I'm not ruling out giant marauding space worms that get attracted to the CO2 enriched atmosphere and end up breaking down the entire crust into sterile lumps no

I'm not ruling out giant marauding space worms that get attracted to the CO2 enriched atmosphere and end up breaking down the entire crust into sterile lumps no bigger than a tortoise, before then leaving for fresh new planets to scour of all life. Not over that sort of timescale anyway. Over that sort of timescale, 'probably' is all we've really got.