Calif. — Carbon and silicate grains in interplanetary
dust particles are helping scientists solve a 40-year-old
a transmission electron microscope, researchers from
Lawrence Livermore National Laboratory have detected
a 5.7-electron volt or 2175 Å (angstrom) wavelength
feature in interstellar grains that were embedded
within interplanetary dust particles (IDPs). They
found that this feature is carried by carbon and amorphous
silicate grains that are abundant in IDPs and may
help explain how some IDPs formed from interstellar
research appears in the Jan. 14 edition of the research
dust particles gathered from the Earth's stratosphere
are complex collections of primitive solar system
and presolar grains from the interstellar medium.
The strongest ultraviolet spectral signature of dust
in the interstellar medium (the gas and dust between
stars, which fills the plane of a galaxy) is the astronomical
2175 angstrom feature or "2175 Å bump."
Production of this interstellar feature is generally
believed to originate from electronic transitions
associated with the surfaces of very small grains.
carbon and silicate grains may have been produced
by irradiation of dust in the interstellar medium.
The measurements may help explain how interstellar
organic matter was incorporated into the solar system.
In addition, they provide new information for computational
modeling, laboratory synthesis of similar grains and
laboratory ultraviolet photo-absorption measurements.
finding potentially breaks a log-jam in the search
for the carrier of the astronomical 2175 Å feature,"
said John Bradley, director of Livermore's Institute
for Geophysics and Planetary Physics and lead author
of the paper. "Over the past 40 years, a whole
variety of exotic materials have been proposed, including
nano-diamonds, fullerenes, carbon ‘onions’ and even
interstellar organisms. Our findings suggest that
organic carbonaceous matter and silicates, the ‘common
stuff’ of interstellar space, may be responsible for
the 2175 Å feature."
Livermore scientists on the project include Zu Rong
Dai, Giles Graham, Peter Weber, Julie Smith, Ian Hutcheon,
Hope Ishii and Sasa Bajt.
collaborators include researchers from UC Davis, Lawrence
Berkeley National Laboratory, Washington University
and NASA-Ames Research Center.
in 1952, Lawrence Livermore National Laboratory is
a national security laboratory, with a mission to
ensure national security and apply science and technology
to the important issues of our time. Lawrence Livermore
National Laboratory is managed by the University of
California for the U.S. Department of Energy's National
Nuclear Security Administration.