First game I started under 90b had me, playing the Terrans, start off in the Cari system. Earth was named Cari 1, not earth. The Caris home world was Cari 2 (Mars equivalent). I have a save demonstrating this if need be.

If all races get their homeworld systems in thie beta as in previous, then I would guess that when the Minor Cari race spawned, it selected "Mars" (or some other world in the Terran Home System), and renamed the system after the new, more famous occupants. However this situation came about, it really sucked for a player (my!) start, because it meant I didn't even have the Terran's Mars to settle as a bonus small world.