Search

Your search keyword '"Howell, Samuel M"' showing total 36 results
Start Over Author "Howell, Samuel M"
36 results on '"Howell, Samuel M"'

1. Science Overview of the Europa Clipper Mission

Author

Pappalardo, Robert T., Buratti, Bonnie J., Korth, Haje, Senske, David A., Blaney, Diana L., Blankenship, Donald D., Burch, James L., Christensen, Philip R., Kempf, Sascha, Kivelson, Margaret G., Mazarico, Erwan, Retherford, Kurt D., Turtle, Elizabeth P., Westlake, Joseph H., Paczkowski, Brian G., Ray, Trina L., Kampmeier, Jennifer, Craft, Kate L., Howell, Samuel M., Klima, Rachel L., Leonard, Erin J., Matiella Novak, Alexandra, Phillips, Cynthia B., Daubar, Ingrid J., Blacksberg, Jordana, Brooks, Shawn M., Choukroun, Mathieu N., Cochrane, Corey J., Diniega, Serina, Elder, Catherine M., Ernst, Carolyn M., Gudipati, Murthy S., Luspay-Kuti, Adrienn, Piqueux, Sylvain, Rymer, Abigail M., Roberts, James H., Steinbrügge, Gregor, Cable, Morgan L., Scully, Jennifer E. C., Castillo-Rogez, Julie C., Hay, Hamish C. F. C., Persaud, Divya M., Glein, Christopher R., McKinnon, William B., Moore, Jeffrey M., Raymond, Carol A., Schroeder, Dustin M., Vance, Steven D., Wyrick, Danielle Y., Zolotov, Mikhail Y., Hand, Kevin P., Nimmo, Francis, McGrath, Melissa A., Spencer, John R., Lunine, Jonathan I., Paty, Carol S., Soderblom, Jason M., Collins, Geoffrey C., Schmidt, Britney E., Rathbun, Julie A., Shock, Everett L., Becker, Tracy C., Hayes, Alexander G., Prockter, Louise M., Weiss, Benjamin P., Hibbitts, Charles A., Moussessian, Alina, Brockwell, Timothy G., Hsu, Hsiang-Wen, Jia, Xianzhe, Gladstone, G. Randall, McEwen, Alfred S., Patterson, G. Wesley, McNutt, Jr., Ralph L., Evans, Jordan P., Larson, Timothy W., Cangahuala, L. Alberto, Havens, Glen G., Buffington, Brent B., Bradley, Ben, Campagnola, Stefano, Hardman, Sean H., Srinivasan, Jeffrey M., Short, Kendra L., Jedrey, Thomas C., St. Vaughn, Joshua A., Clark, Kevin P., Vertesi, Janet, and Niebur, Curt

Published
2024
Full Text
View/download PDF

2. Contributors

Author

Ahrens, Caitlin J., primary, Bierson, Carver J., additional, Brough, Stephen, additional, Butcher, Frances E.G., additional, Castillo-Rogez, Julie, additional, Conway, S.J., additional, Costard, F., additional, Dhingra, R.D., additional, El-Maarry, Mohamed Ramy, additional, Farnsworth, K.K., additional, Gallagher, Colman, additional, Galofre, Anna Grau, additional, Garvin, James B., additional, Godin, E., additional, Hepburn, Adam J., additional, Howell, Samuel M., additional, Hubbard, Bryn, additional, Kalousová, Klára, additional, Keown, Lauren E. Mc, additional, Koutnik, Michelle, additional, Landis, Margaret E., additional, Lasue, Jeremie, additional, Leonard, Erin, additional, Lisse, Carey M., additional, Magaña, L.O., additional, Nathan, E.M., additional, Pathare, Asmin, additional, Philippe, M., additional, Rubanenko, Lior, additional, Scanlon, Kat, additional, Soare, Richard J., additional, Steinbrügge, Gregor, additional, Stillman, D., additional, Williams, Jean-Pierre, additional, and Wolfenbarger, Natalie, additional

