The consensus view is that although the risk of harmful back contamination is likely to be zero, the risk is not demonstrably zero: consequently, any returned samples from Mars must be treated as potentially biohazardous until scientists determine that the returned samples are safe.
The risk of harmful back contamination is likely to be zero. The risk is not demonstrably zero. The consensus view is this. Any returned. This was consequently. Samples from Mars must be treated as potentially biohazardous. The returned samples are safe. Scientists determine this.