• Aflatoxin-free transgenic maize using host-induced gene silencing

      Thakare, Dhiraj; Zhang, Jianwei; Wing, Rod A.; Cotty, Peter J.; Schmidt, Monica A.; Univ Arizona, Sch Plant Sci, BIO5 Inst; Univ Arizona, USDA, ARS; Univ Arizona, Sch Plant Sci (AMER ASSOC ADVANCEMENT SCIENCE, 2017-03-10)
      Aflatoxins, toxic secondary metabolites produced by some Aspergillus species, are a universal agricultural economic problem and a critical health issue. Despite decades of control efforts, aflatoxin contamination is responsible for a global loss of millions of tons of crops each year. We show that host-induced gene silencing is an effective method for eliminating this toxin in transgenic maize. We transformed maize plants with a kernel-specific RNA interference (RNAi) gene cassette targeting the aflC gene, which encodes an enzyme in the Aspergillus aflatoxin biosynthetic pathway. After pathogen infection, aflatoxin could not be detected in kernels from these RNAi transgenic maize plants, while toxin loads reached thousands of parts per billion in nontransgenic control kernels. A comparison of transcripts in developing aflatoxin-free transgenic kernels with those from nontransgenic kernels showed no significant differences between these two groups. These results demonstrate that small interfering RNA molecules can be used to silence aflatoxin biosynthesis in maize, providing an attractive and precise engineering strategy that could also be extended to other crops to improve food security.
    • Annual radiocarbon record indicates 16th century BCE date for the Thera eruption

      Pearson, Charlotte L.; Brewer, Peter W.; Brown, David; Heaton, Timothy J.; Hodgins, Gregory W. L.; Jull, A. J. Timothy; Lange, Todd; Salzer, Matthew W.; Univ Arizona, Lab Tree Ring Res; Univ Arizona, Sch Anthropol; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2018-08)
      The mid-second millennium BCE eruption of Thera (Santorini) offers a critically important marker horizon to synchronize archaeological chronologies of the Aegean, Egypt, and the Near East and to anchor paleoenvironmental records from ice cores, speleothems, and lake sediments. Precise and accurate dating for the event has been the subject of many decades of research. Using calendar-dated tree rings, we created an annual resolution radiocarbon time series 1700-1500 BCE to validate, improve, or more clearly define the limitations for radiocarbon calibration of materials from key eruption contexts. Results show an offset from the international radiocarbon calibration curve, which indicates a shift in the calibrated age range for Thera toward the 16th century BCE. This finding sheds new light on the long-running debate focused on a discrepancy between radiocarbon (late 17th-early 16th century BCE) and archaeological (mid 16th-early 15th century BCE) dating evidence for Thera.
    • Archaeological assessment reveals Earth's early transformation through land use

      Lanoe, Francois; Steffen, Martina L.; Univ Arizona (AMER ASSOC ADVANCEMENT SCIENCE, 2019-08-30)
      Environmentally transformative human use of land accelerated with the emergence of agriculture, but the extent, trajectory, and implications of these early changes are not well understood. An empirical global assessment of land use from 10,000 years before the present (yr B.P.) to 1850 CE reveals a planet largely transformed by hunter-gatherers, farmers, and pastoralists by 3000 years ago, considerably earlier than the dates in the land-use reconstructions commonly used by Earth scientists. Synthesis of knowledge contributed by more than 250 archaeologists highlighted gaps in archaeological expertise and data quality, which peaked for 2000 yr B.P. and in traditionally studied and wealthier regions. Archaeological reconstruction of global land-use history illuminates the deep roots of Earth's transformation and challenges the emerging Anthropocene paradigm that large-scale anthropogenic global environmental change is mostly a recent phenomenon.
    • Battery-free, fully implantable optofluidic cuff system for wireless optogenetic and pharmacological neuromodulation of peripheral nerves

