Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session W5: GP2: Planetary I |
Hide Abstracts |
Chair: Alex Goncharov, Carnegie Institution for Science Room: Cascade I |
Thursday, July 11, 2013 4:00PM - 4:30PM |
W5.00001: Probing planetary interiors: Shock compression of water to 700 GPa and 3.8 g/cc, and recent high precision Hugoniot measurements of deuterium Invited Speaker: Marcus Knudson The past several years have seen tremendous increase in the number of identified extra-solar planetary systems. Our understanding of the formation of these systems is tied to our understanding of the internal structure of these exoplanets, which in turn rely upon equations of state of light elements and compounds such as water and hydrogen. Here we present shock compression data for water with unprecedented accuracy that shows commonly used models for water in planetary modeling significantly overestimate the compressibility at conditions relevant to planetary interiors. Furthermore, we show that its behavior at these conditions, including reflectivity and isentropic response, is well described by a recent first-principles based equation of state. These findings advocate the use of this model as the standard for modeling Neptune, Uranus, and ``hot Neptune'' exoplanets, and should contribute to improved understanding of the interior structure of these planets, and perhaps improved understanding of formation mechanisms of planetary systems. We also present very recent experiments on deuterium that have taken advantage of continued improvements in both experimental configuration and the understanding of the quartz shock standard to obtain Hugoniot data with a significant increase in precision. These data will prove to provide a stringent test for the equation of state of hydrogen and its isotopes. [Preview Abstract] |
Thursday, July 11, 2013 4:30PM - 4:45PM |
W5.00002: Simulation of methane-water mixtures at extreme conditions Sandro Scandolo, Mal-Soon Lee, Nurapati Pantha, Narayan Adhikari Simulations and experiments carried out separately on methane and water, the main components of the middle layers of Neptune and Uranus, show that at those conditions methane disproportionates into carbon-rich species and water dissociates to form an ionic fluid. Water becomes electronically conducting only at the conditions found in the deepest layers of the planets. More recent simulations on water/methane mixtures suggest a pressure-induced softening of the methane-water intermolecular repulsion that points to an enhancement of mixing under extreme conditions. In the mixtures, ionized water causes the progressive ionization of methane and the mixture becomes electronically conductive at milder conditions than pure water. Calculations on the crystalline counterparts, methane hydrate clathrates, suggest however a different picture: mixtures at low temperature become increasingly unstable, with increasing pressure, towards phase separation, despite the prediction of a solid-solid phase transition between MH-III, the known high-pressure form of methane hydrate, and a new hypothetical phase. [Preview Abstract] |
Thursday, July 11, 2013 4:45PM - 5:00PM |
W5.00003: Nanodiamond formation via thermal radiation from an air shock Paul De Carli Nanodiamonds have recently been found in sediments of Younger Dryas age, about 12,900 years ago. Carbon isotope ratios imply that the source of carbon was terrestrial organic matter and rule out the possibility that the diamond was of cosmic origin, e.g., from an influx of meteorites. The nanodiamonds are associated with mineral spherules (and other shapes) that have compositions and textures consistent with the rapid melting and solidification of local soil. The inferred temperatures are much too high for natural events such as forest fires. Similar deposits of nanodiamond have been found in the 65 million year old K-Pg layer associated with the ca. 200 km diameter Chicxulub impact crater. Nanodiamond have also been reported in the vicinity of the Tunguska event, presumed to be the result of an air shock produced by the interaction of a rapidly moving cosmic body with the Earth's atmosphere. We infer that the nanodiamonds were formed when the thermal radiation from the air shock pyrolyzed surface organic matter. Rapid reaction locally depleted the atmosphere of oxygen and the remaining carbon could condense as nanodiamond. A similar mechanism can be invoked to account for the formation of nanodiamond as a froduct of the detonation of ozygen-deficient high explosives. [Preview Abstract] |
Thursday, July 11, 2013 5:00PM - 5:15PM |
