Global Geologic Map of Europa: Usgs Scientific Investigation Map (Sim)

Leonard, Erin; Patthoff, D. A.; Senske, D. A.; Collins, G. C.

doi:10.1130/abs/2017am-300835

Cited by 8 publications

(19 citation statements)

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“…However, it does not correspond to any particular geologic unit (Leonard et al 2017) or any unusual visible morphological or albedo features (USGS 2002). The anomaly is located within a region of relatively low-resolution imaging and was not covered by the published Galileo PPR data, so it is possible that a corresponding morphological, geologic, or thermal feature was simply not seen by Galileo.…”

Section: Fits To Alma Observationsmentioning

confidence: 99%

ALMA Thermal Observations of Europa

Trumbo

Brown

Butler

2018

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We present four daytime thermal images of Europa taken with the Atacama Large Millimeter Array. Together, these images comprise the first spatially resolved thermal data set with complete coverage of Europa's surface. The resulting brightness temperatures correspond to a frequency of 233 GHz (1.3 mm) and a typical linear resolution of roughly 200 km. At this resolution, the images capture spatially localized thermal variations on the scale of geologic and compositional units. We use a global thermal model of Europa to simulate the ALMA observations in order to investigate the thermal structure visible in the data. Comparisons between the data and model images suggest that the large-scale daytime thermal structure on Europa largely results from bolometric albedo variations across the surface. Using bolometric albedos extrapolated from Voyager measurements, a homogenous model reproduces these patterns well, but localized discrepancies exist. These discrepancies can be largely explained by spatial inhomogeneity of the surface thermal properties. Thus, we use the four ALMA images to create maps of the surface thermal inertia and emissivity at our ALMA wavelength. From these maps, we identify a region of either particularly high thermal inertia or low emissivity near 90°west and 23°north, which appears anomalously cold in two of our images.

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Section: Fits To Alma Observationsmentioning

confidence: 99%

ALMA Thermal Observations of Europa

Trumbo

Brown

Butler

2018

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“…Stratigraphic relationships on Europa are complex, and older terrains are a generally poor predictor of current geologic activity (Greeley et al 2000;Figueredo & Greeley 2004;Doggett et al 2009;Leonard et al 2018b). Because past geologic change recorded in the icy surface is not a reliable indicator of future geologic resurfacing, we assume that resurfacing is equally as likely anywhere on the body at any given time.…”

Section: Geologic Basis For Resurfacing Approachmentioning

confidence: 99%

“…This conservative approach assumes that the poles, leading and trailing hemispheres, and Jovian and sub-Jovian hemispheres all experience a high level of geologic activity at present day, resulting in a young average global surface age. We thus formally ignore any potential spatial variations in geologic activity, which may manifest due to, for example, spatial variations in tidal activity (e.g., Ojakangas & Stevenson 1989) or be concealed by poor global coverage of spacecraft observations (e.g., Phillips et al 2000;Doggett et al 2009;Leonard et al 2018b;Schenk 2020).…”

Section: Geologic Basis For Resurfacing Approachmentioning

confidence: 99%

Resurfacing: An Approach to Planetary Protection for Geologically Active Ocean Worlds

DiNicola¹,

Howell²,

McCoy³

et al. 2022

Planet. Sci. J.

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The putative and potential ocean worlds of our solar system span the asteroid belt to the Kuiper Belt, containing within their icy shells past or present global saltwater oceans. Among these worlds, those bearing signs of present-day geologic activity are key targets in the search for past or extant life in the solar system. As the icy surfaces of these bodies are modified by geologic processes, landforms are erased and replaced through what is called “resurfacing.” To avoid contaminating sites for robotic spacecraft exploration, planetary protection requirements obligate missions to these ocean worlds to demonstrate a less than 10−4 probability of introducing a viable terrestrial microorganism into a liquid water body. To constrain the probability of subsurface contamination, we investigate the interaction with geologic resurfacing on an active ocean world. Through the example of Europa, we show how the surface age can be used to constrain the resurfacing rate, a critical parameter to estimate the probability that nonsterile spacecraft material present on the surface is geologically incorporated into the subsurface, and extend this example to mission scenarios at Ganymede and Enceladus. This approach was critical to demonstrating compliance with planetary protection requirements for the Europa Clipper mission, reducing its probability of contamination by two to five orders of magnitude. We also show how a Europa lander mission might be brought close to complying with planetary protection requirements, that a Ganymede impactor could easily comply, and that the situation of Enceladus, while more complex, can greatly benefit from this approach.