      Zhang, Yi; Mickle, Aaron D; Gutruf, Philipp; McIlvried, Lisa A; Guo, Hexia; Wu, Yixin; Golden, Judith P; Xue, Yeguang; Grajales-Reyes, Jose G; Wang, Xueju; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2019-07-05)
      Studies of the peripheral nervous system rely on controlled manipulation of neuronal function with pharmacologic and/or optogenetic techniques. Traditional hardware for these purposes can cause notable damage to fragile nerve tissues, create irritation at the biotic/abiotic interface, and alter the natural behaviors of animals. Here, we present a wireless, battery-free device that integrates a microscale inorganic light-emitting diode and an ultralow-power microfluidic system with an electrochemical pumping mechanism in a soft platform that can be mounted onto target peripheral nerves for programmed delivery of light and/or pharmacological agents in freely moving animals. Biocompliant designs lead to minimal effects on overall nerve health and function, even with chronic use in vivo. The small size and light weight construction allow for deployment as fully implantable devices in mice. These features create opportunities for studies of the peripheral nervous system outside of the scope of those possible with existing technologies.
    • Battery-free, skin-interfaced microfluidic/electronic systems for simultaneous electrochemical, colorimetric, and volumetric analysis of sweat

      Bandodkar, Amay J; Gutruf, Philipp; Choi, Jungil; Lee, KunHyuck; Sekine, Yurina; Reeder, Jonathan T; Jeang, William J; Aranyosi, Alexander J; Lee, Stephen P; Model, Jeffrey B; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2019-01-01)
      Wearable sweat sensors rely either on electronics for electrochemical detection or on colorimetry for visual readout. Non-ideal form factors represent disadvantages of the former, while semiquantitative operation and narrow scope of measurable biomarkers characterize the latter. Here, we introduce a battery-free, wireless electronic sensing platform inspired by biofuel cells that integrates chronometric microfluidic platforms with embedded colorimetric assays. The resulting sensors combine advantages of electronic and microfluidic functionality in a platform that is significantly lighter, cheaper, and smaller than alternatives. A demonstration device simultaneously monitors sweat rate/loss, pH, lactate, glucose, and chloride. Systematic studies of the electronics, microfluidics, and integration schemes establish the key design considerations and performance attributes. Two-day human trials that compare concentrations of glucose and lactate in sweat and blood suggest a potential basis for noninvasive, semi-quantitative tracking of physiological status.
    • Breakdown of the Stokes-Einstein relation above the melting temperature in a liquid phase-change material.

      Wei, Shuai; Evenson, Zach; Stolpe, Moritz; Lucas, Pierre; Angell, C Austen; Univ Arizona, Dept Mat Sci & Engn (AMER ASSOC ADVANCEMENT SCIENCE, 2018-11-01)
      The dynamic properties of liquid phase-change materials (PCMs), such as viscosity η and the atomic self-diffusion coefficient D, play an essential role in the ultrafast phase switching behavior of novel nonvolatile phase-change memory applications. To connect η to D, the Stokes-Einstein relation (SER) is commonly assumed to be valid at high temperatures near or above the melting temperature Tm and is often used for assessing liquid fragility (or crystal growth velocity) of technologically important PCMs. However, using quasi-elastic neutron scattering, we provide experimental evidence for a breakdown of the SER even at temperatures above Tm in the high-atomic mobility state of a PCM, Ge1Sb2Te4. This implies that although viscosity may have strongly increased during cooling, diffusivity can remain high owing to early decoupling, being a favorable feature for the fast phase switching behavior of the high-fluidity PCM. We discuss the origin of the observation and propose the possible connection to a metal-semiconductor and fragile-strong transition hidden below Tm.
    • Clay mineral diversity and abundance in sedimentary rocks of Gale crater, Mars

      Bristow, Thomas F.; Rampe, Elizabeth B.; Achilles, Cherie N.; Blake, David F.; Chipera, Steve J.; Craig, Patricia; Crisp, Joy A.; Des Marais, David J.; Downs, Robert T.; Gellert, Ralf; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2018-06)
      Clay minerals provide indicators of the evolution of aqueous conditions and possible habitats for life on ancient Mars. Analyses by the Mars Science Laboratory rover Curiosity show that similar to 3.5-billion year (Ga) fluvio-lacustrine mudstones in Gale crater contain up to similar to 28 weight % (wt %) clay minerals. We demonstrate that the species of clay minerals deduced from x-ray diffraction and evolved gas analysis show a strong paleoenvironmental dependency. While perennial lake mudstones are characterized by Fe-saponite, we find that stratigraphic intervals associated with episodic lake drying contain Al-rich, Fe3+-bearing dioctahedral smectite, with minor (3 wt %) quantities of ferripyrophyllite, interpreted as wind-blown detritus, found in candidate aeolian deposits. Our results suggest that dioctahedral smectite formed via near-surface chemical weathering driven by fluctuations in lake level and atmospheric infiltration, a process leading to the redistribution of nutrients and potentially influencing the cycling of gases that help regulate climate.
    • Co-occurrence of Acheulian and Oldowan artifacts with Homo erectus cranial fossils from Gona, Afar, Ethiopia

