Durable Mars Rovers Sent Into Third Overtime Period
NASA has approved up to 18 more months of operations for Spirit and Opportunity, the twin Mars rovers that have already surprised engineers and scientists by continuing active exploration for more than 14 months.
“The rovers have proven their value with major discoveries about ancient watery
environments on Mars that might have harbored life,” said Dr. Ghassem Asrar,
deputy associate administrator for NASA’s Science Mission Directorate. “We are
extending their mission through September 2006 to take advantage of having such
capable resources still healthy and in excellent position to continue their
The rovers have already completed 11 months of extensions on top of their
successful three-month prime missions. “We now have to make long-term plans for
the vehicles because they may be around for quite a while,” said Jim Erickson,
rover project manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
Erickson cautioned though, “Either mission could end tomorrow with a random part
failure. With the rovers already performing well beyond their original design
lifetimes, having a part wear out and disable a rover is a distinct possibility
at any time. But right now, both rovers are in amazingly good shape. We’re going
to work them hard to get as much benefit from them as we can, for as long as they
are capable of producing worthwhile science results.”
“Spirit and Opportunity are approaching targets that a year ago seemed well out
of reach,” said Doug McCuistion, director of NASA’s Mars Exploration Program.
“Their successes strengthen NASA’s commitment to a vision with the ambitious
targets of returning samples from Mars and sending human explorers to Mars.”
Opportunity is within a few football fields’ length of a region called “Etched
Terrain,” where scientists hope to find rocks exposed by gentle wind erosion
rather than by disruptive cratering impacts, and rocks from a different time in
Mars’ history than any examined so far.
“This is a journey into the unknown, to something completely new,” said Dr. Steve
Squyres of Cornell University, Ithaca, N.Y., principal investigator for the
rover’s science instruments.
To reach the Etched Terrain, rover planners have been pushing the rover fast.
Opportunity has overtaken Spirit in total distance driven. It has rolled more
than three miles — eight times the original goal. On March 20, Opportunity also
set a new martian record of 722 feet in a single day’s drive. Drive-distance
estimates can vary by a few percent. The long drives take advantage of crossing a
plain so smooth it’s “like an East Coast beach,” said JPL’s Jeff Favretto,
mission manager on the Opportunity shift in recent weeks. Also, Opportunity’s
solar panels, though now dustier than Spirit’s, still generate enough power to
allow driving for more than three hours on some days.
Spirit is in much rougher terrain than Opportunity, climbing a rocky slope toward
the top of “Husband Hill.” However, with a boost in power from wind cleaning its
solar panels on March 9 and with its formerly balky right-front wheel now working
normally, Spirit made some longer one-day drives last week than it had for
months. “We’ve doubled our power,” said JPL’s Emily Eelkema, mission manager. “It
has given us extra hours of operations every day, so we can drive longer and
we’ve used more time for observations.”
The jump in power output has taken some urgency out of Spirit’s southward climb.
With Mars now beginning southern-hemisphere spring, the sun is farther south in
the sky each day. If not for panel-cleaning, Spirit might be facing the prospect
of becoming critically short of power if still on the north-facing slope by early
“We still want to get to the summit of Husband Hill and then head down into the
‘Inner Basin’ on the other side,” Squyres said. “But now we have more flexibility
in how we carry out the plan. Before, it was climb or die.” Cresting the hill is
now not as crucial for solar energy, but it still offers allures of potential
exposures of rock layers not yet examined, plus a vista of surrounding terrain.
In orbital images, the Inner Basin farther south appears to have terracing that
hints of layered rock.
Both rovers do have some signs of wear and exposure. Spirit’s rock abrasion tool
shows indications that its grinding teeth might be worn away after exposing the
interiors of five times more rock targets than its design goal of three rocks.
Researchers probably won’t know the extent of wear until Spirit’s next rock-
grinding attempt, which may be weeks away. Also, troubleshooting continues for
determining whether Opportunity’s miniature thermal emission spectrometer is
still usable despite tests indicating a problem last month. All other instruments
on both rovers are still working normally.
Opportunity used its navigation camera to take the images combined into this 360-degree view on the 399th martian day, or sol, of its surface mission (March 8, 2005).