E.T. in Quarantine - Isolating Extraterrestrial Material
By Jim Oberg
Special to
Quarantines can help a society protect itself from dangerous infections.
The word comes from the French, for the 40 days of isolation once faced by new arrivals who may have been infected. After the quarantine has passed, they were either certified to be disease-free - or dead.
Quarantining an entire planet against potentially harmful extraterrestrial diseases becomes more difficult.
Though the odds are minuscule, what,s needed to prevent something with global consequences? What protections are reasonable?
The launch of Stardust to retrieve a milligram of dust from the Wild-2 comet is the first human attempt to bring back extraterrestrial samples in almost three decades.
NASA would like to bring back samples from Mars in less than 10 years. Other comet missions are also on tap, and the Russians dream of retrieving samples from the Martian moons Phobos and Deimos.
Space Spores
There's also the renewed debate over natural transport, via meteorites and space dust.
A century ago, scientists used the term 'panspermia' to describe the possibility that spores could naturally pass from planet to planet. Today, space experts have asked themselves if the quarantine issue isn't already moot, since new evidence and computer simulations suggest there never has been biological isolation between planets.
Asteroid impacts on Earth, the moon and Mars have flung rocks off each world, circling the sun until they slam into a nearby world.
One extreme view is that life on Earth is the result of contamination from Mars. That smaller planet cooled earlier than Earth, and seems to have had oceans for hundreds of millions of years while Earth's surface was still molten.
Martian rocks bearing spores could have rained upon Earth until our oceans formed and provided a hospitable environment for a few lucky survivors.
Rain From Mars
Even today, a hundred tons of meteorites and space dust fall on Earth every day. About one-tenth of 1 percent of that - perhaps 100 kilograms per day - is from Mars. Four billion years ago, during what planetary scientists call the Period of Heavy Bombardment, there would have been much, much more.
But could microorganisms survive these interplanetary journeys?
During a conference on Mars exploration in Boulder, Colo., last August, retired Swedish industrialist Curt Mileikowsky discussed the work of a European team that evaluated exactly these prospects. The group considered hazards such as shock and heating during ejection off the planet's surface, cosmic rays and heat-induced DNA decay while en route, and heating during impact at the end of the journey.
For some meteorites, the Europeans were astonished to discover that microbial survival rates could be very high even for trips that lasted up to a million years.
While it's commonly thought that meteorites falling to Earth are thoroughly seared by the heat of atmospheric entry, this is a misconception. The outer skin may be burned off during the very brief fireball phase, but most of the meteorite's interior remains at the subfreezing temperature of deep space.
Freshly fallen meteorites, far from being red hot, often have frost on them from condensation. Any microbial passengers would have a gentle landing.
Hazards From Related Life
If ancient Mars life also left modern descendants at home, the biohazard to its cousins on Earth is much higher than that from two independent strands of life. In a 1994 article entitled 'Is It Dangerous To Return Samples From Mars To Earth?,' Carl Sagan wrote: "If putative Martian organisms were originally transferred to Mars by collisions with the Earth, they may be enough like us that they could be pathogenic." The same argument holds if the transfer was from Mars to Earth. Whether Mars had - or has - life that's related to Earth life, some sort of quarantine is called for. NASA has implemented some protocols for its Mars samples, but the issue includes more than just that planet. Last year, the National Research Council in Washington, D.C., issued a report on the 'biological potential' for samples from other solar system bodies, and concluded that while some sources could be judged entirely nonhazardous, others - including comets - still require protective measures.
S Sterilization
Stardust scientists insist that their collecting - high-speed impact of cometary dust grains into the fine aerogel collectors - will automatically sterilize the recovered material. Test results back this up - at least for what we keep calling 'life as we know it.'
Some scientists remain unconvinced that current protections are good enough.
A new group called the International Committee Against Mars Sample Return recently launched a Web site discussing its concerns, with links to other documents on planetary quarantine.
Barry DiGregorio, co-founder of the group, says he's concerned that NASA may relax its standards of Mars samples. One idea even described a special-purpose space station designed to process extraterrestrial samples in absolute isolation from Earth's biosphere - a quarantine for the Space Age.
James Oberg spent 22 years as a rocket scientist for NASA, and has written eight books and numerous articles on space flight.
Life on the Moon, Maybe
It's commonly thought that on at least one occasion, infectious germs were brought back from the moon.
This occurred on the Apollo 12 mission in November 1969, when the crew retrieved pieces of the Surveyor 3 robot that had been on the moon for two years. Subsequent culturing of swabs from various locations gave one positive result - viable Streptococcus mitus spores were picked up from a swab rubbed inside the Surveyor's camera case.
Microbiologists weren't all that startled by the finding, since the temperatures inside the hardware on the lunar surface had stayed well within the range that microbial spores were known to tolerate, even if it had also been in a vacuum (and viable spores have been retrieved from spacecraft brought back after months or even years in Earth orbit).
Unfortunately, the technician collecting the lunar swabs back in 1969 was seen to violate isolation protocol by laying the new swabs down on a non-sterilized table surface. So the positive results could have been caused by somebody sneezing in the room the previous day.
Even though it's intriguing that the one positive was the sample taken from the most sheltered interior location of the hardware, the finding must be chalked up as interesting if true, and left to dangle in perpetual ambiguity.