Spirit Looks Down Into Crater After Reaching Rim
March 11, 2004
NASA's Spirit has begun looking down into a crater it has
been approaching for several weeks, providing a view of
what's below the surrounding surface.
Spirit has also been looking up, seeing stars and the first
observation of Earth from the surface of another planet. Its
twin, Opportunity, has shown scientists a "mother lode" of
hematite now considered a target for close-up investigation.
"It's been an extremely exciting and productive week for both
of the rovers," said Spirit Mission Manager Jennifer Trosper
at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Dr. Chris Leger, a rover driver at JPL, said, "The terrain
has been getting trickier and trickier as we've gotten close
to the crater. The slopes have been getting steeper and we
have more rocks." Spirit has now traveled a total of 335
meters (1,099 feet).
Spirit's new position on the rim of the crater nicknamed
"Bonneville" offers a vista in all directions, including the
crater interior. The distance to the opposite rim is about
the length of two football fields, nearly 10 times the
diameter of Opportunity's landing-site crater halfway around
the planet from Spirit.
Initial images from Spirit's navigation camera do not reveal
any obvious layers in "Bonneville's" inner wall, but they do
show tantalizing clues of rock features high on the far side,
science-team member Dr. Matt Golombek of JPL said at a news
briefing today. "This place where we've just arrived has
opened up, and it's going to take us a few days to get our
arms around it.
Scientists anticipate soon learning more about the crater
from Spirit's higher-resolution panoramic camera and the
miniature thermal emission spectrometer, both of which can
identify minerals from a distance. They will use that
information for deciding whether to send Spirit down into the
crater.
From the crater rim and during martian nighttime earlier
today, Spirit took pictures of stars, including a portion of
the constellation Orion. Shortly before dawn four martian
days earlier, it photographed Earth as a speck of light in
the morning twilight. The tests of rover capabilities for
astronomical observations will be used in planning possible
studies of Mars' atmospheric characteristics at night. Those
studies might include estimating the amounts of dust and ice
particles in the atmosphere from their effects on starlight,
said Dr. Mark Lemmon, a science team member from Texas A&M
University, College Station.
Opportunity has been looking up, too. It has photographed
Mars' larger moon, Phobos, passing in front of the Sun twice
in the past week, and Mars' smaller moon, Deimos, doing so
once.
Opportunity's miniature thermal emission spectrometer has
taken upward-looking readings of the atmospheric temperature
at the same time as a similar instrument, the thermal
emission spectrometer on NASA's Mars Global Surveyor orbiter,
took downward-pointed readings while passing overhead. "They
were actually looking directly along the same path," said
science team member Dr. Michael Wolff of the Martinez, Ga.,
branch of the Space Science Institute, Boulder, Colo. The
combined readings give the first full temperature profile
from the top of Mars' atmosphere to the surface.
When pointed at the ground, Opportunity's miniature thermal
emission spectrometer has checked the abundance of hematite
in all directions from the rover's location inside its
landing-site crater. This mineral, in its coarse-grained
form, usually forms in a wet environment. Detection of
hematite from orbit was the prime factor in selection of the
Meridiani Planum region for Opportunity's landing site.
"The plains outside our crater are covered with hematite,"
said Dr. Phil Christensen of Arizona State University, Tempe,
lead scientist for the instrument. "The rock outcrop we've
been studying has some hematite. Parts of the floor of the
crater, interestingly enough, have virtually none." The
pattern fits a theory that the crater was dug by an impact
that punched through a hematite-rich surface layer, he said.
One goal for Opportunity's future work is to learn more about
that surface layer to get more clues about the wet past
environment indicated by sulfate minerals identified last
week in the crater's outcrop.
Christensen said that before Opportunity drives out of the
crater in about 10 days, scientists plan to investigate one
area on the inner slope of the crater that he called "the
mother lode of hematite."
JPL, a division of the California Institute of
Technology in Pasadena, manages the Mars Exploration
Rover project for NASA's Office of Space Science,
Washington, D.C. Images and additional information
about the project are available from JPL at
http://marsrovers.jpl.nasa.gov and from Cornell
University at http://athena.cornell.edu.
