Astronomers have measured the temperature near the cloudtops of Saturn to be about –143 °C (–225 °F). This temperature increases with depth because the gases are compressed to dramatically greater pressures at depth. Computer models predict that Saturn’s core is as hot as 10,000 °C (18,000 °F). Saturn is about 10 times as far from the Sun as Earth is, so Saturn receives only about 1/100th (1%) as much sunlight per square meter as does Earth. Nevertheless, Saturn is warmer than would be expected if there were a balance between the solar energy absorbed and the energy emitted. Mysteriously, Saturn emits 80% more energy than it absorbs from sunlight. Unlike the rocky Earth and the more massive Jupiter, Saturn should not have any heat left over from its original formation. Thus, there must be a source of heat inside Saturn producing the excess energy. One theory is that the energy comes from the friction of liquid helium raining down in the interior of the planet. Cassini scientists will be exploring Saturn’s energy balance for answers to this puzzle.