146 research outputs found
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Presentation: Life on Europa? Exploring Jupiter's Icy Moon
No full textDo you ever wonder about the possibility of life on other planets? Evidence of a shallow lake of liquid water on Europa, one of Jupiter's moons, suggests the potential for life may exist within our solar system. Dr. Britney Schmidt studies these structures, one of which has a similar volume to the North American Great Lakes. These icy areas may have physical mechanisms that permit the exchange of nutrients and energy between the planet's surface, and a large ocean inferred to lie beneath the ice shell. Dr. Schmidt takes us on a journey that examines some essential environmental conditions necessary to support life, and how these conditions may arise on other planets.Environmental Science Institut
Entrainment and dynamics of ocean-derived impurities within Europa's ice shell
No full textAuthor Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Planets 125(10),(2020): e2020JE006394, doi:10.1029/2020JE006394.Compositional heterogeneities within Europa's ice shell likely impact the dynamics and habitability of the ice and subsurface ocean, but the total inventory and distribution of impurities within the shell are unknown. In sea ice on Earth, the thermochemical environment at the ice‐ocean interface governs impurity entrainment into the ice. Here, we simulate Europa's ice‐ocean interface and bound the impurity load (1.053–14.72 g/kg [parts per thousand weight percent, or ppt] bulk ice shell salinity) and bulk salinity profile of the ice shell. We derive constitutive equations that predict ice composition as a function of the ice shell thermal gradient and ocean composition. We show that evolving solidification rates of the ocean and hydrologic features within the shell produce compositional variations (ice bulk salinities of 5–50% of the ocean salinity) that can affect the material properties of the ice. As the shell thickens, less salt is entrained at the ice‐ocean interface, which implies Europa's ice shell is compositionally homogeneous below ~1 km. Conversely, the solidification of water filled fractures or lenses introduces substantial compositional variations within the ice shell, creating gradients in mechanical and thermal properties within the ice shell that could help initiate and sustain geological activity. Our results suggest that ocean materials entrained within Europa's ice shell affect the formation of geologic terrain and that these structures could be confirmed by planned spacecraft observations.This study was supported by the NASA Earth and Space Science Fellowship, grants NNX16AP43H S01 and NNX16AP43H S002. Britney Schmidt was additionally supported by the Europa Clipper Mission. Resources supporting this work were provided by the NASA High‐End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center.2021-03-2
« We make culture ». "Glee", identités culturelles d’une série télévisée américain
No full textGlee (épisode spécial de 2010, avec Britney Spears) 29 novembre 2012 par Pierre-Olivier Toulza (Université Paris-Diderot
Landslides on Ceres
No full textI analyze landslides on Ceres using several quantitative approaches to constrain the composition and structure of the top few kilometers of Ceres’ crust. I focus on a subset of archetypal landslides classified morphologically as thick, steep-snouted “type 1” (T1) flows and thin spatulate “type 2” (T2) flows (Schmidt et al., 2017) to explore the landslides’ mechanical properties, and supplement with comparison with all landslides combined. The results confirm earlier observations showing that T1 landslides are typically found poleward of 70° latitude and T2 mostly equatorward of 70° latitude. Measurements of landslide drop height and runout length imply effective friction coefficients lower than common friction coefficients in any of Ceres’ identified or suggested non-ice surface materials, including saturated clays. Measurements of the volume and area of landslide scars suggest that T1 landslides can fail to greater depths than T2 specifically and most landslides overall for a given scar area, consistent with depth-limited failure in landslides below 70° latitude. These results are consistent with a layer of lower shear strength material overlying a stronger layer in Ceres’ outer shell at low to mid latitudes, and a single layer without an overlying weak layer at polar latitudes. Combining these observations with known constraints on Ceres’ near-surface composition, I propose that Ceres’ crust at low to mid latitudes consists of a topmost layer with an ice content in excess of the near surface that thins out at high latitudes, and which overlies a somewhat stronger and more ice-rich layer.M.S
Robotic Solutions to Sampling and Sample Handling Challenges on Ocean Worlds
No full textOcean worlds are widely regarded as promising locations in the solar system in the search for life. However, the liquid water oceans that are the most promising locations for potential life lie isolated beneath kilometers of ice, which makes robotics and autonomy required for missions, and introduces new challenges for robotics, especially in sample handling systems. This thesis will address the needs for sampling on ocean worlds by using analog Earth environments and underwater technology development platforms to explore underwater solid sampling (e.g., sediment or ice), and by developing a liquid sampling system with ocean profiling capabilities suitable for a mission concept for a Europa melt probe. These studies will serve to investigate the challenges in sampling and the current state of the technology, concluding with the development of robotic solutions to these challenges. The objectives of this work are to: explore the needs of sampling systems for searching for life on ocean worlds, design robotic solutions to solve the identified challenges in sampling, and to develop benchtop systems to increase the technology readiness levels of these sampling systems for an ocean worlds mission context. To achieve these objectives, three systems were developed and tested in the lab, and, where possible, in a relevant environment: a solid sampling system for use on lightweight under-ice AUVs; a small tether management system for use on board an under-ice ocean profiler; and a milliliter-scale electrodialysis instrument for desalting samples of water in situ. The determination of these systems, the motivation behind each one and how they enable ocean world sampling or sample handling, the design, and results from testing are presented in this thesis.Ph.D
