MIT
Reports to the President 1994-95
Research and education within the Department of Earth, Atmospheric, and
Planetary Sciences (EAPS) engage a broad array of scientific disciplines:
geology, geophysics, geochemistry, physical and chemical oceanography,
meteorology, atmospheric chemistry, and planetary sciences. Particular emphasis
is placed on the study of the complex global geosystems of the atmosphere,
ocean, crust, and deep interior of the Earth and planets. The Department
comprises 40 faculty including one with a primary appointment in Civil and
Environmental Engineering, 211 graduate and undergraduate students, and 118
permanent research staff, postdoctoral appointments and visiting scholars.
At present the EAPS graduate program focuses on the Ph.D. degree. During the
past academic year 186 graduate students were registered in the Department
(Course 12), and the MIT-Woods Hole Oceanographic Institution (WHOI) Joint
Program (Course 12W). The number of graduate students in the Department has
remained constant for the past 15 years, and applicants continue to be among
the best in the national and international pools. Although graduates with
specialized training in geoscience still obtain good jobs, there is a growing
need for scientists capable of approaching problems in a broad,
systems-oriented context who can address environmental issues and problems
associated with ecosystem change. EAPS has responded to these needs by teaching
disciplinary topics within the context of integrated approaches to geosystems,
and this has become a major force toward unifying the earth sciences. A
master's degree Program in Applied Geosystems is now under development. This
innovative program will provide education and training to prepare students for
positions in industry requiring expertise in scientific computing,
visualization and data inference. Students will also be exposed to economic and
policy issues related to utilization of natural resources and mitigation of
environmental problems. The goal of the program is to encourage a broad
understanding of the interdisciplinary approach needed to solve complex
problems encountered in geoscience industries today, as opposed to providing a
narrowly defined curriculum centered on one primary discipline.
EAPS faculty are involved in continuing efforts to improve the quality and
scope of our undergraduate program. The bachelor of science curriculum has been
reorganized to include three areas of concentration: geoscience, physics of
atmospheres and oceans, and planetary science and astronomy. Each area of study
encompasses a set of required courses, a sequence of field or laboratory
subjects, and independent study or thesis preparation. An undergraduate minor
degree program has also been developed to complement degrees in other
disciplines, providing a foundation for careers that incorporate areas of earth
science. The Department has expanded its Independent Activities Program (IAP),
and EAPS now offers more IAP courses for credit than any other MIT department.
The faculty have increased participation in freshman advising seminars, and
this past year EAPS faculty advised 10% of the freshman class. EAPS continues
its substantial participation in the Undergraduate Research Opportunities
Program (UROP).
Two Assistant Professors were appointed to the faculty this year. Kelin
Whipple, who recently received his Ph.D. from the University of Washington, is
an outstanding young geologist specializing in the study of surface processes.
His experience encompasses field work, laboratory experimentation, and
numerical modeling, and his broad research interests offer the possibility for
substantial interaction with other faculty. Robert van der Hilst, a
seismologist from the Australian National University, will join the Department
in January of 1996. His primary research accomplishments involve the
application of seismic tomography to imaging subduction zones, where descending
lithosphere plunges back into the mantle. Professor Marcia K. McNutt, a
geophysicist with extensive experience in oceanographic research, has been
named MIT Director of the MIT-Woods Hole Oceanographic Institution Joint
Program in Oceanography and Oceanographic Engineering. Gordon H. Pettengill,
Professor of Planetary Physics who worked in the area of planetary radar
astronomy retired in February of this year.
Professor Edward Boyle was awarded the A.G. Huntsman award from the Bedford
Institution of Oceanography in recognition of research contributions to the
marine sciences. Professor John Grotzinger was elected Fellow of the American
Association for the Advancement of Science. Dr. Heidi Hammel was awarded both
the Klumpke-Roberts Award of the Astronomical Society of the Pacific and the
Vladimir Karapetoff Award from the MIT Office of the Provost. Professor
Emeritus Edward Lorenz is the recipient of the 1995 Louis J. Batten Author's
Award from the American Meteorological Society for his book, "The Essence of
Chaos". Professor Gordon H. Pettengill was the 1995 recipient of the
American Philosophical Society Magellanic Premium Award and the Fred Whipple
Award from the Planetology Section of the American Geophysical Union (AGU). He
was also elected a Fellow in the AGU. The Measurement of Air Pollution by
Satellite (MAPS) Science Team, of which Professor Reginald E. Newell has been a
member since its inception, received the National Aeronautics and Space
Administration's (NASA) Group Achievement Award. Maureen Raymo was chosen the
1994-95 Joint Oceanographic Institutes Deep Earth Sampling (JOIDES)
Distinguished Lecturer.
