Exploration of Jupiter its first Large mission, replacing its contribution to EJSM, the "Jupiter Ganymede Orbiter" (JGO). The partnership for the Europa Jupiter System Mission has since ended, but NASA will continue to contribute the European mission with hardware and an instrument. The "Europa Clipper" is a mission proposed to NASA to focus on studying Jupiter's moon Europa. In March 2013, funds were authorized for "pre-formulation and/or formulation activities for a mission that meets the science goals outlined for the Jupiter Europa mission in the most recent planetary decadal survey". The proposed mission would be set to launch in the early 2020s and
Moons of Mars satellites, Earth had one and Jupiter had four (known at the time), that Mars by analogy must have two. Furthermore, as they had not yet been discovered, it was reasoned that they must be small and close to Mars. This would lead Swift to making a roughly accurate estimate of their orbital distances and revolution periods. In addition Swift could have been helped in his calculations by his friend, the mathematician John Arbuthnot. Voltaire's 1752 short story "Micromégas", about an alien visitor to Earth, also refers to two moons of Mars. Voltaire was presumably influenced by Swift. In recognition of