      Semaw, Sileshi; Rogers, Michael J; Simpson, Scott W; Levin, Naomi E; Quade, Jay; Dunbar, Nelia; McIntosh, William C; Cáceres, Isabel; Stinchcomb, Gary E; Holloway, Ralph L; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2020-03-06)
      Although stone tools generally co-occur with early members of the genus Homo, they are rarely found in direct association with hominins. We report that both Acheulian and Oldowan artifacts and Homo erectus crania were found in close association at 1.26 million years (Ma) ago at Busidima North (BSN12), and ca. 1.6 to 1.5 Ma ago at Dana Aoule North (DAN5) archaeological sites at Gona, Afar, Ethiopia. The BSN12 partial cranium is robust and large, while the DAN5 cranium is smaller and more gracile, suggesting that H. erectus was probably a sexually dimorphic species. The evidence from Gona shows behavioral diversity and flexibility with a lengthy and concurrent use of both stone technologies by H. erectus, confounding a simple "single species/single technology" view of early Homo.
    • Coherent oscillations of a levitated birefringent microsphere in vacuum driven by nonconservative rotation-translation coupling

      Arita, Yoshihiko; Simpson, Stephen H; Zemánek, Pavel; Dholakia, Kishan; Univ Arizona, Coll Opt Sci (AMER ASSOC ADVANCEMENT SCIENCE, 2020-06-03)
      We demonstrate an effect whereby stochastic, thermal fluctuations combine with nonconservative optical forces to break detailed balance and produce increasingly coherent, apparently deterministic motion for a vacuum-trapped particle. The particle is birefringent and held in a linearly polarized Gaussian optical trap. It undergoes oscillations that grow rapidly in amplitude as the air pressure is reduced, seemingly in contradiction to the equipartition of energy. This behavior is reproduced in direct simulations and captured in a simplified analytical model, showing that the underlying mechanism involves nonsymmetric coupling between rotational and translational degrees of freedom. When parametrically driven, these self-sustained oscillators exhibit an ultranarrow linewidth of 2.2 mu Hz and an ultrahigh mechanical quality factor in excess of 2 x 10(8) at room temperature. Last, nonequilibrium motion is seen to be a generic feature of optical vacuum traps, arising for any system with symmetry lower than that of a perfect isotropic microsphere in a Gaussian trap.
    • The commonness of rarity: Global and future distribution of rarity across land plants

      Enquist, Brian J; Feng, Xiao; Boyle, Brad; Maitner, Brian; Newman, Erica A; Jørgensen, Peter Møller; Roehrdanz, Patrick R; Thiers, Barbara M; Burger, Joseph R; Corlett, Richard T; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2019-11-27)
      A key feature of life’s diversity is that some species are common but many more are rare. Nonetheless, at global scales, we do not know what fraction of biodiversity consists of rare species. Here, we present the largest compilation of global plant diversity to quantify the fraction of Earth’s plant biodiversity that are rare. A large fraction, ~36.5% of Earth’s ~435,000 plant species, are exceedingly rare. Sampling biases and prominent models, such as neutral theory and the k-niche model, cannot account for the observed prevalence of rarity. Our results indicate that (i) climatically more stable regions have harbored rare species and hence a large fraction of Earth’s plant species via reduced extinction risk but that (ii) climate change and human land use are now disproportionately impacting rare species. Estimates of global species abundance distributions have important implications for risk assessments and conservation planning in this era of rapid global change.
    • Disruption of cardiac thin filament assembly arising from a mutation in : A novel mechanism of neonatal dilated cardiomyopathy

