Astrogeology Science Center
Astrogeology Science Center
Dhingra R.D.,University of Idaho |
Barnes J.W.,University of Idaho |
Yanites B.J.,University of Idaho |
Kirk R.L.,Astrogeology Science Center
Icarus | Year: 2018
We seek to address the question of what processes are at work to fill Ontario Lacus while other, deeper south polar basins remain empty. Our hydrological analysis indicates that Ontario Lacus has a catchment area spanning 5.5% of Titan's surface and a large catchment area to lake surface area ratio. This large catchment area translates into large volumes of liquid making their way to Ontario Lacus after rainfall. The areal extent of the catchment extends to at least southern mid-latitudes (40°S). Mass conservation calculations indicate that runoff alone might completely fill Ontario Lacus within less than half a Titan year (1 Titan year = 29.5 Earth years) assuming no infiltration. Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations of clouds over the southern mid and high-latitudes are consistent with precipitation feeding Ontario's large catchment area. This far-flung rain may be keeping Ontario Lacus filled, making it a liquid hydrocarbon oasis in the relatively dry south polar region. © 2017 Elsevier Inc.
Bland M.T.,Astrogeology Science Center |
Raymond C.A.,Jet Propulsion Laboratory |
Schenk P.M.,Lunar and Planetary Institute |
Fu R.R.,Columbia University |
And 9 more authors.
Nature Geoscience | Year: 2016
Before NASA's Dawn mission, the dwarf planet Ceres was widely believed to contain a substantial ice-rich layer below its rocky surface. The existence of such a layer has significant implications for Ceres's formation, evolution, and astrobiological potential. Ceres is warmer than icy worlds in the outer Solar System and, if its shallow subsurface is ice-rich, large impact craters are expected to be erased by viscous flow on short geologic timescales. Here we use digital terrain models derived from Dawn Framing Camera images to show that most of Ceres's largest craters are several kilometres deep, and are therefore inconsistent with the existence of an ice-rich subsurface. We further show from numerical simulations that the absence of viscous relaxation over billion-year timescales implies a subsurface viscosity that is at least one thousand times greater than that of pure water ice. We conclude that Ceres's shallow subsurface is no more than 30% to 40% ice by volume, with a mixture of rock, salts and/or clathrates accounting for the other 60% to 70%. However, several anomalously shallow craters are consistent with limited viscous relaxation and may indicate spatial variations in subsurface ice content. © 2016 Macmillan Publishers Limited.
Lopes R.M.C.,Jet Propulsion Laboratory |
Kirk R.L.,Astrogeology Science Center |
Mitchell K.L.,Jet Propulsion Laboratory |
Legall A.,University of Versailles |
And 13 more authors.
Journal of Geophysical Research E: Planets | Year: 2013
The existence of cryovolcanic features on Titan has been the subject of some controversy. Here we use observations from the Cassini RADAR, including Synthetic Aperture Radar (SAR) imaging, radiometry, and topographic data as well as compositional data from the Visible and Infrared Mapping Spectrometer (VIMS) to reexamine several putative cryovolcanic features on Titan in terms of likely processes of origin (fluvial, cryovolcanic, or other). We present evidence to support the cryovolcanic origin of features in the region formerly known as Sotra Facula, which includes the deepest pit so far found on Titan (now known as Sotra Patera), flow-like features (Mohini Fluctus), and some of the highest mountains on Titan (Doom and Erebor Montes). We interpret this region to be a cryovolcanic complex of multiple cones, craters, and flows. However, we find that some other previously supposed cryovolcanic features were likely formed by other processes. Cryovolcanism is still a possible formation mechanism for several features, including the flow-like units in Hotei Regio. We discuss implications for eruption style and composition of cryovolcanism on Titan. Our analysis shows the great value of combining data sets when interpreting Titan's geology and in particular stresses the value of RADAR stereogrammetry when combined with SAR imaging and VIMS. Key Points Evidence to support volcanic origin of features on Titan Several Cassini data sets used to support the argument Sotra patera and associated features provide strongest evidence of cryovolcanism ©2013. American Geophysical Union. All Rights Reserved.