In collaboration with Professor John Grotzinger, Professor Samuel Bowring's
research group is using high-precision U-Pb zircon ages from volcanic rocks
inter layered with late Precambrian to Cambrian fossil bearing rocks in
Namibia, Canada, and Morocco to calibrate the rates of evolution of the biggest
biological radiation in Earth history. Using this technique, it is possible to
determine ages of rocks approximately 530 million years old with a level of
precision that is less than 1 million years. Professor Grotzinger's research
shows that the radiation of Ediacaran soft-bodied metazoans overlaps in time
with the early Cambrian radiation of hard-bodied metazoans. Previously, these
were regarded as two unrelated events, separated in time by almost 50 million
years. This discovery has major implications for theories of the evolution of
life. Professor Timothy Grove has been investigating the processes that lead to
core formation in the terrestrial planets. By combining experimental studies
and investigation of relative abundances of siderophile elements left in
meteorite samples thought to have formed on Mars, it has been possible to set
limits on the conditions for the formation of the Martian core. Professor Kip
Hodges' work in the field of continental tectonics seeks to understand the
interactions of gravity and plate-convergence forces in determining the
structural architecture of mountain ranges. Results from the Annapurna region
of the central Nepalese Himalayas indicate rapid (< 5 million year)
alternations between contractional and extensional deformation on the scale of
kilometers as the orogenic system attempts to maintain dynamic equilibrium.
Professors Leigh Royden and Clark Burchfiel are continuing their work in China
along the eastern margin of the Tibetan plateau, where they are studying the
history of deformation and uplift of the plateau. Together with Principal
Research Scientist Robert King, they have established a satellite geodetic
network that covers most of the eastern margin of the plateau, a region
approximately 1000 km in length. Results to date show that rocks of the Tibetan
plateau are moving to the north and east relative to stable China, a result
consistent with the geologic history of the region. Professor Fred Frey and
colleagues have completed studies of the first 1 km of drill core from the
Hawaiian Science Drilling Project, and found systematic temporal changes in the
extent of melting, pressure of melt segregation and proportions of
geochemically distinct source components. Dr. Peter Molnar, together with
colleagues at the University of Washington, has synthesized evidence of alpine
glaciation to show that in general alpine glaciers reached their maximum
extents significantly earlier than continental ice sheets during the last
glaciation. Professor John Southard is continuing his work on the intricacies
of movement of sediment by currents and waves.
Professor Chris Marone continues work on the mechanics of earthquakes and
faulting, and the frictional properties of rocks. Marone recently completed a
study of repeating earthquakes on the Calaveras fault in California, in
collaboration with scientists from the U.S. Geological Survey, which shows that
laboratory measurements of fault healing are only consistent with field
estimates if fault strength is high, on the order of 60MPa, and earthquake
stress drop is a fraction of this value. Professor Brian Evans is investigating
the interrelationship between permeability and plastic flow in rocks. Using a
new device, he and his colleagues can now measure the evolution of permeability
as rocks are deforming at high temperature and pressure, allowing measurements
of changes in volume that result in dilation and compaction during deformation.
Results will be important in understanding localization and faulting in the
Earth. Professor Daniel Rothman has combined theoretical analyses, numerical
simulations, and results from experiments to better understand how sedimentary
rocks form and how fluids flow through them. Numerical simulation of multiphase
flow through high-resolution 3D images of real sedimentary rocks has been
compared to experiments, and has elucidated aspects of the size-dependence of
macroscopic transport properties. Professor Thomas Herring has been developing
models for the changes in the rotation of the Earth due to the torques applied
by the Sun, Moon and planets from the analysis of very long baseline
interferometry (VLBI) data. These models will be used to explain short and long
period Earth rotation changes related to the coupling of the fluid core and
solid inner core of the Earth. Herring and his students are also developing
models for asymmetries in atmospheric refraction and for laser altimeter
systems. Professors Herring and Bradford Hager and Dr. Robert King have shown
that the observed surface displacements derived from the Global Positioning
System (GPS) measurements after the Northridge earthquake are not predicted by
the source mechanism inferred from seismology. The unusual displacements more
likely resulted from growth of the folds overlying the fault plane. In a
separate development, Hager has also determined the first reliable estimate of
the average density anomaly associated with the deep keels of the continents.