Published
2024
Full Text
View/download PDF

5. A Recipe for Geophysical Exploration of Enceladus

Author

Ermakov, Anton I., Park, Ryan S., Roa, Javier, Castillo-Rogez, Julie C., Keane, James T., Nimmo, Francis, Kite, Edwin S., Sotin, Christophe, Lazio, T. Joseph W., Steinbrügge, Gregor, Howell, Samuel M., Bills, Bruce G., Hemingway, Douglas J., Viswanathan, Vishnu, Tobie, Gabriel, and Lainey, Valery

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Physics - Geophysics
Abstract

Orbital geophysical investigations of Enceladus are critical to understanding its energy balance. We identified key science questions for the geophysical exploration of Enceladus, answering which would support future assessment of Enceladus' astrobiological potential. Using a Bayesian framework, we explored how science requirements map to measurement requirements. We performed mission simulations to study the sensitivity of a single spacecraft and dual spacecraft configurations to static gravity and tidal Love numbers of Enceladus. We find that mapping Enceladus' gravity field, improving the accuracy of the physical libration amplitude, and measuring Enceladus' tidal response would provide critical constraints on the internal structure, and establish a framework for assessing Enceladus' long-term habitability. This kind of investigation could be carried out as part of a life search mission at little additional resource requirements., Comment: 21 pages, 6 figures. A paper submitted to PSJ, which is an extension of the white paper previously submitted to the decadal survey

Published
2020

6. Ocean Worlds Exploration and the Search for Life

Author

Howell, Samuel M., Stone, William C., Craft, Kate, German, Christopher, Murray, Alison, Rhoden, Alyssa, and Arrigo, Kevin

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

This is a community white paper submitted to the Decadal Survey in Planetary Science and Astrobiology, reflecting the views of the NASA Astrobiology Program's Research Coordination Network for Ocean Worlds (NOW). We recommend the establishment of a dedicated Ocean Worlds Exploration Program within NASA to provide sustained funding support for the science, engineering, research, development, and mission planning needed to implement a multi-decadal, multi-mission program to explore Ocean Worlds for life and understand the conditions for habitability. The two new critical flagship missions within this program would 1) land on Europa or Enceladus in the decade 2023-2032 to investigate geophysical and geochemical environments while searching for biosignatures, and 2) access a planetary ocean to directly search for life in the decade 2033-2042. The technological solutions for a landed mission are already in-hand, evidenced by the successful delta-Mission Concept Review of the Europa Lander pre-flight project in the fall of 2018. Following an initial landed mission, an ocean access mission will require substantial research, development, and analog testing this decade to enable the initiation of a pre-flight project at the start of the following decade., Comment: 8 pages, with cover, 1 table, 1 figure

Published
2020
Full Text
View/download PDF

7. Investigating Europa’s Habitability with the Europa Clipper

Author

Vance, Steven D., Craft, Kathleen L., Shock, Everett, Schmidt, Britney E., Lunine, Jonathan, Hand, Kevin P., McKinnon, William B., Spiers, Elizabeth M., Chivers, Chase, Lawrence, Justin D., Wolfenbarger, Natalie, Leonard, Erin J., Robinson, Kirtland J., Styczinski, Marshall J., Persaud, Divya M., Steinbrügge, Gregor, Zolotov, Mikhail Y., Quick, Lynnae C., Scully, Jennifer E. C., Becker, Tracy M., Howell, Samuel M., Clark, Roger N., Dombard, Andrew J., Glein, Christopher R., Mousis, Olivier, Sephton, Mark A., Castillo-Rogez, Julie, Nimmo, Francis, McEwen, Alfred S., Gudipati, Murthy S., Jun, Insoo, Jia, Xianzhe, Postberg, Frank, Soderlund, Krista M., and Elder, Catherine M.

