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01/12/2005

Rovers and Circadian Rhythms

I’ve just started to read the book “Rhythms of Life” by Russell
G. Foster and Leon Kreitzman, a writer and broadcaster. Foster
is professor of molecular neuroscience at Imperial College in
London and is a leader in the field of chronobiology, a field that
concerns the internal clocks that play important roles in most
living things. Of specific interest are the so-called “circadian
rhythms”. The term circadian derives from the Latin circa,
about, and diem, day. Circadian rhythms are those inherent
biological rhythms built into virtually all life ranging from
bacteria to us humans. The built-in circadian rhythms tell us, for
example, when we should sleep, when we should eat and may
even tell us the best time to take life saving drugs.

One of the problems of modern society is that we have invented
such things as electric lights and TV that extend day into night
and we’ve substituted alarm clocks for our internal biological
clocks. We’ve even invented the term 24/7, disavowing
completely our innate circadian rhythms.

Last week I watched a Nova program on PBS that tied in with
this theme. The program went behind the scenes at the Jet
Propulsion Laboratory (JPL), which manages, monitors and
controls various NASA orbiters, spacecraft and rovers, the rovers
on Mars being the subject of the program. Last week we talked
about global warming as the number one scientific story of 2004.
That was the choice of Discover magazine. On the other hand,
the December 17 issue of Science chose Mars as “Breakthrough
of the Year”. Not the planet, but the wildly successful rovers and
orbiters that have sent back glorious pictures and scientific data
from Mars. The Nova program dealt with the trials and
tribulations of the JPL workers suffering through the glitches and
reveling in the triumphs of these Mars rovers.

In the Science article, Richard Kerr describes how orbiters paved
the way for selecting landing sites for the rovers. The region on
Mars known as Meridiani Planum was the landing site for the
Opportunity rover. The Mars Global Surveyor, as it orbited the
planet, found that the Meridiani area stood out from otherwise
not too exciting surroundings. Infrared measurements showed
the presence there of the mineral hematite, an oxide of iron that
could have evolved from reactions involving water. When
Opportunity arrived and started poking around Meridiani it found
the now famous “blueberries”, small marble-sized spheres of
hematite. These blueberries were scattered all over the place and
were the hematite seen from the orbiter.

Opportunity also found salts of magnesium and calcium sulfates,
the result of weathering of rocks by water, and jarosite, a mineral
that suggests the water was acidic. Chemically, acid is what you
expect if water reacted with sulfur dioxide spewed out from
Martian volcanoes millions or billions of years ago. The acid
presumably leached the calcium and magnesium out of Martian
rocks and flowed out over the Martian surface forming a shallow
sea. When the water evaporated, the salts were left behind. The
weathered rocks turned into plain old Martian dirt. A JPL news
release of December 13, 2004 reports that Spirit, Opportunity’s
twin rover on the opposite side of Mars, has found a mineral
called goethite, which also can form in the presence of water.

The rovers have confirmed an abundance of water in Mars’
distant past. But there’s still some water on Mars and I shouldn’t
have been surprised to read that on some mornings, just like here
on Earth, there was frost on the pumpkin, the pumpkin being the
Opportunity rover itself! The rover is near Mars’ equator so how
come the frost? With the shift in seasons and winter shifting to
the southern hemisphere, water is moving through the Martian
atmosphere from the north pole to the south pole. It’s always
cold on Mars, like minus 40 degrees Fahrenheit, but when the
sun goes down it gets cold enough to condense even the small
amount of water vapor in the thin Martian atmosphere.

As Martian dust has accumulated on the rovers’ solar panels, the
dust has cut the amount of sunlight reaching the panels. Hence
the amount of electrical power generated by the solar panels has
gone down over the past year. Recently, however, there was an
unexpected upsurge in the panels’ power output to Opportunity.
Speculation now is that frost condensing on the solar panels may
cause the dust to clump up, clearing more of the surface of the
panels to receive sunlight and generate more electricity. The
weather gods on Mars are being kind.

This month marks the first anniversary of the rovers’ landings on
Mars and they’re both still going strong. JPL would have been
happy if the rovers had accomplished only their primary 90-day
missions, especially given the rocky start to Spirit’s mission.
The Nova program showed the JPL workers’ concern with the
balky robot. Spirit stopped sending signals, then started sending
garbage, then stayed awake when it should have been sleeping,
thus draining the batteries. While dealing with these problems,
Opportunity was about to land on the opposite side of Mars.
Somehow, they managed to get Spirit back on schedule and
we’ve all seen some of the amazing pictures it sent back to us.

