September 27, 2013
NASA’s Dawn Spacecraft Provides More Answers On Asteroid Vesta
[ Watch the Video: Asteroid Vesta Visited By NASA's Dawn Spacecraft ]
Michael Harper for redOrbit.com – Your Universe Online
The asteroid Vesta, the second largest in the asteroid belt, has been particularly interesting to astronomers since it was first discovered in 1807. Early observations by the Hubble telescope showed the asteroid was mostly composed like Earth; complete with a crust, mantle and core. It was also discovered that the color and composition of Vesta’s surface often change as it rotates on its axis.
Intrigued by this rock, NASA launched the Dawn spacecraft towards Vesta to get an up-close view. Dawn orbited the asteroid between 2011 and 2012 before heading off to the dwarf planet Ceres. Now NASA researchers are comparing the images taken by Dawn with images from the Hubble telescope and say the two sets closely resemble one another. What the Hubble couldn’t come up with, however, was the mineral composition of Vesta and an explanation of why these minerals change color. These explanations and more are now described in a published paper in the journal Icarus.
"A generation of scientific questions framed on the basis of lower-resolution data have been resolved by visiting Vesta with Dawn," said Christopher Russle, Dawn’s principal investigator.
"We chose to go to Vesta because the ground-based telescopes and, later, Hubble told us it was an interesting place. That was true, but we needed Dawn to discern the mineral distribution and history of Vesta's surface. We now know how these data sets tie together and complement each other. This will help us in our telescopic studies of other members of our solar system."
One of Dawn’s discoveries includes the presence of hydrated minerals on the surface of Vesta. The 2012 mission did not find any presence of water, but did present evidence to suggest other passing asteroids and rocks may have bumped into Vesta, distributing their hydrogen-rich minerals on its surface.
Dawn also confirmed the presence of a large impact basin on the south pole of Vesta, a discovery previously made by the Hubble telescope. Dawn took these discoveries one step further by providing detailed images of the crater Rheasilvia, revealing just how light and dark the materials located within are. Furthermore, images from the spacecraft revealed an older impact basin below Rheasilvia that contains plenty of dark and carbon rich materials. NASA researchers now believe the lightest and most vibrant of the materials found on Vesta are native to the rock, while the darker stuff is made of remnants from other rocks that impacted the asteroid in space.
"When Dawn got to Vesta, it showed us how accurate Hubble's data were about Vesta," explained Jian-Yang Li, a Planetary Science Institute researcher and Dawn participating scientist. "And it also showed us how Vesta was so much more interesting up-close."
This new research was good news for the NASA scientists as it yet again proved the Dawn mission to Vesta successful, as well as demonstrated the accuracy of the Hubble telescope.
Dawn is now in the middle of a two-and-a-half year journey to the dwarf planet Ceres. After arriving at Vesta in 2011 and snapping pictures as it orbited for over a year, a special and hyper-efficient ion propulsion engine propels the Dawn spacecraft. This works by using electricity to ionize xenon that generates thrust. NASA now says Dawn will arrive at Ceres in early 2015.