Long journey to Mars in hard vacuum and under UV radiation makes it very unlikely, but bacteria spores are very resilient to harsh conditions. I think it is sti

Long journey to Mars in hard vacuum and under UV radiation makes it very unlikely, but bacteria spores are very resilient to harsh conditions. I think it is still theoretically possible. There are a few papers on this. https://www.ncbi.nlm.nih.gov/m/pubmed/11539977/ https://www.ncbi.nlm.nih.gov/m/pubmed/11539977/