Possibilities:
1. Mercury: No moonphase, because mercury has no moon; should be a special alloy because temperatures fluctuate between _180 and + 420 °C, some sort of titanium will do. Mercury rotates in 58 days so there will be a lot of numbers on your dial; i suggest 58 mercurian hours(days).
2. Venus: No moonphase too, A feminin watch with diamonds and a pink bracelet. Here there will be a problem because venus rotates around the sun every 225 days, but one day takes 243 earth-days. Think we'd better ask mr. Dufour how to solve this one.
3. Earth -no possibility.
4. Mars: Watch must be sand resistant and i guess a little bit water resistant 3atm will do since we are not sure there really is water on mars. A day takes 24 hours and 36 minutes so i guess we take a common watch and slow it a bit down. Ofcourse it becomes more difficult if you want a moonphase since mars has two moons ... and they're actually rocks with a strange shape; we'd better skip moonphases.
5 to 9 (saturn, jupiter .... pluto): No moonphase at all, these planets have way too many moons. Can you imagine a dial with 63 moonphases for jupiter, that would be a very big challenge for our best watchmakers
I would go for option 4: Mars is not that far away and has a lot of advantages: Maybe you can see the earth explode; maybe there's water, maybe there really is life on mars .... and i would definitively take the Breguet La Tradition in pink gold with the brown leather bracelet with me.
I hope this answers your quest-ion.
Greetings,
Filip