News Article | January 27, 2016
Every early-career scientist has hit a stumbling block: a bad grade on an exam, a low score on a grant proposal or the first rejection from a journal. But for many, this normal stuff of science twists into something darker and more insidious — a creeping sense of professional inadequacy that prompts them to question their place in the field, no matter their area of study or their level of brilliance. There is a term for this type of self-doubt, coined in the 1970s by two US psychologists who saw it in their clinical practices: the 'impostor phenomenon'. Now commonly known as impostor syndrome, the condition can manifest itself in myriad professions, from office workers to artists to athletes, says Frederik Anseel, a psychologist at Ghent University in Belgium. Scientists, he says, are especially vulnerable, largely because they work in a hero-oriented field that treats its highest achievers as if they were sports stars, leaving many others to wonder in silence whether they are second-stringers or worse. “Young people think that no one else is having these feelings,” he says. Researchers who struggle with the syndrome have to learn how to tune out feelings of inadequacy and develop a more realistic view of their abilities and their value, he says. In a profession where sporadic failure — in grants, in jobs, in publications — is the norm, the real failure is unnecessarily giving up on a promising career. In 2014, Anseel and his colleagues took a closer look at impostor syndrome in a study of more than 200 Belgian workers in finance, education and human-resource management. The team found that workers who reported feelings that are consistent with impostor syndrome tended to score higher on measures of neuroticism and excessive perfectionism in personality tests ( et al. J. Bus. Psychol. 30, 565–581; 2015). They were also not as happy with their jobs as were colleagues who did not experience the syndrome — even though some of the afflicted had advanced to the upper levels of their professions. Anseel says that his other work — which includes ongoing studies of mental-health issues among young researchers — gives him confidence that his findings about impostor syndrome in the white-collar world apply to science as well. He says that it is easy to see how even successful scientists can feel that they are actually underperformers. Scientists, he says, often trivialize their own achievements. “You get a paper published in PNAS, and you tell yourself, 'That's doable. I'll never get a paper in Nature or Science'.” Similarly, any grant could be larger; any job could be better; any paper could be more highly cited. “You set yourself up to fail one way or the other,” he says. The phenomenon shows up across academia, including at top research institutions. Josh Drew, an evolutionary ecologist at Columbia University in New York City, has seen PhD and master's degree students struggle with self-doubt at the Ivy League school. Every student had passed tough admission standards — but that was not enough to bolster their confidence. For many, their classes at the university represented the first time in their educational experience that they didn't feel as if they were the smartest person in the room. “They were all outstanding students as undergrads,” he says. “Here, being at the top of your class is just average.” In a highly competitive arena, self-doubt can be a career killer that prompts would-be contenders to dismiss chances to vie for important opportunities. “I saw many students who were shooting themselves in the foot,” Drew says. “They weren't applying for grants and awards that they would be competitive for.” He began to address the syndrome in an introduction-to-graduate-school class. The talks drew some buzz, and he soon developed a formal presentation to deliver to other departments at Columbia and beyond (see 'Help for impostors'). Clearly, he had struck a chord. “Every talk I give, people say, 'I thought I was the only person who felt this way',” he says. Drew reassures people who feel like frauds by pointing out that they are in some lofty company. Two years after publishing On the Origin of Species in 1859, Charles Darwin complained that “one lives only to make blunders”. And while working on The Grapes of Wrath (1939), John Steinbeck wrote, “I am assailed by my own ignorance and inability,” fretting that “sometimes, I seem to do a good little piece of work, but when it is done it slides into mediocrity.” While preparing his lecture, Drew solicited Twitter comments from scientists who had struggled to overcome the syndrome with various degrees of success. One respondent, an associate professor of biology, tweeted: “It has crippled my professional life from day one.” Moses Milazzo, a planetary scientist with the Astrogeology Science Center in Flagstaff, Arizona, tweeted, “Because of Impostor Syndrome: I have decided not to pursue opportunities; I am never ready to publish my papers; etc.” Milazzo thinks that impostor syndrome is nearly universal among scientists — at least among those who are self-aware enough to realize that they don't know everything. But he also says that he experienced particularly severe effects of it, and he traces at least some of his unease to his background. He grew up in an off-the-grid adobe house on the border of the Navajo Nation reservation in northern Arizona, which later contributed to his sense that he did not belong in the university crowd. Not many of his instructors, advisers or peers could relate to hardscrabble desert life in a house