Yes, they're rocks that happened to end up on another planet after being thrown out into space by particularly large impactors. This would rule out most life, b

Yes, they're rocks that happened to end up on another planet after being thrown out into space by particularly large impactors. This would rule out most life, but there's still a chance that extremophiles and even some multicellular organisms capable of hibernating in the rock might have survived the trip, similar to ancient microbes and tapeworms locked away in the arctic being able to revive upon reaching survivable conditions again.