Showing papers by "Jet Propulsion Laboratory published in 2021"
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Cardiff University1, SLAC National Accelerator Laboratory2, University of British Columbia3, Smithsonian Institution4, California Institute of Technology5, University of Cincinnati6, University of Minnesota7, University of Chicago8, National Institute of Standards and Technology9, French Alternative Energies and Atomic Energy Commission10, University of Illinois at Urbana–Champaign11, Stanford University12, Jet Propulsion Laboratory13, Institute for the Physics and Mathematics of the Universe14, Brookhaven National Laboratory15
TL;DR: In this paper, the authors present results from an analysis of all data taken by the BICEP2, Keck Array, and BiceP3 CMB polarization experiments up to and including the 2018 observing season.
Abstract: We present results from an analysis of all data taken by the BICEP2, Keck Array, and BICEP3 CMB polarization experiments up to and including the 2018 observing season. We add additional Keck Array observations at 220 GHz and BICEP3 observations at 95 GHz to the previous 95 / 150 / 220 GHz dataset. The Q / U maps now reach depths of 2.8, 2.8, and 8.8 μ K CMB arcmin at 95, 150, and 220 GHz, respectively, over an effective area of ≈ 600 square degrees at 95 GHz and ≈ 400 square degrees at 150 and 220 GHz. The 220 GHz maps now achieve a signal-to-noise ratio on polarized dust emission exceeding that of Planck at 353 GHz. We take auto- and cross-spectra between these maps and publicly available WMAP and Planck maps at frequencies from 23 to 353 GHz and evaluate the joint likelihood of the spectra versus a multicomponent model of lensed Λ CDM + r + dust + synchrotron + noise . The foreground model has seven parameters, and no longer requires a prior on the frequency spectral index of the dust emission taken from measurements on other regions of the sky. This model is an adequate description of the data at the current noise levels. The likelihood analysis yields the constraint r 0.05 0.036 at 95% confidence. Running maximum likelihood search on simulations we obtain unbiased results and find that σ ( r ) = 0.009 . These are the strongest constraints to date on primordial gravitational waves.
263 citations
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University of Manchester1, City University of New York2, Istanbul Technical University3, New York University4, Heidelberg University5, Niels Bohr Institute6, University of Edinburgh7, University of Bologna8, Academy of Athens9, Sapienza University of Rome10, University of Naples Federico II11, Stanford University12, Institut d'Astrophysique de Paris13, University of Portsmouth14, Cardiff University15, Universidade Federal do Espírito Santo16, University of Michigan17, Asia Pacific Center for Theoretical Physics18, University of New Mexico19, University of Barcelona20, Centre national de la recherche scientifique21, Princeton University22, National Autonomous University of Mexico23, Jet Propulsion Laboratory24, INAF25, University of Chicago26, Michigan Technological University27, University of Cambridge28, Imperial College London29, Ruhr University Bochum30, University of Waterloo31, Johns Hopkins University32, University of Pennsylvania33, University of California, Davis34, Birla Institute of Technology and Science35, RWTH Aachen University36, Université libre de Bruxelles37, University of Padua38, Indian Institute of Technology Kharagpur39, Spanish National Research Council40, University of North Carolina at Chapel Hill41, University of Arizona42, University of Oslo43, Jamia Millia Islamia44, National Institute for Space Research45, Fermilab46, Presidency University, Kolkata47, Université Paris-Saclay48, University of Montpellier49, University of Szczecin50, Korea Astronomy and Space Science Institute51, University of California, Los Angeles52, Leiden University53, University of Southern Denmark54, Swarthmore College55, University of Sheffield56, University of Amsterdam57, United College, Winnipeg58, Liaoning Normal University59
TL;DR: In this article, the authors focus on the tension between Planck data and weak lensing measurements and redshift surveys, and discuss the importance of trying to fit multiple cosmological datasets with complete physical models, rather than fitting individual datasets with a few handpicked theoretical parameters.
181 citations
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TL;DR: The goal of this work is to provide an understanding of the technical choices made, the constraints that were imposed, and ultimately the validated performance of the flight model as it leaves Earth, and it will serve as the foundation for Mars operations and future processing of the data.
Abstract: On the NASA 2020 rover mission to Jezero crater, the remote determination of the texture, mineralogy and chemistry of rocks is essential to quickly and thoroughly characterize an area and to optimize the selection of samples for return to Earth. As part of the Perseverance payload, SuperCam is a suite of five techniques that provide critical and complementary observations via Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), visible and near-infrared spectroscopy (VISIR), high-resolution color imaging (RMI), and acoustic recording (MIC). SuperCam operates at remote distances, primarily 2–7 m, while providing data at sub-mm to mm scales. We report on SuperCam’s science objectives in the context of the Mars 2020 mission goals and ways the different techniques can address these questions. The instrument is made up of three separate subsystems: the Mast Unit is designed and built in France; the Body Unit is provided by the United States; the calibration target holder is contributed by Spain, and the targets themselves by the entire science team. This publication focuses on the design, development, and tests of the Mast Unit; companion papers describe the other units. The goal of this work is to provide an understanding of the technical choices made, the constraints that were imposed, and ultimately the validated performance of the flight model as it leaves Earth, and it will serve as the foundation for Mars operations and future processing of the data.
121 citations
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Los Alamos National Laboratory1, Centre National D'Etudes Spatiales2, University of South Carolina3, University of the Basque Country4, Jet Propulsion Laboratory5, Institut supérieur de l'aéronautique et de l'espace6, University of Winnipeg7, École normale supérieure de Lyon8, California Institute of Technology9, University of Copenhagen10, Johns Hopkins University Applied Physics Laboratory11, University of Málaga12, McGill University13, University of Valladolid14, University of Maryland, College Park15, State University of New York System16, University of Massachusetts Lowell17, University of New Mexico18, Search for extraterrestrial intelligence19
TL;DR: The SuperCam body unit (BU) of the Mars 2020 rover as mentioned in this paper was designed to receive light from the mast unit via a 5.8 m opti-cal fiber and the light is split into three wavelength bands by a demultiplexer, and routed via fiber bundles to three optical spectrometers, two of which (UV and violet; 245-340 and 385-465 nm) are crossed Czerny-Turner reflection spectrometer, nearly identical to their counterparts on ChemCam.