      Ahrens-Nicklas, Rebecca C; Pappas, Christopher T; Farman, Gerrie P; Mayfield, Rachel M; Larrinaga, Tania M; Medne, Livija; Ritter, Alyssa; Krantz, Ian D; Murali, Chaya; Lin, Kimberly Y; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2019-09-04)
      Neonatal heart failure is a rare, poorly-understood presentation of familial dilated cardiomyopathy (DCM). Exome sequencing in a neonate with severe DCM revealed a homozygous nonsense variant in leiomodin 2 (LMOD2, p.Trp398*). Leiomodins (Lmods) are actin-binding proteins that regulate actin filament assembly. While disease-causing mutations in smooth (LMOD1) and skeletal (LMOD3) muscle isoforms have been described, the cardiac (LMOD2) isoform has not been previously associated with human disease. Like our patient, Lmod2-null mice have severe early-onset DCM and die before weaning. The infant's explanted heart showed extraordinarily short thin filaments with isolated cardiomyocytes displaying a large reduction in maximum calcium-activated force production. The lack of extracardiac symptoms in Lmod2-null mice, and remarkable morphological and functional similarities between the patient and mouse model informed the decision to pursue cardiac transplantation in the patient. To our knowledge, this is the first report of aberrant cardiac thin filament assembly associated with human cardiomyopathy.
    • Epidermal mechano-acoustic sensing electronics for cardiovascular diagnostics and human-machine interfaces

      Liu, Y.; Norton, J. J. S.; Qazi, R.; Zou, Z.; Ammann, K. R.; Liu, H.; Yan, L.; Tran, P. L.; Jang, K.-I.; Lee, J. W.; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2016-11-16)
      Physiological mechano-acoustic signals, often with frequencies and intensities that are beyond those associated with the audible range, provide information of great clinical utility. Stethoscopes and digital accelerometers in conventional packages can capture some relevant data, but neither is suitable for use in a continuous, wearable mode, and both have shortcomings associated with mechanical transduction of signals through the skin. We report a soft, conformal class of device configured specifically for mechano-acoustic recording from the skin, capable of being used on nearly any part of the body, in forms that maximize detectable signals and allow for multimodal operation, such as electrophysiological recording. Experimental and computational studies highlight the key roles of low effective modulus and low areal mass density for effective operation in this type of measurement mode on the skin. Demonstrations involving seismocardiography and heart murmur detection in a series of cardiac patients illustrate utility in advanced clinical diagnostics. Monitoring of pump thrombosis in ventricular assist devices provides an example in characterization of mechanical implants. Speech recognition and human-machine interfaces represent additional demonstrated applications. These and other possibilities suggest broad-ranging uses for soft, skin-integrated digital technologies that can capture human body acoustics.
    • Fast molecular outflow from a dusty star-forming galaxy in the early Universe

      Spilker, J. S.; Aravena, Manuel; Béthermin, M.; Chapman, S. C.; Chen, C.-C.; Cunningham, D. J. M.; de Breuck, C.; Dong, C.; Gonzalez, Anthony H.; Hayward, C. C.; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2018-09-07)
      Galaxies grow inefficiently, with only a small percentage of the available gas converted into stars each free-fall time. Feedback processes, such as outflowing winds driven by radiation pressure, supernovae, or supermassive black hole accretion, can act to halt star formation if they heat or expel the gas supply. We report a molecular outflow launched from a dust-rich star-forming galaxy at redshift 5.3, 1 billion years after the Big Bang. The outflow reaches velocities up to 800 kilometers per second relative to the galaxy, is resolved into multiple clumps, and carries mass at a rate within a factor of 2 of the star formation rate. Our results show that molecular outflows can remove a large fraction of the gas available for star formation from galaxies at high redshift.
    • The genetic prehistory of the Andean highlands 7000 years BP though European contact

