It is alleged that Szmielew proved that Pasch's axiom is a consequence of the circle axiom. The source is said to be

The Pasch axiom as a consequence of the circle axiom, Bull.Acad.Polon.Sci.Sér.Sci.Math.Astronom.Phys.18 (1970), 751-758

But I don't have a copy of this yet.