Abstract: TheSuperCaminstrumentsuiteprovidestheMars2020rover,Perseverance,with a number of versatile remote-sensing techniques that can be used at long distance as well as within the robotic-arm workspace. These include laser-induced breakdown spectroscopy (LIBS), remote time-resolved Raman and luminescence spectroscopies, and visible and in- frared (VISIR; separately referred to as VIS and IR) reflectance spectroscopy. A remote micro-imager (RMI) provides high-resolution color context imaging, and a microphone can be used as a stand-alone tool for environmental studies or to determine physical properties of rocks and soils from shock waves of laser-produced plasmas. SuperCam is built in three parts: The mast unit (MU), consisting of the laser, telescope, RMI, IR spectrometer, and associated electronics, is described in a companion paper. The on-board calibration targets are described in another companion paper. Here we describe SuperCam’s body unit (BU) and testing of the integrated instrument.
The BU, mounted inside the rover body, receives light from the MU via a 5.8 m opti- cal fiber. The light is split into three wavelength bands by a demultiplexer, and is routed via fiber bundles to three optical spectrometers, two of which (UV and violet; 245–340 and 385–465 nm) are crossed Czerny-Turner reflection spectrometers, nearly identical to their counterparts on ChemCam. The third is a high-efficiency transmission spectrometer contain- ing an optical intensifier capable of gating exposures to 100 ns or longer, with variable delay times relative to the laser pulse. This spectrometer covers 535–853 nm (105–7070 cm−1 Ra- man shift relative to the 532 nm green laser beam) with 12 cm−1 full-width at half-maximum peak resolution in the Raman fingerprint region. The BU electronics boards interface with the rover and control the instrument, returning data to the rover. Thermal systems maintain a warm temperature during cruise to Mars to avoid contamination on the optics, and cool the detectors during operations on Mars.
Results obtained with the integrated instrument demonstrate its capabilities for LIBS, for which a library of 332 standards was developed. Examples of Raman and VISIR spec- troscopy are shown, demonstrating clear mineral identification with both techniques. Lumi- nescence spectra demonstrate the utility of having both spectral and temporal dimensions. Finally, RMI and microphone tests on the rover demonstrate the capabilities of these sub- systems as well.
117 citations
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Saleh Abdalla1, Abdolnabi Abdeh Kolahchi, Michael Ablain, Susheel Adusumilli2 +357 more•Institutions (88)
TL;DR: In 2018, the 25th year of development of radar altimetry was celebrated and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences as discussed by the authors.
105 citations
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Jet Propulsion Laboratory1, Los Alamos National Laboratory2, Jacobs Engineering Group3, Carnegie Learning4, University of Tennessee5, Silver Spring Networks6, University of Southern California7, Johns Hopkins University Applied Physics Laboratory8, Natural History Museum9, Search for extraterrestrial intelligence10, Planetary Science Institute11
TL;DR: The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) is a robotic arm-mounted instrument on NASA's Perseverance rover as mentioned in this paper.
Abstract: The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) is a robotic arm-mounted instrument on NASA’s Perseverance rover. SHERLOC has two primary boresights. The Spectroscopy boresight generates spatially resolved chemical maps using fluorescence and Raman spectroscopy coupled to microscopic images (10.1 μm/pixel). The second boresight is a Wide Angle Topographic Sensor for Operations and eNgineering (WATSON); a copy of the Mars Science Laboratory (MSL) Mars Hand Lens Imager (MAHLI) that obtains color images from microscopic scales (∼13 μm/pixel) to infinity. SHERLOC Spectroscopy focuses a 40 μs pulsed deep UV neon-copper laser (248.6 nm), to a ∼100 μm spot on a target at a working distance of ∼48 mm. Fluorescence emissions from organics, and Raman scattered photons from organics and minerals, are spectrally resolved with a single diffractive grating spectrograph with a spectral range of 250 to ∼370 nm. Because the fluorescence and Raman regions are naturally separated with deep UV excitation (<250 nm), the Raman region ∼ 800 – 4000 cm−1 (250 to 273 nm) and the fluorescence region (274 to ∼370 nm) are acquired simultaneously without time gating or additional mechanisms. SHERLOC science begins by using an Autofocus Context Imager (ACI) to obtain target focus and acquire 10.1 μm/pixel greyscale images. Chemical maps of organic and mineral signatures are acquired by the orchestration of an internal scanning mirror that moves the focused laser spot across discrete points on the target surface where spectra are captured on the spectrometer detector. ACI images and chemical maps (< 100 μm/mapping pixel) will enable the first Mars in situ view of the spatial distribution and interaction between organics, minerals, and chemicals important to the assessment of potential biogenicity (containing CHNOPS). Single robotic arm placement chemical maps can cover areas up to 7x7 mm in area and, with the < 10 min acquisition time per map, larger mosaics are possible with arm movements. This microscopic view of the organic geochemistry of a target at the Perseverance field site, when combined with the other instruments, such as Mastcam-Z, PIXL, and SuperCam, will enable unprecedented analysis of geological materials for both scientific research and determination of which samples to collect and cache for Mars sample return.
92 citations
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TL;DR: In this paper, the authors compare long-term changes in the snowmelt and SWE from snow monitoring stations in western North America and find 34% of stations exhibit increasing winter snow-melt trends, a factor of three larger than the 11% showing SWE declines.