that had no reliable electricity and little contact with the outside world. “I didn't even know what Cosmos was until I got to grad school,” he says of the popular 1980s TV show. Then again, life in middle-of-nowhere Arizona did give him an intimate familiarity with the night sky. During the long walk along a dirt road to the school bus stop, he often navigated by the light of the Milky Way. Milazzo says that he first heard the term impostor syndrome early in his graduate-student days at the University of Arizona in Tucson — and he recognized it immediately. “Having a name put to it made it clear that other people felt it,” he says. But knowing that he was not alone didn't keep him out of the trap. He decided not to apply for a NASA grant for satellite-based research, out of fear of exposing his own ignorance. “I removed myself from the grant process because it would be obvious that I didn't know what I was talking about,” he says. As it turned out, one of the successful proposals was very similar to his idea. “If I had pursued it, I might have been competitive,” he laments now. And even after helping to win a NASA grant to develop a middle-school curriculum that would be based on the space agency's exploration of the Solar System, Milazzo still struggles to persuade himself that he belongs in science. “We put a lot of work into that proposal, but I wasn't very confident that it would get funded,” he says. Matt von Hippel, a researcher at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, says that he, too, feels like an impostor from time to time, but he has a strategy that helps him to push through it. Instead of second-guessing the people who admitted him to graduate school and awarded him a PhD, he decided to embrace their judgement. “You can trust the system to have put you in vaguely the right job,” he says. “If you're invited to give a talk, that's a sign that you're ready to give a talk.” Late last year, he was asked to give a colloquium on mathematical techniques in particle physics at Oregon State University in Corvallis. It was a big opportunity that came sooner in his career than he expected, and he thought about turning it down. Ultimately, he opted to adhere to his strategy. “I decided to say 'yes' and see how it goes,” he says. In his view, the talk was a success. Biologist Victoria Metcalf had plenty of opportunities to doubt herself and second-guess her career choices. Her low point came in early 2000 during her PhD studies in New Zealand, when television-news crews surrounded her lab and a regulatory authority threatened to throw her and her supervisors in prison. Her lab had cloned genes from the tuatara (Sphenodon punctatus) — a treasured native New Zealand reptile — but lacked the permits that a new law had retroactively made mandatory. Authorities eventually dropped their threats, but her research was stalled for six months while she obtained the proper permits. “Those were really soul-destroying times,” she says. “It had a huge impact on how I perceived my worth in academia.” Scientists are accustomed to measuring things in precise detail, but their own value can be difficult for them to quantify. Anseel thinks that many researchers would be more confident — and thus more likely to write the grant, submit the paper, apply for the job — if they were to embrace the inevitability of failure. “When one of my students gets a rejection letter, I can show them five or ten of my own,” he says. “The academic environment should be more open to failure stories.” Drew reminds young researchers that even the chairs of their departments — scientists who seemingly have it made — do not always get their grants funded or their papers accepted. It would be telling, he says, if everyone published a 'shadow CV' of all their rejections to go along with the standard CV that lists successes. Researchers can also help to ease their distress by making an effort to stop comparing themselves with colleagues in their lab or department. “Comparisons won't make you happy, so don't do it,” Anseel says. Instead, he says, researchers should set their own personal standards of achievement and then do their best to meet them. Metcalf has mostly won her battle over her sense of inadequacy, although her career has had its ups and downs. After she earned her PhD, she took a postdoc position in the United States that she quit after only six months, an outcome that made her feel even more like a scientific impostor. “I had a low sense of self-worth,” she says. But she pushed through it, quickly found another post and went on to have a successful career that included research trips to the Antarctic and a highly sought-after faculty position at Lincoln University in Christchurch, New Zealand. Yet her troubles didn't end. In 2011, she lost her faculty job after an earthquake damaged much of the city. Instead of taking that setback as a sign that she needed to abandon science completely, she shifted from research to outreach. She is now the national coordinator of the Participatory Science Platform, a New Zealand government programme that promotes research collaborations between scientists and communities. “Anyone who knows me knows that I was meant for this job,” she says. As part of her duties, Metcalf has had many chances to speak to young people with different backgrounds and career aspirations. Many of them are already experiencing the symptoms of impostor syndrome, which gives her an opportunity to inspire by example. “My story really resonates,” she says. “I've had my battles. You just have to keep fighting.”
