-Th)/He geochronology and cosmogenic 3He in iron oxides reveal mineral precipitation ages as old as 55 Ma and exposure ages greater than 5 Ma for canga-cemented plateaus in the Quadrilátero Ferrífero (QF), Brazil, showing that lateritic profiles overlying banded iron-formation (BIF) landscapes in tropical regions have a long history of surface exp...