Science with EJSM-Laplace
EJSM-Laplace will carry out an in-depth study of the Jovian system and its four largest satellites, with particular emphasis on Ganymede and Europa. It will utilize two spacecraft, the Jupiter Ganymede Orbiter (JGO) and the Jupiter Europa Orbiter (JEO), flying on complementary trajectories and carrying complementary instruments. The mission sets out to achieve the following science objectives: characterize Ganymede and Europa as planetary objects and potential habitats; study Ganymede, Europa, Callisto and Io in the broader context of the system of Jovian satellites; and focus on the science of Jupiter itself including the planet, its atmosphere, magnetosphere, irregular satellites and rings. The two spacecraft will also investigate, in depth, complex couplings with the Jovian system.
Jupiter is the archetype for the giant planets of the Solar System and for the numerous giant planets now known to orbit other stars. Moreover, Jupiter's diverse Galilean satellites - three of which are believed to harbour internal oceans - are central to understanding the habitability of icy worlds.
Understanding the Jovian system and unravelling its history, from its origin to the possible emergence of habitable environments, will give us a better insight into how gas giant planets and their satellites form and evolve. In addition, new light should be shed on the potential for the emergence of life in Jupiter-like exoplanetary systems.
The EJSM-Laplace mission will address two themes of ESA's Cosmic Vision programme: What are the conditions for planet formation and emergence of life? and How does the Solar System work?
Internal oceans - habitable worlds?
The overarching theme for EJSM-Laplace is to “study the emergence of habitable worlds around gas giants". Of particular interest is how the Jovian system came to have such diverse components and how much this is affected by interactions between them. In particular, EJSM-Laplace aims to characterize the conditions that might have led to the emergence of two internally active ocean-bearing worlds, Europa and Ganymede, with particular reference to the gravitational coupling of Io, Europa and Ganymede (the so-called Laplace Resonance), playing a role in tidally heating the satellites — the primary heat source for these moons.
To further understand the Galilean satellites as a system, Europa and Ganymede are singled out for detailed investigation as they provide a natural laboratory for comparative analysis of the nature, evolution, and potential habitability of icy worlds. The primary focus is on an in-depth comparative analysis of their internal oceans, current and past environments, surface and near-surface compositions, and their geologic histories. Objectives for studying the other two Galilean satellites, Io and Callisto, have also been defined and EJSM-Laplace will study these objects with a resolution and coverage far beyond what was achieved by the Galileo mission between 1989 and 2003. In addition, a broader study of Jupiter's atmosphere and magnetosphere will take place to complement the more in-depth analysis of the system's individual components.
The two orbiters will first trace out a trajectory around Jupiter that includes many flybys of the Galilean moons before diverging, with JEO orbiting Europa and JGO encircling Ganymede. These two moons have many geophysical similarities as well as some important differences. With EJSM-Laplace, it will be possible to perform an in-depth comparison of this pair of "false twins", to understand the origin of their geophysical dichotomy and to better understand the unique characteristics of Ganymede and Europa with emphasis on their habitability.
Science synergies with two spacecraft in the Jupiter system
The fact that EJSM-Laplace consists of two separate spacecraft offers unique opportunities for synergistic and complementary observations that will significantly enhance the overall science return of the mission. Studying the moons separately will also provide an unprecedented opportunity for comparative planetology of icy satellites. The provisional mission timeline foresees both JEO and JGO co-operating in the Jovian system, but their arrival times will be staggered and they will have different trajectories. This provides the opportunity for the following synergistic science:
Specific science goals for JGO
The main science objectives of JGO can be summarized as follows: