Ancient Chinese astronomers named the planet Mars the "Fire Star." And according to ancient Chinese mythology, Mars is personified as a
powerful red-faced warrior, living at the east end of heaven causing many wars.
"I won't tell you that I like this kind of behavior," says Dr. Alian Wang, a senior research scientist at the Department of Earth and Planetary
Sciences at Washington University. What Alian does like, however, is the study of this "warrior" called Mars.
"I always wanted to be a scientist," she says. "I guess scientific discoveries and scientific reasoning -- What and Why-- are fascinating for
a curious person like me." As a teenager in China, Dr. Wang bounced between her loves of biology and physics, but she had to postpone her
university studies because all of the universities in China were closed by Chairman Mao. Luckily, the universities re-opened, and Wang was
able to study optics, which led her to spectroscopy, or the study of the interaction between light and matter.
And what does spectroscopy have to do with Mars?
Says Alian, "I love spectroscopy, it's the reason I keep doing this for 25 years. But I'd always been amazed by space exploration, mainly
because it signifies the extremely high levels of science and technology existing in my lifetime."
When she came to work in the U.S., Alian was asked by some top-notch planetary scientists at Washington University which spectroscopic methods
might be most useful for space exploration -- especially for understanding the materials on the surface of other planets. She suggested Raman
spectroscopy, and the rest, as they say, is history.
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Alian and Dr. Larry Haskin (PI of Athena-Raman
system) are working at the first breadboard of the planetary Raman system at
Washington University.
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Since then, Alian has been involved with preparations for using Raman spectroscopy to study the surface of Mars. "My real interest in Mars
now is to show how well our Raman instrument can identify minerals that will tell us about past environments that might have supported life there."
Every molecule, in solid, liquid or gaseous states, has its own fingerprint Raman spectrum. Raman spectroscopy uses these spectra to
distinguish among the molecules, and to characterize their structural and compositional features. Raman spectra are normally obtained
by shining a focused laser beam onto the sample, and then collecting the scattered light from the sample.
The Raman scattering phenomenon was first discovered in 1928 by Indian scientist Dr. C. V. Raman, who won the 1930 Nobel Prize in
Physics for his discovery.
"A very small portion (less than one photon in a million) of the scattered light contains the information we want, thus we need good
instruments to detect it," says Wang. By studying the Raman spectra of rocks and soils on the surface of Mars, scientists will be able
to classify them and identify the minerals of which they are made.
"For example, if we get the spectra of water-bearing minerals, or the spectra of the minerals (carbonates or sulfates) which were
deposited from ancient rivers, lakes, or oceans, then we can say that sometime in the past, a large amount of water did exist on Mars.
These waters could have provided a life-friendly environment on Mars."
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Alian (far left) is visiting the clean assembly room at the
Jet Propulsion Laboratory, where instruments are assembled for flight to
Mars.
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Alian also uses Raman spectroscopy for another passion of hers: the study of Martian meteorites.
"It is an intriguing experience to get a real piece of Mars in hand, and use all kinds of laboratory techniques to learn what it is, how
it came to Earth, and what events it has been through."
Two Martian meteorites that have been studied in detail at her Raman laboratory are Zagami, found in Nigeria in 1962, and EETA79001, found
in Antarctica in 1979. Alian and her colleagues are about to start the study of a newly identified Martian meteorite named Los Angeles,
which was identified in 1999.
How do we know that these meteorites are actually from Mars?
"For one thing," explains Alian, "the isotopic ratios in the gas trapped inside of these meteorites are like those observed in the Mars
atmosphere, but not like those on the Earth. Also, there is no known means of producing the melts that gave rise to these meteorites this
late in the history of the solar system except on planet-sized objects, so they could not have come from asteroids."
Alian's experiments demonstrate that we can identify major, minor, and trace minerals in actual rocks from Mars using Raman spectroscopy.
Dr. Alian Wang believes that the upcoming 2003 mission to Mars will be far more informative than previous landed missions, and, she says,
"our Raman spectrometer will be a major contribution to that improvement."
