Going to Mars Summary
(Mar 16, 2006): It'll be a snap
to identify gemstones once Robert Downs finishes his library
of spectral fingerprints for all the Earth's minerals.
Tricorder Going to Marsbased on an University of Arizona
|Azurite crystals. |
the Downs laboratory, The University of Arizona.
It'll be a snap to identify
gemstones once Robert Downs finishes his library of spectral
fingerprints for all the Earth's minerals.
almost halfway there. So far, the associate professor of
geosciences at The University of Arizona in Tucson has
cataloged about 1,500 of the approximately 4,000 known
minerals using a technique called Raman spectroscopy. The
effort is known as the RRUFF Project.
a tricorder," Downs said, referring to the instrument used on
the "Star Trek" television show that could be waved over
materials to identify their chemical
Downs' work is destined for space.
Although Downs' current Raman spectrometer takes up an area
the size of a tabletop, his colleague M. Bonner Denton, a UA
professor of chemistry and of geosciences, is developing a
pocket-sized Raman spectrometer to be used on the 2009 Mars
Downs is collaborating with George Rossman of
the California Institute of Technology in Pasadena to develop
the database of minerals.
The technology being
developed for Mars will help create handheld instruments for
use on Earth.
One use for a hand-held instrument would
be the identification of gemstones. Downs and Denton both gave
presentations on that aspect of the project on Sunday
afternoon, March 12, at the 57th Annual Pittsburgh Conference
on Analytical Chemistry and Applied Spectroscopy (PITTCON
Other ways to accurately identify minerals, such
as X-ray diffraction and electron microprobe, require grinding
a bit of the sample to powder or polishing the sample in a
However, such rough treatment may not
be the method of choice to determine that a glittering
gemstone is truly a diamond, rather than just a piece of cubic
Unlike other methods of identifying minerals,
a Raman spectrometer does not require destructive sampling. It
shoots a laser beam at the sample. The laser excites atoms
within the sample, which then emit a very weak light of a
wavelength in a pattern characteristic of the
|Robert Downs adjusts a piece of the
mineral corundum in a Raman spectrometer. Rubies are
red-colored corundum; sapphires are blue-colored
Photo Credit: the Downs laboratory, The
University of Arizona
like a fingerprint," Downs said.
The technique is named
after Sir C.V. Raman, who won a 1930 Nobel Prize for figuring
out the underlying physics.
But no Raman spectrometer,
big or small, can conclusively identify Mars rocks or any
other kinds of minerals without the kind of comprehensive
database Downs is creating.
When an unknown material is
analyzed with a Raman spectrometer, it can be identified by
comparing it with reference information from a
In Downs' lab, a small army of undergraduate
researchers is helping complete the RRUFF Project, the first
comprehensive database containing the Raman spectra of all the
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Thursday, March 16, 2006