Why prophet married aisha.

[remy]

Sayyidah Aisha said: ‘When a girl is nine years old, she is a woman (meaning, she has attained puberty).’ (Tirmidhi, Hadith 1109).

If you believe that bullshit you are as bad as fucking mohammed....except mohammed has no more contemporary evidence for his existence than jesus so you are pretty much out there on your own.

Perhaps you want to make a bit study about the science of hadith. There's a lot of read about how hadith work you know.
http://en.wikipedia.org/wiki/Hadith_studies
http://en.wikipedia.org/wiki/Introductio..._of_Hadith

Basically there're three types of hadith : authentic, weak (dhaif) and even false (maudhu').

The key of this science lies in it's sanad (chain of narrators) and matan (arabic content). I know not much about the detail, because it's quite a big field, plus i am not even a scholar.

except mohammed has no more contemporary evidence for his existence

what kind of evidence do you want.