As if the stress of possibly seeing years of work go down the
drain weren’t enough, what about the JPL workers’ circadian
rhythms? The rovers are put to sleep at night and awakened at
sunrise, the same kind of schedule as that of most workers here
on Earth. However, with the two rovers on opposite sides of the
planet, it takes two teams of workers, one to monitor and control
each rover. So, one crew works the day shift and the other the
night shift, right? Not exactly. The Martian day is some 40
minutes longer than our day. So, for the Earthly workers to keep
on a Martian schedule, those alarm clocks have to be set 40
minutes later each day! Talk about jet lag!

The Nova program left me with the troubling impression that
each crew follows this schedule continuously, monitoring one
rover throughout. With the work schedule rolling from an Earth
day shift to night shift to day shift, any circadian rhythms would
be totally fouled up. It seemed to me that it would be impossible
to maintain any semblance of a normal life. Accordingly, I
called a friend, Gerry, who worked at JPL to check on the actual
situation. Gerry referred me to Kumar and Richard, who are
closer to the day-to-day operations. Today, happily, it seems that
everyone is working on Earth time. However, for roughly the
first 90 to 110 sols (a sol is a Martian day), the crews were on
Martian time. A crew might consist of 5 people, 2 working 12-
hour shifts together for roughly four to four and a half days with
three to three and a half days off. The 2-person crew would be
spelled by another 2-person crew. The fifth member of the team
would fit in the progression to provide overlapping of the crews
for continuity purposes.

My impression is that these crews performed the monitoring as
opposed to the planning, which I understand involves the
programming of the future activities of the rovers. If I
understand correctly, the planners operated on Martian time for
about half a year. Now they plan ahead for the next two or three
sols and hopefully live lives more consistent with their circadian
rhythms, about which we’ll have more to say as I delve further
into the book. The book, incidentally, was a gift from Brian
Trumbore, our Editor, who suggested it would contain material
for a column or so. We mustn’t ignore the wishes of our Editor!

Allen F. Bortrum



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Dr. Bortrum

01/12/2005

Rovers and Circadian Rhythms

I’ve just started to read the book “Rhythms of Life” by Russell
G. Foster and Leon Kreitzman, a writer and broadcaster. Foster
is professor of molecular neuroscience at Imperial College in
London and is a leader in the field of chronobiology, a field that
concerns the internal clocks that play important roles in most
living things. Of specific interest are the so-called “circadian
rhythms”. The term circadian derives from the Latin circa,
about, and diem, day. Circadian rhythms are those inherent
biological rhythms built into virtually all life ranging from
bacteria to us humans. The built-in circadian rhythms tell us, for
example, when we should sleep, when we should eat and may
even tell us the best time to take life saving drugs.

One of the problems of modern society is that we have invented
such things as electric lights and TV that extend day into night
and we’ve substituted alarm clocks for our internal biological
clocks. We’ve even invented the term 24/7, disavowing
completely our innate circadian rhythms.

Last week I watched a Nova program on PBS that tied in with
this theme. The program went behind the scenes at the Jet
Propulsion Laboratory (JPL), which manages, monitors and
controls various NASA orbiters, spacecraft and rovers, the rovers
on Mars being the subject of the program. Last week we talked
about global warming as the number one scientific story of 2004.
That was the choice of Discover magazine. On the other hand,
the December 17 issue of Science chose Mars as “Breakthrough
of the Year”. Not the planet, but the wildly successful rovers and
orbiters that have sent back glorious pictures and scientific data
from Mars. The Nova program dealt with the trials and
tribulations of the JPL workers suffering through the glitches and
reveling in the triumphs of these Mars rovers.

In the Science article, Richard Kerr describes how orbiters paved
the way for selecting landing sites for the rovers. The region on
Mars known as Meridiani Planum was the landing site for the
Opportunity rover. The Mars Global Surveyor, as it orbited the
planet, found that the Meridiani area stood out from otherwise
not too exciting surroundings. Infrared measurements showed
the presence there of the mineral hematite, an oxide of iron that
could have evolved from reactions involving water. When
Opportunity arrived and started poking around Meridiani it found
the now famous “blueberries”, small marble-sized spheres of
hematite. These blueberries were scattered all over the place and
were the hematite seen from the orbiter.