Published
2023
Full Text
View/download PDF

9. Exploring the Interior of Europa with the Europa Clipper

Author

Roberts, James H., McKinnon, William B., Elder, Catherine M., Tobie, Gabriel, Biersteker, John B., Young, Duncan, Park, Ryan S., Steinbrügge, Gregor, Nimmo, Francis, Howell, Samuel M., Castillo-Rogez, Julie C., Cable, Morgan L., Abrahams, Jacob N., Bland, Michael T., Chivers, Chase, Cochrane, Corey J., Dombard, Andrew J., Ernst, Carolyn, Genova, Antonio, Gerekos, Christopher, Glein, Christopher, Harris, Camilla D., Hay, Hamish C. F. C., Hayne, Paul O., Hedman, Matthew, Hussmann, Hauke, Jia, Xianzhe, Khurana, Krishan, Kiefer, Walter S., Kirk, Randolph, Kivelson, Margaret, Lawrence, Justin, Leonard, Erin J., Lunine, Jonathan I., Mazarico, Erwan, McCord, Thomas B., McEwen, Alfred, Paty, Carol, Quick, Lynnae C., Raymond, Carol A., Retherford, Kurt D., Roth, Lorenz, Rymer, Abigail, Saur, Joachim, Scanlan, Kirk, Schroeder, Dustin M., Senske, David A., Shao, Wencheng, Soderlund, Krista, Spiers, Elizabeth, Styczinski, Marshall J., Tortora, Paolo, Vance, Steven D., Villarreal, Michaela N., Weiss, Benjamin P., Westlake, Joseph H., Withers, Paul, Wolfenbarger, Natalie, Buratti, Bonnie, Korth, Haje, and Pappalardo, Robert T.

Published
2023
Full Text
View/download PDF

10. Constraining the Thickness of the Conductive Portion of Europa's Ice Shell Using Sparse Radar Echoes.

Author

Schroeder, Dustin M., Wolfenbarger, Natalie S., Steinbrügge, Gregor B., Culberg, Riley, Howell, Samuel M., Spiers, Elizabeth, and Styczinski, Marshall

Subjects
LUNAR surface, GEOPHYSICAL observations, MELTWATER, PLANETARY observations, ELECTROMAGNETIC induction
Abstract

Ice penetrating radar sounding is the primary geophysical technique for imaging the subsurface of planetary ice shells and has the potential to directly detect the ice–ocean interface. However, many sounding measurements may lack laterally extensive features that would aid their physical interpretation. In this scenario, the detection of sparse echoes can also provide rich information on ice shell properties. To explore and demonstrate this possibility, we consider three cases of isolated radar signatures: pore‐curing, eutectic melt, and unattributed echoes. We show that through detection of unattributed sparse echoes, the thickness of the conductive portion of Europa's ice shell can be constrained. These constraints can be improved by attributing sparse echoes to thermally diagnostic signatures such as pore‐curing and eutectic melt. Notably, this approach to radar sounding echo analysis is particularly compatible with joint inversions with other planetary geophysical observations such as tidal deformation, magnetic induction, and rotation state. Plain Language Summary: Upcoming missions to explore Europa, the icy moon of Jupiter, include ice penetrating radar sounders as part of their instrument payloads. One of the primary goals of these instruments is to investigate the subsurface structure and thickness of Europa's ice shell. It's possible that the radar profiles returned by these instruments will include imagery of the ice‐ocean interface across much of the moon, providing a direct measurement of ice‐shell thickness. However, we show that, even in the absence of such imagery, a small number of isolated radar echoes can be used to measure the thickness and structure of the ice shell. These echoes include scattering from porous ice near the moon's surface and pockets of melt water within the shell. Key Points: Radar‐detectable interfaces from the subsurface of Europa's ice shell can be thermally diagnosticThe thickness of the conductive portion of Europa's ice shell can be constrained without direct detection of the ice—ocean interfaceThe detection of sparse echoes places a lower bound on conductive ice shell thickness based on the two‐way integrated radar attenuation [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

14. Camilla: A centaur reconnaissance and impact mission concept

Author

Howell, Samuel M., Chou, Luoth, Thompson, Michelle, Bouchard, Michael C., Cusson, Sarah, Marcus, Matthew L., Smith, Harrison B., Bhattaru, Srinivasa, Blalock, John J., Brueshaber, Shawn, Eggl, Siegfried, Jawin, Erica R., Miller, Kelly, Rizzo, Maxime, Steakley, Kathryn, Thomas, Nancy H., Trent, Kimberly R., Ugelow, Melissa, Budney, Charles J., Mitchell, Karl L., and Lowes, Leslie

