Yes, a high chance, if the planet has habitats for life and the spacecraft hits one of them. Because there are many species of microbes, including extremophiles, that can survive almost anywhere but are also found on our skin, in the soil etc and are found in spacecraft assembly rooms. Even in a hospital, even in an operating theater, there are numerous species of microbes. It's almost impossible to get rid of them completely with modern technology - just reduce numbers.
Heat sterilization does it, but you either have to make it very hot, or else, heat the spacecraft for a long time - and both methods can destroy modern electronics or put delicate components out of shape etc. And then - you have the problem, how do you make sure it doesn't get re-infected, even if you do get it completely sterilized?
So far we don't have any way of sterilizing a spacecraft completely. The best sterilized spacecraft ever were the two Viking landers, which were sterilized through heat treatment in a low temperature oven. But they still had an estimated 30 viable cultivable spores on the exterior of the spacecraft and could potentially have a hundred times that many non cultivable dormant microbes. Because of the hostile conditions on Mars, the requirement nowadays is reduction to 300,000 spores over entire spacecraft, though if it goes to a region where there might be habitats for life, then it's back to the Viking requirements (so far no spacecraft been sent sterilized to Viking levels since Viking).
It is more of an issue if you send a spacecraft to somewhere with liquid water habitats which it could contact directly.
If the planet doesn't have any habitats, then no chance, because there's nowhere for the life to reproduce. In that case, the life on the surface would just sit there dormant until eventually, over several hundred thousand years, it is all sterilized by cosmic radiation.
This is the basis of planetary protection and why our spacecraft are sterilized.
They classify the destinations for spacecraft in our solar system according to whether there is any chance of Earth life surviving there, or whether it is of direct interest for study of evolution or origin of life.
So, it's with Category IV that you need to take great care not to introduce life. Requirements depend on the mission. For instance if there are habitats for life there, but the mission doesn't go anywhere near them, then requirements are less. If it is a life detection mission or there's a chance of it coming into contact with a habitat where life can survive then has to be thoroughly sterilized.
For more about this, see Planetary protection
Heat sterilization does it, but you either have to make it very hot, or else, heat the spacecraft for a long time - and both methods can destroy modern electronics or put delicate components out of shape etc. And then - you have the problem, how do you make sure it doesn't get re-infected, even if you do get it completely sterilized?
So far we don't have any way of sterilizing a spacecraft completely. The best sterilized spacecraft ever were the two Viking landers, which were sterilized through heat treatment in a low temperature oven. But they still had an estimated 30 viable cultivable spores on the exterior of the spacecraft and could potentially have a hundred times that many non cultivable dormant microbes. Because of the hostile conditions on Mars, the requirement nowadays is reduction to 300,000 spores over entire spacecraft, though if it goes to a region where there might be habitats for life, then it's back to the Viking requirements (so far no spacecraft been sent sterilized to Viking levels since Viking).
It is more of an issue if you send a spacecraft to somewhere with liquid water habitats which it could contact directly.
If the planet doesn't have any habitats, then no chance, because there's nowhere for the life to reproduce. In that case, the life on the surface would just sit there dormant until eventually, over several hundred thousand years, it is all sterilized by cosmic radiation.
This is the basis of planetary protection and why our spacecraft are sterilized.
They classify the destinations for spacecraft in our solar system according to whether there is any chance of Earth life surviving there, or whether it is of direct interest for study of evolution or origin of life.
- Category I, such as the Sun or Mercury, no requirements at all. Of no interest for study of evolution, and no chance of Earth life surviving there.
- Category II, if it has significant interest for study of evolution and origins of life, but remote chance of contamination compromising the investigations. So that's the Moon, Venus, comets, and undifferentiated asteroids. In that case, no need for sterilization, and just simple documentation of what the mission did, impact site, etc.
- Category III - flybys or orbiters, protection mainly by trajectory biasing - making sure that your spacecraft is never on a trajectory that would lead to it hitting the object. Also may have some element of sterilization such as clean room assembly and bioburden reduction.
- Category IV - landers on an object that may have habitats for life. So far main ones here are Mars, Europa and Enceladus. But quite a few are "provisional category II" e.g. Ceres. Where it's not known for sure if there are habitats for life there or not. With discovery of water plume from Ceres, they decided that we have to avoid impact of a spacecraft onto its surface, so Dawn will go into a permanent orbit around Ceres instead for planetary protection reasons.
So, it's with Category IV that you need to take great care not to introduce life. Requirements depend on the mission. For instance if there are habitats for life there, but the mission doesn't go anywhere near them, then requirements are less. If it is a life detection mission or there's a chance of it coming into contact with a habitat where life can survive then has to be thoroughly sterilized.
For more about this, see Planetary protection
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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