Mars Rover Wanders Through Littered Landscape
By Leonard David
Senior Space Writer
posted: 31 December 2004
03:47 pm ET
BOULDER, Colo. -- Like the adage here on Earth, so goes it for Mars:
One person’s junk is another’s gold mine -- in this case, charred and
busted up pieces of a heat shield.
NASA’s Opportunity Mars rover is circling leftovers from its entry,
descent and landing system that fell to the planet nearly a year ago.
Both scientists and engineers are finding value in an up-close
inspection of spent entry shield hardware that was shed at high
altitude above Mars and fell with a thump onto the expanse of terrain
that is Meridiani Planum.
The rover has been edging toward the damaged goods for several days.
The Mars machinery is now in position to start detailed studies of
the busted up hardware using its robotic arm.
Interesting targets
"We have circled around to a secondary debris site we are calling the
‘flank piece’", noted Christine Szalai, JPL’s leader of the heat
shield observations team. "These are some pieces that broke off of
the main heat shield after impact," she told SPACE.com.
Szalai said that a set of "interesting targets" have been identified
– targets to home in on with the rover’s Microscopic Imager for
carrying out fracture cross-section looks this weekend.
"This data will hopefully tell us the char depth through the
thickness of the thermal protection system material. After we are
done with this investigation, we are going to continue the spiral to
survey the main heat shield and come in close to obtain more imaging
data," Szalai explained.
Hometown hardware
Nobody could be happier about Opportunity’s stroll through roughed up
spacecraft hardware than Bill Willcockson. He led the Mars
Exploration Rover entry systems work at Lockheed Martin Space Systems
in nearby Denver.
"It’s just amazing to see something that you crafted right here in
your hometown sitting right there on the surface of Mars. It’s just
indescribable," Willcockson told SPACE.com.
The plan now scripted calls for Opportunity to wheel up to one of the
large pieces of heat shield, then deploy the robot’s arm-mounted
Microscopic Imager. That device, he said, will carefully scan the
shield’s thermal protection system (TPS).
"We think we’re seeing some good regions where the outer TPS is still
visible to us. But we won’t really know until we get right up on top
of it," Willcockson said.
Artificial meteor
The rover is wheeling around to inspect two big pieces of entry
shield. There is one larger segment that appears tent-like as it sits
on Mars. The other big chunk of junk is dubbed the flank piece,
Willcockson noted.
"The shield came down at something like 170 miles per hour, smacked
into the ground going pretty much nose down. It made this big divot,
rebounded and broke apart with the two pieces landing a few feet away
into their final positions," Willcockson said.
The impact area is also the scene of bits and pieces of TPS, as well
as other debris that includes springs that pushed the heat shield
away from the other entry, descent and landing hardware. Once
released, the 198-pound (90-kilogram) shield fell through the martian
atmosphere some four miles (nearly 7 kilometers) before pounding
Mars’ surface.
Taking on the role of an artificial meteor, the heat shield struck
the red planet and created a small impact crater that should yield
clues to scientists about the soil properties of Mars, Willcockson
added.
Unknown unknowns
By taking an up-close look at the entry shield, Willcockson said,
engineers are hoping to see the depth of the TPS char layer – just
how well the entry shield took the high heating as it skyrocketed
through the martian atmosphere.
"We think maybe two-tenths of an inch…but it could be more or less.
This is the first chance to actually measure this [TPS charring] on
the surface of another planet," Willcockson pointed out. Entry
hardware is generally not instrumented, he said, "so you have no idea
of how well it worked…you just know it worked or whether it didn’t."
Data gleaned from surveying Opportunity’s heat shield will be useful
in designing and testing future entry shields, to gain a better
understanding of how the TPS material responds in a "real world"
environment and help grapple with the "unknown unknowns", Willcockson
stated.
"You might learn some unanticipated things by looking at a piece of
space hardware that’s been sitting on Mars," Willcockson concluded.
"So this is totally a once in a lifetime experience…once in a
lifetime information."
Impenetrable barrier
Following its foray into the swath of discarded hardware, where next
for Opportunity?
Steve Squyres, lead scientist for the Mars Exploration Rover program
from Cornell University, said the robot has a very tough next
assignment. The driving objective for Opportunity is etched terrain
to the south of Endurance crater – a large impact feature in which
the robot recently completed six months of rewarding science work.
"The distance we'll have to cover to reach the etched terrain is
something like three kilometers [some two miles], so it's a very
aggressive goal. If we can reach the etched terrain, we expect that
exploring it will take a substantial amount of effort and time,"
Squyres told SPACE.com.
"We don't currently know whether or not it will be possible to
traverse a significant distance into the etched terrain. From orbit
it appears to be pretty rugged stuff, so it may represent an
impenetrable barrier to further southward exploration. We'll see when
we get there," Squyres advised.
On the far side of that etched terrain is the huge Victoria crater.
Chances of the rover reaching that geological paradise of a hole in
the ground "are probably not good," Squyres said. "But if we did
somehow manage to make it across the etched terrain, Victoria would
be a very exciting next objective," he added.
Squyres said that next week, he will discuss "an interesting
intermediate goal" -- something on the path from the heat shield to
the etched terrain -- at a Mars Exploration Rover press briefing.
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