Do you ever wonder why, when you hold a crystal up to the window on a summer day, the colors of
the rainbow begin to dance around the room? Different materials will absorb different colors,
both those that are visible to the naked eye, and those that are not. We can identify both
minerals and ices by their signature measured at many wavelengths, called a 'spectrum'. Think
about the crystal again--as the light passes through the prism, the colors that you see are
the 'spectrum' of sunlight. Each material has its own signature, kind of like a fingerprint.
The study of this signature is called 'spectroscopy,' which is the backbone of Dr. Wendy Calvin's
Dr. Calvin and her colleagues work on satellite and aircraft pictures that are taken at a
number of visible and infrared wavelengths to study surface rocks and minerals on Earth and
other planets. As a member of the science team for the 2003 Mars Exploration Rover (MER)
Mission, Calvin will analyze data as it comes back from the infrared spectrometer called
Mini-TES. Interpreting the spectra of Mars will involve comparisons to minerals we find here
on Earth and measurements we’ve made, both in the laboratory and in the field. This
builds on Calvin’s previous research, nearly 15 years spent studying Martian spectra, as
well as terrestrial rock and mineral signatures.
Dr. Calvin uses a field instrument to measure the infrared spectrum of rocks near Virginia City, NV.
The Mini-Thermal Emission Spectrometer, or Mini-TES, is an instrument that sees infrared
radiation emitted by objects. Scanning mirrors reflect light to the instrument located at the
bottom of the rover's mast. The Mini-TES will determine from afar the mineral composition of
Martian surface features and select specific rocks and soils to investigate in detail. In
addition to determining mineral composition of Martian surface materials, Mini-TES will be
pointed upward to make the first ever high-resolution temperature profiles through the Martian
atmosphere's boundary layer.
Calvin is particularly interested in ices. On Earth we have water ice and dry ice (CO2), but
far out in the solar system things like nitrogen and methane also freeze. And, since there is
so much oxygen here on Earth and so little on Mars, Calvin is curious about how minerals on
the surface of Mars should weather. She's hoping the MER rovers will uncover more clues about
Calvin's interest in ices includes her hobbies of backcountry and downhill skiing. Here she listens in on the avalanche potential of an alpine snowpack.
In preparation for the MER Mission, Calvin studies the surface materials of our planet. She
works with three graduate students who research materials that may be similar to those found on
Mars. They work on a computer analyzing pictures taken from airplanes or from satellites in
orbit, and they often go out to the areas where the pictures were taken to confirm that what
they see in the aerial photography is, in fact, what they find on the ground. The team takes
field instruments along with them on these expeditions. Calvin considers this to be one of the
most enjoyable parts of her job--hiking around, looking at rocks, and using field equipment.
Calvin had a spark for science at a young age. As a kid, she loved solving story problems and
basic algebra, and she loved playing around with science equipment. She remembers demonstrating
interference phenomena "in a pool of water and standing waves on a wire with a little battery
and a magnet." She thought this was all "pretty cool." She also loved reading Harriet the Spy
and especially liked Harriet's buddy, Janie, who blew up the house with the chemistry set in her
room. Interestingly enough, one of her favorite high school experiments was charting the orbit
of Mars. "We had to observe its position every week for several months," says Calvin. Fortunately
she lived where the night skies were very dark and Mars was easy to find!
Calvin in her office studies a geologic map of Mars.
While maintaining the curiosity and excitement that she felt as a child, Calvin also holds a
deep respect for the challenges inherent in planetary exploration. She recalls the Samurai
saying, "Expect nothing; be prepared for anything." By its nature, exploration is fraught with
detours, unexpected outcomes, and things that work only part-way. "Just think of Columbus,"
Calvin says, "who went to find a new route to Asia and got the West Indies instead--or Scott,
who wanted to be first to the South Pole but lost his life and his crew in the process." She
remembers being in grad school when the Shuttle Challenger blew up--a sobering reminder of the
potential danger involved in the active quest for knowledge. Along the way there have been
both spectacular successes and disheartening losses. “We must learn from the failures,
but we must always have the courage to continue,” says Calvin.