The Stardust spacecraft, launched in February 1999, made its rendezvous with Comet Wild 2 in January 2004, collecting samples of dust from the comet’s comathe gas and dust envelope that surrounds its nucleusfor return to Earth. The Stardust mission is the first mission designed to return samples to Earth from a comet. This mission is classified Category V, unrestricted Earth return, for planetary protection purposes.
The Comet and Interplanetary Dust Analyzer aboard the Stardust spacecraft contains two parts considered sensitive to contamination: a dust detector and an aerogel tray of dust collection surfaces. These components were cleansed by a nitrogen purge before the spacecraft was launched. The Stardust sample return capsule (SRC), which contains the aerogel tray, is designed to keep out other materials that could interfere with analyses of the dust samples. The SRC features filtered vents to limit the potential for contaminating samples during reentry.
The Stardust SRC successfully parachuted to Earth at the U.S. Army’s Utah Test and Training Range on January 15, 2006. Once on the ground, the SRC was enclosed in a dry nitrogen environment and flown to NASA’s sample curation laboratory at Johnson Space Center, where samples—expected to total 1 microgram in mass—are being carefully handled and contained to preserve their pristine condition for scientific studies. Approximately six months of preliminary investigation preceded the release of dust samples to the worldwide science community.
The Stardust spacecraft is now in hibernation mode in deep space. Its next Earth flyby is expected in January 2009, and NASA is keeping options open for possible reuse of the spacecraft for future investigations.
For more information about Stardust sample handling,
The Mars Viking Lander
NASA’s Viking mission to Mars in 1976 placed two spacecraft in orbit about the planet and two landers on its surface. To ensure against forward contamination, NASA cleaned the Viking landers until their total surface bioburden was no more than 3 × 105 bacterial spores, with an average of no more than 300 bacterial spores per square meter, and their total bioburden (surface, mated, and encapsulated for launch) was 5 × 105 spores. Each lander was then fully enclosed in a bioshield (resembling a large casserole dish) and baked in an oven at 111.7 degrees Celsius (233.1 degrees Fahrenheit) for 30 hours in a dry-heat sterilization procedure.
Among many investigations the landers carried out were three biology experiments designed to look for possible signs of life. Though scientists continue to debate over the meaning of their results, these experiments provided no clear evidence for the presence of living microorganisms in soil near the landing sites. The consensus was that Viking observations revealed a surface of Mars much drier and less benign than expected.
In 1992, the National Research Council’s Space Studies Board recommended easing forward contamination requirements for missions to Mars. NASA and the international Committee for Space Research subsequently altered their requirements for Mars lander missions, establishing the Viking presterilization surface bioburden standard as the requirement for Mars landers not attempting life detection experiments and the full Viking standard as the requirement for missions focused on life detection. Today, spacecraft going to any solar system body with the potential to support present-day Earth life must undergo stringent cleaning and sterilization.
Mars Polar Lander/Deep Space 2
The Mars Polar Lander mission, launched January 3, 1999, was intended to perform surface science and to sample and analyze water ice near the planet’s south polar cap. The mission also included two small Deep Space 2 probes, which were intended to impact the surface of Mars to perform sub-surface science and test new technologies. NASA lost contact with the lander and the probes upon their arrival at Mars on December 3, 1999.
This mission was classified Category IVa for planetary protection purposes. Since the lander and the probes were intended to contact the surface of Mars, they were subject to appropriate planetary protection requirements aimed at preventing forward contamination. Bioburden reduction for the lander met a requirement of less than 300,000 spores at launch, with a surface distribution of no more than 300 culturable bacterial spores per square meter of surface area. The bioburden on the lander was reduced by the alcohol wipe method, dry heat microbial reduction, and assembly in a class 100,000 cleanroom. The interior surfaces of the probes were also subject to planetary protection mission requirements. The probes were assembled in Class 100 clean benches, and integrated into an aeroshell that prevented recontamination of accountable interior surfaces. Much of the probe hardware was dry heat processed, although some encapsulated burden was not adequately subjected to this process. The effectiveness of this process was measured by microbial assay techniques.
For more information about Mars Polar Lander, see this page at the Science Mission Directorate website.
Mars Pathfinder was launched on December 3, 1996, landed at its destination on July 4, 1997, and delivered the small rover Sojourner to the surface of the planet. Since the Pathfinder Lander and Sojourner Rover were intended make contact with the surface of Mars, this mission was categorized Category IVa for planetary protection purposes, and subject to appropriate requirements for preventing forward contamination.
The Mars Observer spacecraft, launched on September 25, 1992, was intended to study the geology, geophysics, and climate of Mars. This mission was classified Category III for planetary protection purposes. NASA lost contact with the spacecraft in August 1993, just as it was about to enter orbit around Mars. Though the fate of Mars Observer is not known, it is possible that pieces of the spacecraft could have inadvertently impacted the surface of Mars, posing a risk of forward contamination.
For more information on Mars Observer, see this page at the Science Mission Directorate website.
Mars Global Surveyor
The Mars Global Surveyor orbiter was launched on November 7, 1996, and entered orbit about Mars on September 11, 1997. The mission has studied the Martian surface, atmosphere, and interior during the past eight years. This mission is classified Category III for planetary protection purposes, imposing specific limitations on the probability that any launched hardware would inadvertently impact Mars during a specified time period after launch. Global Surveyor’s orbit may be raised at the end of its mission to ensure against inadvertent entry into the planet’s atmosphere.
