P41C-01
Quantifying the Planetary - Solar Interaction
The potential energy of planetary orbits relative to the solar surface was modeled. The planetary - solar attracting
energy was related to the launch energy (proportional to launch velocity) that is necessary to move an object from
the solar surface to the planetary orbit (vp,‘planetary launch velocity'). This launch energy is related to the
planetary potential energy relative to the solar surface.
The planetary launch velocities range from 613.830 (Mercury) to 617.526 km/s (Pluto). The difference between
solar escape velocity (vs, 617.547km /s) and planetary launch speeds represents the strength of adhesion to the
Sun relative to infinity. The velocity difference ranges from 3.7km/s (Mercury) to 0.037 km/s (Pluto).
The planetary orbits are expanding and orbital periods are increasing with time due to solar mass loss by
thermonuclear radiative process,mass loss by solar wind, and the weak binding of the planets. Separation rates
were calculated and range from 4.32E-04 to 14.6 km/yr for Mercury and Eris, respectively. The predicted present
orbital separation rates are within the range of experimental observation. The planets will escape the solar
system when the solar escape velocity decreases below the planetary launch velocity. From this, the planetary
separation time is calculated for the current solar mass loss rate to 133.8 and 0.76 billion years for Mercury and
Eris, respectively. The model implies that the planets were significantly closer to the sun after the formation of the
solar system. The transition from water to ice for Mars was correccly predicted to about 3.6 billion years ago(2005
AGU Fall Meting).
http:www.rocherresearch.us
P41C-02
Evolution of Mars' Atmosphere and Climate
Carbon dioxide is the primary component of Mars' atmosphere at present. It is conventional wisdom that CO2 was the dominant atmospheric gas from the time of earliest degassing of the Martian interior. The dominant degassed volatile on/near the Martian surface was (and probably is) water. The evidence for very large volumes of water in Mars' distant past is indisputable. Greenhouse gas (usually considered to be CO2) concentrations in the Martian atmosphere at present are obviously insufficient to either produce a warm enough climate or high enough atmospheric pressure to sustain liquid water for any significant length of time. Considering the increase in luminosity of the sun over the last 4.5 BY, the presence of liquid water on Mars' surface in the distant past would require even higher concentrations of greenhouse gases at that time. To get from such an early warm wet climate, with a faint sun and high atmospheric CO2 levels, to the present cold climate seems to require loss of huge quantities of CO2 and perhaps water (hydrogen). Recent results suggest that atmospheric loss mechanisms are not sufficient to the task. Even worse, surface robotic missions provide little or no evidence for the carbonate minerals that should be abundantly produced by a water and CO2-rich surface environment. Clearly we have a problem. The solution is simple. The primary carbon species degassed from Mars' interior was methane, probably accompanied by ammonia, and certainly by a much larger amount of water. Methane is a much more potent greenhouse gas than CO2. Although atmospheric photochemistry destroys methane by producing various polymerized and oxidized organic species, deposition of these molecules on the Martian surface and in the early Martian ocean provides a large reduced carbon reservoir from which methane can be regenerated through hydrothermal reactions driven by volcanism. Equable surface climates (and flowing water) can be maintained as long as hydrothermal activity produces enough methane to offset photochemical destruction, at sufficient levels for greenhouse warming. Over time (and continuing until the present) the loss of hydrogen to space leads to oxidation of the surface and the production of CO2. Because of Mars relatively small size, the loss of internal heat sources eventually reduces volcanism and hydrothermal activity below the point at which methane can be regenerated to maintain greenhouse warming, even with the increasing luminosity of the sun. At this point Mars lapses into the cold regime of the present day. The transition may well have been punctuated by occasional outbursts of methane to temporarily restore mild conditions. With secular cooling the water of the Martian ocean froze, along with its residual reservoir of carbonaceous compounds. The oxidized surface we see may be a thin veneer produced and maintained by hydrogen loss (oxygen production) from the small amount of water released into the atmosphere over time.
