One of the major reasons for scheduling work during the Martian daylight hours is because them Mars dune doggies is solar-powered. If they run them at night they will use battery power which will not be replenished until the sun do come up again, one night and 39 minutes later. Much better to save the batteries for night-time emergencies like going out for

KSR came up with a good scheme for those 39 minutes. In his novels the clocks just stopped for 39 minutes then took off again!