You raise a good question about the ancient gases trapped within the rock chemically matching those of Mars’ *recent* atmosphere. The rock is believed to have been blasted off of Mars roughly 16 million years ago by an impact. So even if they have dated the gases to 16 million years ago (I have no idea what age they have for the gases), the atmosphere could have changed since then, although there really hasn’t been much going on on Mars for its atmosphere to have changed very much, especially within the past 20 million years or so. Earth’s atmosphere changes due to the huge amount of biologic, volcanic and other complex activity we have here. Our atmosphere is also much denser than Mars’ thin and comparatively simple one.
Two possible view:
1. God didn’t create a dead universe.
or
2. What are the chances of a rock, sitting on earth for millions of years, not being contaminated with fossils from life on earth?