August 19, 2002
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Contents of this News Tip:
Pluto's Atmosphere During Cosmic Event
Astronomers who observed a rare cosmic event in July
have announced that Pluto's atmosphere has undergone
drastic changes in the past 14 years.
Pluto, the farthest planet from the sun, has never
been seen clearly from Earth, or even from space telescopes.
However, in an "occultation" on July 19, the planet
passed directly in front of the star P126A, blocking
the star's light. Marc Buie of Lowell Observatory
in Flagstaff, Ariz., and Oscar Saa of Cerro Tololo
Inter-American Observatory in Chile used a 14-inch
portable telescope in northern Chile to observe the
event. By recording the dimming of the starlight,
Buie's team was able to calculate the density, pressure
and temperature of Pluto's atmosphere.
During observations of the last occultation in 1988,
the light from the star winked out completely, suggesting
a "smog" layer over Pluto or a sharp decline in its
atmospheric temperature. However, during the recent
viewing, the star's light gradually dimmed as the
planet passed in front. Comparing the two results,
James Elliot of the Massachusetts Institute of Technology
said one possible explanation is that the "smog" layer,
or the temperature drop, that extinguished the starlight
the first time has now dropped to a lower altitude
or disappeared. Another possibility, according to
Elliot, is that Pluto is undergoing global warming.
The scientists hope to obtain more information during
an occultation predicted for August 20, 2002, when
Pluto will pass in front of the star P131.1. These
events are becoming more common because Pluto is moving
into line with the Milky Way, where stars are more
abundant, Elliot said.
The National Science Foundation (NSF) partially supports
this research, and scientists used NSF's Cerro Tololo
observatory to help predict when and where the event
could be observed. [Amber Jones]
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Survey Reveals Continuing Impact of 9/11
Although most Americans returned to their normal activities
with resilience after the events of September 11,
2001, the impact of the tragedy continued to be felt
throughout society, reports the National Opinion Research
Center at the University of Chicago in a follow-up
to an earlier NSF-supported study.
A research team found that people's feeling of national
pride, enhanced by public response to the 9/11 events,
continued to be unusually high. They also found that
people's faith in others, which was also heightened
by the response to the events, did not fade with the
passing of time.
However, some groups were more severely affected by
the tragedy and are having greater difficulty recovering
from 9/11, according to surveys taken three to five
months later. For example, New Yorkers were more likely
than the rest of the nation to be worried about more
terrorist attacks (27 percent versus 17 percent) and
Democrats expressed greater worry than Republicans
(17 percent versus 3 percent).
On average, people in follow-up interviews were less
likely to report negative moods, such as depression,
anxiety about being criticized and restlessness than
they did immediately after the attacks. However, New
Yorkers had a rate of recovery about half that of
others in the country, the surveyors found.
Among the other groups that had greater difficulty
recovering were those with family incomes less than
$40,000 a year and people with less than a high school
education. Members of minority groups also reported
greater difficulty recovering from the events than
the general population.
The findings are part of the study "America Recovers:
A Follow-Up to a National Study of Public Responses
to the September 11 Terrorist Attacks." The research
team, headed by senior research scientist Kenneth
A. Rasinski, and Tom W. Smith, Director of the General
Social Survey, based the report on re interviews with
805 of the 1,013 people interviewed nationally in
the first sample that was taken immediately after
September 11. The survey also included 406 people
initially interviewed in New York of whom 296 were
interviewed in the follow-up.
In addition to NSF, the initial survey was funded by
the Russell Sage Foundation and the Robert Wood Johnson
Foundation. The MacArthur Foundation funded this second
round. [Bill Harms]
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Excitons to go the Distance
Scientists have found a new way to create and move
a small bit of optical energy called an exciton over
long distances. Such motion is an important step in
the path to developing semiconductors in which excitons
are shuttled and controlled to form "excitonic circuits."
In conventional semiconductors, electrons or their
absence (a so-called hole) move in circuits to perform
functions such as computation and storage of information.
In the exciton research, laser light is used to separate
an electron from an atom in a semiconductor. The "excited"
electron plus the hole remaining on the atom compose
an exciton, which moves like an energy particle and
could potentially carry information.
In most cases, the exciton exists for only a few nanoseconds
(billionths of a second) and travels only a few microns
before the electron and hole "recombine" and re-emit
David Snoke of the University of Pittsburgh, with support
from NSF and the Department of Energy, used nanoscale
structures to increase the distance traveled by the
excitons to several millimeters. Snoke and his colleagues
report their findings in the August 15 Nature.
Previous experiments had shown that excitons could
be forced to move from one place to another with pressure
or an electric field. These studies, combined with
the current results on long distance exciton motion,
strengthen the possibility that researchers will be
able to develop circuits based on exciton movement
rather than electron movement.
"This research is an example of rapid developments
occurring at the interface of condensed matter physics,
which produces semiconductor structures, and optical
science," said Hollis Wickman, a program manager in
NSF's materials research division. "The interface
represents an emerging field called condensed matter
optics." [Amber Jones]
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Volcanoes Yield New Clues About Earth's Processes
A chain of Central America's most active volcanoes
has given a team of researchers a novel glimpse into
fundamental Earth processes. By comparing volatile
gasses leaving Guatemalan and Costa Rican volcanoes,
scientists tracked elements cycling between Earth's
underlying mantle and its surface reservoirs - such
as the crust, oceans, and atmosphere.
The study, funded by NSF and affiliated with the University
of New Mexico, the Scripps Institution of Oceanography,
and Northern Illinois University, was initially conducted
on Costa Rican volcanoes in January 2001. A second
expedition concentrated on Guatemalan volcanoes in
These volcanoes are created by a process called subduction,
a process seen around the world, wherein one of the
plates that makes up the Earth's crust slips beneath
another and is driven down into the planet's interior.
The researchers sampled the gasses that escape from
the Central American volcanoes and analyzed the nitrogen
From a study of these elements, the researchers determined
whether subducted crust travels deep into the Earth
before melting and arising out of a volcano or if
the top of the crust is sheared off as the remaining
plate drives downward.
"Volcanoes are basically transfer conduits between
the Earth's surface and the underlying mantle," explained
David Hilton, a geochemist at Scripps.
Having taken samples of sediments offshore, the researchers
knew the crust material being driven into the subduction
zone were virtually the same in both Guatemala and
Costa Rica. However, the volatile gasses that came
out - specifically nitrogen gas - surprised the researchers.
In the Guatemalan volcano system, nitrogen from the
subducted crust was driven deep down before rising
back to Earth's surface. Yet in Costa Rica, the scientists
did not find evidence that nitrogen was coming from
the subducting plate. The nitrogen data supported
other evidence showing that the uppermost sedimentary
veneer on this section of crust is removed by the
subduction process before it reached the area where
magma is generated.
"The research is significant because not much is known
about nitrogen coming out of volcanoes," said Tobias
Fischer, a volcanologist at University of New Mexico.
"We clearly show that in the Guatemalan subduction
zone, up to 95 percent of the nitrogen in volcanic
gasses comes from subducted marine sediments. The
situation is different in Costa Rica, where the nitrogen
is predominantly of mantle origin," said Fischer.
The study, one of the first clear descriptions of how
and where nitrogen travels during subduction, gives
researchers a new glimpse into the long-term evolution
of Earth's mantle. The researchers now plan to address
nitrogen and helium relationships in other subduction
zones bordering the Pacific Ocean (the so called "Ring
of Fire"), as well as at mid-ocean ridges and oceanic
hotspots such as Hawaii. [Cheryl Dybas]
For descriptions of the expedition, see: http://scripps.ucsd.edu/volcano
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