NASA Orbiter Reveals
New Details of Mars, Young and Old
(16 October 2006) During its first
week of observations from low orbit, NASA's newest Mars spacecraft is already
revealing new clues about both recent and ancient environments on the red
planet.
Scientists hope the Mars Reconnaissance Orbiter will
answer questions about the history and distribution of Mars' water by combining
data from the orbiter's high-resolution camera, imaging spectrometer, context
camera, ground-penetrating radar, atmospheric sounder, global colour camera,
radio and accelerometers.
Between Sept. 29 and Oct. 6, science
instruments on the spacecraft viewed dozens of sites that reflect different
episodes in Mars' history. The diverse sites provide a good test for the
capabilities of the spacecraft instruments. The orbiter will begin its primary
science mission phase in early November when Mars re-emerges from passing
nearly behind the sun.
The instruments are seeing details in the shapes
and icy composition of geologically young layering near the Martian north pole.
Other views offer details of a mid-latitude valley whose upper layers have been
eroded away, revealing an underlying clay layer that formed a few billion years
ago, when wet conditions produced the clay. Observations of a
southern-hemisphere crater show fine-scale details of more recent gullies,
adding evidence that they were carved by flowing water.
"In this opening
phase we have tested the instruments, and they are working perfectly," said Dr.
Steve Saunders, Mars Reconnaissance Orbiter program scientist at NASA
Headquarters, Washington. "The teams are getting amazing science data. They are
ready to fulfil the mission's science objectives and to support other Mars
missions. One image is already helping the Mars Exploration Rover team choose a
route to explore Victoria Crater. Others will help guide the selection of a
safe site for the future Phoenix Mars Lander."
In Chasma Boreale, a vast
valley that juts into the north polar ice cap, the orbiter's spectrometer sees
layers that vary in soil composition and in how much ice is mixed with the
soil. A dark underlying layer contains little ice, but just beneath it lies
ice-rich material resembling higher layers. The spectrometer takes pictures
both in visible-light and infrared wavelengths useful for identifying what a
target is made of.
"You see more-ice-rich and less-ice-rich layers,
which tells you that conditions changed from the time one layer was deposited
to the time another layer was deposited," said Dr. Scott Murchie of Johns
Hopkins University Applied Physics Laboratory, Laurel, Md. Murchie is the
principal investigator for the spectrometer on the spacecraft. "These layers
are geologically young - on the order of thousands or millions of years - and
may hold clues about climate cycles."
A lower-latitude target was Mawrth
Vallis. The European Mars Express spacecraft previously discovered ancient
deposits of clay minerals that could form only if water were present for a long
time at Mawrth Vallis. The Mars Reconnaissance Orbiter's spectrometer has
resolved smaller-scale compositional features and detected differing clay
mineral content. The clay-rich areas show some of the best evidence for
conditions possibly favourable for life on ancient Mars, Murchie
said.
The mission's High Resolution Imaging Science Experiment camera
has shown unprecedented detail in orbital images of Mars. An example was
released recently showing the Opportunity rover at Victoria Crater. The camera
imaged 64 areas on Mars during the testing week. "These images are truly
beautiful, and since they resolve features the size of people, you can
visualise yourself hiking around in these diverse terrains," said the camera's
principal investigator, Dr. Alfred McEwen of the University of Arizona,
Tucson.
The high-resolution camera, the imaging spectrometer and the
orbiter's wider-looking Context Camera all observed Mawrth Vallis. Details
visible in the new observations, such as small channels, are consistent with
past wet conditions, McEwen said.
Another observation of an unnamed
southern crater shows relatively young gullies, like those seen in many Mars
locations viewed by NASA's Mars Global Surveyor orbiter. Braided channels
characteristic of sediment-rich streams are visible in the new observations.
This reinforces the interpretation that these geologically young gullies formed
at least in part from erosion by flowing water. Original discovery of the many
geologically young gullies on Martian slopes was by Dr. Michael Malin of Malin
Space Science Systems, San Diego.
The Mars Reconnaissance Orbiter is
managed by the Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Science
Mission Directorate, Washington.
(source: NASA Jet Propulsion
Laboratory)