'Star Trek'-like device for Mars mission
UA tool peeks inside rocks
Renee Sauer / Staff
The laser of the
spectrometer Robert Downs, left, and M. Bonner
Denton are building will divulge a rock's composition
Renee Sauer / Staff
cavity diode laser is part of the
Mars-bound spectrometer being developed by two UA
'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 Mars mission.
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 mission.
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
"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, Denton said.
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
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,
"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 them."
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
"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 it."
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
"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
"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," Downs said.
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 said.
"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 said.
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
"Right now, it would cost about $130,000 to build one
for somebody, but that's eventually going to come down,"
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
"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 for those."
* Contact reporter Thomas Stauffer at 573-4197 or
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