Abstract: In many mountainous regions, winter precipitation accumulates as snow that melts in the spring and summer, which provides water to one billion people globally Climate warming and earlier snowmelt compromise this natural water storage Although snowpack trend analyses commonly focus on the snow water equivalent (SWE), we propose that trends in the accumulation season snowmelt serve as a critical indicator of hydrological change Here we compare long-term changes in the snowmelt and SWE from snow monitoring stations in western North America and find 34% of stations exhibit increasing winter snowmelt trends (P < 005), a factor of three larger than the 11% showing SWE declines (P < 005) Snowmelt trends are highly sensitive to temperature and an underlying warming signal, whereas SWE trends are more sensitive to precipitation variability Thus, continental-scale snow water resources are in steeper decline than inferred from SWE trends alone More winter snowmelt will complicate future water resource planning and management Mountain snowpack declines are often tracked using snow water equivalent trends sensitive to highly variable precipitation Observational work proposes temperature-driven daily snowmelt during the accumulation season as an alternative metric, with increases that are three times more widespread
73 citations
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University of Manchester1, City University of New York2, Istanbul Technical University3, New York University4, Heidelberg University5, Niels Bohr Institute6, University of Edinburgh7, University of Bologna8, Academy of Athens9, Sapienza University of Rome10, University of Naples Federico II11, Stanford University12, Pierre-and-Marie-Curie University13, Istituto Nazionale di Fisica Nucleare14, Cardiff University15, Universidade Federal do Espírito Santo16, University of Michigan17, Asia Pacific Center for Theoretical Physics18, University of New Mexico19, University of Barcelona20, National Autonomous University of Mexico21, Jet Propulsion Laboratory22, University of Chicago23, Michigan Technological University24, University of Cambridge25, Ruhr University Bochum26, Johns Hopkins University27, University of Pennsylvania28, University of California, Davis29, Birla Institute of Technology and Science30, RWTH Aachen University31, Université libre de Bruxelles32, University of Padua33, Indian Institute of Technology Kharagpur34, Spanish National Research Council35, University of North Carolina at Chapel Hill36, University of Arizona37, University of Oslo38, Jamia Millia Islamia39, National Institute for Space Research40, Fermilab41, University of Paris42, University of Montpellier43, University of Szczecin44, Korea Astronomy and Space Science Institute45, University of Southern California46, Centre national de la recherche scientifique47, Leiden University48, Swarthmore College49, University of Sheffield50, University of Amsterdam51, Chinese Academy of Sciences52, United College, Winnipeg53, Liaoning Normal University54
TL;DR: In particular, the Planck Cosmic Microwave Background power spectra, assuming the nominal likelihood, prefer a closed universe at more than 99% confidence level as mentioned in this paper. But this anomaly may be the result of an unresolved systematic error or just a statistical fluctuation.
63 citations
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TL;DR: In this article, the authors reviewed the research on the Reversed Field Pinch in the last three decades and concluded that substantial experimental and theoretical progress and transformational changes have been achieved since the last review.
Abstract: This paper reviews the research on the Reversed Field Pinch in the last three decades. Substantial experimental and theoretical progress and transformational changes have been achieved since the last review (Bodin, 1990). The experiments have been performed in devices with different sizes and capabilities. The largest one are RFX-mod in Padova (Italy) and MST in Madison (US). The experimental community includes also EXTRAP-T2R in Sweden, RELAX in Japan and KTX in China. Impressive improvements in the performance are the result of exploration of two lines: the high current operation with the spontaneous occurrence of helical equilibria with good magnetic flux surfaces and the active control of the current profile. A crucial ingredient for the advancements obtained in the experiments has been the development of state-of-art active feedback control systems allowing the control of MHD instabilities in presence of a thin shell. Contributions of the RFP line to the fusion grand challenge will be reported. The balance between achievements and still open issues leads us to the conclusion the RFP can be a valuable and diverse contributor in the quest for fusion electricity.
61 citations
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Deutscher Wetterdienst1, Environment Canada2, Alfred Wegener Institute for Polar and Marine Research3, Danish Meteorological Institute4, Finnish Meteorological Institute5, Met Office6, University of Bremen7, Royal Netherlands Meteorological Institute8, Royal Meteorological Institute9, MeteoSwiss10, University of Toronto11, Cooperative Institute for Research in Environmental Sciences12, National Center for Atmospheric Research13, Agencia Estatal de Meteorología14, Jet Propulsion Laboratory15, Bureau of Meteorology16, University of Wollongong17, National Institute of Water and Atmospheric Research18, Goddard Space Flight Center19, European Centre for Medium-Range Weather Forecasts20, National Oceanic and Atmospheric Administration21
TL;DR: In this article, the COVID-19 related emissions reductions appear to be the major cause for the observed reduced free tropospheric ozone in 2020, over several months, and at so many stations, has not been observed in any previous year since at least 2000.
Abstract: Throughout spring and summer 2020, ozone stations in the northern extratropics recorded unusually low ozone in the free troposphere. From April to August, and from 1 to 8 kilometers altitude, ozone was on average 7% (≈4 nmol/mol) below the 2000 to 2020 climatological mean. Such low ozone, over several months, and at so many stations, has not been observed in any previous year since at least 2000. Atmospheric composition analyses from the Copernicus Atmosphere Monitoring Service and simulations from the NASA GMI model indicate that the large 2020 springtime ozone depletion in the Arctic stratosphere contributed less than one quarter of the observed tropospheric anomaly. The observed anomaly is consistent with recent chemistry‐climate model simulations, which assume emissions reductions similar to those caused by the COVID‐19 crisis. COVID‐19 related emissions reductions appear to be the major cause for the observed reduced free tropospheric ozone in 2020.
61 citations
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Johns Hopkins University Applied Physics Laboratory1, Goddard Space Flight Center2, Jet Propulsion Laboratory3, Ithaca College4, Ames Research Center5, Planetary Science Institute6, Southwest Research Institute7, Smithsonian Institution8, NASA Headquarters9, University of Oxford10, Honeybee Robotics11, ETH Zurich12
TL;DR: The Dragonfly mission as discussed by the authors was the first NASA mission to explicitly incorporate the search for signs of life into its mission goals since the Viking landers in 1976, along with Perseverance.