Published
2018
Full Text
View/download PDF

19. Exploring the Interior of Europa with the Europa Clipper

Author

Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences, Roberts, James H., McKinnon, William B., Elder, Catherine M., Tobie, Gabriel, Biersteker, John B., Young, Duncan, Park, Ryan S., Steinbrügge, Gregor, Nimmo, Francis, Howell, Samuel M., Castillo-Rogez, Julie C., Cable, Morgan L., Abrahams, Jacob N., Bland, Michael T., Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences, Roberts, James H., McKinnon, William B., Elder, Catherine M., Tobie, Gabriel, Biersteker, John B., Young, Duncan, Park, Ryan S., Steinbrügge, Gregor, Nimmo, Francis, Howell, Samuel M., Castillo-Rogez, Julie C., Cable, Morgan L., Abrahams, Jacob N., and Bland, Michael T.

Abstract

The Galileo mission to Jupiter revealed that Europa is an ocean world. The Galileo magnetometer experiment in particular provided strong evidence for a salty subsurface ocean beneath the ice shell, likely in contact with the rocky core. Within the ice shell and ocean, a number of tectonic and geodynamic processes may operate today or have operated at some point in the past, including solid ice convection, diapirism, subsumption, and interstitial lake formation. The science objectives of the Europa Clipper mission include the characterization of Europa’s interior; confirmation of the presence of a subsurface ocean; identification of constraints on the depth to this ocean, and on its salinity and thickness; and determination of processes of material exchange between the surface, ice shell, and ocean. Three broad categories of investigation are planned to interrogate different aspects of the subsurface structure and properties of the ice shell and ocean: magnetic induction, subsurface radar sounding, and tidal deformation. These investigations are supplemented by several auxiliary measurements. Alone, each of these investigations will reveal unique information. Together, the synergy between these investigations will expose the secrets of the Europan interior in unprecedented detail, an essential step in evaluating the habitability of this ocean world.

Published
2023

25. A Recipe for the Geophysical Exploration of Enceladus

Author

Ermakov, Anton I., primary, Park, Ryan S., additional, Roa, Javier, additional, Castillo-Rogez, Julie C., additional, Keane, James T., additional, Nimmo, Francis, additional, Kite, Edwin S., additional, Sotin, Christophe, additional, Lazio, T. Joseph W., additional, Steinbrügge, Gregor, additional, Howell, Samuel M., additional, Bills, Bruce G., additional, Hemingway, Douglas J., additional, Viswanathan, Vishnu, additional, Tobie, Gabriel, additional, and Lainey, Valery, additional

Published
2021
Full Text
View/download PDF

27. Enabling the Next Frontiers in Astrobiology — Ocean and Ice Worlds Explorations with a Radioisotope Power System Inside a Pressure Vessel

Author

Balint, Tibor, primary, Lee, Young H., additional, Howell, Samuel M., additional, Perl, Scott M., additional, Craft, Kathleen, additional, Hurford, Terry A., additional, Cable, Morgan L., additional, MacKenzie, Shannon, additional, Bairstow, Brian K., additional, Johnson, Stephen G., additional, Clarke, Eric S., additional, Donitz, Benjamin P., additional, and Schmitz, Paul C., additional

Published
2021
Full Text
View/download PDF

28. A Recipe for Geophysical Exploration of Enceladus

Author

Ermakov, Anton, primary, Castillo-Rogez, Julie C., additional, Park, Ryan S., additional, Sotin, Christophe, additional, Lazio, Joseph, additional, Howell, Samuel M., additional, Keane, James T., additional, Hemingway, Douglas J., additional, Nimmo, Francis, additional, Kite, Edwin, additional, Viswanathan, Vishnu, additional, Steinbrügge, Gregor, additional, Tobie, Gabriel, additional, and Lainey, Valery, additional