The Habitable Ocean World Box (HOWBox) Model: Coupling Europa's Thermal and Chemical Evolution
No full textEuropa, a moon of Jupiter, has evidence for a liquid water ocean in contact with a rocky mantle beneath its icy surface. Due to the presence of this ocean, Europa has been a primary target for investigations of habitability within our solar system. Europa’s ocean has remained liquid, in part, due to tidal heating in the interior. However, this interior tidal heat production has likely varied and potentially even been oscillatory over Europa’s history due to evolving orbital eccentricity. Such thermal oscillations will affect Europa’s interior geochemistry, defining changes to chemical and energy inventories for putative biology. Therefore, Europa’s long-term habitability depends on both geochemical pathways and thermodynamics—modulated by tidal evolution—that define chemical and energy inventories. Here, we demonstrate how thermally-modulated volumetric changes to Europa’s ice shell, ocean, and fluid-accessible rocky mantle affect oceanic composition in Europa’s interior due to variation in salinity, reduced volatile flux from the seafloor, and oxidized material delivery from the ice shell. We find that Europa may have undergone major oxidation events in its past during periods of increased orbital eccentricity, with oxidant flux increasing by up to 10 orders of magnitude, affecting the composition of the ocean. We also find that stable hydrogen flux into the ocean from serpentinization is tied to the water activity of the ocean and pore fluids, which also vary with heat production. Periods of fluctuating heat production, driven by orbital dynamics, can result in substantial oscillations to hydrogen flux ranging from 100 -1013 moles of H2 per year, with the degree of variability controlled by the dissolved ion composition and concentration. These results suggest new ways that water activity and salinity of the ocean are important to stability of habitable conditions in ocean worlds. By demonstrating that Europa’s ocean composition will be sensitive to its orbital dynamics and the degree to which it undergoes oscillatory tidal heat production, we reinforce that Europa’s long-term habitability is directly tied to its thermal-orbital history.Ph.D
A Measurement of the Limiting Magnitude of the VERITAS-SII Instrument with Bayesian Statistics and Eta UMa (Alkaid)
No full text64 pagesSeveral independent groups have pursued and realized the creation of modern SII instruments to perform high angular resolution observations at optical wavelengths, one such instrument being VERITAS-SII (Very Energetic Radiation Imaging Telescope Array System with Stellar Intensity Interferometry). An analysis methodology customized for signal extraction of VERITAS-SII data is presented. Systematics which effect the measured instrumental sensitivity are explored and subsequently corrected for. An observationally driven statistical framework is implemented to perform Bayesian inference with a uniform disk squared visibility model, subsequently measuring the instrumental sensitivity of the VERITAS-SII system with VERITAS-SII data taken of Eta UMa on December 20th, 2021. The statistical framework is expandable to more complex squared visibility models like limb darkened uniform disk and binary models. The sensitivity measurement presented can be used to extrapolate the sensitivity limitations of the VERITAS-SII instrument and future SII instruments
A Novel Model for through ice Acoustic Data Transfer
No full textWireless communication in harsh, icy environments is an enterprising technological field. Through- and under-ice networking for autonomous sensing (AUV/ROV/glider surveys) and long-term climate-related environmental monitoring at Earth’s poles is a frontier that requires robust localization and data transmission. Meanwhile, missions envisioned by NASA to ocean worlds like Jupiter’s moon Europa require analogous systems for auxiliary through-ice communication (“comms”) and environmental profiling. While Radio Frequency (RF) comms systems are established on Earth and in space, they are not robust in mixed media (ice/water mixtures) and require large antennas for which maintenance, size, and power resources are high, posing technical challenges for remote operation. Alternatively, acoustic comms have extensive heritage in underwater applications, and attestation as reliable, low-power science sensing and environmental characterization devices through ice at Earth’s polar regions. Due to the budding nature of acoustics through-ice research, no link budgets or channel models currently exist for estimating and optimizing hardware and software needs. This knowledge gap hinders technological advancement and investigative use-cases, necessitating optimization and range/data capability estimation to occur in-situ—which, in harsh polar or remote environments, may become a costly, resource-intensive, and potentially iterative endeavor. To fill this gap, I have created a novel, adaptable model for acoustic attenuation and signaling through ice, incorporating acoustic and material physics, empirical equations, and data over a wide range of frequencies (~1-100kHz) for transmission loss parameters from in-situ characterization investigations. Using GNU Radio, the acoustic model is incorporated into a signal chain for which users input parameters of the target ice environment and signal type. Paired with a link budget, optimal system parameters may be estimated.M.S
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