et al. 2004 suggests that in order for Mars to have had a functional dynamo, the Martian core was initially hotter by 150 K than the mantle (agreeing with the differentiation history of the planet, as well as the impact hypothesis), and with a liquid core potassium-40 would have had opportunity to partition into the core providing an additional source of heat. The model further concludes that the core of mars is entirely liquid, as the latent heat of crystallization would have driven a longer-lasting (greater than one billion years) dynamo. If the core of Mars is liquid, the lower bound for sulfur would be five weight %. Ganymede Ganymede has an observed magnetic field generated within its metallic core. Jupiter Jupiter has an observed magnetic field generated within its core, indicating some metallic substance is present. Its magnetic field is the strongest in the Solar System after the Sun's. Jupiter has a rock and/or ice core 10–30 times the mass of the Earth, and this core is likely soluble in the gas envelope above, and so primordial in composition. Since the core still exists, the outer envelope must have originally accreted onto a previously existing planetary core. Thermal contraction/evolution models support the presence of metallic hydrogen within the core in large abundances (greater than Saturn). Saturn Saturn has an observed magnetic field generated within its metallic core. Metallic hydrogen is present within the core (in lower abundances than Jupiter). Saturn has a rock and or ice core 10–30 times the mass of the Earth, and this core is likely soluble in the gas envelope above, and therefore it is primordial in composition. Since the core still exists, the envelope must have originally accreted onto previously existing planetary cores. Thermal contraction/evolution models support the presence of metallic hydrogen within the core in large abundances (but still less than Jupiter). Remnant planetary cores Missions to bodies in the asteroid belt will provide more insight to planetary core formation. It was previously understood that collisions in the solar system fully merged, but recent work on planetary bodies argues that remnants of collisions have their outer layers stripped, leaving behind a body that would eventually become a planetary core. The Psyche mission, titled “Journey to a Metal World,” is aiming to studying a body that could possibly be a remnant planetary core. Extrasolar As the field of exoplanets grows as new techniques allow