'Star Trek" explorers who analyzed objects with a
miraculous hand-held device had nothing on a pair of UA
scientists designing their own version of a "tricorder" for a
Chemist M. Bonner Denton and geoscientist Robert Downs of the University of Arizona
are principal investigators on a $1.5 million, NASA-funded
project to develop a Raman spectrometer slated for a 2009
Back the rover up to the rock of your choice and the
instrument will bounce a laser beam off it and seconds later
tell you the rock's chemical composition, not unlike the
instruments used in the "Star Trek" TV series.
"We're building a tricorder, that's pretty much what we're
doing," Downs said. "And we've got the dream of someday making
it into a hand-held instrument that could be used for a
variety of applications."
Lots of different methods are used to figure out what a
solid or liquid actually is, but most of them involve
destroying the sample or placing it in certain containers,
A Raman spectrometer can analyze most samples by merely
pointing at them without preparing samples or modifying their
form, he said.
The prototype Denton and Downs have been working on has
already been used to test the legitimacy of diamonds in rings
worn by people in the chemistry and geosciences departments.
Two of the "diamonds" in the geosciences department turned out
to be cubic zirconia, Downs said.
The Raman spectrometer could eventually be used by anyone
who wants to test the legitimacy of a solid or liquid.
Gemologists buying gems, pharmacists who want to know the
purity of a drug, and environmental workers who want to figure
out what is in a 55-gallon drum are just a few of the people
who could benefit from the technology, Denton said.
"We were working with the Environmental Protection Agency
on this because they could take it into the field for rogue
dumpsites," Denton said. "If someone dumps a bunch of barrels
containing toxic waste in the desert, this is a device you
could stick into those barrels to find out what's in
The spectrometer works by shooting a laser beam at an
object and collecting the different rays of light that bounce
back. The vast majority of light gathered has a similar energy
to that which the laser sent out, but about one out of a
million photons, or particles of light, have a shifted
frequency or color. These shifted photons act as a fingerprint
for the object they're emitted from.
"It's almost like tapping a rock and listening to it ring,"
Denton said. "Each different mineral has a whole series of
complicated bands that are unique, and that's how we identify
Downs' task in the process is to catalog the unique
signatures of more than 4,000 minerals into a database. He
does this by comparing Raman spectrometer signatures to
another method called powder diffraction X-ray analysis.
"Bob happens to be a world expert in the field of powder
diffraction, which today is the current gold standard for
mineral identification," Denton said.
One of the biggest problems Downs has faced has been that
many minerals he analyzed were initially misidentified,
forcing him to run backup tests to figure out what they really
are, he said.
Eventually, Downs' database will be worked onto a silicon
chip for the Mars rover so that it can not only test a rock
but also autonomously compare it to the list of known
minerals. For the Mars mission that will save precious
bandwidth, the amount of information that needs to be sent
back and forth between the craft and mission control.
"The minerals you're really interested in are those that
differ from that on Earth, so this instrument will be able to
kind of cancel out all the minerals that aren't interesting,"
Bandwidth on space missions is rapidly consumed by sending
things like high-resolution images and other data to mission
control, and sending instructions to the rover, Denton
"That's why we felt a novel aspect of our program was to
minimize that bandwidth," he said. "It'll only take it up when
it finds something that doesn't compare to minerals on Earth,
and that's information you definitely want to have."
In addition to bandwidth, other limiting factors on
instruments include weight, volume and power consumption.
Working a prototype instrument that takes up the surface of a
dining table down to one smaller than a toaster will not be
easy, but shouldn't require a leap of technology, Denton
Getting the spectrometer to meet those parameters will mean
that the technology is not that far away from being worked
into an instrument that could fit in your hand.
"Right now, it would cost about $130,000 to build one for
somebody, but that's eventually going to come down," Denton
Sir C.V. Raman invented the Raman spectrometer and won the
Nobel Prize for it in 1930. Denton's team has greatly
increased the sensitivity of the technology, allowing the
detection of samples as small as a few parts per million.
The Raman spectrometer aboard the 2009 rover would go a
long way toward NASA's Mars mantra of "following the water"
for evidence of past or present life on the red planet.
"Is there limestone on Mars, which would mean there were
oceans?" Downs said. "And if there is still water, it could be
stored in certain minerals called zeolites, so we could look