Opportunity also found salts of magnesium and calcium sulfates,
the result of weathering of rocks by water, and jarosite, a mineral
that suggests the water was acidic. Chemically, acid is what you
expect if water reacted with sulfur dioxide spewed out from
Martian volcanoes millions or billions of years ago. The acid
presumably leached the calcium and magnesium out of Martian
rocks and flowed out over the Martian surface forming a shallow
sea. When the water evaporated, the salts were left behind. The
weathered rocks turned into plain old Martian dirt. A JPL news
release of December 13, 2004 reports that Spirit, Opportunity’s
twin rover on the opposite side of Mars, has found a mineral
called goethite, which also can form in the presence of water.

The rovers have confirmed an abundance of water in Mars’
distant past. But there’s still some water on Mars and I shouldn’t
have been surprised to read that on some mornings, just like here
on Earth, there was frost on the pumpkin, the pumpkin being the
Opportunity rover itself! The rover is near Mars’ equator so how
come the frost? With the shift in seasons and winter shifting to
the southern hemisphere, water is moving through the Martian
atmosphere from the north pole to the south pole. It’s always
cold on Mars, like minus 40 degrees Fahrenheit, but when the
sun goes down it gets cold enough to condense even the small
amount of water vapor in the thin Martian atmosphere.

As Martian dust has accumulated on the rovers’ solar panels, the
dust has cut the amount of sunlight reaching the panels. Hence
the amount of electrical power generated by the solar panels has
gone down over the past year. Recently, however, there was an
unexpected upsurge in the panels’ power output to Opportunity.
Speculation now is that frost condensing on the solar panels may
cause the dust to clump up, clearing more of the surface of the
panels to receive sunlight and generate more electricity. The
weather gods on Mars are being kind.

This month marks the first anniversary of the rovers’ landings on
Mars and they’re both still going strong. JPL would have been
happy if the rovers had accomplished only their primary 90-day
missions, especially given the rocky start to Spirit’s mission.
The Nova program showed the JPL workers’ concern with the
balky robot. Spirit stopped sending signals, then started sending
garbage, then stayed awake when it should have been sleeping,
thus draining the batteries. While dealing with these problems,
Opportunity was about to land on the opposite side of Mars.
Somehow, they managed to get Spirit back on schedule and
we’ve all seen some of the amazing pictures it sent back to us.

As if the stress of possibly seeing years of work go down the
drain weren’t enough, what about the JPL workers’ circadian
rhythms? The rovers are put to sleep at night and awakened at
sunrise, the same kind of schedule as that of most workers here
on Earth. However, with the two rovers on opposite sides of the
planet, it takes two teams of workers, one to monitor and control
each rover. So, one crew works the day shift and the other the
night shift, right? Not exactly. The Martian day is some 40
minutes longer than our day. So, for the Earthly workers to keep
on a Martian schedule, those alarm clocks have to be set 40
minutes later each day! Talk about jet lag!

The Nova program left me with the troubling impression that
each crew follows this schedule continuously, monitoring one
rover throughout. With the work schedule rolling from an Earth
day shift to night shift to day shift, any circadian rhythms would
be totally fouled up. It seemed to me that it would be impossible
to maintain any semblance of a normal life. Accordingly, I
called a friend, Gerry, who worked at JPL to check on the actual
situation. Gerry referred me to Kumar and Richard, who are
closer to the day-to-day operations. Today, happily, it seems that
everyone is working on Earth time. However, for roughly the
first 90 to 110 sols (a sol is a Martian day), the crews were on
Martian time. A crew might consist of 5 people, 2 working 12-
hour shifts together for roughly four to four and a half days with
three to three and a half days off. The 2-person crew would be
spelled by another 2-person crew. The fifth member of the team
would fit in the progression to provide overlapping of the crews
for continuity purposes.

My impression is that these crews performed the monitoring as
opposed to the planning, which I understand involves the
programming of the future activities of the rovers. If I
understand correctly, the planners operated on Martian time for
about half a year. Now they plan ahead for the next two or three
sols and hopefully live lives more consistent with their circadian
rhythms, about which we’ll have more to say as I delve further
into the book. The book, incidentally, was a gift from Brian
Trumbore, our Editor, who suggested it would contain material
for a column or so. We mustn’t ignore the wishes of our Editor!

Allen F. Bortrum