What now looks like a blurry potato should, within nine months, blossom into detailed pictures of Vesta, the brightest asteroid in the sky. This view (at right) is one of several taken by the Hubble telescope’s Wide Field Camera 3 to provide a better look at the space rock before the arrival of the Dawn spacecraft in July 2011.
“The latest Hubble images refine our understanding of Vesta and will help define the mission,” says planetary scientist Richard Binzel of the Massachusetts Institute of Technology in Cambridge.
The Dawn mission, which will also visit the asteroid Ceres in 2015, will be the first to explore large main belt asteroids in detail. It is expected to shed light on the earliest objects in our inner solar system, similar to those that subsequently became the building blocks for larger bodies, such as Earth.
Hubble’s images were taken at various points during Vesta’s 5.34-hour rotation period and show features approximately 40 kilometers in size, including a previously described crater that covers around 80% of Vesta’s diameter. Analysis of the pictures reveal the asteroid’s tilt is approximately four degrees more to the east than previously thought, a fact that will need to be taken into account when planning for Dawn’s arrival.
“When you have a spacecraft on its way you want to be as smart about your destination as possible,” says Binzel.
Vesta is only the third solar system object (other than the moon and Mars) where scientists have a laboratory sample of its surface, in the form of meteorites that fell to Earth following the impact that created Vesta’s giant crater. Indeed, some researchers estimate that about 5 percent of all meteorites have their origin at Vesta.
Spectroscopic images reveal that Vesta’s surface is mostly basaltic rock, a remnant of lava flows from early in the asteroid’s formation. This view stands in contrast to the idea that asteroids are cold, dead rocks and will be explored in detail by Dawn.
“Vesta has been an enigma for decades; it’s hard to believe that we’re almost there,” says Binzel.
Image: NASA/ESA/STScI/UMd