The Europa Jupiter System Mission – Laplace (EJSM/Laplace) was a proposed joint NASA

NASA

The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

/ESA unmanned space mission slated to launch around 2020 for the in-depth exploration of Jupiter

Jupiter

Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

's moons with a focus on Europa

Europa (moon)

Europa Slightly smaller than Earth's Moon, Europa is primarily made of silicate rock and probably has an iron core. It has a tenuous atmosphere composed primarily of oxygen. Its surface is composed of ice and is one of the smoothest in the Solar System. This surface is striated by cracks and...

, Ganymede

Ganymede (moon)

Ganymede is a satellite of Jupiter and the largest moon in the Solar System. It is the seventh moon and third Galilean satellite outward from Jupiter. Completing an orbit in roughly seven days, Ganymede participates in a 1:2:4 orbital resonance with the moons Europa and Io, respectively...

 and Jupiter's magnetosphere

Magnetosphere

A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...

. The mission would comprise at least two independent elements, NASA's Jupiter Europa Orbiter

Jupiter Europa Orbiter

As a part of the Europa Jupiter System Mission , the Jupiter Europa Orbiter is a proposed orbiter probe slated for lift-off in 2020 and planned for detailed studies of Jupiter's moons Europa and Io as well as the Jovian magnetosphere...

 (JEO) and ESA's Jupiter Ganymede Orbiter

Jupiter Ganymede Orbiter

As a part of the international Europa Jupiter System Mission , the Jupiter Ganymede Orbiter is a proposed orbiter probe by the ESA slated for lift-off in 2020. Plans for the mission include detailed studies of Jupiter's moons Ganymede and Callisto as well as the Jovian magnetosphere.-See...

 (JGO), to perform coordinated studies of the Jovian system.

In April 2011, ESA stated that it seemed unlikely that a joint US-Europe mission will happen in the early 2020s given NASA's budget, so ESA is investigating the possibility of proceeding with a European-led mission.