Professor Marcia McNutt has nearly completed analysis of 44,000 gravity
measurements obtained from the People's Republic of China. The principal
finding is that the Tibet Plateau has deformed in the manner of a "jelly
sandwich" to the collision of India with Asia, such that geological deformation
at the surface is de-coupled from plate tectonic motions in the mantle by a
weak lower crust. During the past year Professor Thomas Jordan's research has
been focused in two areas. The first is the study of an anomalous class of
seismic events called "slow earthquakes". This work has shown that these
earthquakes, which occur most frequently in the vicinity of mid-ocean ridges,
are compound events, comprising an ordinary (fast) rupture, which is often
preceded by a "quiet", or very slow, earthquake. These results have significant
implications for theories of earthquake nucleation and, possibly, for
short-term earthquake prediction. The second area of research is on the
structure of the earth's upper mantle beneath continents. Studies have shown
that the so-called Lehmann discontinuity is a feature that separates a region
of seismic wave anisotropy in the shallow mantle from a more isotropic region
at greater depths. This result has implications for the theories of the
structure and evolution of continental deep structure. Professor Nafi Toksoz
and Principal Research Scientist Robert Reilinger of the Earth Resources
Laboratory headed an international GPS campaign in the Eastern
Mediterranean/Middle East. This work has provided the first quantitative
estimates of deformation rates in this zone of complex plate interaction,
including slip rates on the N. Anatolian fault, shortening across the Caucasus
Mountains, and large-scale crustal "extrusion". Principal Research Scientist
Arthur Cheng and Research Associate William Rodi developed an improved
algorithm to locate and characterize hydraulic fractures using the relative
positions of each successive micro-earthquake generated in the fracturing
process. It has potential applications in hydraulic fracturing in the
geothermal, waste disposal, and petroleum industries. Professor Dale Morgan has
continued to broaden the scope of the Earth Resources Laboratory in the
directions of rock physics and environmental and engineering geophysics.
Dr. Heidi Hammel, Principal Research Scientist was the Team Leader for Hubble
Space Telescope (HST) imaging of the spectacular collision of comet
Shoemaker-Levy 9 with Jupiter in July 1994, and was a team member of the NASA
Infrared Telescope Facility comet crash observations. The event provided new
data for probing Jupiter's upper stratospheric winds and atmospheric chemistry,
along numerous other results. In collaboration with staff from the Lowell
Observatory and Goddard Space Flight Center, she recently published HST images
showing that Neptune's Great Dark Spot has disappeared, and that a new dark
spot has developed in the northern hemisphere. Professor Timothy Dowling mapped
and measured the speed of atmospheric waves emanating from the comet
Shoemaker-Levy 9 impact sites on Jupiter from Hubble Space Telescope images,
and determined a speed of 454 +/- 20 m/s, which implies a radius of deformation
for the atmosphere of 1800 km. Professor James Elliot and colleagues have
continued analyses of a stellar occultation by the comet Chiron, which is
unusual in two respects. It exhibits outbursts at great distances from the sun,
and its nucleus is much larger than any other known comet. They conclude that
they have possibly detected a bound coma and that the jet-like features
observed provide evidence that the coma material originates from just a few,
small active areas, rather than from uniform sublimation over the entire
nucleus. Professor Jack Wisdom is continuing his studies of the long term
evolution of the solar system, including the evolution of the spin axis of Mars
over the last 100 million years subject to torques from the chaotically
evolving planetary system. It has been found that the obliquity, the tilt of
the spin axis to the orbit normal, is wildly chaotic on this time scale. His
group has studied the dynamical evolution of comets in the proposed Kuiper
belt, a belt of comets outside the orbit of Neptune analogous to the asteroid
belt. It was found that comets in this region evolve chaotically and slowly
leak into Neptune-crossing orbits by a dynamical path quite analogous to the
path that transports meteorites from the asteroid belt. Professor Charles
Counselman, III having developed radio interferometry techniques for measuring
the Earth's crustal motions, has begun applying these techniques to locate
cellular-telephone "911" callers and cosmic sources of high-energy gamma rays.
