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Physical Oceanography in the Solar System and Beyond

A key controller of a planet’s rotational evolution, and hence habitability, is tidal dissipation, which on Earth occurs primarily in the oceans. As the discovery of habitable exoplanets is a primary objective of exoplanet research, it is imperative that we understand how “exo-oceans” behave. Despite this importance, little research has investigated the physical oceanography of worlds other than Earth. This oversight has occurred even though the Earth science community has studied tidal flows in Earth’s oceans for over a century and developed sophisticated models that exquisitely match satellite altimetry data, e.g. Here, we present a) models of tidal effects on exoplanets to motivate the problem, b) the application of a physical oceanography model to a putative ancient Venus ocean, and c) the application of that model to an ensemble of “alternative Earths” with a range of continental configurations and seafloor properties. We find that oceanic tidal dissipation can span 5 orders of magnitude, revealing that simulating exo-oceans with Earth science tools will provide fundamental insight into exoplanet evolution and habitability

Physical Oceanography↗
NASA NTRS1992

Chemical differentiation of a convecting planetary interior - Consequences for a one plate planet such as Venus

Simple models of the thermal and chemical evolution of a planetary interior are developed to explore the possible consequences of a chemically buoyant depleted mantle layer for planetary evolution. As the depleted layer thickens the melting temperature at the top of the underlying convecting mantle also increases and the degree of partial melting of the mantle added to the depleted layer decreases. As the less depleted mantle with less positive compositional buoyancy is added, the negative thermal buoyancy of the layer eventually exceeds its positive compositional buoyancy. The depleted layer then sinks into and mixes with the convecting interior. On Venus the population of impact craters is indistinguishable from a random distribution over the surface and gives a surface age of about 500 Myr. It is suggested that the above mechanism may explain this episodic global resurfacing of Venus.

Parmentier, E. M.↗
NASA NTRS1986

Planetary volatile history - Principles and practice

The history and evolution of planetary volatile inventories are considered. Planetary bulk volatile inventories are greatly affected by the distance from the preplanetary nebula center at which material accreted, with volatile contents increasing with increasing distance from the nebula center. Other significant factors include: planetary energetics and internal thermal history, planetary volatile sinks (including space), and operation of external variables such as solar energy on the transient, steady-state array of surface volatiles. The net result of all these processes is a volatile history that is itself a controlling factor in overall planetary history.

Fanale, F. P.↗
NASA NTRS1994

Abundances, planetary nebulae, and stellar evolution

Among Henry Norris Russell's many achievements were his contributions to solar and stellar spectroscopy, in particular, to an analysis of the chemical composition of the solar atmosphere. The question of composition differences between stars was hotly debated; some distinguished astronomers argued that all stars had the solar composition. Some early challenges to this doctrine are described. Determinations of chemical compositions of gaseous nebulae were much more difficult. If we observe the lines of a given chemical element in one ionization stage in a stellar spectrum, we can deduce readily the abundance of that element. No such luxury is available for a planetary or diffuse gaseous nebula. We must measure lines of as many ionization stages as we can. Furthermore, a nebula is an extended object. Often detailed spectroscopy is at hand only for narrow pencil columns taken through the image. Different observers use a variety of apertures. Fortunately it is possible to calculate theoretical spectra for any arbitrary cross section taken through a symmetrical model, so UV, optical, and IR observations all can be compared properly with a prediction. The value of high-resolution spectra obtained with instruments such as the Hamilton Echelle Spectrograph at Lick Observatory is emphasized. Improved fluxes for weak but important transitions are found. Close blends of lines of different ions can be resolved, and checks can be made on predictions of atomic parameters such as Einstein A-values and collision strengths. High spectral resolution data have been obtained and reduced for 22 planetary nebulae of varying size, structure, stellar population membership, dustiness, level of excitation, evolutionary status, and chemical compositions. The promise seems justified that with such extensive, high quality data, additional insights on nebular genesis and late states of stellar evolution can be found. The present survey is confined to nebulae of high surface brightness, but among these are found some engaging objects such as NGC 7027, IC 4997, and NGC 6572.

Aller, Lawrence H.↗
NASA NTRS2011

The James Webb Space Telescope: Capabilities for Exoplanet Science

The James Webb Space Telescope (JWST) is a large aperture (6.5 meter), cryogenic space telescope with a suite of near and mid-infrared instruments covering the wavelength range of 0.6 micron to 28 micron. JWST's primary science goal is to detect and characterize the first galaxies. It will also study the assembly of galaxies, stellar and planetary system formation, and the formation and evolution of planetary systems. We will review the design of JWST, and discuss the current status of the project, with emphasis on recent progress in the construction of the observatory. We also review the capabilities of the observatory for observations of exosolar planets and debris disks by means of coronagraphic imaging, and high contrast imaging and spectroscopy. This discussion will focus on the optical and thermal performance of the observatory, and will include the current predictions for the performance of the observatory, with special reference to the demands of exoplanet science observations.