      Lindo, John; Haas, Randall; Hofman, Courtney; Apata, Mario; Moraga, Mauricio; Verdugo, Ricardo A; Watson, James T; Viviano Llave, Carlos; Witonsky, David; Beall, Cynthia; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2018-11-01)
      The peopling of the Andean highlands above 2500 m in elevation was a complex process that included cultural, biological, and genetic adaptations. Here, we present a time series of ancient whole genomes from the Andes of Peru, dating back to 7000 calendar years before the present (BP), and compare them to 42 new genome-wide genetic variation datasets from both highland and lowland populations. We infer three significant features:a split between low- and high-elevation populations that occurred between 9200 and 8200 BP; a population collapse after European contact that is significantly more severe in South American lowlanders than in highland populations; and evidence for positive selection at genetic loci related to starch digestion and plausibly pathogen resistance after European contact. We do not find selective sweep signals related to known components of the human hypoxia response, which may suggest more complex modes of genetic adaptation to high altitude.
    • Histone deacetylase activity governs diastolic dysfunction through a nongenomic mechanism

      Jeong, Mark Y.; Lin, Ying H.; Wennersten, Sara A.; Demos-Davies, Kimberly M.; Cavasin, Maria A.; Mahaffey, Jennifer H.; Monzani, Valmen; Saripalli, Chandrasekhar; Mascagni, Paolo; Reece, T. Brett; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2018-02-07)
      There are no approved drugs for the treatment of heart failure with preserved ejection fraction (HFpEF), which is characterized by left ventricular (LV) diastolic dysfunction. We demonstrate that ITF2357 (givinostat), a clinical-stage inhibitor of histone deacetylase (HDAC) catalytic activity, is efficacious in two distinct murine models of diastolic dysfunction with preserved EF. ITF2357 blocked LV diastolic dysfunction due to hypertension in Dahl salt-sensitive (DSS) rats and suppressed aging-induced diastolic dysfunction in normotensive mice. HDAC inhibitor-mediated efficacy was not due to lowering blood pressure or inhibiting cellular and molecular events commonly associated with diastolic dysfunction, including cardiac fibrosis, cardiac hypertrophy, or changes in cardiac titin and myosin isoform expression. Instead, ex vivo studies revealed impairment of cardiac myofibril relaxation as a previously unrecognized, myocyte-autonomous mechanism for diastolic dysfunction, which can be ameliorated by HDAC inhibition. Translating these findings to humans, cardiac myofibrils from patients with diastolic dysfunction and preserved EF also exhibited compromised relaxation. These data suggest that agents such as HDAC inhibitors, which potentiate cardiac myofibril relaxation, hold promise for the treatment of HFpEF in humans.
    • Identification of the substrate recruitment mechanism of the muscle glycogen protein phosphatase 1 holoenzyme

      Kumar, Ganesan Senthil; Choy, Meng S; Koveal, Dorothy M; Lorinsky, Michael K; Lyons, Scott P; Kettenbach, Arminja N; Page, Rebecca; Peti, Wolfgang; Univ Arizona, Dept Chem & Biochem (AMER ASSOC ADVANCEMENT SCIENCE, 2018-11-01)
      Glycogen is the primary storage form of glucose. Glycogen synthesis and breakdown are tightly controlled by glycogen synthase (GYS) and phosphorylase, respectively. The enzyme responsible for dephosphorylating GYS and phosphorylase, which results in their activation (GYS) or inactivation (phosphorylase) to robustly stimulate glycogen synthesis, is protein phosphatase 1 (PP1). However, our understanding of how PP1 recruits these substrates is limited. Here, we show how PP1, together with its muscle glycogen-targeting (GM) regulatory subunit, recruits and selectively dephosphorylates its substrates. Our molecular data reveal that the GM carbohydrate binding module (GMCBM21), which is amino-terminal to the GM PP1 binding domain, has a dual function in directing PP1 substrate specificity: It either directly recruits substrates (i.e., GYS) or recruits them indirectly by localization (via glycogen for phosphorylase). Our data provide the molecular basis for PP1 regulation by GM and reveal how PP1-mediated dephosphorylation is driven by scaffolding-based substrate recruitment.
    • Increased atmospheric vapor pressure deficit reduces global vegetation growth

