Philosophical Society of Washington

Minutes of the 2137th Meeting


Speaker: John Rummel, Planetary Protection Officer, National Aeronautics and Space Administration
Topic: “Protecting All of the Planets, All of the Time”

President McDiarmid called the 2137th meeting to order at 8:15 p.m. on November 30, 2001. The Recording Secretary read the minutes of the 2136th meeting and they were approved.

The speaker for the evening was John Rummel, Planetary Protection Officer, National Aeronautics and Space Administration. The title of his presentation was “Protecting All of the Planets, All of the Time”.


Earth formed in the solar nebula about 4.5 gigayears ago, and by 3.5 gigayears ago there were photosynthetic bacteria, known from microfossils found in the Warrawoona Group of Western Australia. These may have been similar to present-day cyanobacteria. Using sunlight, cyanobacteria break water into hydrogen to reduce carbon and produce the waste product oxygen, so that from 4.5 to 0.5 gigayears ago Earth's atmosphere evolved from having less than 0.01% to 21% O2. Earth is a living planet. The predominant form of life is microbial. There is almost no extreme environment on Earth where life has not been found. Life has been found in hydrothermal vents at 250 Atm pressure and more than 113°C, in geothermal vents at 100°C, in hot deserts and Antarctic dry valleys, in mine seepage at pH less than 1, in subsurface rocks more than 3 km deep, in rocks more than 1 km below the seafloor, and in areas exposed to more than 5 megarads of ionizing radiation. Through spacecraft observations we are learning that environments capable of supporting Earth-life may, indeed, exist elsewhere within our Solar System.

From what we have learned about Mars, a planet that seems to have had the same opportunity, we must question why life didn't also get started there. Missions up to and including Mariner 9 showed that Mars has craters, polar “ice” caps, and what appear to be ancient riverbeds. The Viking Landers found sufficient water vapor in the atmosphere to form frost, determined that the polar caps were composed of carbon dioxide and water, and that the soil was highly oxidized, iron-rich clay. The life detection experiments were designed and conducted by the Viking Biology Team, which included a group led by Gil Levin [see PSW Meeting 2127 Minutes ]. The results of those three experiments were equivocal and are still being debated, but most of the team were convinced that the results from the Gas Chromatograph/Mass Spectrometer of Klaus Biemann were due to chemistry, not biology. The Mars Pathfinder mission in 1997 was a “proof of concept” for planetary landing and roving robot exploration. The Mars Global Surveyor produced photos of Noachis Crater with features like riverine channels, possibly of recent origin, that are comparable to features on the same scale in photos of Mount St. Helens. The Mars Odyssey is now in its aerobraking phase. Its missions are to map mineralogy and surface morphology, to map elemental composition at the surface and the abundance of hydrogen in the subsurface, and to measure near-space radiation. Plans call for two rovers to be launched in 2003 and land in 2004. Another orbiter will launch in 2005. In 2007 unmanned Scout missions are planned to conduct activities such as drilling and seismometry, and could possibly launch balloons or airplanes. Sometime around 2014, there may be a sample return mission.

We are using our understanding about life in extreme environments on Earth to design new efforts to look for life elsewhere. The strategy for finding evidence of life on Mars should be “follow the water”. Chris McKay believes that when life was emerging on Earth, there was abundant water on Mars. Meteorite ALH 84001, which came from Mars, contains carbonates that must have formed in water. Those carbonates contain microscopic forms suggestive of, but much smaller than, cells, but may be artifacts of sample preparation for electron microscopy.

Exploration of the Jovian system has shown us other worlds where life might be found. The moon Europa may have water oceans as deep as 100 km under ice as deep as 20 km. The deepest ocean on Earth is 11 km; there may be twice as much water on Europa as there is on Earth. There are tides and surface melting with disruptions giving the appearance of faults and “ice rafts”. A computer generated movie of the topographic features visible in photographs show extended ice faults that look much like the New Jersey Turnpike (without tolls). The European Huygens probe carried aboard the NASA Cassini Mission will be targeted in 2004 to study the massive atmosphere of the moon Titan.

We also are planning the Stardust mission to return cometary and cosmic dust in 2006.

As we learn more about these environments, the need to avoid contamination becomes more compelling. The NASA Planetary Protection Policy (NPD 8020.7E) is (1) to preserve planetary conditions for future biological and organic constituent explorations, and (2) to protect Earth and its biosphere from potential extraterrestrial sources of contamination. This policy follows Article IX of the Outer Space Treaty of 1967. For both scientific and ethical reasons, we must prevent “forward contamination” from any biological presence on Earth spacecraft. Simple prudence dictates that we prevent “back contamination” of the Earth from any extraterrestrial sample through failure of containment or hazard analysis. When Mars samples are returned, recommendations formulated in 1997 provide that

  1. samples should be contained and treated as hazardous until proven safe;
  2. if sample containment cannot be verified in route, the sample and craft should be sterilized in space or not returned to Earth;
  3. the integrity of sample containment should be maintained throughout reentry and retrieval;
  4. the distribution of unsterilized samples should occur only if analysis determines they are not hazardous; and
  5. planetary protection measures adopted for the first sample should not be relaxed until there is a thorough scientific review.

No humans will land on Mars until it is well established that there are no biological hazards.



Mr. Rummel kindly answered questions from the floor. President McDiarmid thanked Mr. Rummel for the society, and welcomed him to its membership. The President made announcements about volunteers for office, the next meeting, parking, and refreshments, and adjourned the 2137th meeting to the social hour at 9:38 p.m.

Attendance: 37
Temperature: 9.7°C
Weather: cloudy
Links: Charter of the Planetary Protection Advisory Committee
JPL Planetary Protection Homepage

Respectfully submitted,
 
John S. Garavelli
Recording Secretary

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