[meteorite-list] Stardust Success Could Signal More Sample Return Missions

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Jan 26 13:54:56 2006
Message-ID: <200601261853.k0QIrEn19253_at_zagami.jpl.nasa.gov>

http://space.com/missionlaunches/060126_sample_capsules.html

Capsules From the Cosmos: Stardust Success Could Signal More Sample Missions
By Leonard David
space.com
26 January 2006

When the Stardust capsule blazed its way through Earth's atmosphere to a
parachute landing in Utah earlier this month, the event was a preview of
extraterrestrial attractions to come.

Scientists are elated at the Stardust collectibles - pristine specimens of
interstellar dust and comet particles from deep space.

Attention is now turning toward other objects: the Moon, Mars, comets
and asteroids, even Venus and Saturn's Titan - all are appetizing targets
in the celestial sweet shop of cosmic sampling.

Cleanroom fresh

Following nearly seven years of travel, the Stardust sample return
capsule became a long-distance, express mail, record-setting delivery.
It achieved the highest return velocity - 29,000 miles per hour (12.8
kilometers a second) of any human-made Earth reentry object to date

"The capsule showed excellent performance," said Jim Crocker, vice
president of civil space at Lockheed Martin Space Systems of Denver. The
company designed, built, and operated Stardust.

"There was no evidence of heatshield distress or any unexpected grooving
or pitting. When the capsule was opened, it was pristine inside. There
was no evidence of any leaking or heating trauma. It all looks cleanroom
fresh on the inside. That's extremely good news," Crocker told SPACE.com.

Space engineers are keen to do detailed engineering measurements on how
much the capsule ablated during its fiery plunge to Earth on January 15.
An essential element of the capsule was its heatshield, resembling a
blunt-nosed cone that thwarted the blistering temperatures reached
during Earth reentry.

Right on target

Stardust's sample return capsule heatshield consisted of two parts: a
lightweight aeroshell structure and a thermal protection system (TPS).
The TPS is a flight-qualified version of the high-energy ablator PICA
(Phenolic Impregnated Carbon Ablator) invented by NASA Ames Research
Center. Stardust represented the first flight of this material.

The backshell TPS is the same material used for the heatshields with the
Mars Pathfinder mission and the Mars Exploration Rover missions - Spirit
and Opportunity - and was first developed by Lockheed Martin for use on
the Viking missions to Mars in the 1970s.

In September 2004, the Genesis spacecraft - also built by Lockheed Martin
for NASA - delivered its return capsule right on target into Utah. But due
to improper placement of onboard components that would activate the
capsule's parachute recovery system, that hardware plowed into desert
landscape at high-speed. Despite this ballistic blemish of an ending,
scientists have apparently recovered meaningful science from
Genesis-snared solar wind samples.

Crocker said that the Stardust and Genesis capsules - as well as rover
Opportunity's surveying of its own heatshield that plummeted onto
Mars - all yield data extremely useful in designing future sample return
hardware.

"Every kilogram of material that you put on a heatshield that's in
excess of what you need for a reasonable margin - that's a kilogram of
payload that you can't put down on the planet," Crocker said. "By
reducing the uncertainty of how these things perform, it greatly
improves our performance of the whole mission."

Down Earth advice

"Stardust is really a trailblazer for an inexpensive way of returning
extraterrestrial materials to Earth - and it worked wonderfully," said
Laurie Leshin, Director of Sciences and Exploration at NASA's Goddard
Space Flight Center in Greenbelt, Maryland.

Leshin said she and other scientists are anxious to dive into Stardust's
captured comet grains and study them in detail. She is a member of the
Preliminary Examination Team that will get an early look-see at the samples.

"I predict that we will be blown away by the discoveries we will make in
the next few months," Leshin told SPACE.com. "We simply can't fly in
space the equivalent of the thousands of tons of sophisticated lab
equipment we have here on Earth. So if we can't bring the instruments to
the comet, we've got to bring the comet to the instruments," she added.

"SCIMing" off the top

Thanks to Stardust's success, Leshin said, it's time to ask whether the
same approach can be utilized to bring precious samples from other
objects back to Earth.

One such concept for a Stardust-like mission is tagged SCIM - short for
Sample Collection for Investigation of Mars. This proposed idea would
"scim" through the martian atmosphere, sweeping up dust and gas samples
for analysis back here on Earth, Leshin explained.

