Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996. / Includes bibliographical references. / by Dawn Marie Chamberlain. / B.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2009. / Includes bibliographical references. / Despite a number of human and robotic missions to the Moon, there are still important unanswered questions about its early evolution, and how it came to be the object we observe today. Here we use observational, experimental, and theoretical techniques to examine three important events that took place early in lunar history and have left a lasting signature. The first event is the formation of the largest basin on the Moon, the South Pole-Aitken Basin. We develop a systematic method to define the previously unknown boundaries of this degraded structure and quantify its gross shape. We also combine a number of remote sensing data sets to constrain the origin of heat producing elements in its interior. The second event we examine is the evolution of the lunar orbit, and the coupling between the Moon's early geophysical properties and the growth of orbital eccentricity. We use analytical models for tidal deformations and orbit evolution to show that the shape of the Moon suggests its early orbit was highly eccentric. However, we are also able to explain the presently high eccentricity entirely by traditional, secular tidal growth while the early Moon was hot. The third event we examine is the magnetization of lunar samples. We perform extensive paleomagnetic measurements of an ancient, deep-seated lunar sample, and determine that a long-lived magnetic field like that of a core dynamo is the most plausible explanation for its magnetic remanence. In sum, the earliest portion of lunar history has been largely obscured by later geologic events, but a great deal can still be learned from this formative epoch. / by Ian Garrick-Bethell. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2001. / Includes bibliographical references (leaf 41). / We present a new method of calculating model lightcurves for stellar occultations by the Jovian planets. We model the occulting planet as a three-dimensional body of non-zero ellipticity, and define two ellipses of intersection with the body which dictate the appearance of the lightcurve. These include the visible-limb plane ellipse, which is the observed figure of the body as seen in the sky, and the line-of-sight ellipse, which contains the line of sight to the occulted star, and is the plane in which the starlight is refracted. The observed stellar flux during the occultation is primarily dictated by the ellipticity and subsequent radius of curvature of the instantaneous ellipse in the line-of-sight plane. This new method is applied to several test cases, as well as to the Jovian occultation of HIP9369 on 10 October 1999. Lightcurves generated by this model are compared to identical situations using the method published in Hubbard et al. (1997), showing that the Hubbard model works well for low-latitude occultations, but fails at higher latitudes. In the case of the high-latitude Jovian occultation, the best-fit lightcurve, produced from this new method, yielded a half-light equatorial radius of 71,343±1.2 km with a scale height of 19.25±0.5km, and an isothermal temperature of 139K. The same data, fit using a lightcurve generated by the method described in Hubbard et al. (1997), resulted in a half-light equatorial radius of 71,819km with a scale height of 17.9km with errors comparable to the previous fit, resulting in an isothermal temperature of 129K. Lightcurves are numerically generated for an ellipsoidal planet and, for comparison, an approximation to the ellipsoidal case consisting of a sphere with radius equal to the radius of curvature of the ellipsoid at the half-light point. We find that in the case of an occultation where the line-of-sight ellipticity does not vary, that the radius of curvature approximation matches the ellipsoidal planet lightcurve to within 0.007%. For an oblique occultation however, the line-of-sight ellipticity varies, and the approximation, using only a single radius of curvature sphere, is only good to about 1%. As a result, we find that using a model such as that presented in Baum and Code (1953) to fit the lightcurve of an ellipsoidal planet can return values for half-light radius (after accounting for the distance between the center of curvature and the center of the body) which may match the local distance to the center of the ellipsoid to a fraction of a percent, while returning values of scale height which may be in error by several percent. Test cases are also then put through numerical inversions, to obtain temperature versus pressure profiles. Test cases with spherical planets return temperature profiles that match those used to create the lightcurves, while test cases with ellipsoidal planets return temperature profiles which can differ from the input temperatures by tens of degrees, assuming a constant local gravity over the course of the occultation. / by Bryan Hilbert. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1992. / Title as it appears in the M.I.T. Graduate List, June 1992: Advances in the theory of elastic wave propagation in anisotropic media, source theory, traveltime computations and migration. / Includes bibliographical references (p. 214-222). / by Arcangelo Gabriele Sena. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2001. / Includes bibliographical references (p. 118-134). / The oceans are a small source of non-methane hydrocarbons (NMHC), a suite of volatile organics whose chemical destruction mechanism by reaction with hydroxyl radical can significantly affect the oxidation capacity of the atmosphere. Little is known about the water column cycling processes that constrain this source; previous work has established a photochemical source for many alkenes, and a phytoplanktonic source for isoprene. The focus of this thesis was to gain further insight on marine microbiological cycling of NMHC. This included investigations on two main themes. The first was the effect of different physiological conditions on phytoplanktonic isoprene production. A variety of phytoplankton were examined for the ability to produce isoprene. All were found to have constant isoprene production rates per cell during exponential growth, with decreasing rates as the populations senesced. A positive allometric relationship between isoprene production rate and cell volume was found; highest production rates were found for the largest cell tested, Emiliania huxleyi, and lowest rates for Prochlorococcus, the smallest. Isoprene production in Prochlorococcus was found to be a function of light intensity and temperature, with patterns similar to the relationships between growth rate of this species and these environmental parameters. The second theme investigated was the effect that heterotrophic marine plankton might have on NMHC cycling. We detected no clear production or consumption of any NMHC, except isoprene, from any of the phytoplankton or other organisms tested. / (cont.) The heterotrophic bacteria examined had no detectable effect on isoprene production per Prochlorococcus cell in a dual-species culture, but a temporary production of isoprene was detected from bacterial cultures grown in organically-enriched media. Nanoflagellate grazing by Cafeteria roenbergensis on Prochlorococcus had no detectable effect on NMHC cycling except to control the total phytoplankton counts, and thus total isoprene production. Besides controlling phytoplankton counts, phage lysis of Prochlorococcus had no detectable effect on NMHC cycling except to decrease isoprene production per Prochlorococcus cell during the latent period of infection. Any other effect these particular organisms may have on NMHC cycling likely involves other processes, such as photochemistry. / by Stephanie Lyn Shaw. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, February 2001. / "May 2000." Cataloged from PDF version of thesis. / Includes bibliographical references (page 43). / Clusters of asteroids within the main-belt are referred to as dynamical families because they are believed to have originated as the result of collisional destructions of large parent bodies. Family members are the remnants of the parent body break-up and often retain some of the parent body's original rotational information. Previous studies have indicated that the Koronis dynamical family may have been relatively recently formed due to the non-random nature of the orientation of its members spin vectors. This project was undertaken to contribute to the rotational data on Koronis family members in order to better understand the unusual properties observed. The goal of this project was to determine the directions of spin of Koronis family members 158 Koronis and 720 Bohlinia. Observations were made at the MIT Wallace Astrophysical Observatory in Westford, Massachusetts during 1999. Both of the targets were determined to have a retrograde sense of rotation, which is in agreement with the previously known sense of rotation of Koronis family member 243 Ida. In addition, the synodic period of 158 Koronis was confirmed by these observations, and a new value for the sidereal period of 720 Bohlinia was found to be 8.920 ± 0.005 hours. During the course of the observations, an uncataloged asteroid was discovered and has since been assigned the designation 1999 QQ2 by the IAU Minor Planet Center. / by Lucy Crespo da Silva. / S.B.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 41-42). / The advent of global Digital Elevation Models of the lunar surface, obtained from the Lunar Orbiter Laser Altimeter (LOLA), has allowed for a quantitative assessment of crater morphometry. 351 simple and complex craters in the Mare Serenitatis, far side highlands, near side highlands, and South Pole-Aitken basin are decomposed into 50 elevation profiles, from which key geometric crater properties are extracted. The geometric properties and their respective standard variation, such as height-to-diameter ratios, and average elevation profile are compared on a global level to investigate regional differences in terrain rheology and study the transition between the simple and complex crater regime. Furthermore, the relationship between known degradation mechanisms and crater morphometry is discussed, as well as the current state of quantitative methods to assess crater degradation. The resulting regional differences observed in crater morphometry are explained in the context of lunar geologic history. Finally, the addition of other crater geometric properties in future quantitative assessments will broaden the study of crater morphometry, and improvements to current methods are necessary to conclusively define degradation states in terms of quantitative factors. / by Matthieu Jean Talpe. / S.B.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2009. / Cataloged from PDF version of thesis. Page 40 blank. / Includes bibliographical references (pages 36-37). / Sediment sorting in fluvial rivers produces great variation in the grain-size of deposit over the length of a river. Knowledge of the pattern of sediment deposition may help to shed light on the processes that sort by grain size. A simple geometric model was developed to predict the location of the transition between coarse and fine sediment in a bimodal sediment distribution and tested against flume-created deposits with a variety of flow and depositional conditions. The models agreed well with the overall form of plane-bed clinoform deposits but not with rippled-bed clinoform deposits, thus a new model for predicting transitions in rippled-bed deposits is needed. / by Sarah E. Baumgardner. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989. / Includes bibliographical references (leaves 182-198). / by Gregory Christian Beroza. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1986. / Microfiche copy available in Archives and Science. / Vita. / Includes bibliographies. / by Glen T. Shen. / Ph.D.