Before revision: Potential ressource extraction NASA has speculated on the feasibility of mining the atmospheres of the outer planets, particularly for helium-3, an isotope of helium that is rare on Earth and could have a very high value per unit mass as thermonuclear fuel.Robert Zubrin, Entering Space: Creating a Spacefaring Civilization, section: Settling the Outer Solar System: The Sources of Power, pp.
After revision: Potential resource extraction NASA has speculated on the feasibility of mining the atmospheres of the outer planets, particularly for helium-3, an isotope of helium that is rare on Earth and could have a very high value per unit mass as thermonuclear fuel.Robert Zubrin, Entering Space: Creating a Spacefaring Civilization, section: Settling the Outer Solar System: The Sources of Power, pp.