"In the book, he has to spell out messages in rocks on the ground that the orbiters can photograph because there isn't enough space in his vehicle to haul the old rover landing platform around."
Did you even read the book????
He did not communicate with rocks because he couldn't fit the pathfinder in the rover with him, he fried it leaning the modified drill against the rover.
"- but the book is definitely worth a read." - Then I suggest you actually read it.