London, May 25 : A new study has expressed concerns about other star systems being contaminated by Earth microbes, which might be present on spacecrafts traveling to extra-solar planets.
According to a report in New Scientist, the study has been done by Charles Cockell of the Centre for Earth, Planetary, Space and Astronomical Research at Open University in Milton Keynes, UK.
Cockell says that though technology needed to send a robotic probe to another solar system is far in the future, it's not too soon to start thinking about how to avoid contaminating extra-solar planets with hitchhiking microbes from Earth.
As to why interstellar contamination should be avoided, according to Cockell, it might be the utilitarian desire to preserve examples of other life of potentially enormous scientific interest.
In previous writings, he has also argued that humans have an ethical responsibility to avoid harming life in other solar systems.
There may also be a legal issue in this case, as far as NASA is concerned.
According to Cassie Conley, NASA's planetary protection officer, the 1967 outer space treaty stipulates that countries should avoid "harmful contamination" of the Moon and other celestial bodies.
To respect the treaty, NASA follows guidelines for planetary protection set out by a Paris-based group of international experts called the Council on Space Research (COSPAR), which advises the United Nations and promotes international cooperation on space research.
In practical terms, this means NASA sterilizes spacecraft heading for potentially habitable locations in the solar system.
Though the issue of interstellar planetary protection has not come up at NASA yet, according to Conley, the same principle of avoiding contamination would probably be applied to any mission to another star system.
Interstellar missions may even be easier to sterilize than interplanetary ones. The extra travel time provides more exposure to space radiation, which gradually kills off stowaways.
This should get rid of any microbes clinging to the four NASA spacecraft that are already on their way out of the solar system, which include the Pioneer 10 and 11 and Voyager 1 and 2 probes.
These spacecraft are simply coasting on momentum left over from their investigations of the outer solar system, and were not targeted towards any particular star systems.
"Given the tiny volume of space that planets occupy in the universe, it is unlikely that any of them will intersect with a planet, let alone one that is habitable," said Cockell.
But, if future spacecraft are deliberately sent towards habitable planets around other stars, there is a possibility of an "unplanned interception" - an unintentional crash landing, in other words, which could deliver Earth microbes to such a planet.