Abstract: NASA's Dragonfly mission will send a rotorcraft lander to the surface of Titan in the mid-2030s. Dragonflyʼs science themes include investigation of Titan's prebiotic chemistry, habitability, and potential chemical biosignatures from both water-based "life as we know it" (as might occur in the interior mantle ocean, potential cryovolcanic flows, and/or impact melt deposits) and potential "life, but not as we know it" that might use liquid hydrocarbons as a solvent (within Titan's lakes, seas, and/or aquifers). Consideration of both of these solvents simultaneously led to our initial landing site in Titan's equatorial dunes and interdunes to sample organic sediments and water ice, respectively. Ultimately, Dragonflyʼs traverse target is the 80 km diameter Selk Crater, at 7°N, where we seek previously liquid water that has mixed with surface organics. Our science goals include determining how far prebiotic chemistry has progressed on Titan and what molecules and elements might be available for such chemistry. We will also determine the role of Titan's tropical deserts in the global methane cycle. We will investigate the processes and processing rates that modify Titan's surface geology and constrain how and where organics and liquid water can mix on and within Titan. Importantly, we will search for chemical biosignatures indicative of past or extant biological processes. As such, Dragonfly, along with Perseverance, is the first NASA mission to explicitly incorporate the search for signs of life into its mission goals since the Viking landers in 1976.
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12 Jul 2021
TL;DR: In this paper, the authors proposed an approach for assessing traversability and planning a safe, feasible, and fast trajectory in real-time, which relies on rapid uncertainty-aware mapping and traversability evaluation, tail risk assessment using the Conditional Value-at-Risk (CVaR), and efficient risk and constraint-aware kinodynamic motion planning using sequential quadratic programming-based predictive control.
Abstract: Although ground robotic autonomy has gained widespread usage in structured and controlled environments, autonomy in unknown and off-road terrain remains a difficult problem. Extreme, off-road, and unstructured environments such as undeveloped wilderness, caves, and rubble pose unique and challenging problems for autonomous navigation. To tackle these problems we propose an approach for assessing traversability and planning a safe, feasible, and fast trajectory in real-time. Our approach, which we name STEP (Stochastic Traversability Evaluation and Planning), relies on: 1) rapid uncertainty-aware mapping and traversability evaluation, 2) tail risk assessment using the Conditional Value-at-Risk (CVaR), and 3) efficient risk and constraint-aware kinodynamic motion planning using sequential quadratic programming-based (SQP) model predictive control (MPC). We analyze our method in simulation and validate its efficacy on wheeled and legged robotic platforms exploring extreme terrains including an abandoned subway and an underground lava tube.
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TL;DR: In this paper, the authors present a model that incorporates randomized injection of reducing greenhouse gases and oxidation due to hydrogen escape to investigate the conditions responsible for these diverse observations, and find that Mars could have transitioned repeatedly from reducing (hydrogen-rich) to oxidizing (oxygen-rich), atmospheric conditions in its early history.
Abstract: Reconciling the geology of Mars with models of atmospheric evolution remains a major challenge. Martian geology is characterized by past evidence for episodic surface liquid water, and geochemistry indicating a slow and intermittent transition from wetter to drier and more oxidizing surface conditions. Here we present a model that incorporates randomized injection of reducing greenhouse gases and oxidation due to hydrogen escape to investigate the conditions responsible for these diverse observations. We find that Mars could have transitioned repeatedly from reducing (hydrogen-rich) to oxidizing (oxygen-rich) atmospheric conditions in its early history. Our model predicts a generally cold early Mars, with mean annual temperatures below 240 K. If peak reducing-gas release rates and background carbon dioxide levels are high enough, it nonetheless exhibits episodic warm intervals sufficient to degrade crater walls, form valley networks and create other fluvial/lacustrine features. Our model also predicts transient build-up of atmospheric oxygen, which can help explain the occurrence of oxidized mineral species such as manganese oxides at Gale Crater. We suggest that the apparent Noachian–Hesperian transition from phyllosilicate deposition to sulfate deposition around 3.5 billion years ago can be explained as a combined outcome of increasing planetary oxidation, decreasing groundwater availability and a waning bolide impactor flux, which dramatically slowed the remobilization and thermochemical destruction of surface sulfates. Ultimately, rapid and repeated variations in Mars’s early climate and surface chemistry would have presented both challenges and opportunities for any emergent microbial life. Mars’s early climate and surface chemistry varied between a generally cold, oxidizing environment and warmer, more reducing conditions, according to a model of atmospheric evolution driven by stochastic, random injection of greenhouse gases.
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TL;DR: In this article, the authors present synoptic measurements of dust, temperature, ice, water and hydrogen on Mars during a regional dust event, demonstrating that individual dust events can boost planetary hydrogen escape by a factor of five to ten.
Abstract: Mars has lost most of its initial water to space as atomic hydrogen and oxygen. Spacecraft measurements have determined that present-day hydrogen escape undergoes large variations with season that are inconsistent with long-standing explanations. The cause is incompletely understood, with likely contributions from seasonal changes in atmospheric circulation, dust activity and solar extreme ultraviolet input. Although some modelling and indirect observational evidence suggest that dust activity can explain the seasonal trend, no previous study has been able to unambiguously distinguish seasonal from dust-driven forcing. Here we present synoptic measurements of dust, temperature, ice, water and hydrogen on Mars during a regional dust event, demonstrating that individual dust events can boost planetary H loss by a factor of five to ten. This regional storm occurred in the declining phase of the known seasonal trend, establishing that dust forcing can override this trend to drive enhanced escape. Because similar regional storms occur in most Mars years, these storms may be responsible for a large fraction of Martian water loss and represent an important driver of Mars atmospheric evolution.
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TL;DR: In this paper, the authors summarized two decades (2000-2019) of climatology and trends in aerosol loading and optical properties using a high spatial resolution data obtained from NASA's MODIS MAIAC and MISR aerosol products supplemented by moderate resolution aerosol data from OMI sensor over South Asia (SA).
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Johns Hopkins University Applied Physics Laboratory1, University of Maryland, College Park2, Goddard Space Flight Center3, Ames Research Center4, Cornell University5, Jet Propulsion Laboratory6, Southwest Research Institute7, Tufts University8, Free University of Berlin9, University of California, Berkeley10, Woods Hole Oceanographic Institution11, German Aerospace Center12, INAF13
TL;DR: Orbilander, a mission concept that would first orbit and then land on Enceladus, represented the best balance as discussed by the authors, including a more detailed science operations plan during both orbital and landing phases, landing site characterization and selection analyses, and landing procedures.
Abstract: Enceladus’s long-lived plume of ice grains and water vapor makes accessing oceanic material readily achievable from orbit (around Saturn or Enceladus) and from the moon’s surface. In preparation for the National Academies of Sciences, Engineering and Medicine 2023–2032 Planetary Science and Astrobiology Decadal Survey, we investigated four architectures capable of collecting and analyzing plume material from orbit and/or on the surface to address the most pressing questions at Enceladus: Is the subsurface ocean inhabited? Why, or why not? Trades specific to these four architectures were studied to allow an evaluation of the science return with respect to investment. The team found that Orbilander, a mission concept that would first orbit and then land on Enceladus, represented the best balance. Orbilander was thus studied at a higher fidelity, including a more detailed science operations plan during both orbital and landed phases, landing site characterization and selection analyses, and landing procedures. The Orbilander mission concept demonstrates that scientifically compelling but resource-conscious Flagship-class missions can be executed in the next decade to search for life at Enceladus.
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TL;DR: In this article, the authors reviewed the first 15 years of the Microwave Limb Sounder (MLS) measurements from the NASA's 190 GHz subsystem, along with other 190 GHz information, with a focus on their longterm stability, largely based on comparisons with measurements from other sensors.
Abstract: . The Microwave Limb Sounder (MLS), launched on NASA's Aura spacecraft
in 2004, measures vertical profiles of the abundances of key
atmospheric species from the upper troposphere to the mesosphere
with daily near-global coverage. We review the first 15 years of
the record of H2O and N2O measurements from the MLS
190 GHz subsystem (along with other 190 GHz
information), with a focus on their long-term stability, largely
based on comparisons with measurements from other sensors. These
comparisons generally show signs of an increasing drift in the MLS
“version 4” (v4) H2O record starting around 2010.
Specifically, comparisons with v4.1 measurements from the
Atmospheric Chemistry Experiment Fourier Transform Spectrometer
(ACE-FTS) indicate a ∼ 2 %–3 % per decade drift over much of
the stratosphere, increasing to as much as ∼ 7 % per decade
around 46 hPa. Larger drifts, of around 7 %–11 % per decade, are seen
in comparisons to balloon-borne frost point hygrometer measurements
in the lower stratosphere. Microphysical calculations considering
the formation of polar stratospheric clouds in the Antarctic winter
stratosphere corroborate a drift in MLS v4 water vapor measurements
in that region and season. In contrast, comparisons with the
Sounding of the Atmosphere using Broadband Emission Radiometry
(SABER) instrument on NASA's Thermosphere Ionosphere Mesosphere
Energetics and Dynamics (TIMED) mission, and with ground-based Water
Vapor Millimeter-wave Spectrometer (WVMS) instruments, do not show
statistically significant drifts. However, the uncertainty in these
comparisons is large enough to encompass most of the drifts
identified in other comparisons. In parallel, the MLS v4
N2O product is shown to be generally decreasing over the
same period (when an increase in stratospheric N2O is
expected, reflecting a secular growth in emissions), with a more
pronounced drift in the lower stratosphere than that found for
H2O . Comparisons to ACE-FTS and to MLS N2O
observations in a different spectral region, with the latter available
from 2004 to 2013, indicate an altitude-dependent drift, growing from
5 % per decade or less in the mid-stratosphere to as much as 15 % per decade
in the lower stratosphere. Detailed investigations of the behavior
of the MLS 190 GHz subsystem reveal a drift in its “sideband
fraction” (the relative sensitivity of the 190 GHz receiver
to the two different parts of the microwave spectrum that it observes).
Our studies indicate that sideband fraction drift accounts for much
of the observed changes in the MLS H2O product and some
portion of the changes seen in N2O . The 190 GHz
sideband fraction drift has been corrected in the new “version 5” (v5)
MLS algorithms, which have now been used to reprocess the entire MLS
record. As a result of this correction, the MLS v5 H2O
record shows no statistically significant drifts compared to
ACE-FTS. However, statistically significant drifts remain between
MLS v5 and frost point measurements, although they are reduced.
Drifts in v5 N2O are about half the size of those in v4 but
remain statistically significant. Scientists are advised to use MLS
v5 data in all future studies. Quantification of interregional and
seasonal to annual changes in MLS H2O and N2O will
not be affected by the drift. However, caution is advised in
studies using the MLS record to examine long-term (multiyear)
variability and trends in either of these species, especially
N2O ; such studies should only be undertaken in consultation
with the MLS team. Importantly, this drift does not affect any of
the MLS observations made in other spectral regions such as
O3 , HCl, CO, ClO, or temperature.
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National Center for Atmospheric Research1, University of Toronto2, Dalhousie University3, Université libre de Bruxelles4, University of Paris5, Jet Propulsion Laboratory6, University of California, Los Angeles7, Goddard Space Flight Center8, University of Maryland, College Park9, National Oceanic and Atmospheric Administration10, Ames Research Center11
TL;DR: In this paper, the authors used the long-term records of CO from the Measurements of Pollution in the Troposphere (MOPITT) and AOD from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument.
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Johns Hopkins University Applied Physics Laboratory1, Southwest Research Institute2, Ames Research Center3, University of Grenoble4, NASA Lunar Science Institute5, Jet Propulsion Laboratory6, University of Texas at San Antonio7, Massachusetts Institute of Technology8, University of Colorado Boulder9, University College London10, Birkbeck, University of London11, Washington University in St. Louis12, Lowell Observatory13, Herzberg Institute of Astrophysics14, Stanford University15, New Mexico State University16, University of California, Los Angeles17, Columbia University18, University of Central Florida19, Planetary Science Institute20, University of Texas at Austin21, University of Maryland, College Park22, Goddard Space Flight Center23, Aix-Marseille University24
TL;DR: In this article, the long-term nature of the stable majority ices that could be present in Kuiper Belt object (KBO) 2014 MU69 (also called Arrokoth; hereafter “MU69”) after its 4.6 Gyr residence in the Edgeworth-Kuiper belt (EKB) as a cold classical object was discussed in a thermodynamic, geologically empirical way.