Published
2021
Full Text
View/download PDF

29. Potential Ocean Worlds

Author

Hendrix, Amanda R., primary, Hurford, Terry, additional, Patterson, Gerald W., additional, Mandt, Kathleen E., additional, Beddingfield, Chloe B., additional, Cartwright, Richard J., additional, Castillo-Rogez, Julie C., additional, Lopes, Rosaly M. C., additional, Howell, Samuel M., additional, Quick, Lynnae C., additional, Neveu, Marc, additional, Poston, Michael J., additional, and Mills, Alyssa C., additional

Published
2021
Full Text
View/download PDF

34. Magmatic and tectonic extension at the Chile Ridge : evidence for mantle controls on ridge segmentation

Author

Howell, Samuel M., Ito, Garrett T., Behn, Mark D., Martinez, Fernando, Olive, Jean-Arthur, Escartin, Javier E., Howell, Samuel M., Ito, Garrett T., Behn, Mark D., Martinez, Fernando, Olive, Jean-Arthur, and Escartin, Javier E.

Abstract

We use data from an extensive multibeam bathymetry survey of the Chile Ridge to study tectonomagmatic processes at the ridge axis. Specifically, we investigate how abyssal hills evolve from axial faults, how variations in magmatic extension influence morphology and faulting along the spreading axis, and how these variations correlate with ridge segmentation. The bathymetry data are used to estimate the fraction of plate separation accommodated by normal faulting, and the remaining fraction of extension, M, is attributed primarily to magmatic accretion. Results show that M ranges from 0.85 to 0.96, systematically increasing from first-order and second-order ridge segment offsets toward segment centers as the depth of ridge axis shoals relative to the flanking highs of the axial valley. Fault spacing, however, does not correlate with ridge geometry, morphology, or M along the Chile Ridge, which suggests the observed increase in tectonic strain toward segment ends is achieved through increased slip on approximately equally spaced faults. Variations in M along the segments follow variations in petrologic indicators of mantle melt fraction, both showing a preferred length scale of 50 ± 20 km that persists even along much longer ridge segments. In comparison, mean M and axial relief fail to show significant correlations with distance offsetting the segments. These two findings suggest a form of magmatic segmentation that is partially decoupled from the geometry of the plate boundary. We hypothesize this magmatic segmentation arises from cells of buoyantly upwelling mantle that influence tectonic segmentation from the mantle, up.

Published
2016

36. Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply

Author

Olive, Jean-Arthur L., Behn, Mark D., Ito, Garrett T., Buck, W. Roger, Escartin, Javier E., Howell, Samuel M., Olive, Jean-Arthur L., Behn, Mark D., Ito, Garrett T., Buck, W. Roger, Escartin, Javier E., and Howell, Samuel M.

Abstract

Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of American Association for the Advancement of Science for personal use, not for redistribution. The definitive version was published in Science 350 (2015): 6258, doi:10.1126/science.aad0715., Recent studies have proposed that the bathymetric fabric of the seafloor formed at mid-ocean ridges records rapid (23–100 kyr) fluctuations in ridge magma supply caused by sea level changes that modulate melt production in the underlying mantle. Using quantitative models of faulting and magma emplacement, we demonstrate that, in fact, seafloor-shaping processes act as a low-pass filter on variations in magma supply, strongly damping fluctuations shorter than ~100 kyr. We show that the systematic decrease in dominant seafloor wavelengths with increasing spreading rate is best explained by a model of fault growth and abandonment under a steady magma input. This provides a robust framework for deciphering the footprint of mantle melting in the fabric of abyssal hills, the most common topographic feature on Earth., Funding was provided by NSF grants OCE-1154238 (J.-A.O., M.D.B), OCE-1155098 (G.I., S.H.), EAR-1009839 (W.R.B), CNRS support to JE, and an LDEO Postdoctoral Fellowship for J.-A.O., 2016-04-16

Published
2015

Catalog

Books, media, physical & digital resources
See catalog results