Steven Squyres, the principal investigator for
the science instruments aboard the Spirit and Opportunity Mars
rovers, juggles his commitments to the four space missions he is
actively involved in, as well as to his teaching and advising duties,
with an energetic ease that makes some wonder if he has found the
secret to a 25-hour day.

Well yes, actually, he has.

Not 25 hours, to be exact, but 24 hours, 39 minutes and 35 seconds,
the length of one Martian day, or “sol.”

Squyres is preparing to live on Mars time for the duration of the
two-rover mission, expected to be at least four months. Spirit is
scheduled to touch down in the red planet’s Gusev Crater on Jan. 3 at
11:35 p.m. EST; its twin, Opportunity, will land at Meridiani Planum
on Jan. 25 at 12:05 a.m. EST.

The Jet Propulsion Laboratory (JPL) in Pasadena, a division of the
California Institute of Technology, manages the Mars Exploration
Rover project for NASA’s Office of Space Science, Washington, D.C.
Cornell University, Ithaca, N.Y., is managing the science suite of
instruments carried by the two rovers.

“Our vehicles are tied to the Martian day/night cycle,” says Squyres,
who is professor of astronomy at Cornell. “They rely on a vision
system to avoid obstacles,” and being solar powered they must operate
during daylight and “sleep” at night.

Because the rovers’ daily communications windows also are tied to
this cycle, Squyres, along with more than 200 other scientists and
engineers, must lengthen his days to stay in sync.

Squyres admits that the longer days, at first, seem attractive —
“you get to sleep in

39 minutes later every day” — but points out that there is “very
little hard data on the physiological impact of extended Mars-time

The fundamental problem, says Squyres, is that team members must keep
a longer day while exposed to outside stimuli that run on an exact
24-hour cycle.The entire rover team will work at the mission control
center at JPL. They already have rented apartments in a quiet
neighborhood equipped with light-tight blackout shades, and some of
them will wear specially made Mars watches that record an additional
39 minutes, 35 seconds every day. But when rover team members step
outside, they will be bombarded with external stimuli running on the
24-hour clock to which their bodies are accustomed.

“We decided we needed to get some serious advice in this area,” says
Squyres. When, jet-lagged and exhausted, he ran into Cornell sleep
researcher James Maas at Pittsburgh airport in 2000, both realized
that a collaboration would be a boon for data-hungry sleep
researchers and for the rover team.

“While we were doing our own experiments, there was the opportunity
for us to be the subject of someone else’s experiment,” says Squyres.

Consequently about 40 members of the rover team will be the subjects
of the sleep study. Small wristwatch-like accelerometers will keep a
record of the scientists’ motion through the days and nights of the
Mars mission. From the accelerometer readings, the sleep-research
team will deduce when the scientists were awake and when they were

Workshops with sleep experts from Harvard, Brown, Stanford and the
NASA Ames research center also have helped shape the Mars team’s

“The key is not to overschedule people,” says Squyres. Scientists
will stick to a six-sol workweek, working four sols and taking a
two-sol weekend.

But engineers on the team with permanent homes in Pasadena will get a
longer, three-sol weekend. The engineers “have groceries to buy,
lawns to mow, PTA meetings to go to,” and must contend with more
signals from the 24-hour world than the visiting scientists, says

He is most worried, though, about the “wicked case of Martian jet
lag” he will get when Opportunity lands Jan. 25. The rover’s landing
site is almost 180 degrees away from Spirit’s, meaning that when
Squyres leaves the Spirit team to join the Opportunity group, he will
be about 12 hours off schedule. It is the Martian equivalent of a
trip from New York to Australia — without the benefit of a daylong
plane ride during which to adjust.

There is one vestige of Earth time Squyres won’t be able to escape,
though: the press conference. So if, come January, Squyres looks a
bit bleary-eyed in front of the cameras, remember that it might just
be 2:30 a.m. back in Gusev Crater.