Clampin, Mark↗
NASA NTRS1992

Energy transformations associated with the synoptic and planetary scales during the evolution of a blocking anticyclone and an upstream explosively-developing cyclone

The eddy kinetic energy (KE), release of eddy potential energy, generation of eddy kinetic energy, and exchange between eddy and zonal kinetic energy are investigated for a blocking anticyclone over the North Atlantic Ocean and an extratropical cyclone that developed during January 17-21, 1979. The results indicate that KE was maintained by baroclinic conversion of potential to kinetic. As released potential energy was being used to generate KE, a portion of the KE was barotropically converted to zonal KE. These transformations were dominated by the synoptic-scale component. While changes in the mass field depended not only on the synoptic scale but also on the interactions between the synoptic and planetary scales, the corresponding changes in the eddy motion fields responded largely to synoptic-scale processes.

Smith, Phillip J.↗
NASA NTRS1988

The isotopic and chemical evolution of planets: Mars as a missing link

The study of planetary bodies has advanced to a stage where it is possible to contemplate general models for the chemical and physical evolution of planetary interiors, which might be referred to as UMPES (Unified Models of Planetary Evolution and Structure). UMPES would be able to predict the internal evolution and structure of a planet given certain input parameters such as mass, distance from the sun, and a time scale for accretion. Such models are highly dependent on natural observations because the basic material properties of planetary interiors, and the processes that take place during the evolution of planets are imperfectly understood. The idea of UMPES was particularly unrealistic when the only information available was from the earth. However, advances have been made in the understanding of the general aspects of planetary evolution now that there is geochemical and petrological data available for the moon and for meteorites.

Depaolo, D. J.↗
NASA NTRS1989

Mass transfer during ice particle collisions in planetary rings

Experimental results are presented from laboratory environment simulations of the ice particle collisional properties defining the structure and dynamical evolution of planetary rings. It is inferred from these data that there is a dependence of the interacting volume on the impact velocity. Although the volume fraction exchanged during a collision is small, the net amount of material transferred can be substantially smaller. Attention is given to the implications of these determinations for planetary ring structure and evolution.

Mcdonald, J. S. B.↗
NASA NTRS1973

Studies of hydrodynamic events in stellar evolution. 3: Ejection of planetary nebulae

The dynamic behavior of the H-rich envelope (0.101 solar mass) of an evolved star (1.1 solar mass) as the luminosity rises to 19000 solar luminosity during the second ascent of the red giant branch. For luminosities in the range 3100 L 19000 solar luminosity the H-rich envelope pulsates like a long-period variable (LPV) with periods of the order of a year. As L reaches 19000 solar luminosity, the entire H-rich envelope is ejected as a shell with speeds of a few 10 km/s. The ejection occurs on a timescale of a few LPV pulsation periods. This ejection is associated with the formation of a planetary nebula. The computations are based on an implicit hydrodynamic computer code. T- and RHO-dependent opacities and excitation and ionization energies are included. As the H-rich envelope is accelerated off the stellar core, the gap between envelope and core is approximated by a vacuum, filled with radiation. Across the vacuum, the luminosity is conserved and the anisotropy of the radiation is considered as well as the solid angle subtended by the remnant star at the inner surface of the H-rich envelope. Spherical symmetry and the diffusion approximation are assumed.

Sparks, W. M.↗
NASA NTRS1974

Studies of hydrodynamic events in stellar evolution. III Ejection of planetary nebulae

Investigation of the dynamic behavior of the hydrogen-rich envelope (0.101 solar mass) of an evolved star (1.1 solar mass) as the luminosity rises to 19,000 solar luminosities during the second ascent of the red-giant branch. For luminosities in the range 3100 less than L less than 19,000 solar luminosities the H-rich envelope pulsates like a long-period variable (LPV) with periods of the order of a year. As L reaches 19,000 solar luminosities, the entire H-rich envelope is ejected as a shell with speeds of a few times 10 km sec. The ejection occurs on a time scale of a few LPV pulsation periods. This ejection is shown to be related to the formation of a planetary nebula. The computations are based on an implicit hydrodynamic computer code. Tand rho-dependent opacities and excitation and ionization energies are included. As the H-rich envelope is accelerated off the stellar core, the gap between envelope and core is approximated by a vacuum filled with radiation.