Watters T.R.,Smithsonian Institution |
Selvans M.M.,Smithsonian Institution |
Banks M.E.,Smithsonian Institution |
Hauck S.A.,Case Western Reserve University |
And 2 more authors.
Geophysical Research Letters | Year: 2015
The surface of Mercury is dominated by contractional tectonic landforms that are evidence of global-scale crustal deformation. Using MESSENGER orbital high-incidence angle imaging and topographic data, large-scale lobate thrust fault scarps have been mapped globally. The spatial distribution and areal density of the contractional landforms are not uniform; concentrations occur in longitudinal bands and between the north and south hemispheres. Their orientations are generally north-south at low latitude to midlatitude and east-west at high latitudes. The spatial distribution and distribution of orientations of these large-scale contractional features suggest that planet-wide contraction due to interior cooling cannot be the sole source of global stresses. The nonrandom orientations are best explained by a combination of stresses from global contraction and tidal despinning combined with an equator-to-pole variation in lithospheric thickness, while the nonuniform areal density of the contractional features may indicate the influence of mantle downwelling or heterogeneities in lithospheric strength. ©2015. American Geophysical Union. All Rights Reserved.
News Article | November 30, 2015
The rendering of the James Webb Space Telescope in space. Image credit: Northrop Grumman. NASA's James Webb Space Telescope (JWST), often touted as Hubble's successor, is slated to be launched in 2018 to study every phase of cosmic history, mainly by observing the most distant objects in the universe. The telescope will also be useful for investigating extrasolar planetary systems as well as planets within our solar system. Now, a team of researchers led by Laszlo Kestay, the director of the U.S. Geological Survey's Astrogeology Science Center, has laid out its plan to use the telescope's capabilities to better understand our planetary neighborhood by putting emphasis on outer solar system moons and their geology. The team proposes two main scientific goals for JWST when it comes to observing these moons. The first task would be completing the infrared survey of major satellites. The second goal is geology-related and described as "monitoring surface changes of active satellites." The researchers presented their proposal in a paper published on the arXiv. "The James Webb Space Telescope will allow observations with a unique combination of spectral, spatial, and temporal resolution for the study of outer planet satellites within our solar system. We highlight the infrared spectroscopy of icy moons and temporal changes on geologically active satellites as two particularly valuable avenues of scientific inquiry," the scientists wrote in the paper. JWST will be equipped in four scientific instruments: the Near InfraRed Camera (NIRCam), the Near InfraRed Spectrograph (NIRSpec), the Mid-Infrared Instrument (MIRI) and the Fine Guidance Sensor/Near Infrared Imager and Slitless Spectrograph (FGS/NIRISS). These instruments provide a unique opportunity to obtain high spectral resolution infrared spectra from planetary satellites in wavelength regions that cannot be observed from Earth. JWST's results could complement observations of outer solar system moons conducted by Voyager and Cassini missions. The scientists hope that the telescope's key scientific contribution could be determining the compositions of giant gas planets' irregular satellites. They note that even at very low spatial resolution, near-infrared spectroscopy is sensitive to H2O and other ices, as well as silicates and spectral slopes characteristic of complex organic "tholins" (heteropolymer molecules formed by solar ultraviolet irradiation of simple organic compounds such as methane or ethane). "JWST has the sensitivity to provide unique compositional data on irregular satellites. For example, in the one to 2.5 micron region of the near-infrared, amorphous vs. crystalline surface composition of icy bodies could be surveyed extensively using JWST NIRSpec," the paper reads. Irregular satellites are important sources of dust in the giant planet systems. Dust orbits evolve under effects of radiation pressure and solar tides. By linking the sizes, densities, and albedos of dust particles to the source satellite surface compositions, JWST could offer new insights into the role of these satellites in the production of dust particles. The observations of geologic activity of the outer solar system moons, described by Kestay and his colleagues as the second main goal for JWST could also bring remarkable scientific results. The telescope will be able to detect changes on the surface that are indicative of temporal variations in composition and temperature. Many of the outer planet satellites are remarkably active. For instance, Jupiter's moon Io, Neptune's largest moon Triton, and Enceladus, Saturn's icy satellite, have active eruptions. The