Mars Climate Orbiter
Mars Climate Orbiter (MCO), launched Dec. 11, 1998, was intended to function as an interplanetary weather satellite and a communications relay for the Mars Polar Lander. The MCO mission was classified Category III for planetary protection purposes. NASA lost contact with the MCO spacecraft on Sept. 23, 1999, upon its arrival at Mars. Though the cause of the loss of MCO is not certain, the spacecraft most likely inadvertently entered the atmosphere of Mars and probably burned up during entry. If, instead, MCO survived entry to impact the surface of Mars, the debris could pose the possibility of forward contamination. For more information on Mars Climate Orbiter, see this page at the Science Mission Directorate website.
The sun and the planets in our solar system are believed to have originated from the gravitational collapse of a cloud of gas, dust and ice. Scientists hope to learn more about the origin and nature of the planets by examining the solar wind, particles emanating from the surface of the sun.
NASA’s Genesis mission was launched in August 2001 to collect samples of the solar wind for return to Earth for laboratory analysis. After a three-year journey around the sun, the Genesis science canister landed in the Utah desert on September 8, 2004. Because of a parachute failure, the canister made a hard landing and cracked open upon impact. While scientists were concerned about the possible contamination of solar wind samples due to this breach of containment, no risk of biological contamination of the terrestrial environment was posed by the breach. The scientific consensus is that solar wind samples would not contain any biological contamination.
The canister was moved into a clean room at NASA’s Johnson Space Center where mission scientists began examaining its contents. Scientists have closely examined four Genesis spacecraft collectors, vital to the mission’s top science objective, and found them in excellent shape, despite the spacecraft’s hard landing. Further, more detailed scientific analyses of the samples returned by Genesis are planned.
This mission is classified Category V, unrestricted Earth return, for planetary protection purposes. The Genesis spacecraft’s sample collection hardware was cleaned and assembled in a Class 10 cleanroom, containing no more than one 10-micron-size particle per cubic foot of air. Solar wind samples collected and returned to Earth by Genesis have been stored and cataloged under ultra-pure cleanroom conditions, and are being made available to mission scientists for study.
NASA’s Galileo mission to Jupiter was launched on October 18, 1989, and arrived at Jupiter in December 1995. The spacecraft spent nearly eight years collecting vast amounts of scientific data on the planet and its moons.
The Galileo mission was classified Category II for planetary protection purposes, requiring documentation only reporting probabilities of impact, contamination control procedures used during assembly, and disposition of all launched hardware at completion of the mission. Microbiological assays were not required. Documentation included the Project Galileo Planetary Protection Plan, the Galileo Planetary Protection Pre-Launch Report, the Galileo Planetary Protection Post-Launch Report, and the Galileo Planetary Protection End of Mission Report.
The End of Mission Report included the option of taking steps to ensure that the spacecraft would not inadvertently impact a place of potential interest to astrobiological investigators. Because Galileo collected evidence of water on Europa, Ganymede and Callisto, this end-of-mission option was exercised. On September 21, 2003, mission managers sent Galileo into the atmosphere of Jupiter to burn up at the end of its operating life, thereby preventing inadvertent collision with and possible contamination of one of Jupiter’s icy moons.
Apollo Lunar Landing and Sample Return
NASA’s Apollo lunar spacecraft recovery procedures were designed to isolate spacecraft and astronauts from Earth’s biosphere. One gap in these procedures was that the crew would have to leave the command module upon return to Earth by opening the hatch and climbing into a recovery raft. To compensate, NASA provided astronauts biological isolation garments and applied biocide to the spacecraft. NASA abandoned crew quarantine requirements after the third lunar landing. Biological and chemical examination of returned samples of lunar material did not yield any evidence that life had ever existed on the Moon.
(From Where No Man Has Gone Before: A History of Apollo Lunar Exploration Missions, by W. David Compton, NASA Special Publication 4214, NASA History Series, 1989)
Sample Quarantine and Management
In 1965, the National Research Council’s Space Science Board (now the Space Studies Board) issued a formal statement that Earth must be protected from back contamination by any organisms that might be brought back from the Moon. Biological containment was thus established as necessary for Apollo lunar sample returns, and it was the most difficult requirement established for Apollo lunar sample handling. From construction of the Lunar Receiving Laboratory at NASA’s Manned Spaceflight Center (now Johnson Space Center) to Apollo mission operations, preventing contact between Earth’s biosphere and all objects and persons that had been to the Moon added to the cost and complexity of the Apollo program.
NASA’s first lunar landing mission, Apollo 11, returned nearly 21 kilograms (50 pounds) of lunar material to Earth. Apollo missions 11, 12, 14, 15, 16 and 17 all together returned a total of 382 kilograms (842 pounds) of lunar samples. NASA’s Apollo-era Lunar Receiving Laboratory was responsible for distributing samples to the scientific community, performing time-critical sample measurements, permanently storing a portion of each sample and testing samples, spacecraft and astronauts for contamination. The 8,000 square meter (86,000 square feet) facility employed remotely controlled manipulators to process samples in a sterile and chemically clean vacuum chamber. JSC also built a Sample Storage and Processing Laboratory to store samples securely and cleanly under nitrogen and prepare samples requested by researchers.
Today, NASA lunar sample curators are responsible for maintaining the sample collection and distributing samples for research and educational use. In 1994, JSC sample curation officials updated their tool and container cleaning procedures to replace freon cleaning fluid with new ultrapure water cleaning. JSC is constantly improving control of sample inventory, security and accountability as well.
(From 25 Years of Curating Moon Rocks, by Judy Allton, Lockheed Engineering & Sciences Company. See also: Chapter 7, “Lessons Learned from the Quarantine of Apollo Lunar Samples” in The Quarantine and Certification of Martian Samples (2002), Space Studies Board, National Research Council. Also see the Johnson Space Center’s Curator for Astromaterials Samples.)
For more information about lunar sample handling, see http://curator.jsc.nasa.gov/lunar/index.cfm.