Date: July 15, 1998
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Special Handling Required for Samples
From Some Space Objects
NASA is planning several missions in the next decade to collect samples from a variety of small solar system bodies and planetary satellites. At the request of the agency, a task force of the National Research Council surveyed the potential for microscopic life existing on moons, asteroids, comets, and cosmic dust, and determined that a few cases may pose enough risk of contaminating Earth to require special handling procedures when the samples are brought home.
To establish its risk criteria, the task force first looked at the range of conditions under which life can propagate. These conditions include the presence of water and organic compounds, availability of energy sources, suitable temperatures, and protection from radiation. The group also considered conditions under which life can be dormant. And, they considered the possibility that materials containing life forms could have been transported to objects from elsewhere in the solar system -- for example, on a meteorite.
Although the chances of encountering life forms are extremely low, samples meeting the task force's criteria would require strict containment procedures modeled on those recommended for samples brought back from Mars, as outlined in a 1997 Research Council report. These procedures include quarantine, screening, and otherwise treating the materials as if they were biohazards until proved safe.
Of the space objects considered in the report, two of Jupiter's moons -- Europa and Ganymede -- offer the greatest potential of harboring microscopic life. Europa is the prime candidate among the objects studied for the possibility of past or present life based on evidence from the Voyager and Galileo space probes of an ocean beneath the moon's icy crust. Because Ganymede may once have had an ocean as well, caution in handling samples taken from there is also warranted. Sufficient temperatures for the existence of life and protection from radiation may also be present given the moons' positions orbiting Jupiter.
In addition, samples from certain types of asteroids -- the P- and D-types found in the outer parts of the asteroid belt between Mars and Jupiter -- merit strict procedures as a precaution because so little is known about their origin and composition. The task force recommended that dust particles collected near Europa, Ganymede, and these asteroids be approached with the same caution.
The report notes cases in which no special handling or containment procedures are necessary because these objects have been determined to be lifeless or because their conditions preclude the presence of life. These objects include the Earth's moon, new comets, and cosmic dust exposed to sterilizing radiation in space.
However, the report calls for scrutiny in any case where a lack of complete data cannot eliminate all risks. To reduce uncertainties in these cases, the task force recommended creating a database that charts the capacity of earthly microbes to survive extreme temperatures and radiation similar to those found in space. Such data could help determine the levels needed to sterilize samples.
The study was funded by NASA. The National Research Council is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering. It is a private, non-profit institution that provides science and technology advice under a congressional charter. A task force roster follows.
Read the full text of Evaluating the Biological Potential in Returned Samples from Planetary Satellites and Small Solar System Bodies: Framework for Decision Makingfor free on the Web, as well as more than 1,800 other publications from the National Academies. Printed copies are available for purchase from the National Academy Press Web siteor at the mailing address in the letterhead; tel. (202) 334-3313 or 1-800-624-6242. Reporters may obtain a pre-publication copy from the Office of News and Public Information at the letterhead address (contacts listed above).
NATIONAL RESEARCH COUNCIL
Commission on Physical Sciences, Mathematics, and Applications
Space Studies Board
Task Group on Sample Return from Small Solar System Bodies
Senior Fellow and Research Professor
Salk Institute for Biological Studies
Professor of Astronomy
Computer and Space Science
University of Maryland
Professor of Marine Chemistry, and
Director of NSCORT/Exobiology Program
Scripps Institution of Oceanography
University of California, San Diego
Professor of Marine Biology
School of Oceanography
University of Washington
Southwest Research Institute
Director of the Lunar and Planetary Laboratory, and
Head of the Department of Planetary Sciences
University of Arizona
Department of Chemistry
University of California
Margaret S. Race
Mountain View, Calif.
Director, Bay Paul Center for Comparative
Molecular Biology and Evolution
Marine Biological Laboratory
Woods Hole, Mass.
Professor, Department of Astronomy
Center for Radiophysics and Space Research
RESEARCH COUNCIL STAFF
Joseph L. Zelibor Jr.
(*) Member, National Academy of Sciences