Of course they survive...
...but they're called 'Earthlings' now.
Paul Davies pointed out that an origin of life on Mars was probably easier than on Earth, and exchange of meteorite debris between the two guarantees they cross-infected each other. Mars probably even infected early wet-Venus and early 'hot'-Titan too. Whether anything survived the decline of clement weather on those two is fun speculation too - or so David Grinspoon reckons.
Adam
