[jmyeet]

I've seen one estimate that 1% of Mercury's mass is sufficient to build a full Dyson Swarm around the Sun.

That's part of what makes Dyson Swarms attractive: planets are incredibly inefficent uses of mass in terms of living area created.

Why Mercury? It's metal-rich, has no atmosphere, has relatively low mass and energy is incredibly abundant due to proximity to the Sun.

Many seem to think we would need to dismantle the Solar System. We do not.