Earth is more massive than Mars, so its escape velocity is higher — which means that a much larger (therefore rarer) collision would have been needed to blast life-engendering material off Earth onto a Mars-intersecting orbit, rather than the other way around. Still possible, of course, but not as likely. And since Earth and Mars are both in free orbit around the sun, any collision debris would be also, and as likely to go outward from the sun as inward toward it..Besides, organic chemistry has been seen to be so common in the universe that it’s just as likely that life originated in both places — or maybe neither, and it was seeded from somewhere else — and survived wherever it found a comfy home. That doesn’t make it any less wonderful: even here, it took life a billion years to come up with anything as sophisticated as a slime mold, and another couple of billion to come up with plants, animals…and us, just yesterday or so (comparatively speaking)..I hope this doesn’t degenerate into another debate about Genesis and the Bible…it just isn’t necessary. Galileo said it best: the Bible tells how to go to Heaven, not how the heavens go. (Galileo was something of a smartass, which is the real reason he got in hot water with the Church at the time.)
Earth is more massive than Mars, so its escape velocity is higher — which means that a much larger (therefore rarer) collision would have been needed to blast life-engendering material off Earth onto a Mars-intersecting orbit, rather than the other way around. Still possible, of course, but not as likely. And since Earth and Mars are both in free orbit around the sun, any collision debris would be also, and as likely to go outward from the sun as inward toward it..Besides, organic chemistry has been seen to be so common in the universe that it’s just as likely that life originated in both places — or maybe neither, and it was seeded from somewhere else — and survived wherever it found a comfy home. That doesn’t make it any less wonderful: even here, it took life a billion years to come up with anything as sophisticated as a slime mold, and another couple of billion to come up with plants, animals…and us, just yesterday or so (comparatively speaking)..I hope this doesn’t degenerate into another debate about Genesis and the Bible…it just isn’t necessary. Galileo said it best: the Bible tells how to go to Heaven, not how the heavens go. (Galileo was something of a smartass, which is the real reason he got in hot water with the Church at the time.)