According to Birch, bombarding Venus with hydrogen and reacting it with carbon dioxide could produce elemental carbon (graphite) and water by the Bosch reaction. It would take about 4 × 1019 kg of hydrogen to convert the whole Venusian atmosphere, and such a large amount of hydrogen could be obtained from the gas giants or their moons' ice. Another possible source of hydrogen could be somehow extracting it from possible reservoirs in the interior of the planet itself. According to some researchers, the Earth's mantle and/or core might hold large quantities of hydrogen left there since the original formation of Earth from the nebular cloud. Since the original formation and inner structure of Earth and Venus are generally believed to be somewhat similar, the same might be true for Venus.