That is certainly a possibility. However contamination of Mars will make coming to that conclusion, if the evidence points to it, a great deal harder.
(Well, obviously contaminating Mars is itself panspermia, but not really of the interesting sort. A confirmed instance of "natural" panspermia would tell us a lot about what we can expect about the distribution of life throughout the universe.)
(Well, obviously contaminating Mars is itself panspermia, but not really of the interesting sort. A confirmed instance of "natural" panspermia would tell us a lot about what we can expect about the distribution of life throughout the universe.)