The existence of water on Mars has long been a subject of curiosity and debate. A recently published study presents compelling evidence of ancient “wave ripples” in rocks that were shaped by Martian water and winds billions of years ago.
These ripples, imprinted on the Martian surface, speak to a time when shallow bodies of water were open to the Martian air.
Asteroid ejecta from Mars has reached Earth so many times, we can assume the opposite has happened too. So if Mars was warm and wet, it seems likely it was seeded with life from Earth. This suggests another question, did life on Earth arrive from elsewhere via this method?