not applicable

Mariner 10 Plasma Experiment (PLS) derived ELECTRON MOMENTS data at Mercury.

Abstract ======== This data set consists of the MESSENGER MAG calibrated observations, also known as CDRs. The MAG experiment is a miniature three-axis ring-core fluxgate magnetometer with low- noise electronics. There are five MAG CDR data products, which mainly differ in the coordinate system.

Abstract ======== This data set consists of the MESSENGER MAG reduced observations, also known as RDRs. The MAG experiment is a miniature three-axis ring-core fluxgate magnetometer with low- noise electronics. There are five types of MAG RDR data products, which differ in the coordinate system. For each type, one or more averaging intervals are available.

The Sacramento / San Joaquin River Delta (SSJRD) is contaminated with legacy mercury (Hg) from historical mining and mineral processing activities throughout the watershed, as well as from contemporary atmospheric and industrial inputs. The current project was designed for the purpose of developing high-resolution spatial and temporal models for estimating concentrations of mercury species in surface waters of the SSJRD. The field component of the project brings together three high-resolution platforms for collecting water-quality data (fixed continuous monitoring stations (CMS) outfitted with in-situ sensors, spatial mapping using boat-mounted flow-through sensors, and satellite-based remote sensing) coupled with a discrete sample collection program for mercury species and ancillary water-quality metrics. The four mercury species targeted in the study include both particulate and filter-passing fractions of total mercury and methylmercury. Field data were collected during the period July 2019 through July 2021. Sampling at the four primary CMS sites included discrete sample collections during all station operations and maintenance visits (approximately every six weeks) and during four 13-hour to 15-hour tidal sampling events, during which samples were collected every 2 hours (approximately) over a full tidal cycle. This tidal sampling occurred once per season (winter, spring, summer, and fall) at each of the four CMS locations. Likewise, four seasonal boat-mapping sampling events were conducted, each over a 3-day period and coincident with Landsat 8 satellite overpasses on the 2nd day of sampling and within 2 days of a Sentinel 2 A/B satellite overpass. Each boat-mapping event included collection of discrete water samples for mercury species and other water-quality metrics at 33 sites over a three-day period, covering approximately 210 kilometers through the SSJRD. The models constructed to estimate concentrations of mercury species are organized into four types (Tiers), which are based on which high-resolution water-quality data platform is being emphasized, as follow: Tier 1 Models – those based only on in-situ sensor derived turbidity and dissolved organic matter fluorescence, which are the two metrics most relevant to the satellite-based data collection platforms; Tier 2 Models – those based only on CMS in situ sensor data; Tier 3 Models – those based only on data from boat-mounted flow-through sensors, including spectrophotometric measurements, associated with the spatial mapping events; and Tier 4 models – based on sensor data from both the CMS sites and boat-mapping events, but limited to sensor data common to both. The information presented herein falls under six categories, which are associated with the following six Child pages: a) Discrete Sample Data – represents laboratory analytical results and field measurements associated with discrete surface-water samples collected from both the CMS and boat-mapping sampling events; b) Optical Spectral Data – represents excitation-emissions matrix spectra (EEMs) and absorption data associated with discrete surface-water samples collected from both the CMS and boat mapping sampling events; c) High-resolution (15 minute) Temporal Data from CMS Locations – includes time series in-situ sensor data collected from the four primary fixed CMS sampling locations; d) High-Resolution Boat Mapping Data – data collected with boat mounted flow-through sensor arrays during the four mapping events; e) Remote Sensing Data – GeoTIFF image files of turbidity and dissolved organic matter (DOM) products derived from Sentinel 2 A/B imagery of the SSJRD from June 2019 – May 2021; and f) Model Archive Summaries – documentation of the 16 top global models (four model types x four mercury species) in terms of modeling approach, model statistics, validation, and final equations. In addition, a geospatial file (SSJRD_Sites.kmz) is provided on this Parent page, which identifies all of the study fixed

