Subject: [DPS Members] DPS Mailing #10-16: In Memoriam : T. Ahrens,	R.
Baldwin, D. Hunten, B. Marsden

Issue10-16, December 17, 2010

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Obituaries : T. Ahrens, R. Baldwin, D. Hunten, B. Marsden
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Dear Colleagues:

We are saddened to bring you news of several recent deaths in the DPS
family. We will provide further details on memorials and tributes as they
become available. Please hold the Memory of these valued colleagues and
friends in your hearts as you carry on their tradition of excellence in
both research and community service.

Warm regards to all,
Melissa McGrath
Chair, Division for Planetary Sciences


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OBITUARIES

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Tom Ahrens (1936-2010)

Thomas J. Ahrens, one of the leading figures in mineral physics,
geophysics, and planetary sciences during the Twentieth Century and a
member of the Seismological Laboratory, passed away on November 24, 2010 at
the age of 74.
Ahrens spent more than forty years at Caltech and was the Fletcher Jones
Professor of Geophysics, Emeritus when he passed away. His vast research
accomplishments and impact touched on the origin, differentiation and
evolution of the Earth and planets. An experimentalist at heart, he was
widely known for starting and leading the Lindhurst Laboratory of
Experimental Geophysics. Through the more than thirty graduate students and
fifteen post docs and visiting associates he mentored, his impact on
science will be felt for many years to come.
Born in Germany, Ahrens received his BS from the Massachusetts Institute of
Technology in 1957, his MS from Caltech in 1958, and his PhD from
Rensselaer Polytechnic Institute in 1962. He was a geophysicist with the
Pan American Petroleum Corporation from 1958 to 1959, worked as a second
lieutenant for the U.S. Army in the Ballistics Research Laboratory from
1959 to 1960, and was the head of the geophysics section in the Poulter
Laboratory of the Stanford Research Institute from 1962 to 1967.
He became professor of geophysics in 1976 and was the W. M. Keck Foundation
Professor of Earth Sciences from 1996 to 2001. In 2004, he was named the
Fletcher Jones Professor of Geophysics and became Jones Professor,
Emeritus, in 2005. He made the link between the Earth’s seismic
structure, its composition, and its physical properties. Exploring the
pressures and temperatures opened by the shock wave facility, he and his
associates determined the first experimentally based equations of the state
of the deep mantle and core and made the first experimentally based
estimates of the temperature of the core.

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Ralph Baldwin (1912-2010)

Dr. Ralph Belknap Baldwin died peacefully on October 23, 2010, at age 98.
Born on June 6, 1912, he graduated from the University of Michigan with a
B.S. in 1934, an M.S. in 1935, and a Ph.D. in Astronomy (Physics) in 1937.
He taught astronomy at the Universities of Michigan, Pennsylvania, and
Northwestern. Baldwin received three honorary degrees, an LLD from Michigan
in 1975, an ScD from Grand Valley State University in 1989, and an ScD from
Aquinas College in 1999. During World War II he was a Senior Physicist at
the Applied Physics Laboratory of Johns Hopkins University, helping develop
the radio proximity fuze. After the war he returned to Grand Rapids and
joined Oliver Machinery Company where he became its President in 1970.
Baldwin's most important work was in astronomy. His studies proved that the
craters on the Moon were produced by the impacts of large and small
asteroid-like bodies rather than volcanic in origin. Baldwin's early work
culminated in his book, "The Face of the Moon" (1949), which may properly
be considered the generating force behind modern research in both
terrestrial impact craters and lunar surface features. He followed up his
original work with a second book, "The Measure of the Moon" in 1965.
Baldwin was a Fellow in the Meteoritical Society, the American Geophysical
Union, the American Association for the Advancement of Science, and the
American Academy of Arts and Sciences. The Royal Astronomical Society of
Canada made him an Honorary Member.


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Donald Hunten (1925-2010)

Donald Mount Hunten passed away on the 14th of December, 2010.
He was born in Montreal, before his family moved to London, Ontario where
Don attended the Western Ontario University In 1946 he enrolled in the
Ph.D. program at McGill University, back in Montreal, where he obtained his
PhD in 1950. He later became assistant professor at the University of
Saskatchewan. After Joe Chamberlain moved to Kitt Peak National Observatory
in Tucson to form a space research group, he invited Don to join it and so
Don moved to Tucson. In 1974 he became professor at the Lunar and Planetary
Lab. In 1982 he was inducted into the National Academy of Sciences and he
eventually became a Regents Professor at LPL, UA.
Borrowing from a citation by T. Owen at the 1998 John Adam Fleming Medal of
the American Geophysical Union honoring Don:
“Donald M. Hunten is a model for all of us engaged in the study of
planetary atmospheres. He is first of all a superb scientist, one of the
finest aeronomers our planet has produced. He is that rare combination of
instrumentalist, observer, theorist, and responsible representative of his
field that makes a "compleat" scientist. Don's contributions are evident
everywhere in the record of terrestrial and planetary aeronomy. In the
1950s, he was preeminent among those who developed the ground-based
instruments that obtained the spectra required for an understanding of the
excitation of Earth's airglow and aurora, and he also developed the
theories that explained the data. In the early 1960s, he contributed to the
deflation of the Martian atmosphere by demonstrating the weak points in
earlier attempts to derive the red planet's surface pressure. Don was the
godfather of the Pioneer Venus mission and a key scientist in its highly
successful implementation and the analysis of the results.
One of his greatest achievements was the development of the theory of
diffusion-limited escape and the subsequent analysis of escape of hydrogen
from the planets Turning to the outer solar system, Don developed a model
for the atmosphere of Titan prior to the Voyager 1 encounter in 1980 that
was so good it became the standard after the data came in confirming it.
With his extraordinary intuition and insight, he had correctly surmised
that Titan must have a massive, molecular nitrogen atmosphere, well before
there was any detection of N or N2 on this intriguing satellite. In the
following decade, Don used his excellent grasp of physics together with his
extensive experience in deep space missions to play a critical role in the
design of the Cassini-Huygens mission, now safely on its way to Saturn and
Titan.”
Don Hunten also worked on the analysis of data from the Galileo Probe into
Jupiter's atmosphere and investigated the tenuous, gaseous envelopes around
Mercury and the Moon. He has been an inspiration and a mentor for many of
the currently confirmed planetologists.


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Brian Marsden (1937-2010)

Brian Geoffrey Marsden was born on August 5, 1937, in Cambridge, England.
He was an undergraduate at New College, University of Oxford. By the time
he received his undergraduate degree, in mathematics, he had already
developed somewhat of an international reputation for the computation of
orbits of comets, including new discoveries, and spent part of his first
two undergraduate summer vacations working at the British Nautical Almanac
Office. After Oxford, in 1959, he worked at the Yale University
Observatory, where he started computing the orbits of comets. Recalling his
earlier interest in Jupiter's moons, he completed the requirements for his
Ph.D. degree with a thesis on "The Motions of the Galilean Satellites of
Jupiter". At the invitation of director Fred Whipple, he joined the staff
of the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts in
1965 where he developed a way to incorporate forces over and above those of
gravitation directly into the equations that governed the motion of a
comet. It is noteworthy that the procedure devised and developed by Marsden
is still widely used to compute the non-gravitational effects of comets,
with relatively little further modification by other astronomers.
Marsden succeeded Dr. Owen Gingerich as the CBAT director in 1968 and in
1978 the IAU asked him to also take over the direction of the MPC.
Marsden was also interested in the "transneptunian objects". More
specifically, he was the first to suggest, correctly, that three further
transneptunian objects discovered in 1993 were exactly like Pluto in the
sense that they all orbit the Sun twice while Neptune orbits it thrice.
This particular recognition set him firmly on the quest to "demote" Pluto.
Success required the discovery of transneptunian objects more comparable to
Pluto in size, something that finally happened in 2005 with the discovery
of the object that came to be known as Eris. At its triennial meeting in
2006 in Prague, the IAU voted to designate these objects, together with two
further transneptunian objects now known as Makemake and Haumea, as well as
the largest asteroid, Ceres, members of a new class of "dwarf planet". It
was also at the IAU meeting in Prague that Marsden stepped down as MPC
director, and he was quite entertained by the thought that both he and
Pluto had been retired on the same day.
Marsden served as an associate director of the Harvard-Smithsonian Center
for Astrophysics for more than 15 years; he was chair of the Division of
Dynamical Astronomy of the American Astronomical Society during 1976-1978
and president of the IAU commissions that oversaw the operation of the
minor Planet Center (1976-1979) and the Central Bureau for Astronomical
Telegrams (2000-2003). He continued to serve subsequently on the two
solar-system nomenclature committees of the IAU, being the perennial
secretary of the one that decides on names for asteroids. He also continued
to publish a "Catalogue of Cometary Orbits", the first of these having
appeared in 1972 and its successors roughly at intervals of two years.
B. Marsden passed away on 18 November and will be sorely missed by our
community.


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