If they can't communicate with each other, why would they want to meet?
Assuming Mars is featureless (if it has features, they can both climb Olympic mons, for instance, as Mike Ash already said) and they cannot leave Mars (if hey do, they could have agreed before to meet in a bar in, say, Paris), the solutions I can think of all are a bit impractical:
- both dig a hole to the center of Mars and wait there for the other to arrive.
- both spread themselves out over half the area of Mars.
- both self-replicate until they cover the surface.
- at least one of them starts annihilating Mars.
If they are allowed to discuss strategy beforehand, the following will work:
Both walk straight ahead along a great circle. When (not if; great circles cannot not intersect and not be the same) they meet the trail of the other, the slower one stops at the intersection, and waits for the faster one to return on its path.
It's easier to go to the North or South Pole, instead of the center of the planet, because you don't have to dig so much. As a guide you can use a gyrocompass that don't need a magnetic field for orientation: http://en.wikipedia.org/wiki/Gyrocompass IANARS
Assuming Mars is featureless (if it has features, they can both climb Olympic mons, for instance, as Mike Ash already said) and they cannot leave Mars (if hey do, they could have agreed before to meet in a bar in, say, Paris), the solutions I can think of all are a bit impractical:
- both dig a hole to the center of Mars and wait there for the other to arrive.
- both spread themselves out over half the area of Mars.
- both self-replicate until they cover the surface.
- at least one of them starts annihilating Mars.
If they are allowed to discuss strategy beforehand, the following will work:
Both walk straight ahead along a great circle. When (not if; great circles cannot not intersect and not be the same) they meet the trail of the other, the slower one stops at the intersection, and waits for the faster one to return on its path.