Very cool. The real trick is going to be observing such a thing without affecting it.
@ Bereft_of_Faith - Regarding relativity, the state of the crystal will vary depending on the observer's motion relative to the crystal.
@ IAmFirst - Sure, the definition of a unit of time is arbitrary, just as the definition for a unit of length or mass, but during those 19 revolutions of Mars, 35 years worth of seconds will have still passed, on Earth as well as on Mars.