Get set for more cosmic samplings

Quantum step forward
“Stardust is a huge success of a mission,” said Stephen Mackwell, director of the Lunar and Planetary Institute in Houston. “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 be answered for the most part only 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 liftoff 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.

The Lunar and Planetary Institute’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 said, 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.”

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