W5.00004: Apophis, Earth and Moon I.V. Lomonosov, A.M. Kazantsev, V.V. Kim, A.V. Ostrik The asteroid Apophis is of great potential danger for our civilization. According to results of astronomical observations and calculations, it will fly at 40000 km distance from the Earth centre without collision in 2029. However, the greater risk of collision is estimated in 2036. Traditionally, it is only proposed to correct this asteroid orbit for preventing the collision in 2036. In such a case the estimation of consequences of this correction is not obviously possible in the long period of time after 2036. So, the deviation of Apophis from a collision trajectory will not solve the problem completely. We propose to target Apophis on the Moon. It will remove totally the danger of the asteroid strike on the Earth and will give us a possibility to study the structure of the Moon. Note, that it requires a pretty small correction of the asteroid's orbit. As a result of calculations, the correction of Apophis orbit is necessary on January, 9$^{\mathrm{th}}$ 2013 with an increment of speed of 7.4 m/s. It will provide passage of asteroid Apophis on distance from the Moon surface hardly more than its radius on April 14th 2029. The second correction will guarantee the collision with the Moon surface. We notice that strong sensitivity of the solution to indignations doesn't allow to carry out the correction with the guaranteed result in one stage. We also discuss methods of changing the orbit, evaluate the impact crater and the amount of ejected matter and seismic disturbances resulting from the impact. [Preview Abstract] |
Thursday, July 11, 2013 5:15PM - 5:30PM |
W5.00005: Rocky Planet Paradox Florentin Smarandache The science tells us that a rocky body in the Solar system whose mass exceeds 3$\times $10$^{21}$ kg should be round. The Moon is 7.3$\times $10$^{22}$ kg, therefore its shape is round. But the Moon rotates around the Earth, therefore it should get flatter in the direction of rotation according to the relativistic length contraction, since the Moon's radius which is perpendicular on the trajectory is unchanged while the Moon's radius in the direction of the motion should get contracted. Yet, although the Moon orbits the Earth for geological time, it is not flat! In general, let's consider a rocky non-rotating cosmic body, with mass exceeding 3$\times $10$^{21}$ kg that orbits the Sun or one of the solar planets. The larger is the cosmic body's orbit, the simpler is to get a small part of its orbit that looks linear. Then this cosmic body should flatten in the direction of motion, according to the Theory of Relativity, but this is in contradiction to the previous science law that this cosmic body should be round. [Preview Abstract] |
Thursday, July 11, 2013 5:30PM - 5:45PM |
W5.00006: Gravitational Collapse of Small Cores in Two-Phase Celestial Bodies Michael Grinfeld, Pavel Grinfeld The phenomenon of gravitational collapse (GC) is well-known in theoretical astro- and planetary physics. It occurs when the incompressibility of substances is unable to withstand the pressure due to gravitational forces in celestial bodies of sufficiently large mass. The GC never occurs in incompressible models -- homogeneous or layered. This situation changes dramatically when different incompressible layers appear to be different phases of the same chemical substance and the mass exchange between the phases can occur due to phase transformation. The possibility of destabilization in such system becomes realistic, as it was first discovered in the Ramsey static analysis [1,2]. We will present our generalization of the Ramsey's results using dynamic approach.\\[4pt] [1] W.H. Ramsey, ``On the instability of small planetary cores,'' Mon. Not. R. Astron. Soc. 110 (4), 325-338 (1950). [2] H. Jeffreys, ``The Earth: Its Origin, History, and Physical Constitution.'' Cambridge University Press (1976). [Preview Abstract] |
Thursday, July 11, 2013 5:45PM - 6:00PM |
W5.00007: Equation of State of Ammonia Roberta Mulford, Sebastien Hamel, Damian Swift Ammonia and water are critical components of extraterrestrial bodies, determining the density and physical properties of the Outer Planets, their moons and of extrasolar planets. Several EOS are presented for ammonia and for mixtures of ammonia, water, and methane and their properties discussed, and compared with quantum molecular dynamics predictions of the properties and evolving compositions of these mixtures as pressure and temperatures become extreme. The NH$_{4}$OH hydrate of ammonia is known to exist as a separate molecular species at pressures above about 5 GPa, and an effort is made to include reaction between NH$_{3}$ and H$_{2}$O in the description of effective EOS for mixtures. A thermodynamically complete quasiharmonic EOS for ammonia is constructed, taking into account the vibrational state splitting by molecular inversion, in determination of the heat capacity. The EOS obtained are intended for application in mass-radius relations which bound the possible interpretations of composition and structure for extraterrestrial bodies of unknown composition, in particular exoplanets. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700