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“…After the Galileo mission, RAND and the USGS created a combined Voyager‐Galileo control network, which was subsequently used to produce a global, relatively controlled, orthorectified (to a sphere) image basemap at 500 m per pixel (Becker et al., 2001 ; Davies et al., 1998 ) ( https://astrogeology.usgs.gov/search/map/Europa/Voyager-Galileo/Europa_Voyager_GalileoSSI_global_mosaic_500m ). This image base has been used extensively, including recently for global geologic mapping (Leonard et al., 2018 ). In an independent effort, a global color image basemap (also orthorectified to a sphere) was generated using updated image geometry by Paul Schenk at 200 m per pixel https://repository.hou.usra.edu/handle/20.500.11753/1412 .…”

Section: Motivationmentioning

confidence: 99%

“…All mosaics are provided in a planetocentric east‐positive, 0–360° longitude system for consistency with the current geologic map (Leonard et al., 2018 ) and the requirements of the Jupiter Icy moons Explorer and Clipper missions. An east‐positive standard is also more readily used in GIS applications.…”

Section: Released Data Productsmentioning

confidence: 99%

Improving the Usability of Galileo and Voyager Images of Jupiter's Moon Europa

Bland

Weller

Archinal

et al. 2021

Earth and Space Science

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For a planetary imaging data set to be of maximum use to the science community, the absolute and relative location of the images on the surface of a planet must be known with high accuracy and precision. For some planetary missions in which images are acquired from orbit, image locations derived from reconstructed Spacecraft, Planet, Instrument, C-matrix (pointing), and Events (SPICE) kernels (Acton et al., 2017) are sufficient for many scientific applications (e.g., morphologic analysis). However, the spatial accuracy of such reconstructed data is insufficient for investigating change detection, planning surface mission operation (e.g., rover traverse), or deriving higher-order data products (e.g., digital terrain models, DTMs). For missions in which data are acquired by multiple fast flybys of distant objects (e.g., many missions to the outer Solar System), uncertainties in the spacecraft and body locations and orientations are large enough to result Abstract NASA's Voyager 1, Voyager 2, and Galileo spacecraft acquired hundreds of images of Jupiter's moon Europa. These images provide the only moderate-to high-resolution views of the moon's surface and are therefore a critical resource for scientific analysis and future mission planning. Unfortunately, uncertain knowledge of the spacecraft's position and pointing during image acquisition resulted in significant errors in the location of the images on the surface. The result is that adjacent images are poorly aligned, with some images displaced by more than 100 km from their correct location. These errors severely degrade the usability of the Voyager and Galileo imaging data sets. To improve the usability of these data sets, we used the U.S. Geological Survey Integrated Software for Imagers and Spectrometers to build a nearly global image tie-point network with more than 50,000 tie points and 135,000 image measurements on 481 Galileo and 221 Voyager images. A global least-squares bundle adjustment of our final Europa tie-point network calculated latitude, longitude, and radius values for each point by minimizing residuals globally, and resulted in root mean square (RMS) uncertainties of 246.6 m, 307.0 m, and 70.5 m in latitude, longitude, and radius, respectively. The total RMS uncertainty was 0.32 pixels. This work enables direct use of nearly the entire Galileo and Voyager image data sets for Europa. We are providing the community with updated NASA Navigation and Ancillary Information Facility Spacecraft, Planet, Instrument, C-matrix (pointing), and Events kernels, mosaics of Galileo images acquired during each observation sequence, and individual processed and projected level 2 images.

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Global Geologic Map of Europa: Usgs Scientific Investigation Map (Sim)

Cited by 8 publications

References 0 publications

ALMA Thermal Observations of Europa

ALMA Thermal Observations of Europa

Resurfacing: An Approach to Planetary Protection for Geologically Active Ocean Worlds

Improving the Usability of Galileo and Voyager Images of Jupiter's Moon Europa

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