Here's onfo on communications from Mars and the rovers to earth.
It's a "dog" circuit-wise,, but...
FRom the JPL NASA site
http://marsrovers.jpl.nasa.gov/mission/comm_data.html How Fast and How Much Data the Rovers Can Send Back
The data rate direct-to-Earth varies from about 12,000 bits per second to 3,500
bits per second (roughly a third as fast as a standard home modem). The data
rate to the orbiters is a constant 128,000 bits per second (4 times faster than a
home modem). An orbiter passes over the rover and is in the vicinity of the sky
to communicate with the rovers for about eight minutes at a time, per sol. In
that time, about 60 megabits of data (about 1/100 of a CD) can be transmitted
to an orbiter. That same 60 megabits would take between 1.5 and 5 hours to
transmit direct to Earth. The rovers can only transmit direct-to-Earth for at most
three hours a day due to power and thermal limitations, even though Earth may
be in view much longer.
Mars is rotating on its own axis so Mars often "turns its back" to Earth, taking
the rover with it. The rover is turned out of the field of view of Earth and goes
"dark", just like nighttime on Earth, when the sun goes out of the field of view of
Earth at a certain location when the Earth turns its "back" to the sun. The
orbiters can see Earth for about 2/3 of each orbit, or about 16 hours a day. They
can send much more data direct-to-Earth than the rovers, not only because
they can see Earth longer, but because they can operate their radio for much
longer since their solar panels get light most of the time, and they have bigger
antennas than the rovers.