What's the best mode of transportation from Marseille Airport to Aix bus or train. Is the the train station adjacent to the Marseille airport?
The airport is about as far from Marseille as it from Aix. The Marseilles train station is in the middle of town. Look for the bus ranks as you come out the airport One will say Aix. Pay the driver about ten bucks. They leave every very frequently or even more often.
Marseille airport operates a very useful website http://www.marseille-airport.com/ You can see that there is a quick bus shuttle from the airport to Aix, where there are two train stations, one local and one for the TGV. No need to detour through Marseille itself.
There is a small train station adjacent to the airport for some local service, mostly to the southwest and including Avignon. You can find the details on whichever SNCF website you use such as http://en.voyages-sncf.com/en/