These layers evidence that Comet 67P originated from Mars and that Comet 67P was not presolar (presolar: before the sun), for the following reasons:
1. The space is nearly vacuum.
2. The comet has no magnetism/volcano/river/ocean/lake.
3. Therefore, the comet cannot form numerous layers by itself. Such layers should have been formed somewhere else.
4. In our solar system only Mars has the features of Comet 67P, as both of them have ice, organics, animals fossils, and layers of rock, but lack active magnetic fields ( note 1 ). So, such layers should have come from Mars instead of other planets or their moons.
5. Mars did not exist before the sun was formed.
Note 1: In our solar system, only Mars and Venus have no active magnetism. Venus has no ice, owing to its temperature of 462 degrees Celsius. All other planets and their moons have magnetic fields. Ref.: www.reddit.com/r/askscience/comments/1yehec/do_all_the_pl..and