In article , Robert Casey
writes:

Contests working Earth-Mars contacts should be interesting, when
you remember that speed'o light means that radio signals take
about 5 to 15 minutes one way to make the trip...

If my math is right, the one-way transmission time works out to between 188
seconds at closest approach to 688 seconds maximum.

But you can count on contest ops to figure a way to make that work. Use the
transmission time as a 'buffer' of sorts. Not a problem.

SO2R is just the beginning.

73 de Jim, N2EY