14 DAY TRIAL // There are already several tens of spacecrafts wandering through the solar system, each one a possible carrier of microbes originating on Earth. It's no secret that some life forms on Earth are extremely resilient to space radiation and may possibly reach other planets and their moons to colonize them. In the case of these vehicles there is nothing much that we can do to prevent a future contamination, although researchers believe that the human race has the responsibility to prevent a possible contamination of any extrasolar planets we might visit.
Of course, the technology today would require at least several tens of thousands of years to reach the closest star system, Proxima and Alpha Centary, but the possible appearance of future faster space propulsion systems and the problem of a potential contamination with Earth life are still concerning issues. But why is this aspect so important?
"There is the utilitarian desire to preserve examples of other life of potentially enormous scientific interest", says Charles Cockell from the Center fro Earth, Planetary, Space and Astronomical Research at Open University. The general worry is that Earth life would somehow come to compete with alien life in other solar systems, possibly destroying it in the process.
So, in 1967 a treaty was issued saying that countries involved in space operations should try as much as possible to prevent the contamination with life of other celestial bodies except Earth. This meant that any spacecraft visiting a possibly habitable environment in the solar system must be sterilized.
In the meantime, NASA learned that some spacecrafts, such as those sent to the surface of Mars, don't necessarily require sterilization since the ultraviolet radiation coming from the Sun would kill any microbial life within several centimeters beneath the surface of the planet. In the case of the Phoenix Mars Lander however, sterilization is critical. The spacecraft expected to land tomorrow on the surface of the Red Planet, will have the role of digging in the ice crust in the vicinity of the north pole. Also, there is evidence that ice may eventually melt from time to time in that specific location, possibly creating a habitable environment for microbial life.
In the case of planets in the solar system the issue is settled, although it turns out that in the case of extrasolar planets NASA has no protocol regarding the possible contamination with Earth life. "We currently don't have a policy for that", Conley said. The same principle should apply, especially if we take into consideration that sterilizing interplanetary spacecrafts may be even simpler than in the case of spacecrafts in the solar system, since the long exposure to space radiation should kill the vast majority of microbes traveling along with it.
Spacecrafts such as the Pioneer 10 and 11 or Voyager 1 and 2, which have already exited the solar system should in fact be completely sterilized by now, even though it is highly unlikely that they will ever reach a distant exoplanet, considering that they were never intended to do so.
With the help of faster propulsion technology, says Cockell, spacecrafts would get lower and lower exposure to space radiation, meaning that microbes such as Deinococcus radiodurans could easily survive a trip to another solar system. To ensure that the spacecraft is completely sterilized as it enters another solar system, Cockell proposes for it to be heated up while en route to ensure that any trace of DNA is destroyed by the time the final destination is reached.