Sample return missions examined after Genesis crash
By Leonard David
SPACE.com
(SPACE.com) -- NASA's Genesis sample capsule not only stirred up dust and dirt when it crashed in Utah last week, but also debate concerning the return to Earth of future extraterrestrial samples, particularly from Mars.
While the high-speed impact of the return canister was not planned, the capsule's design permitted the survival of some samples. However, due to a breach of the science canister caused by the crash, the space specimens were contaminated once exposed to Earth's atmosphere.
The Genesis probe, along with the homeward bound Stardust spacecraft carrying bits of a comet and interstellar particles, serve as precursor missions to snag, bag, and lug back to Earth pieces of Martian real estate.
NASA engineers and scientists have been grappling for decades with methods, procedures, and the price tag for robotically returning Mars samples.
One concern that Martian samples could contain microbial life. Whether that's the case or not, great care in handling specimens of Mars is a high priority -- not only to protect our planet from virulent biology, albeit a low probability, but also guarding the samples from Earth contamination.
Twisted hardware
The Genesis sample canister crashed into the Utah Test and Training Range at a speed of nearly 200 miles per hour (322 kilometers per hour). The plan called for a mid-air helicopter recovery of the sample return capsule descending by parafoil -- a wing-like parachute.
But the parachute system failed to deploy. The return sample canister was severely damaged by the high-speed impact, leaving scientists to sift through mangled hardware in the hopes of salvaging science data.
"We'll have to wait and see what the results and lessons learned from the Genesis mishap reviews are to see how they will affect Mars Sample Return designs," said Mark Adler, Mars Exploration Rover Mission Manager and an engineer at the Jet Propulsion Laboratory (JPL) in Pasadena, California.
Other return missions are already using different technology.
Maintain containment
As currently envisioned, the Mars Sample Return mission uses a completely passive entry vehicle. A return craft holding the specimen canister would be aerodynamically stable throughout its landing on Earth. The MSR entry craft would not require a parachute, Adler said.
"The samples of Martian rock and soil would be in a container designed to withstand the impact and maintain its integrity as well as the integrity of the samples," Adler said.
This design has been the lead candidate for about seven years, and a full-scale model was drop-tested at UTTR in 2000, he said.
A Mars Sample Return mission is at least nine years away, so statements about the MSR final design should be taken "with the appropriate-sized grain of salt," he noted.
"It is clear, though, that the Genesis experience bolsters the previous conclusion that an MSR entry vehicle must be designed to maintain containment of the samples in the event that a parachute or any other entry, descent, and landing deployment or actuation fails," Adler said.
Breached canister
"The Mars Sample Return mission needs to be rethought entirely," said Barry DiGregorio, a research associate with the Cardiff Center for Astrobiology in the United Kingdom.
DiGregorio is also director for the International Committee Against Mars Sample Return, an activist group established to increase public awareness regarding Mars-to-Earth transit of samples, along with any possible negative consequences from a breached MSR canister on Earth.
In 2000, DiGregorio said, NASA was moving forward with its "faster, better cheaper" plan to return Martian soil samples as soon as 2003 and 2005 in a capsule design not unlike Genesis, with the exception that the MSR capsule would not use a parafoil or drogue chute. Instead it would use atmospheric friction to slow its descent and then directly impact the same general area in the Utah desert that Genesis did, he said.
Given the Genesis experience, DiGregorio argues that NASA's new moon, Mars and beyond quest should include the establishment of a human-tended planetary sample quarantine facility on the moon as a part of any scientific outpost there.
"Examining martian soil and rock samples on the moon offers a 100 percent guarantee that Earth's biosphere would not become back-contaminated with any possible martian microorganisms," DiGregorio said.
Exobiology perspective
John Rummel, Planetary Protection Officer at NASA Headquarters in Washington, D.C., advised that there will likely always be a desire to bring back materials from elsewhere, and study that material in the most capable laboratories that are available, which are on Earth.
Genesis involved a mid-air snatch, the softest way to land, due to the fragile nature of its collection devices and the requirement for molecular-level purity for its sub-microscopic samples of the solar wind, Rummel said.
NASA's Stardust mission will bring comet samples back to Earth in January 2006. The collection material, aerogel, is also fairly fragile, although the particles are bigger, Rummel said. Therefore, Stardust will land by parachute in Utah, without the mid-air helicopter catch.
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