Mars bar?

N.A.S.A. has announced that despite possessing any other qualities deemed essential to qualify them for selection as part of a group planned to be among the first humans to land on planet Mars, anyone also known to be an Extrovert by nature need not waste their time applying for consideration.

The contention is that displaying those tendencies on an extremely long and closely confined voyage would become insufferable for people of more austere needs and demeanour.