One of the biggest challenges of deep space exploration is communicating over links spanning distances of solar system scale. Compared to a typical commercial link between a geostationary satellite and a user on the Earth's surface, which spans a distance of roughly 40,000 km (25,000 mi), a link between Mars and Earth can be up to 4 × 10⁸ km (2.5 × 10⁸ mi), and links to a Jupiter spacecraft can approach 10⁹ km (6 × 10⁸ mi). Because the performance of a communications system scales inversely as the square of link distance, these deep-space links pose unique problems and, in many cases, fundamentally limit the quantity of scientific data that can be returned.