Professor Edward Boyle completed the first field deployment of a moored in-situ
trace element sampler for examining surface ocean chemical variability. Boyle
also has recovered a proxy variability record for the chemical changes in the
deep Pacific during the past 150,000 years, and has shown that the upper waters
of the northwestern Indian Ocean were nutrient-depleted during the last glacial
maximum. Professor John Edmond's group made a 1,700 km water sampling transit
down the Upper Lena River in Siberia as part of a comparative study of chemical
weathering processes in cold climates with those in the Tropics. Edmond's group
recently participated in a successful ALVIN cruise to the Mid Atlantic Ridge
(MAR) to investigate the effects of recent drilling on a major, active
hydrothermal ore body. Professor Maureen Raymo is using carbon isotopes in
marine organic matter as a proxy for past levels of CO2 in the ocean and
atmosphere for studying climate variations over geological time scales.
Professor Jochem Marotzke has combined historical hydrographic data from the
Indian Ocean with a general circulation model he has devised to determine heat
gain or loss across open boundaries in regional ocean models. Use of this
method reverses the estimated flow direction of the deep currents. The results
challenge the conventional interpretation that there is strong deep inflow from
the south leading to anomalously strong upwelling. Professor John Marshall and
his collaborators have developed a state-of-the-art ocean circulation model
designed to exploit the new generation of massively parallel computers. A large
multi-national sea-going experiment to observe convection in the Labrador Sea
is planned for next year. Professor Paola Malanotte-Rizzoli and collaborators
have been modeling the ocean's circulation in different regions using data
assimilation to improve the models. Professor Glenn Flierl and his students are
conducting research on packets of planetary waves in the Gulf Stream. In
cooperation with the Globec program, Professor Flierl is also investigating the
physical and biological dynamics of the Georges Bank region. The
TOPICS/POSEIDON altimeter satellite continues to provide Professor Carl Wunsch
and his group with unprecedented global coverage of the world ocean
circulation. The observations render the sea surface topography with an
absolute accuracy now approaching two centimeters, and are leading to
descriptions of the time-evolving ocean which would otherwise be impossible.
Professor Mario Molina and his students have investigated the mechanism of
formation of polar stratospheric clouds. They have shown that at low
temperatures significant amounts of nitric acid may be incorporated into liquid
cloud particles; these particles freeze over Antarctica, but do not always
freeze in the Arctic stratosphere. Laboratory results show that the cold,
liquid particles are as efficient as ice in the catalytic activation of
chlorine, which leads to high-latitude ozone depletion. Professor Ronald Prinn
and his colleagues have recently reported results of 16 years of global
measurements of the trace gas trichloroethane. This gas is important because it
is involved in ozone depletion, and the hydroxyl (OH) concentrations determined
from its atmospheric lifetime provide estimates of the lifetimes of most
hydrogen containing gases involved in the ozone layer and climate. The deduced
lifetimes are about 20% shorter than previously estimated, and OH
concentrations are therefore about 20% higher. Professor Peter Stone and his
colleagues have been coupling the climate model they developed to the
Terrestrial Ecosystems Model developed at the Marine Biological Laboratory in
Woods Hole. They have found that the ecosystems are sensitive to changes in
temperature and CO2 concentrations, but not to changes in precipitation and
cloud cover. Professor Kerry Emanuel developed a theory for the formation of
the hurricane eye, and continued research on the statistical equilibrium
characteristics of moist convection. He devised and implemented a method of
optimizing schemes for representing cumulus convection in climate models. He
also proposed a theory linking bolide impacts with global species extinction.
Professor Richard Lindzen has shown that mixing by transient eddies conditions
the extra tropical atmospheric response to stationary forcing by orography and
heating. The intensity of these eddies is related to the geographical
distribution of tropical heating. One consequence of this, confirmed by
observational analysis, has been that the extra tropical consequences of El
Niño and La Niña events is changed eddy variance rather than a
particular pattern. Professor Reginald Newell's group, while studying the
transport of carbon monoxide in the atmosphere based on MAPS results,
discovered that some atmospheric trace constituents move about in the lower
atmosphere in the form of filamentary structures, typically about 500 km wide
and up to 12,000 km long. Water vapor is one such constituent, and its
filaments are called atmospheric rivers. Last year the group discovered that
when one of these rivers was entrained into a cyclone, it deepened rapidly and
moved toward the head of the river, indicating possible consequences for
weather forecasting. Professor Alan Plumb's group has advanced the concept of a
"tropical pipe" within which most tropical air ascends with little injection of
air from middle latitudes. They argue that knowing how much injection takes
place is crucial to assessing the impact of supersonic aircraft on
stratospheric ozone. Professor Edmund Chang continues to study factors
affecting mid-latitude cyclogenesis using modeling and observational studies.
Thomas H. Jordan
MIT
Reports to the President 1994-95