      Yuan, Wenping; Zheng, Yi; Piao, Shilong; Ciais, Philippe; Lombardozzi, Danica; Wang, Yingping; Ryu, Youngryel; Chen, Guixing; Dong, Wenjie; Hu, Zhongming; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2019-08-14)
      Atmospheric vapor pressure deficit (VPD) is a critical variable in determining plant photosynthesis. Synthesis of four global climate datasets reveals a sharp increase of VPD after the late 1990s. In response, the vegetation greening trend indicated by a satellite-derived vegetation index (GIMMS3g), which was evident before the late 1990s, was subsequently stalled or reversed. Terrestrial gross primary production derived from two satellite-based models (revised EC-LUE and MODIS) exhibits persistent and widespread decreases after the late 1990s due to increased VPD, which offset the positive CO2 fertilization effect. Six Earth system models have consistently projected continuous increases of VPD throughout the current century. Our results highlight that the impacts of VPD on vegetation growth should be adequately considered to assess ecosystem responses to future climate conditions.
    • Informing trait-based ecology by assessing remotely sensed functional diversity across a broad tropical temperature gradient

      Durán, Sandra M; Martin, Roberta E; Díaz, Sandra; Maitner, Brian S; Malhi, Yadvinder; Salinas, Norma; Shenkin, Alexander; Silman, Miles R; Wieczynski, Daniel J; Asner, Gregory P; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2019-12-04)
      Spatially continuous data on functional diversity will improve our ability to predict global change impacts on ecosystem properties. We applied methods that combine imaging spectroscopy and foliar traits to estimate remotely sensed functional diversity in tropical forests across an Amazon-to-Andes elevation gradient (215 to 3537 m). We evaluated the scale dependency of community assembly processes and examined whether tropical forest productivity could be predicted by remotely sensed functional diversity. Functional richness of the community decreased with increasing elevation. Scale-dependent signals of trait convergence, consistent with environmental filtering, play an important role in explaining the range of trait variation within each site and along elevation. Single- and multitrait remotely sensed measures of functional diversity were important predictors of variation in rates of net and gross primary productivity. Our findings highlight the potential of remotely sensed functional diversity to inform trait-based ecology and trait diversity-ecosystem function linkages in hyperdiverse tropical forests.
    • Magnetization switching using topological surface states

      Li, Peng; Kally, James; Zhang, Steven S-L; Pillsbury, Timothy; Ding, Jinjun; Csaba, Gyorgy; Ding, Junjia; Jiang, J S; Liu, Yunzhi; Sinclair, Robert; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2019-08-30)
      Topological surface states (TSSs) in a topological insulator are expected to be able to produce a spin-orbit torque that can switch a neighboring ferromagnet. This effect may be absent if the ferromagnet is conductive because it can completely suppress the TSSs, but it should be present if the ferromagnet is insulating. This study reports TSS-induced switching in a bilayer consisting of a topological insulator Bi2Se3 and an insulating ferromagnet BaFe12O19. A charge current in Bi2Se3 can switch the magnetization in BaFe12O19 up and down. When the magnetization is switched by a field, a current in Bi2Se3 can reduce the switching field by ~4000 Oe. The switching efficiency at 3 K is 300 times higher than at room temperature; it is ~30 times higher than in Pt/BaFe12O19. These strong effects originate from the presence of more pronounced TSSs at low temperatures due to enhanced surface conductivity and reduced bulk conductivity.
    • Measurement and implications of Saturn's gravity field and ring mass

      Iess, L; Militzer, B; Kaspi, Y; Nicholson, P; Durante, D; Racioppa, P; Anabtawi, A; Galanti, E; Hubbard, W; Mariani, M J; et al. (AMER ASSOC ADVANCEMENT SCIENCE, 2019-06-14)
      The interior structure of Saturn, the depth of its winds, and the mass and age of its rings constrain its formation and evolution. In the final phase of the Cassini mission, the spacecraft dived between the planet and its innermost ring, at altitudes of 2600 to 3900 kilometers above the cloud tops. During six of these crossings, a radio link with Earth was monitored to determine the gravitational field of the planet and the mass of its rings. We find that Saturn's gravity deviates from theoretical expectations and requires differential rotation of the atmosphere extending to a depth of at least 9000 kilometers. The total mass of the rings is (1.54 ± 0.49) × 1019 kilograms (0.41 ± 0.13 times that of the moon Mimas), indicating that the rings may have formed 107 to 108 years ago.