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TL;DR: This paper presented the first description of key facies in the sulfate-bearing unit, recently observed in the distance by the Curiosity rover, and proposed a model for changes in depositional environments.
Abstract: The Curiosity rover is exploring Hesperian-aged stratigraphy in Gale crater, Mars, where a transition from clay-bearing units to a layered sulfate-bearing unit has been interpreted to represent a major environmental transition of unknown character. We present the first description of key facies in the sulfate-bearing unit, recently observed in the distance by the rover, and propose a model for changes in depositional environments. Our results indicate a transition from lacustrine mudstones into thick aeolian deposits, topped by a major deflation surface, above which strata show architectures likely diagnostic of a subaqueous environment. This model offers a reference example of a depositional sequence for layered sulfate-bearing strata, which have been identified from orbit in other locations globally. It differs from the idea of a monotonic Hesperian climate change into long-term aridity on Mars and instead implies a period characterized by multiple transitions between sustained drier and wetter climates.
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TL;DR: In this article, a numerical analysis based on detached eddy simulations is conducted to investigate vortex instabilities in the wake of a preswirl pumpjet propulsor, and three models are established to separate the roles that the rotor, stator and duct play in the vortex structure of the pumpjet propeller.
Abstract: A numerical analysis based on detached eddy simulations is conducted to investigate vortex instabilities in the wake of a preswirl pumpjet propulsor. Three models are established to separate the roles that the rotor, stator, and duct play in the vortex structure of the pumpjet propulsor. In this paper, only the vortex structure of the rotor is considered. The results show that the vortex system of the rotor is mainly composed of the tip vortices, a hub vortex, the trailing tip vortices, and the trailing root vortices. The trailing tip vortices are generated by the premature shedding of the tip vortices in the rotor model compared with a normal single propeller. The existence of trailing root vortices increases the stability of the hub vortex. Furthermore, a unique multi-inductance instability mode of the tip vortex, called the “overlap–forward” phenomenon, is found for low values of the advance coefficient J. It is found that the instability of the tip vortex depends not only on the spiral-to-spiral distance but also on the highest-efficiency point of the propeller. The instability inception point of the tip vortex moves farther downstream with increasing J, whereas when J is greater than the highest-efficiency point of the propeller, the stable length of the tip vortices drops sharply. The energy transfer process from blade harmonics to shaft harmonics of the tip vortices depends on J and is related to the spatial evolution of the tip vortices.
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TL;DR: The record of the coevolution of oxygenic phototrophs and the environment is preserved in three forms: genomes of modern organisms, diverse geochemical signals of surface oxidation and diagnostic P...
Abstract: The record of the coevolution of oxygenic phototrophs and the environment is preserved in three forms: genomes of modern organisms, diverse geochemical signals of surface oxidation and diagnostic P...
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Lawrence Livermore National Laboratory1, University of Trento2, Australian National University3, Barcelona Supercomputing Center4, Jet Propulsion Laboratory5, Lawrence Berkeley National Laboratory6, Linköping University7, University of Toulouse8, Argonne National Laboratory9, National Center for Atmospheric Research10, Geophysical Fluid Dynamics Laboratory11, World Meteorological Organization12
TL;DR: With a number of interacting services and a large volume of data anticipated for CMIP6, the CMIP Data Node Operations Team (CDNOT) was formed and coordinated and implemented a series of CMIP 6 preparation data challenges to test all the interacting components in the ESGFCMIP6 software ecosystem.
Abstract: . The distribution of data contributed to the Coupled Model Intercomparison Project Phase 6 (CMIP6) is via the Earth System Grid Federation (ESGF). The ESGF is a network of internationally distributed sites that together work as a federated data archive. Data records from climate modelling institutes are published to the ESGF and then shared around the world. It is anticipated that CMIP6 will produce approximately 20 PB of data to be published and distributed via the ESGF. In addition to this large volume of data a number of value-added CMIP6 services are required to interact with the ESGF; for example the citation and errata services both interact with the ESGF but are not a core part of its infrastructure. With a number of interacting services and a large volume of data anticipated for CMIP6, the CMIP Data Node Operations Team (CDNOT) was formed. The CDNOT coordinated and implemented a series of CMIP6 preparation data challenges to test all the interacting components in the ESGF CMIP6 software ecosystem. This ensured that when CMIP6 data were released they could be reliably distributed.
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TL;DR: In this paper, the authors investigated whether a regional-scale reduction of anthropogenic CO 2 emissions during the COVID-19 pandemic can be detected using space-based observations of atmospheric CO 2, and analyzed a small ensemble of OCO-2 and GOSAT satellite retrievals of column-averaged dry-air fraction of CO 2.
Abstract: . The COVID-19 pandemic resulted in reduced anthropogenic
carbon dioxide (CO 2 ) emissions during 2020 in large parts of the world.
To investigate whether a regional-scale reduction of anthropogenic CO 2
emissions during the COVID-19 pandemic can be detected using space-based
observations of atmospheric CO 2 , we have analysed a small ensemble of
OCO-2 and GOSAT satellite retrievals of column-averaged dry-air mole
fractions of CO 2 , i.e. XCO 2 . We focus on East China and use a
simple data-driven analysis method. We present estimates of the relative
change of East China monthly emissions in 2020 relative to previous periods,
limiting the analysis to October-to-May periods to minimize the impact of
biogenic CO 2 fluxes. The ensemble mean indicates an emission reduction
by approximately 10 % ± 10 % in March and April 2020. However, our
results show considerable month-to-month variability and significant
differences across the ensemble of satellite data products analysed. For
example, OCO-2 suggests a much smaller reduction ( ∼ 1 %–2 % ± 2 %). This indicates that it is challenging to reliably detect and
to accurately quantify the emission reduction with current satellite data
sets. There are several reasons for this, including the sparseness of the
satellite data but also the weak signal; the expected regional XCO 2
reduction is only on the order of 0.1–0.2 ppm. Inferring COVID-19-related
information on regional-scale CO 2 emissions using current satellite
XCO 2 retrievals likely requires, if at all possible, a more
sophisticated analysis method including detailed transport modelling and
considering a priori information on anthropogenic and natural CO 2 surface
fluxes.