This MESSENGER Magnetic field data set contains cruise-phase magnetic field vectors in RTN coordinates at time resolutions typically of 0.5 s or 1.0 s and sometimes as fine as 0.05 s. The Mercury Surface, Space Environment, Geochemistry, and Ranging, MESSENGER, mission is designed to study the characteristics and environment of Mercury from orbit. The nominal orbit is planned to have a periapsis of 200 km at 60° N latitude, an apoapsis of 15,193 km, a period of 12 hours, and an inclination of 80°. The periapsis will slowly rise due to solar perturbations to over 400 km at the end of 88 days, one Mercury year, at which point it will be readjusted to a 200 km, 12 hour orbit via a two burn sequence. Data will be collected from orbit for one Earth year, the nominal primary mission was planned to end in March 2012. Specifically, the scientific objectives of the mission are to characterize: * the chemical composition of the surface of Mercury * the geologic history * the nature of the magnetic field * the size and state of the core * the volatile inventory at the poles * the nature of the Hermean exosphere and magnetosphere The MESSENGER mission should also yield: * global composition maps * a 3-D model of the magnetosphere of Mercury * topographic profiles of the northern hemisphere * gravity field to degree and order sixteen * altitude profiles of elemental species * a characterization of the volatiles in permanently shadowed craters at the poles The MESSENGER spacecraft is a squat box (1.27 m ⨯ 1.42 m ⨯ 1.85 m) with a semi-cylindrical thermal shade, roughly 2.5 m tall and 2 m wide, for protection from the Sun and two solar panel wings extending radially about 6 m from tip to tip. Five science instruments are mounted externally on the bottom deck of the main body: the Mercury Dual Imaging System, MDIS, Gamma-Ray and Neutron Spectrometer, GRNS, X-ray Spectrometer, XRS, Mercury Laser Altimeter, MLA, and Atmospheric and Surface Composition Spectrometer, MASCS. Radio Science, RS, experiments will use the existing communications system. The Energetic Particle and Plasma Spectrometer, EPPS, is mounted on the side and top deck, and the magnetometer, MAG, is at the end of the 3.6 m boom. The Messenger MAG instrument is a miniature three-axis ring-core fluxgate magnetometer with low-noise electronics. It is mounted on a 3.6 m boom in the anti-sunward direction. The MAG has ±1530 and ±51300 nT ranges with 20-bit internal resolution and 17-bit output resolution. The MAG probe samples magnetic field values along the X, Y, and Z axes at a rate of up to 20 samples/s. The rate is commandable and can vary. This data set has 3-axis calibrated samples of the magnetic field in heliospheric RTN coordinates, Br, Bt, Bn, in units of nT. The spacecraft position data in these files are identified by radial distance from the Sun, latitude above the ecliptic plane, and azimuth with respect to the Earth-Sun line in the ecliptic plane. The MESSENGER Magnetometer data are also available from the Planetary Data System, Planetary Plasma Interactions, PDS/PPI, node via the URL; https://pds-ppi.igpp.ucla.edu/search/view/?f=yes&id=pds://PPI/MESS-E_V_H_SW-MAG-3-CDR-CALIBRATED-V1.0/DATA/RTN/. Hovever, the data are listed in plain text, space delimeted ASCII tables. Note that this SPASE Numerical Description only describes the MESSENGER Magnetometer data stored in Common Data Files.

The movement of mercury (Hg) from the atmosphere to the biosphere occurs by both wet and dry deposition to solid surfaces, water, and vegetation. Most of the annual dry atmospheric Hg deposition in deciduous forests is believed to originate from litterfall which consists mainly of dead leaves that fall to the earth’s surface, primarily during the autumn and winter seasons. Atmospheric Hg reaches an annual maximum concentration in leaves at the time of leaf fall. Analysis of litterfall samples helps to quantify total annual atmospheric Hg deposition to forests when combined with precipitation Hg data. This data set is derived from litterfall samples collected during 2017-18 and 2018-19 at 27 selected National Atmospheric Deposition Program (NADP) sites in 12 states located across the eastern half of the United States. Through the Litterfall Mercury Monitoring Initiative (LMMI), operated by the U.S. Geological Survey (USGS), litterfall sample collectors were distributed to the selected NADP sites where site operators retrieved multiple 4-week-long samples during the leaf fall period. These samples were collected and shipped to the USGS Mercury Research Laboratory where they were analyzed for concentrations of total Hg and methylmercury (MeHg), and litterfall dry mass was also determined. The samples for total Hg and MeHg analysis represent composites from 4 collectors across all sample collections at each site during the litterfall season. Litterfall dry mass was determined from all 8 sample collectors across all sample collections.

USGS conducted preliminary assays on aged (3 mo.) surface sediment (0-4 cm) collected from 13 sites during October 1998 in order to decipher general spatial trends in Hg-speciation, microbiology and relevant biogeochemistry. During the second field campaign sample processing and incubations were conducted at ambient temperature within hours of sediment collection to provide a more accurate measure of in-situ process rates and analyte concentrations. The third field sampling (October 1999), involving 14 sampling and was conducted with a similar approach as in June 1999. The latter two data sets provide a direct seasonal comparison (summer/fall, high/lo flow conditions) of Hg transformation dynamics in the CRS. Sediment depth profiles (0-16 cm) were investigated at four sites during June 1999 and at two of these four during October 1999. Eroding vertical bank material was sampled in the Hg-contaminated Fort Churchill region during both 1999 dates. Laboratory experiments were conducted using sediment collected during the latter two sampling dates. The study purpose sought to: a) identify important zones of net methylmercury (MeHg) production and consumption within the CRS, b) determine which environmental factors most strongly influence these processes and c) provide estimates of seasonal variability. Measurements were made of microbial Hg-transformations (via radiotracer) and in-situ Hg speciation (total mercury (Hgt), MeHg, and particle-associated acid-extractable Hg(II)). Acid extractable Hg(II) was used as a surrogate measure for the Hg(II) most readily available to bacteria for methylation. A novel Hg-biosensor technique was also used to assess bioavailable Hg(II) in pore-water. A suite of ancillary microbial processes and sediment geochemical parameters were also measured to more fully characterize each site, and to relate these measurements to observed Hg-transformation rates and Hg-speciation. The EPA is publishing this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU2 Remedial Investigation Report (EPA, 2017), which describes the nature and extent of contamination from the Site. The report contains the Human Health Risk Assessment and Ecological Risk Assessment. Literature and other source Hg data are summarized in the RI for surface waters, sediments, and biological tissues.