recent suggestion of active plumes above Europa, orbiting Jupiter, is especially exciting because it may provide samples from a habitable environment that is otherwise extremely challenging to access. The scientists believe that the best moon for these observations would be Io. They note that JWST could observe significant surface changes on this satellite where volcanic activity is very high. "The observations every six months that JWST can make of the Jovian system is very well suited for monitoring the creation and fading of colorful plume deposits on Io which typically happen on a timescales of several months and have diameters of many hundreds of kilometers," the researchers wrote. They are convinced that JWST observations could also resolve other scientific problems related to Io, such as the eruption temperature of its lavas and the uncertainty about the composition and state of its mantle. This could be crucial to our understanding of how tidal heating works in the Jovian system. The researchers conclude that these two types of JWST observations will enable compelling science of outer solar system moons. They present the telescope as an important tool for studying planetary satellites, underlining that the road to understanding the origins of the universe leads through the observations of our outer solar system. Finally, they encourage the scientific community to use their paper to formulate more specific observation plans. More information: Observing Outer Planet Satellites (except Titan) with JWST: Science Justification and Observational Requirements, arXiv:1511.03735 [astro-ph.EP] arxiv.org/abs/1511.03735 Abstract The James Webb Space Telescope (JWST) will allow observations with a unique combination of spectral, spatial, and temporal resolution for the study of outer planet satellites within our Solar System. We highlight the infrared spectroscopy of icy moons and temporal changes on geologically active satellites as two particularly valuable avenues of scientific inquiry. While some care must be taken to avoid saturation issues, JWST has observation modes that should provide excellent infrared data for such studies.
News Article | September 26, 2016
A composite image shows suspected plumes of water vapor erupting at the seven o'clock position off the limb of Jupiter's moon Europa in a NASA Hubble Space Telescope picture taken January 26, 2014 and released September 26, 2016. NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center/Handout via Reuters (Reuters) - Astronomers on Monday said they have spotted evidence of water vapor plumes rising from Jupiter's moon Europa, a finding that might make it easier to learn whether life exists in the warm, salty ocean hidden beneath its icy surface. The apparent plumes detected by the Hubble Space Telescope shoot about 125 miles (200 km) above Europa's surface before, presumably, raining material back down onto the moon's surface, NASA said. Europa, considered one of the most promising candidates for life in the solar system beyond Earth, boasts a global ocean with twice as much water as in all of Earth's seas hidden under a layer of extremely cold and hard ice of unknown thickness. While drilling through the ice to test ocean water for signs of life would be a daunting task, sampling water from the plumes might be a simpler project. "If the plumes are real, it potentially gives us easier access to the ocean below ... without needing to drill into miles of ice," said lead researcher Williams Sparks of the Space Telescope Science Institute in Greenbelt, Maryland. Europa is about 1,900 miles (3,100 km) in diameter, slightly smaller than Earth’s moon. Among Jupiter's four largest moons, Europa is the second closest to the biggest planet in the solar system. The telescope observed the plumes three times in 2014, mostly around Europa's southern polar region, scientists told a conference call with reporters. On Earth, life is found everywhere where there is water, energy and nutrients, so scientists have a special interest in places elsewhere in the solar system, like Europa, with similar characteristics, said Paul Hertz, director of NASA's astrophysics division. The findings, which will be published in The Astrophysical Journal, follow an initial Hubble sighting of a water vapor plume over Europa's south pole in December 2012. Scientists got their first hint that bright, icy Europa, which is crisscrossed by dark bands and ridges, contains an underground ocean from NASA's twin Voyager probes, which flew by Jupiter in 1979. The follow-on Galileo spacecraft, which circled around and through Jupiter's system from 1995 to 2003, detected a magnetic field that likely was triggered by a salty, global ocean beneath Europa's surface. Two more missions are in development to visit Europa. A NASA spacecraft, targeted for launch in the mid-2020s, would make more than 40 close flybys of the moon and possibly sample material in any plumes shooting out from its surface. Jupiter has 67 known moons, plus many smaller ones that have not yet been named.