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TL;DR: In this paper, the authors use established SLR scenarios and flooding thresholds to demonstrate how the combined effects of SLR and nodal cycle modulations of tidal amplitude lead to acute inflections in projections of future high-tide flooding.
Abstract: Coastal locations around the United States, particularly along the Atlantic coast, are experiencing recurrent flooding at high tide. Continued sea-level rise (SLR) will exacerbate the issue where present, and many more locations will begin to experience recurrent high-tide flooding (HTF) in the coming decades. Here we use established SLR scenarios and flooding thresholds to demonstrate how the combined effects of SLR and nodal cycle modulations of tidal amplitude lead to acute inflections in projections of future HTF. The mid-2030s, in particular, may see the onset of rapid increases in the frequency of HTF in multiple US coastal regions. We also show how annual cycles and sea-level anomalies lead to extreme seasons or months during which many days of HTF cluster together. Clustering can lead to critical frequencies of HTF occurring during monthly or seasonal periods one to two decades prior to being expected on an annual basis. High-tide flooding (HTF) is more likely with sea-level rise. Projections along the United States coastline, considering likely sea-level rise and tidal amplitude cycles, suggest increased HTF event clustering in time and rapid increases in annual HTF frequency as early as the mid-2030s.
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University of Western Australia1, University of California, Santa Cruz2, University of Miami3, University of Washington4, Woods Hole Oceanographic Institution5, Commonwealth Scientific and Industrial Research Organisation6, Macquarie University7, Dalhousie University8, National Oceanic and Atmospheric Administration9, Deakin University10, Jet Propulsion Laboratory11, University of St Andrews12, Edmund Mach Foundation13, University of Konstanz14, Max Planck Society15, Swedish University of Agricultural Sciences16, King Abdullah University of Science and Technology17, University of Queensland18, Spanish National Research Council19, Murdoch University20, University of Tasmania21, University of Hawaii at Manoa22, Monterey Bay Aquarium Research Institute23, Silver Spring Networks24, Federal University of São Paulo25, University of Southampton26, Office of Naval Research27
TL;DR: A standardisation framework adhering to existing data principles and involving the use of simple templates to create a data flow from manufacturers and researchers to compliant repositories is proposed, and will provide a starting point for broader efforts to establish interoperable bio‐logging data formats across all fields in animal ecology.
Abstract: Bio-logging data obtained by tagging animals are key to addressing global conservation challenges. However, the many thousands of existing bio-logging datasets are not easily discoverable, universally comparable, nor readily accessible through existing repositories and across platforms, slowing down ecological research and effective management. A set of universal standards is needed to ensure discoverability, interoperability and effective translation of bio-logging data into research and management recommendations.We propose a standardisation framework adhering to existing data principles (FAIR: Findable, Accessible, Interoperable and Reusable; and TRUST: Transparency, Responsibility, User focus, Sustainability and Technology) and involving the use of simple templates to create a data flow from manufacturers and researchers to compliant repositories, where automated procedures should be in place to prepare data availability into four standardised levels: (a) decoded raw data, (b) curated data, (c) interpolated data and (d) gridded data. Our framework allows for integration of simple tabular arrays (e.g. csv files) and creation of sharable and interoperable network Common Data Form (netCDF) files containing all the needed information for accuracy-of-use, rightful attribution (ensuring data providers keep ownership through the entire process) and data preservation security.We show the standardisation benefits for all stakeholders involved, and illustrate the application of our framework by focusing on marine animals and by providing examples of the workflow across all data levels, including filled templates and code to process data between levels, as well as templates to prepare netCDF files ready for sharing.Adoption of our framework will facilitate collection of Essential Ocean Variables (EOVs) in support of the Global Ocean Observing System (GOOS) and inter-governmental assessments (e.g. the World Ocean Assessment), and will provide a starting point for broader efforts to establish interoperable bio-logging data formats across all fields in animal ecology.
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Dartmouth College1, University of North Carolina at Chapel Hill2, University of Texas at Austin3, University of Tokyo4, University of Wisconsin-Madison5, American Museum of Natural History6, Cadi Ayyad University7, Smithsonian Institution8, University of Kansas9, University of Arizona10, American Association of Variable Star Observers11, Massachusetts Institute of Technology12, Western Connecticut State University13, University of New Mexico14, Swarthmore College15, George Mason University16, Keele University17, University of Toronto18, Université de Montréal19, NASA Exoplanet Science Institute20, Jet Propulsion Laboratory21, University of California, Riverside22, Max Planck Society23, California Institute of Technology24, Ames Research Center25, Goddard Space Flight Center26, Princeton University27
TL;DR: In this article, the authors presented the discovery of the young planetary system TOI 451 (TIC 257605131, Gaia DR2 4844691297067063424), a member of the 120-Myr-old Pisces-Eridanus stream (Psc--Eri).
Abstract: Young exoplanets can offer insight into the evolution of planetary atmospheres, compositions, and architectures. We present the discovery of the young planetary system TOI 451 (TIC 257605131, Gaia DR2 4844691297067063424). TOI 451 is a member of the 120-Myr-old Pisces--Eridanus stream (Psc--Eri). We confirm membership in the stream with its kinematics, its lithium abundance, and the rotation and UV excesses of both TOI 451 and its wide binary companion, TOI 451 B (itself likely an M dwarf binary). We identified three candidate planets transiting in the TESS data and followed up the signals with photometry from Spitzer and ground-based telescopes. The system comprises three validated planets at periods of 1.9, 9.2 and 16 days, with radii of 1.9, 3.1, and 4.1 Earth radii, respectively. The host star is near-solar mass with V=11.0 and H=9.3 and displays an infrared excess indicative of a debris disk. The planets offer excellent prospects for transmission spectroscopy with HST and JWST, providing the opportunity to study planetary atmospheres that may still be in the process of evolving.
