Dawn Closing in on Vesta

NASA’s Dawn spacecraft is closing in on its target, the asteroid Vesta, which NASA describes as a “protoplanet” that almost formed into a planet.

Dawn is designed to go into orbit around Vesta on July 18. NASA announced today that the spacecraft is now using cameras instead of radio signals for navigation as it requires more precise measurements to achieve orbit. After a year in orbit at Vesta, the spacecraft is expected to travel to another large body, Ceres. It should arrive there in 2015.

Vesta and Ceres are the largest bodies in the asteroid belt, which lies between Mars and Jupiter. Ceres actually is currently designated a “dwarf planet” rather than an asteroid. Vesta is approximately 530 kilometers wide, big for an asteroid, but not big enough to be a dwarf planet like Ceres, which is about 950 kilometers in diameter (though there is debate about its size). The dwarf planet designation was created by the International Astronomical Union (IAU) in 2006 when Pluto was “demoted” from being a planet. The IAU now classifies Ceres, Pluto, Eris, Makemake and Haumea as dwarf planets and expects more to join the list as new discoveries are made and more is learned about existing known objects.

Scientists want to study asteroids and their dwarf planet cousins because they provide clues about the earliest days of solar system formation and because asteroids have collided with Earth in the past and are expected to do so in the future. The more that is known about the various types of asteroids, the better equipped scientists will be in determining how to deflect or destroy one before it wreaks destruction on our planet.