Geoscience Reference
In-Depth Information
elongation to the Sun is 28
◦
. It is therefore visible for only 2 h at most and at
very low altitude either before sunrise or after sunset. This makes detailed
observations of the planet for large ground-based telescopes as well as the
Hubble Space Telescope very complicated or impossible, because none of
them can take measurements this close to the Sun. Nevertheless, only one
spacecraft, Mariner 10, ever visited Mercury about 30 years ago, perform-
ing three fly-bys in 1974-1975. During these short fly-bys Mariner 10 was
able to image about 45% of the planet's surface, to discover its unex-
pected magnetic field, the existence of gaseous species forming an exo-
sphere and the presence of a unique magnetosphere. However, nothing is
known about Mercury's interior structure or its elemental and mineralogical
composition.
Drawing conclusions on the formation and evolution of Mercury requires
a complete description of the planet and its environment. The BepiColombo
mission shall provide the detailed information necessary to understand Mer-
cury and its magnetospheric environment and to find clues to the origin
and evolution of a planet close to its parent star. In addition, the mission
provides unique possibilities for testing Einstein's theory of general rela-
tivity. The scientific background and the objectives of the mission have
been outlined in Refs. 1 and 2. The main issues to be addressed are as
follows
•
Origin and evolution of a planet close to its parent star.
•
Mercury's figure, interior structure, and composition.
•
Interior dynamics and origin of its magnetic field.
•
Exogenic and endogenic surface modifications, cratering, tectonics,
volcanism.
•
Composition, origin, and dynamics of Mercury's exosphere and polar
deposits.
•
Structure and dynamics of Mercury's magnetosphere.
•
Test of Einstein's theory of general relativity.
The complexity of these fundamental scientific objectives poses high
requirements on the payload of the mission. None of the objectives concern-
ing Mercury can be reached through measurements of any single instrument.
However, the combination of the measurements of the various instruments
aboard BepiColombo will provide answers to many outstanding questions
related to the origin and evolution of the innermost member of the group
of the terrestrial planets.
