[RightWhale]

Perhaps they could meet only for dinner, or only for Sunday dinner. Or by appointment. Probably they will have few opportunities to work together since there would be nothing to do aside from keeping up the journals and running some inane experiments for some scientists two hundred million miles away.

[BenLurkin]

Meeting for meals would be ideal, along with opportunities for some low key competitive and cooperative pursuits.

Chess would be my choice (if they ever decide to send a fat old guy into space), or cards, playing music, forming a small choir -- maybe they could vie for who has the best results in keeping in good physical condition.