LONDON: When the first Apollo astronauts returned from the moon, they were kept in quarantine. Remember Richard Nixon talking to Neil Armstrong through the window of the isolation module? Millions were spent ensuring that alien micro-organisms could not infect us.

In other tests, lunar soil was injected into mice and birds, and moon dust was rubbed on to plants to see whether anomalous growth occurred. Nothing untoward was noted. The moon was sterile, so far as could be seen. That is obvious now but in the 1960s, the question exercised much agitation within the US Public Health Service.

The next set of astronauts did bring back bacteria not carried on the outward trip. But they were Earthly microbes. In November 1969, Apollo 12 landed just 170 yards from Surveyor 3, a robotic craft that had achieved the first soft lunar landing by an American probe two-and-a-half years before. Parts from the TV camera on Surveyor 3 were brought back by the astronauts, under sterile conditions, and between 50 and 100 living micro-organisms were extracted from the polyurethane foam insulation that covered its interior circuit boards.

These were identified by bacteriologists as being of the strain streptococcus mitis, a benign bacterium found in the nose and throat. You have around 10 billion in your mouth alone. The astronauts ferried back the contents of a sneeze by a worker assembling Surveyor 3.

The point, however, is important. The microbes did live, in the frigid conditions and vacuum of space, for years after leaving the more hospitable environment in which they originated. Might we unwittingly do the same, seeding presently sterile, but potentially life-supporting, planets with terrestrial micro-organisms?

There are several reasons we would not want to do this. If there are indigenous life forms on Mars, or in the icy ocean of Jupiter’s moon Europa, terrestrial life could supplant them, just as rabbits have displaced small marsupials in Australia. Or our viruses and bacteria could infect and kill them, just as the common cold and syphilis were imported to the Americas and the Pacific islands by early seafarers, with devastating consequences. Infecting a planet would limit our ability to discover extraterrestrial life.

Thirty-five years ago, our moon was the only place humans were aiming to tread, but now there are plans for manned missions to Mars within decades. Probes carrying astronauts to asteroids have also been proposed. The time is right for more strict guidelines on planetary protection to be drawn up, and this task has been undertaken by a joint team of Cospar and the International Astronomical Union.

A mission from the mid-1970s provides the benchmark. When Nasa sent two robotic Viking landers to Mars, both had been sterilized to a level comparable to the best operating theatre.

And the lesson of the bacteria from Surveyor 3 is that microbes can survive for extended periods in space, and then proliferate on Earth.—Dawn/The Guardian News Service.