The Mars
Exploration Rovers have weathered two drab winters on the Martian surface, and
mission managers are already looking ahead to yet a third chilly season. All
this from a mission that was only designed to last 90 days.
The Spirit
rover is searching for a spot to stick it out during the upcoming Martian
winter, which will last from March 2008 through October 2008, according to
a statement from NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Although
Mars has a tilt similar to Earth's, Martian seasons last longer because the
planet takes almost twice as long to circle the Sun—almost 687 Earth days.
"When
you're talking about the rovers surviving winter on Mars, planning many months
in the future is really important," said Steve Squyres, principal scientist of the Mars
Exploration Rover team at Cornell University in Ithaca, New York. "But
it's too soon to tell where we might situate them."
Science
on a hill
The
solar-powered robots take an energy hit during the dim conditions, Squyres
explained.
"The
sun gets very low in the sky, giving us a lot less solar power to work
with," Squyres said. Fewer gusts of wind are around to clean dust from the
rovers' solar panels gathered during recent dust storms,
he added, which compounds the problem.
So how do
the rovers survive the winter while still doing plenty
of science, as they did in 2004 and 2006?
"We
try and park them on a broad, north-facing slope that helps them gather more
sunlight," Squyres said. Scientists not only prefer a good slope, but a
large and scientifically interesting one. "During the winter, it's
essentially science on a hill," Squyres said. "If we're stuck on a
small slope, we're much more limited in what we can investigate."
'Dirty'
obsession?
Even if a
rover gets "stranded" on a tiny hill, however, it's not necessarily
the end of the world.
"Being
stuck in one place allows us to do science we normally can't because we're in a
hurry, driving the rovers around," he said. "It also allows us to
intensively study a single, small area, like landers do."
During the
last winter, Squyres said, Spirit
studied a palm-sized area of Martian soil for months.
"It's
probably the best-studied patch of dirt in the solar system beyond Earth,"
he said.
Although
Squyres said the rovers have led impressively long lives to this point—each now
more than 1,324 Earth-days beyond their warranty—he said it's impossible to
predict their ability
to survive.
"Their
long lives are experiments in progress," Squyres said. "They could
die three years from now, or in the next hour. There's simply no way for us to
know, so we're trying to do as much as we can with what time we might have
left."
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