AstroNews: Messenger - Sonde bei Merkur

January 30, 2008
Surprises Stream back from Mercury's MESSENGER

After a journey of more than 2.2 billion miles and three and a half years, NASA’s MESSENGER spacecraft made its first flyby of Mercury just after 2 PM Eastern Standard Time on January 14, 2008. All seven scientific instruments worked flawlessly, producing a stream of surprises that is amazing and delighting the science team. The 1,213 mages conclusively show that the planet is a lot less like the Moon than many previously thought, with features unique to this innermost world. The puzzling magnetosphere appears to be very different from what Mariner 10 discovered and first sampled almost 34 years ago.

Mercury, Venus, Earth, and Mars are terrestrial (rocky) planets. Among these, Mercury is an extreme: the smallest, the densest (after correcting for self-compression), the one with the oldest surface, the one with the largest daily variations in surface temperature, and the least explored. Understanding this "end member" among the terrestrial planets is crucial to developing a better understanding of how the planets in our solar system formed and evolved. To develop this understanding, the MESSENGER mission, spacecraft, and science instruments are focused on answering six key outstanding questions that will allow us to understand Mercury as a planet.

Mercury's density implies that a metal-rich core occupies at least 60% of the planet's mass, a figure twice as great as for Earth! MESSENGER will acquire compositional and mineralogical information to distinguish among the current theories for why Mercury is so dense.

Only 45% of the surface of Mercury has been imaged by a spacecraft! Using its full suite of instruments, MESSENGER will investigate the geologic history of Mercury in great detail, including the portions of the planet never seen by Mariner 10.

Mercury has a global internal magnetic field, as does Earth, but Mars and Venus do not. By characterizing Mercury's magnetic field, MESSENGER will help answer the question of why the inner planets differ in their magnetic histories.

Through a combination of measurements of Mercury's gravity field and observations by the laser altimeter, MESSENGER will determine the size of Mercury's core and verify that Mercury's outer core is molten.

At Mercury's poles, some crater interiors have permanently shadowed areas that contain highly reflective material at radar wavelengths. Could this material be ice, even though Mercury is the closest planet to the Sun? MESSENGER will find out.

MESSENGER will measure the composition of Mercury's thin exosphere, providing insights into the processes that are responsible for its existence.

Die Texte stammen von der Messenger-Homepage, die viele weitere Infos, Bilder, Filme etc. enthält!http://messenger.jhuapl.edu/index.php