P41C-03
Oxygen and Carbon Isotope Ratios in CO2on Mars
The major problems in spectroscopic determinations of the oxygen and carbon isotope ratios on Mars are uncertainties associated with (1) equivalent widths of the observed absorption lines, (2) line strengths in spectroscopic databases, and (3) thermal structure of the Martian atmosphere during the observation. We have made special efforts to reduce all these uncertainties. We observed Mars using Fourier Transform Spectrometer at the Canada-France-Hawaii Telescope. While the previous measurements of the oxygen and carbon isotope ratios on Mars were byproducts in observations of other species, our observation was specifically aimed at the isotope ratios. The observation covered a range of 6020 to 6310 cm-1 with the highest resolving power of 400,000 and a signal-to-noise ratio of 180 in the middle of the spectrum. The chosen spectral range involves 512 lines of the main isotope, 197 lines of 13CO2, 184 lines of CO18O, and 120 lines of CO17O. (Lines with strengths exceeding 10-27 cm at 220 K are considered here.) Due to the high spectral resolution, most of the lines are not blended. Uncertainties of retrieved isotope abundances are in inverse proportion to resolving power, signal-to-noise ratio, and square root of the number of lines. One of us (R.A. Toth) is making laboratory studies of the CO2isotope line strengths in the range of our observation. This work is aimed to achieve an accuracy of ~1% in the line strengths. Detailed observations of temperature profiles and dust abundances using MGS/TES are used to simulate each absorption line at various heights in each part of the instrument field of view and then sum up the results. Thermal radiation of Mars' surface and atmosphere is negligible in the chosen spectral range, and this reduces errors associated with uncertainties in the thermal structure on Mars. Using a combination of all these factors, we plan to achieve the highest accuracy in measuring the CO2isotope ratios. The results will be reported.
P41C-04
Tidal Excitation of the Core Dynamo of Mars
The lack of magnetic anomalies inside the giant impact basins Hellas, Isidis, Utopia and Argyre, inside the northern low lands, over the Tharsis bulge, and over the Tharsis and Olympus mounts suggests that the core field of Mars ceased to exist by about 4 Gyr ago, almost when the giant basins were formed. On the other hand, the giant basins are located on a great circle, implying that the basins were likely produced by fragments of a large asteroid that broke apart as it entered the Roche limit of Mars. This scenario offers a causative relationship for the apparent coincidence of the formation of the giant basins and the cessation of the core dynamo. We suggest that the core dynamo was excited by tidally driven elliptical instability in the Martian core. The breaking of the asteroid and its final impact on Mars eliminated the excitation and thus killed the dynamo. We show that a retrograde asteroid captured in a Keplerian orbit around Mars at a distance of about 50,000-100,000 km could orbit Mars for several hundreds of millions of years before impacting the planet due to the tidal coupling of the asteroid and Mars. Because of relatively very short growth time of the elliptical instability, less than 50,000 years, the asteroid was capable of retaining the elliptical instability and energizing the core dynamo for a geologically long period prior to 4 Ga. Our laboratory observations of a parametric instability of a rotating incompressible fluid, contained in a flexible-walled spherical cavity, confirm the possibility that an early Martian dynamo could have been powered by tidal straining.
P41C-05
A Computational Technique to Study Heat Trasfer From Surfaces With Diverse Cavities
Three-dimensional single and multiple cavity flows with heat transfer enhancement are investigated. Cavities are composed of spherical dimples with various depths and dimple distances. They are placed on a flat, heat conducting channel. When fluid flows over the cavities, its flow characteristics such as pressure, temperature, velocity profiles, and turbulent shear stresses change. This study investigates the relationship of these characteristics to the heat transferring phenomena on the surface. The results of the computational study of the impact of single concave cavity on the aerodynamic resistance and heat transfer coefficient compared with experimental data are presented. The study involves advanced computational techniques in modeling and simulation and is relevant to problems on earth and in space dealing with surfaces.
