Actually, as discussed in a separate thread elsewhere on this forum, the parity explanation might have more to do with this than panspermia does;
see this link
http://query.nytimes.com/gst/fullpag...52C1A960948260
Note that I personally don't dismiss all forms of panspermia, especially lithopanspermia within planetary systems (and perhaps between member stars of a cluster) but that process, even if widespread, wouldn't explain the handedness of molecules in space.