Hm, you're right, largest chunks are said to be several meters in diameter. They'd probably have to drag the rings with a ginormous net to achieve the same vol

Hm, you're right, largest chunks are said to be several meters in diameter. They'd probably have to drag the rings with a ginormous net to achieve the same volumes. For propulsion, I would go with a solar sail. Use it to get the craft to the rings, then it becomes a net to scoop up the water ice, and the craft could harvest the water for fuel to get home. You could get a whole army of these things flying back and forth, and within a century or so, Mars could, as you suggest, become terraformed.