MASTER F2/F3 mission - background information
Introduction
This mission includes both a Mars and an asteroid fly-by and will make full use of the capabilities of the Mars Express spacecraft. The Mars fly-by, needed to gain extra speed ("delta V") to reach the Main Belt Asteroids, offers a unique opportunity to carry out remote observations and possibly to deploy landers to the Martian surface. The asteroid part of the mission starts after the Mars fly-by, when the MASTER spacecraft is inserted into a trajectory that will lead it to fly-by one or more asteroids. Several asteroids were considered in the course of the study each of them offering different mission scenarios. However, Vesta is by far the most appealing among the inner main belt objects.
The MASTER mission, Mars and Asteroid Vesta fly-by
Asteroid Vesta
Vesta is the third largest asteroid, and orbits the Sun at 2.4 AU. The 520 km diameter of Vesta leads us to believe that this asteroid has undergone mineralogical differentiation during its accretion phase, making it similar to a miniature planet. Vesta's surface spectral reflectance is unique in the asteroid belt and it is thought that Vesta might be the parent body of all basaltic achondrite meteorites. Its albedo of 0.38 is higher than that of any other asteroid and its surface has a patchy appearance. Indeed, HST observations have lead to the discovery of a 460 km impact basin. This is characterised by a pronounced central peak protruding from the crater floor, located at a negative elevation of 12 km. The presence of the impact basin supports the idea that Vesta is responsible for the birth of the so-called "Vestoids". This is a cluster of V-type asteroids extending from the region surrounding Vesta to the edge of the 3:1 resonance at 2.5 AU. These small V-type objects, which are considered as ejecta from the impact basin, can be rapidly transferred to Earth crossing orbits from the chaotic 3:1 resonance region. There are therefore convincing observational and dynamic grounds to believe that Vesta is indeed the actual parent body for the suite of basaltic achondrite meteorites (howardites, eucrite and diogenites, the HED group). As such Vesta would represent one of only four known Solar System bodies for which actual rock samples are available in terrestrial laboratories. In conclusion, Vesta is a small world frozen in time at a unique and unexplored epoch of early Solar System formation and evolution. Because it is the smallest surviving body to have undergone terrestrial processes such as heating, melting and differentiation, the space-borne exploration of Vesta will reveal unique clues to early planetary evolution of the Earth, Moon, Mars, Venus and Mercury.
Scientific objectives and payload
The scientific objectives of the MASTER mission at Vesta are multiple; this is thanks to the low relative velocity of the asteroid fly-by (about 3 km/s). The determination of the size, shape, mass, density, rotation speed, pole orientation and magnetic environment will provide us with a physical characterisation of Vesta. A medium angle camera, a flux gate magnetometer and a plasma package will address these objectives. The surface will be studied morphologically with a resolution of about 30m/pixel, mineralogical and chemical investigation will also be conducted using an IR spectral reflectance imaging photometer and an X-ray spectrometer. The internal structure of the asteroid will be investigated with radio science techniques with the aim of investigating the presence and size of a core.
Netlander probes
MASTER also provides a great opportunity to put Europe in a leading position in the exploration of Mars by carrying and deploying the four probes called NETLANDERS to the surface of the red planet. A European Consortium formed by a large number of ESA member states will provide these well-known probes, dedicated to the seismological, meteorological and mineralogical investigation of Mars.