Solar system life may turn turn out t chemically similar. That is because it arose on one body, then cross-infected other other bodies by meteorite transfer over many millions of years.
Mars became geologically stable before Earth, so it could have been the earliest place for life. Then Martian meteors infected Earth.
How could a meteor have launched from Mars and reached Earth? It stretches my mind to imagine a situation where a meteor drops down, picks up life, then drops it off on the next planet. Are there records of meteoric impacts like that?
The best situation I can think of is a catastrophic volcanic explosion which launches a chunk of the planet into space, but that still sounds far-fetched to me.
Mars became geologically stable before Earth, so it could have been the earliest place for life. Then Martian meteors infected Earth.