Mount C.P.,Arizona State University |
Titus T.N.,Astrogeology Science Center
Journal of Geophysical Research E: Planets | Year: 2015
Small-scale variations of seasonal ice are explored at different geomorphic units on the Northern Polar Seasonal Cap (NPSC). We use seasonal rock shadow measurements, combined with visible and thermal observations, to calculate density over time. The coupling of volume density and albedo allows us to determine the microphysical state of the seasonal CO2 ice. We find two distinct end-members across the NPSC: (1) Snow deposits may anneal to form an overlying slab layer that fractures. These low-density deposits maintain relatively constant densities over springtime. (2) Porous slab deposits likely anneal rapidly in early spring and fracture in late spring. These high-density deposits dramatically increase in density over time. The end-members appear to be correlated with latitude. Key Points Albedo and density are used to constrain evolution of seasonal CO2 ice There are two seasonal CO2 end-members Conceptual models are developed for each end-member. © 2015 American Geophysical Union. All Rights Reserved.
Becerra P.,University of Arizona |
Byrne S.,University of Arizona |
Sori M.M.,University of Arizona |
Sutton S.,University of Arizona |
Herkenhoff K.E.,Astrogeology Science Center
Journal of Geophysical Research E: Planets | Year: 2016
The stratigraphy of the layered deposits in the polar regions of Mars is theorized to contain a record of recent climate change linked to insolation changes driven by variations in the planet's orbital and rotational parameters. In order to confidently link stratigraphic signals to insolation periodicities, a description of the stratigraphy is required based on quantities that directly relate to intrinsic properties of the layers. We use stereo digital terrain models (DTMs) from the High Resolution Imaging Science Experiment to derive a characteristic of north polar layered deposit (NPLD) strata that can be correlated over large distances: the topographic protrusion of layers exposed in troughs, which is a proxy for the layers' resistance to erosion. Using a combination of image analysis and a signal-matching algorithm to correlate continuous depth-protrusion signals taken from DTMs at different locations, we construct a stratigraphic column that describes the upper ~500 m of at least 7% of the area of the NPLD and find accumulation rates that vary by factors of up to 2. We find that, when coupled with observations of exposed layers in images, the topographic expression of the strata is consistently continuous across large distances in the top 300–500 m of the NPLD, suggesting that it is better related to intrinsic layer properties than the brightness of exposed layers alone. ©2016. American Geophysical Union. All Rights Reserved.
Keszthelyi L.P.,Astrogeology Science Center |
Jaeger W.L.,Astrogeology Science Center |
Dundas C.M.,University of Arizona |
Martinez-Alonso S.,University of Colorado at Boulder |
And 2 more authors.
Icarus | Year: 2010
We provide an overview of features indicative of the interaction between water and lava and/or magma on Mars as seen by the High Resolution Imaging Science Experiment (HiRISE) camera during the Primary Science Phase of the Mars Reconnaissance Orbiter (MRO) mission. The ability to confidently resolve meter-scale features from orbit has been extremely useful in the study of the most pristine examples. In particular, HiRISE has allowed the documentation of previously undescribed features associated with phreatovolcanic cones (formed by the interaction of lava and groundwater) on rapidly emplaced flood lavas. These include "moats" and "wakes" that indicate that the lava crust was thin and mobile, respectively [Jaeger, W.L., Keszthelyi, L.P., McEwen, A.S., Dundas, C.M., Russel, P.S., 2007. Science 317, 1709-1711]. HiRISE has also discovered entablature-style jointing in lavas that is indicative of water-cooling [Milazzo, M.P., Keszthelyi, L.P., Jaeger, W.L., Rosiek, M., Mattson, S., Verba, C., Beyer, R.A., Geissler, P.E., McEwen, A.S., and the HiRISE Team, 2009. Geology 37, 171-174]. Other observations strongly support the idea of extensive volcanic mudflows (lahars). Evidence for other forms of hydrovolcanism, including glaciovolcanic interactions, is more equivocal. This is largely because most older and high-latitude terrains have been extensively modified, masking any earlier 1-10 m scale features. Much like terrestrial fieldwork, the prerequisite for making full use of HiRISE's capabilities is finding good outcrops.