OP doesn't suggest anywhere in the question that we forward-contaminate other celestials, or indeed that we do that on any that it could possibly matter. E.g. we've inadvertently already done that on the Moon during the Apollo missions. Neither does OP suggest any mode of preserving the genetic makeup of life on Earth. It's entirely possible to construct such a
Noah's ark that would sterilize any samples if breach of a sealed environment is detected. It is also possible to send it to such a place where this would happen naturally with exposure to the environment. —
Noordung ♦ 22 mins ago