P41C-06
The Acapulco Parent Planetesimal: An Early Collisional History in the Solar System
The Acapulco, Mexico, meteorite was recovered in 1976 from a crater of approx. 30 cm diameter. An old crystallization age of 4.60 (error 0.03) Ga (Prinzhofer et al., 1992) establishes that its parent object is one of the oldest known planetesimals in the solar system, although not in a pristine form. Other dating systems indicated somewhat younger ages and isotopic variabilities in several elements documented a complex early history. The younger ages date the closure times in secondary minerals. The initial parent object was in a partially molten state when isotopically distinct foreign matter invaded the chondritic parent and some of the isotopic signatures survived. Nitrogen in the primitive achondrite Acapulco was found to have distinct isotopic signatures for the metal and silicate phases and also in different morphologies of graphites (El Goresy, 1995, 2005). The delayed collisional event probably disrupted the parent object, as Acapulco cooled very rapidly. Nitrogen in the injected metal and graphite did not isotopically exchange with the host silicates. We observed nitrogen isotopic signatures of several separated mineral phases which cover a range of delta 15N values from -150 permil to +13 permil. The lightest nitrogen signatures observed in metal separates are comparable to those in some morphologies of Acapulco graphites. The heavy N signatures observed in several silicate minerals are consistent with each other, while nitrogen in chromite is distinctly light (delta 15N of -80 permil), intermediate between those of metal and silicates. The incipient rapid cooling history is well documented down to approx. 120° C, as recorded by U/Th-4He ages in phosphates (Min et al., 2003). The history of the Acapulco parent object was uneventful after its early evolution in an environment where no perturbation by collisions occurred, until the meteorite's recent (6.0 Ma ago) injection into an earth-crossing orbit. References: El Goresy, A., Zinner, E., and Marti, K. (1995), Nature 373, 496-499. El Goresy A., Zinner E., Pellas P., and Caillet C. (2005), Geochim. et Cosmochim. Acta 69 (18), 4535. Min K., Farley K. A., Renne P. R. and Marti K. (2003), Earth Planet. Sci. Lett. 209, 323-336. Prinzhofer, A., Papanastassiou, D.A., Wasserburg, G.J. (1992), Geochim. et Cosmochim. Acta 56: 797-815.
P41C-07
Carbonaceous Matter Inside Individual Chondrules of the Allende Meteorite
We report new results of petrographic and geochemical analyses of a suite of individual chondrules retrieved from a fragment of the CV3 Allende meteorite. Allende is a well known intensively studied meteorite from the relatively rare group of carbonaceous chondrites, which fell on February 1969 in Chihuahua, northern Mexico. For this work, we concentrate on the characterization of the minerals inside chondrules by Raman spectroscopy. Results from Raman spectroscopy, together with ion microprobe and scanning electron microscopy, etc, confirm occurrence of carbonaceous matter in the form of microdiamonds, graphite and fullerenes inside the chondrules. Observations are discussed in terms of the spatial and textural distribution in the chondrules and matrix of the Allende. Carbon and hydrogen have strong oxidizing and reducing properties and their occurrence and distribution in chondrules and matrix are critical in understanding the conditions in the early solar nebula.
P41C-08
Single Chondrule K/Ar ages of Mexican Meteorites Using ID-TIMS.
We have determined the K/Ar ages of two H5 ordinary meteorites: Cosina and Nuevo Mercurio, neither dated until this study. We analyzed several single chondrules - weighing few milligrams - of each meteorite. Ages were obtained by using very precise K content determined by isotope dilution mass spectrometry. The K content in chondrules ranges between 650 and 1400 ppm. The 40Ar was measured by static vacuum noble gas mass spectrometry. Samples were fused with an infrared CO2 laser. Chondrule ages vary from 3.66 to 4.59 Ga for Cosina and from 4.20 to 4.87 Ga for Nuevo Mercurio. A comparison between our data and the published K/Ar ages of H and L whole rocks shows that dates obtained from single chondrules are older than those obtained from whole rocks and seem to preserve older events not evidenced in the WR ages. This implies that chondrules can preserve K/Ar ages very close to U-Pb crystallization ages.