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Massachusetts Institute of Technology1, Space Telescope Science Institute2, Wayne State University3, Virginia Tech4, University of California, Irvine5, University of Wyoming6, Spectral Sciences Incorporated7, University of St Andrews8, Chinese Academy of Sciences9, Leiden University10, Netherlands Institute for Space Research11, Durham University12, Spanish National Research Council13, Georgia State University14, University of California, Berkeley15, University of Haifa16, University of Padua17, INAF18, University of Kentucky19, Herzberg Institute of Astrophysics20, Tel Aviv University21, University of Leicester22, National Autonomous University of Mexico23, Jet Propulsion Laboratory24, University of Arizona25, York University26, Peking University27, University of Hamburg28, University of Belgrade29, Brigham Young University30, Ohio State University31, Western Michigan University32, Academy of Sciences of the Czech Republic33, University of Southampton34, University of Nevada, Las Vegas35, Universidade Federal do Rio Grande do Sul36, University of California, Los Angeles37, University of Copenhagen38, Shanghai Jiao Tong University39
TL;DR: In this paper, the first results from the ongoing, intensive, multi-wavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817 were presented, showing that the X-ray spectrum is highly absorbed, and there are new blueshifted,broad and narrow UV absorption lines, which suggest that a dust-free, ionized, cobalt-obscurer located at the inner broad line region partially covers the central source.
Abstract: We present the first results from the ongoing, intensive, multi-wavelength
monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this AGN
was, in part, selected for its historically unobscured nature, we discovered
that the X-ray spectrum is highly absorbed, and there are new blueshifted,
broad and narrow UV absorption lines, which suggest that a dust-free, ionized
obscurer located at the inner broad line region partially covers the central
source. Despite the obscuration, we measure UV and optical continuum
reverberation lags consistent with a centrally illuminated Shakura-Sunyaev thin
accretion disk, and measure reverberation lags associated with the optical
broad line region, as expected. However, in the first 55 days of the campaign,
when the obscuration was becoming most extreme, we observe a de-coupling of the
UV continuum and the UV broad emission line variability. The correlation
recovers in the next 42 days of the campaign, as Mrk 817 enters a less obscured
state. The short CIV and Ly alpha lags suggest that the accretion disk extends
beyond the UV broad line region.
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European Southern Observatory1, Leiden University2, ETH Zurich3, University of California, Santa Cruz4, University of Amsterdam5, University of Grenoble6, Space Telescope Science Institute7, Jet Propulsion Laboratory8, California Institute of Technology9, University of Chile10, University of Exeter11, Max Planck Society12, University of Lyon13, University of Cambridge14, Valparaiso University15, Paris Diderot University16, Aix-Marseille University17, Diego Portales University18
TL;DR: In this paper, the authors measured the near-infrared linear polarization of 20 known directly imaged exoplanets and brown dwarf companions with the SPHERE-IRDIS at the Very Large Telescope.
Abstract: Context. Young giant planets and brown dwarf companions emit near-infrared radiation that can be linearly polarized up to several percent. This polarization can reveal the presence of an (unresolved) circumsubstellar accretion disk, rotation-induced oblateness of the atmosphere, or an inhomogeneous distribution of atmospheric dust clouds.Aims. We aim to measure the near-infrared linear polarization of 20 known directly imaged exoplanets and brown dwarf companions.Methods. We observed the companions with the high-contrast imaging polarimeter SPHERE-IRDIS at the Very Large Telescope. We reduced the data using the IRDAP pipeline to correct for the instrumental polarization and crosstalk of the optical system with an absolute polarimetric accuracy We report the first detection of polarization originating from substellar companions, with a polarization of several tenths of a percent for DH Tau B and GSC 6214-210 B in H -band. By comparing the measured polarization with that of nearby stars, we find that the polarization is unlikely to be caused by interstellar dust. Because the companions have previously measured hydrogen emission lines and red colors, the polarization most likely originates from circumsubstellar disks. Through radiative transfer modeling, we constrain the position angles of the disks and find that the disks must have high inclinations. For the 18 other companions, we do not detect significant polarization and place subpercent upper limits on their degree of polarization. We also present images of the circumstellar disks of DH Tau, GQ Lup, PDS 70, β Pic, and HD 106906. We detect a highly asymmetric disk around GQ Lup and find evidence for multiple scattering in the disk of PDS 70. Both disks show spiral-like features that are potentially induced by GQ Lup B and PDS 70 b, respectively.Conclusions. The presence of the disks around DH Tau B and GSC 6214-210 B as well as the misalignment of the disk of DH Tau B with the disk around its primary star suggest in situ formation of the companions. The non-detections of polarization for the other companions may indicate the absence of circumsubstellar disks, a slow rotation rate of young companions, the upper atmospheres containing primarily submicron-sized dust grains, and/or limited cloud inhomogeneity.
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TL;DR: The AMBITION project as discussed by the authors is a mission to return the first-ever cryogenically stored sample of a cometary nucleus, that has been proposed for the ESA Science Programme Voyage 2050.
Abstract: We describe the AMBITION project, a mission to return the first-ever cryogenically- stored sample of a cometary nucleus, that has been proposed for the ESA Science Programme Voyage 2050. Comets are the leftover building blocks of giant planet cores and other planetary bodies, and fingerprints of Solar System’s formation pro- cesses. We summarise some of the most important questions still open in cometary science and Solar System formation after the successful Rosetta mission. We show that many of these scientific questions require sample analysis using techniques that are only possible in laboratories on Earth. We summarize measurements, instrumen- tation and mission scenarios that can address these questions. We emphasize the need for returning a sample collected at depth or, still more challenging, at cryogenic tem- peratures while preserving the stratigraphy of the comet nucleus surface layers. We provide requirements for the next generation of landers, for cryogenic sample acqui- sition and storage during the return to Earth. Rendezvous missions to the main belt comets and Centaurs, expanding our knowledge by exploring new classes of comets, are also discussed. The AMBITION project is discussed in the international context of comet and asteroid space exploration.