Kutter, G. S.↗
NASA NTRS1991

Planetary surface structure and evolution of Mars

The surface of the planet Mars is characterized by two different hemispheres: old densely cratered structures in the Southern Uplands, and sparsely cratered younger topographically lower regions covering approximately the northern third of the planet's surface. The model for explaining these global surface structures is characterized by the following features: (1) homogeneous accretion of Mars; (2) formation of a metal melt layer; (3) northward translation of the undifferentiated core due to a Rayleigh-Taylor instability; (4) vigorous convection in the southern parts and formation of the Southern Uplands' crust; (5) fragmentation of the primordial core, slowly dissolving rockbergs, beginning of Tharsis uplift and volcanism; (6) formation of the Northern Lowlands' crust from only weakly differentiated silicatic material; and (7) reaching of the present state with symmetrically placed core and further thermal evolution.

Franck, Siegfried↗
NASA NTRS2000

The Evolution and Disruption of Planetary Systems

Planetary systems that encounter passing stars can experience severe orbital disruption, and the efficiency of this process is greatly enhanced when the impinging systems are binary pairs rather than single stars. Using a Monte Carlo approach, we have performed nearly half a million numerical experiments to examine the long term ramifications of planetary scattering on planetary systems. We have concluded that systems which form in dense environments such as Orion's Trapezium cluster have roughly a ten percent chance of being seriously disrupted. We have also used our programs to explore the long-term prospects for our own Solar system. Given the current interstellar environment, we have computed the odds that Earth will find its orbit seriously disrupted prior to the emergence of a runaway greenhouse effect driven by the Sun's increasing luminosity. This estimate includes both direct disruption events and scattering processes that seriously alter the orbits of the Jovian planets, which then force severe changes upon the Earth's orbit. We then explore the consequences of the Earth being thrown into deep space. The surface biosphere would rapidly shut down under conditions of zero insolation, but the Earth's radioactive heat is capable of maintaining life deep underground, and perhaps in hydrothermal vent communities, for some time to come. Although unlikely for the Earth, this scenario may be common throughout the universe, since many environments where liquid water could exist (e.g., Europa and Callisto) must derive their energy from internal (rather than external) heating.

Laughlin, Gregory↗
NASA NTRS2003

A Study of Planetary System Formation and Evolution Using a Dual Channel Adaptive Optics Imaging Polarimeter

The award I received from the Graduate Student Research Program in 2001, and the renewal award in 2002, supported the gathering and processing of my thesis data, and the presentation of my scientific results at astronomy conferences. Ultimately, this led to a successful defense of my PhD thesis. In the thesis work, I built, calibrated, and observed with the first dual imaging polarimeter ever used in series with a high order adaptive optics system and on an 8 meter class telescope. The instrument was arguably the most sensitive instrument for the high-contrast detection of the scattered light from circumstellar disks. The success of the instrument has provided the impetus for the construction of several similar simultaneous adaptive optics imaging polarimeters. In the course of the observations, a number of circumstellar disks were resolved for the first time in their scattered light, such as the disk around the classical T-tauri stars, LkCa 15 and LkHa 262. A sample of 24 young, nearby, solar-analog stars were observed with the instrument in search of the scattered light signature from debris disks around these stars. Although none of the stars revealed any obvious scattered light signatures, a meaningful limit was placed on the dust population around these stars. Also, a brown dwarf binary system was found to be a companion to one of the solar-analog stars observed, HD130948. A careful monitoring of the orbit of the binary brown dwarf will result in a dynamical mass determination of the objects, providing a valuable calibration of the physical models explaining brown dwarf evolution.

Potter, Daniel E.↗
NASA NTRS1987

Textural evolution of partially-molten planetary materials in microgravity

Recent Earth-based experiments examining the textural evolution of partially-molten rocks have revealed two important ways in which surface energy considerations affect magma. An initial experimental program addressing surface-energy effects on partially-molten materials in microgravity would involve simple, isothermal treatment of natural samples (meteorites, perioditic komatiite) at preselected temperatures in the melting range. Textural evolution would be assessed by time studies in which the only experiment variable would be run duration. Textural characterization of each sample would be done by quenching, recover, and sectioning for generally later, computer-aided interpretation of features.

Watson, E. B.↗
NASA NTRS2003

Magnetite-Magnesioferrite Phase Relations and Application to ALH84001

Oxygen fugacity (fO2) is an important factor in planetary formation and evolution. Certain minerals or assemblages of minerals are stable only under certain fO2 conditions (at a constant T and P) and can be recorders of ambient fO2 during geologic processes. The best estimate of oxygen fugacity from mineral assemblages has implications, from large-scale models of planetary evolution to interpretation of single meteorites. For example, redox conditions are part of the discussion of the origin and history of shergottites, basaltic rocks in meteorites from Mars [1-4]. In addition oxygen fugacity may be an important factor to consider in the interpretation of the carbonate and magnetite assemblages seen in ALH84001 [5].

Koziol, Andrea M.↗