"Scientists have been calling for sample return missions from Mars for
over 30 years, but they have always proven too technically challenging
and expensive to undertake," Leshin said. "With a mission like SCIM, we
can get martian dirt back to Earth for about 1/10th the cost of a more
traditional sample return mission, and for about half the cost of the
Mars Rovers!"

Leshin is part of a team currently working on a proposal to NASA to fly
SCIM in 2011.

Quantum step forward

"Stardust is a huge success of a mission," said Stephen Mackwell,
Director of the Lunar and Planetary Institute (LPI) in Houston, Texas.
"In the coming months, as the samples are analyzed, I anticipate a
quantum step forward in our understanding of comets - bodies that still
contain material from the earliest evolutionary stages of the solar
system," he said.

Material snatched from space by Stardust will be available to scientists
from around the world. Researchers can study the samples using a broad
array of conventional and innovative techniques.

"It really does give great support to the concept of grabbing materials
for analysis here on Earth. You can do so much more here than using
instruments on a remote vehicle," Mackwell noted.

For instance, take the work of the Spirit and Opportunity Mars rovers.

Mackwell offered one hypothetical: "Just think what more we could have
done with a scoop of Mars dirt, including a few blueberries, or a chunk
of sedimentary layering, with a full chemical analysis and age dating,
etc. back here on Earth," he said. The rovers have highlighted so many
new questions that can only be answered for the most part by returned
samples, he said.

Some level of paranoia

The question of sample return is much debated in the planetary sciences
community, Mackwell advised.

"Because sample return involves two-way travel, potentially including
second lift-off from a body with significant gravity - Mars or Venus, for
example - and issues of planetary protection - these missions are almost
always expensive relative to orbital missions, or even landed missions
with or without rovers," Mackwell said.

Added to the technical difficulty and cost, Mackwell continued, are
societal issues with returning samples from planetary bodies that may
have once sustained some form of life.

"Even the remote chance that such lifeforms might be capable of
biological interaction with Earth organisms induces some level of
paranoia, justified or not," Mackwell said. "For these reasons, sample
return missions from Mars have remained just at the edge of the future
planning cycle for decades and have only recently been pushed even
further out. Return missions from comets, asteroids and other small
lifeless bodies are still technically challenging, but cheaper and less
likely to invoke fear," he suggested.

Dig and dash

NASA is not alone in bringing back the goods from space via automated
capsules.

The former Soviet Union used the robotic dig and dash technique to fly
back to Earth lunar specimens.

Then there's Japan's valiant Hayabusa probe. Late last year it reached
out and touched an asteroid. That craft suffered hardware problems and
is now limping back to Earth for a 2010 capsule landing. Scientists
still hold onto hope that Hayabusa may well have tucked away bits and
pieces of asteroid.

LPI's Mackwell spotlighted the value of sample return missions to other
planetary bodies, notably Titan, with its exotic surface, and Venus, so
much like Earth and yet so different.

"Such missions would greatly advance our knowledge of our solar system
and evolution of the interiors and surfaces of the planetary bodies and
the diversity of environments that exist within our corner of the
universe," Mackwell said.

The gift that keeps on giving

The inevitable question is ascribing value of sample return to Earth
contrasted to one-way landers, surface rovers and other mobile hardware.
And these tactics can be compared to what instrument-laden orbiters
bring to the table.

The difficulty here, Mackwell said, is just how much instrumentation can
fit on outward-bound spacecraft. Not only are there power and mass
issues, but what size sample can be assessed and in what state.

"Samples are pieces of the surface and can provide ground truth for
remotely sensed data, allowing calibration of orbital or balloon
measurements. Thus, they make remotely sensed data far more valuable. In
addition, data derived from samples provide a unique perspective not
offered by either orbital or in-situ [on-the-spot] data," Mackwell said.

Samples brought back to Earth "are the gift that keeps on giving,"
Mackwell added, given analytical experiments on samples that can be
modified "as logic and technology dictates."

And finally, returned samples, properly handled, permit scientists to
assess any biological hazard on another planet, prior to sending humans,
Mackwell concluded. "Given the huge potential return in science from
samples returned to the Earth for analysis, the additional cost of these
missions is easily justified."
Received on Thu 26 Jan 2006 01:53:14 PM PST