Rosetta - Scientific aims

As comets have not yet been analyzed in-situ, many questions concerning their structure and composition still remain unanswered. Therefor, the scientific objectives of the Rosetta mission are the followings:

• a global characterization of the nucleus
• the determination of its dynamic properties
• the surface morphology and composition
• the determination of chemical, mineralogical and isotopic compositions of volatiles and refractories in the cometary nucleus
• the determination of the physical properties and interrelation of volatiles and refractories in the cometary nucleus
• studies of the development of cometary activity and the processes in the surface layer of the nucleus and inner coma, that is dust/gas interaction
• studies of the evolution of the interaction region of the solar wind and the outgassing comet during perihelion approach

The interaction between the comet and the solar wind can be characterized by plasma properties as for example plasma waves plasmaboundaries. It depends on the solar wind intensity, on the comets outgassing rate increasing with its vicinity to the sun and its potentially intrinsic magnetic field. The magnetic properties of comets could hint at its own origin: Up to now, it is not yet well understood, how and why dust and ice stuck together to form comets. Magnetic attraction could possibly have contributed to this process. Hence, both the orbiter as the lander are equipped with a combined

Numerical simulations of the particle densities and magnetic field strengths nearby the comets nucleus in 1.75 Astronomical Units distance from the sun. Click to enlarge.

plasma and magnetometer experiment (RPC onboard the orbiter and ROMAP onboard the Lander). To estimate the required instruments sensitivity, numerical simulations concerning the interactions between the solar wind plasma and the comets ionosphere were performed at the Institut for Theoretical Physics. They shed light on the plasmaphysical environment of the comets nucleus. Besides the electromagnetic field distribution also energy spectra of the involved ion species are computed by these simulations. According to these simulations, C-G has to be classified as a "weak comet", meaning that the qualitative conditions in the plasma environment are significantly different in comparison to the classical description of a strong comet. Therefore, the simulations provide precious assistance at the mission planning as well as at the interpretation of the measurement results.