Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989. / Includes bibliographical references (leaves 73-75). / by Deborah Klatt Barber. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991. / Includes bibliographical references (p. 167-172). / by Bradfield Lyon. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2000. / Includes bibliographical references (leaves 69-74). / Previously undescribed fossils of weakly calcified metazoans were recently discovered in the terminal Proterozoic Nama Group of central and southern Namibia (Grotzinger et al., 1995), in sediments that contain the terminal Proterozoic index fossil Cloudina. The new fossils are closely associated with thrombolites and stromatolites that form laterally continuous biostromes, isolated patch reefs, and isolated pinnacle reefs. Because these fossils are preserved as calcitic void-fill in a calcite matrix, individual specimens cannot be freed by conventional techniques. Rocks containing the fossils are ground and digitally photographed at thickness intervals of 25 pm. A battery of image processing techniques is used to obtain the contour outlines of the fossils in serial cross sections. A Delaunay triangulation method is then used to reconstruct the morphology from tetrahedral components which connect the contours in adjacent layers. It is found that most of the fossils resemble a single morphology with some well-defined characters that vary slightly among individual specimens. This fossil morphology is described in this thesis as Namacalathus hermanastes. A mathematical description of the morphology is used to obtain a database of randomly-oriented synthetic cross sections. This database reproduces the vast majority of cross sections observed in outcrop. In addition, the most common orientation, the mean size, and other population statistics are measured for Namacalathus fossils within an individual rock sample. / by Wesley Andrés Watters. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 49-50). / Ooids - small, concentrically laminated carbonate grains - are an important component of the sedimentary rock record, yet many details of their formation are not well understood. In particular, the role of microorganisms and organic matter is controversial. To learn about the geochemical and biological environment in which ooids form, modern ooids from two localities (Carbla Beach, Shark Bay, Western Australia, and Highborne Cay, Bahamas) were dissolved incrementally. Analysis of radiocarbon by accelerator mass spectrometry of C02 liberated during incremental dissolution of ooid carbonate provided information about the timescale of ooid formation and the ages of these particular ooids: Highborne Cay ooids began forming at least 1,000 years ago, with a possible erosional event approximately 500 years ago, and Carbla Beach ooids began forming at least 1,250 years ago. Each dissolution step liberated lipids, which were analyzed by gas chromatography-mass spectrometry and gas chromatography-isotope ratio mass spectrometry. The organic component of the ooids, which is -3% by weight, is composed primarily of straight-chain, saturated fatty acids with chain lengths that vary between C=12 and C=30. Also present are branched, short-chain fatty acids, and long-chain fatty ketones. Most compounds have oD 13C values that fall between -12%o and -30%o, and oD values between -50%o and -150%o. The distribution of lipids and their stable isotope signatures, which is consistent through incremental dissolutions, provides a fingerprint of the complex microbial community that lives in close proximity to growing ooids. These results suggest it is possible that this consortium of microbes alters the microenvironment of growing ooids in such a way that stimulates carbonate precipitation and protects ooids from dissolution. / by Aimée L. Gillespie / S.M.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1984. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN. / Includes bibliographies. / by Julie Dianne Morris. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2004. / Includes bibliographical references (leaves 73-75). / Remote sensing techniques are widely used in planetary science for acquiring precise, global inforniation about an object. One of these techniques consists of the study of the radio signals emitted by a spacecraft, from which it is possible to derive the forces acted upon it. For this project, we used the radio science data from the Mars-orbiting spacecraft "IMars Odyssey". Launched in April 2001, more than two years of daily radio tracking of this satellite are now available, allowing for Precision Orbit Determination. Using the program Geodyn, the position of the spacecraft with respect to the centre of mass of Mars is typically determined down to a few meters, while the velocity precision is better than 1 mm/s. Once a large number of orbits have been calculated, it is possible to use the residuals (misfits of the data to the modeled trajectory) to solve for some of the model parameters. Here, we determine the coefficients of the spherical harmonic expansion of the gravity field, as well as the drag coefficient of the satellite (a proxy for atmospheric density). To obtain such results, many high-precision data sets and models are combined: electromagnetic wave propagation, with tropospheric and ionospheric corrections; tracking station positions, including tidal and tracking station corrections; solar and thermal radiation; ephemerides of all the major bodies in the Solar System, plus the Martian moons. The inputs of the orbit determination program are the radio signals (Doppler and range), the angular momentum desaturations t.inings, the attitude (of the main bus of course, but also of the high-gain antenna and the solar panels), and a model of the spacecraft. Some results of this radio science experiment are pre-sented here, in the form / (cont.) of gravity field spherical harmonic expansions sensed by the spacecraft. / by Erwan Matías Alexandre Mazarico. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008. / Includes bibliographical references (p. 217-225). / In this thesis, I investigate the response of a simple atmospheric general circulation model to applied forcings to learn whether the annular mode patterns are a preferred model response to the forcings. The thesis is inspired by the appearance of annular mode patterns in Earth's atmosphere in response to a number of forcings. Climatologies of the model under the influence of applied torques or perturbations to the reference temperature profile are compiled and compared to a control run with neither type of forcing. In most cases the differences in climatologies are annular mode-like, suggesting the patterns are the preferred response of the model to the forcings. The strength of the response typically increases for either an increase in the strength of the forcing, or an increase in the strength of the projection of the forcing on the model's annular mode patterns. Trials with a response which was not annular mode-like usually featured a poor projection of the forcing on the annular modes, or substantial interference with tropical dynamics. A zonally symmetric version of the model is also used to test the direct response of the model to the forcing versus the response caused by changes in eddy feedback processes. The direct forcing alone is found to be insufficient to produce either the correct strength or shape of the annular mode patterns. Instead the changes in eddy fluxes must be included to produce the correct shape and amplitude of the anomalies. / by Michael John Ring. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 231-239). / Stellar occultations provide a high-resolution view of a single chord through Pluto's atmosphere. This thesis presents three projects related to stellar occultation observations of Pluto. The first project concerns the ground testing of the High-speed Imaging Photometer for Occultations (HIPO), a camera aboard the Stratospheric Observatory For Infrared Astronomy (SOFIA). Differential photometry was found to be reliable to one part in 104. The second project is a modern determination of the light ratio of Charon and Pluto, essential for predicting future occultations. The final project considers twenty years worth of Pluto stellar occultation results, including new measurements using HIPO, and determines whether temperature asymmetries can be seen in fits for the upper atmosphere. These measurements allow the first Earth-based assessment of Pluto's geographic temperature distribution. Included is a description of the extensive test modeling to determine the boundary selection methods for the upper atmosphere for each differently-shaped light curve. The temperature asymmetries or lack thereof, are considered in the context of time of day, average insolation and surface features in the vicinity of the area near the occultation half-light radius. No clear correlation was found for any of the three metrics, suggesting that Pluto's atmosphere is spatially isothermal. / by Amanda Marie Zangari. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 36-38). / The soil transport coefficient D represents the relationship between local topographical gradient and soil flux in the landscape evolution model. This work presents new estimates of the soil transport coefficient D at 9 sites and compares them, along with a compilation of 16 previously published estimates of D, against three climate proxies (mean annual precipitation, aridity index, and mean annual temperature) with the goal of characterizing climatic influences on soil transport efficiency. The new measurements were performed at sites that extend the range into both drier and wetter climates than those published. Together the data suggest that D increases with mean annual precipitation and aridity in dry climates, and levels off or decreases gradually in wetter climates. / by Naomi D. Schurr. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008. / Includes bibliographical references (p. 133-136). / A technique for the accounting for parametric model error in the Ensemble Kalman Filter (EnKF) is investigated within the framework of Additive Error Approximation (AEA). The AEA needs an estimate of the model error covariance structure. The state-dependent model error structure is the sensitivity of the local attractor to the parameter. The Multimodel Method (MMM) and Parametric Vector Method (PVM) to estimate this state-dependent sensitivity are introduced and investigated in the low-dimensional Ikeda and L63 systems. The MMM involves assimilating data independently into multiple models. PVM aims at obtaining the estimate given by MMM using a single model. At the heart of the PVM is the concept of adjoint sensitivity which is obtained using parametric singular vectors. It is found that PVM is able to estimate the correct state-dependent model error structure if the parametric vectors are constructed over an optimization time (T0p) which is equal to the state-dependent optimal time (Tm). The optimal time is the time taken by a state to go from an off- attractor location to an on-attractor location. If Top < rm then the parametric vector gives the transient sensitivity which is the incorrect model error structure. On the other hand, if rp > Tom the sensitivity obtained is non-local and tends to point in the direction of largest state error growth. The average (over the phase space) Tom is calculated for the Ikeda and L63 systems. MMM and PVM give lower average analysis and forecast errors than state-independent estimates of model error structure. Parameter estimation is a typical example of reduction of model error. The state-dependent parameter estimation (parameter tuning) in the Ikeda system is successful in partially compensating for structural model error thus resulting in lower analysis and forecast errors. However, parameter tuning is not able to completely eliminate structural model error. Nonetheless, parameter tuning can be used to identify processes in the model that have large model error. The parameters in the Emanuel convection scheme are tuned in the NOGAPS model. This parameter tuning is able to partially compensate for structural model error in the vertical flux parametrization. / by Vikram Khade. / Ph.D.