Hubble Images of Asteroids Help Astronomers Prepare for Spacecraft Visit

Jun 20, 2007
Hubble Images of Asteroids Help Astronomers Prepare for Spacecraft Visit
These Hubble Space Telescope images of Vesta and Ceres show two of the most massive asteroids in the asteroid belt, a region between Mars and Jupiter. The images are helping astronomers plan for the Dawn spacecraft's tour of these hefty asteroids. Credits for Vesta: NASA; ESA; L. McFadden and J.Y. Li (University of Maryland, College Park); M. Mutchler and Z. Levay (Space Telescope Science Institute, Baltimore); P. Thomas (Cornell University); J. Parker and E.F. Young (Southwest Research Institute); and C.T. Russell and B. Schmidt (University of California, Los Angeles) Credits for Ceres: NASA; ESA; J. Parker (Southwest Research Institute); P. Thomas (Cornell University); L. McFadden (University of Maryland, College Park); and M. Mutchler and Z. Levay (Space Telescope Science Institute)

Telescope images of Vesta and Ceres show two of the most massive asteroids in the asteroid belt, a region between Mars and Jupiter. The images are helping astronomers plan for the Dawn spacecraft's tour of these hefty asteroids.

On July 7, NASA is scheduled to launch the spacecraft on a four-year journey to the asteroid belt. Once there, Dawn will do some asteroid-hopping, going into orbit around Vesta in 2011 and Ceres in 2015. Dawn will be the first spacecraft to orbit two targets. At least 100,000 asteroids inhabit the asteroid belt, a reservoir of leftover material from the formation of our solar-system planets 4.6 billion years ago.

Dawn also will be the first satellite to tour a dwarf planet. The International Astronomical Union named Ceres one of three dwarf planets in 2006. Ceres is round like planets in our solar system, but it does not clear debris out of its orbit as our planets do.

To prepare for the Dawn spacecraft's visit to Vesta, astronomers used Hubble's Wide Field Planetary Camera 2 to snap new images of the asteroid. The image at right was taken on May 14 and 16, 2007. Using Hubble, astronomers mapped Vesta's southern hemisphere, a region dominated by a giant impact crater formed by a collision billions of years ago. The crater is 285 miles (456 kilometers) across, which is nearly equal to Vesta's 330-mile (530-kilometer) diameter. If Earth had a crater of proportional size, it would fill the Pacific Ocean basin. The impact broke off chunks of rock, producing more than 50 smaller asteroids that astronomers have nicknamed "vestoids." The collision also may have blasted through Vesta's crust. Vesta is about the size of Arizona.

Previous Hubble images of Vesta's southern hemisphere were taken in 1994 and 1996 with the wide-field camera. In this new set of images, Hubble's sharp "eye" can see features as small as about 37 miles (60 kilometers) across. The image shows the difference in brightness and color on the asteroid's surface. These characteristics hint at the large-scale features that the Dawn spacecraft will see when it arrives at Vesta.

Hubble's view reveals extensive global features stretching longitudinally from the northern hemisphere to the southern hemisphere. The image also shows widespread differences in brightness in the east and west, which probably reflects compositional changes. Both of these characteristics could reveal volcanic activity throughout Vesta. The size of these different regions varies. Some are hundreds of miles across.

The brightness differences could be similar to the effect seen on the Moon, where smooth, dark regions are more iron-rich than the brighter highlands that contain minerals richer in calcium and aluminum. When Vesta was forming 4.5 billion years ago, it was heated to the melting temperatures of rock. This heating allowed heavier material to sink to Vesta's center and lighter minerals to rise to the surface.

Astronomers combined images of Vesta in two colors to study the variations in iron-bearing minerals. From these minerals, they hope to learn more about Vesta's surface structure and composition. Astronomers expect that Dawn will provide rich details about the asteroid's surface and interior structure.

The Hubble image of Ceres on the left reveals bright and dark regions on the asteroid's surface that could be topographic features, such as craters, and/or areas containing different surface material. Large impacts may have caused some of these features and potentially added new material to the landscape. The Texas-sized asteroid holds about 30 to 40 percent of the mass in the asteroid belt.

Ceres' round shape suggests that its interior is layered like those of terrestrial planets such as Earth. The asteroid may have a rocky inner core, an icy mantle, and a thin, dusty outer crust. The asteroid may even have water locked beneath its surface. It is approximately 590 miles (950 kilometers) across and was the first asteroid discovered in 1801.

The observations were made in visible and ultraviolet light between December 2003 and January 2004 with the Advanced Camera for Surveys. The color variations in the image show either a difference in texture or composition on Ceres' surface. Astronomers need the close-up views of the Dawn spacecraft to determine the characteristics of these regional differences.

Source: Space Telescope Science Institute

Explore further: Two families of comets found around nearby star Beta Pictoris

add to favorites email to friend print save as pdf

Related Stories

Feds: Don't expect winter to be polar vortex redux

30 minutes ago

(AP)—Federal forecasters don't expect a return of frequent cold blasts from the polar vortex this winter. Nor should the weather system that blocked rain from California last winter come back.

WASP has printer, will travel, to make houses

34 minutes ago

At Maker Faire Rome, an Italian 3D printer company is demonstrating a tall, portable machine that will bring 3D-printed dwellings to impoverished countries. WASP has been exploring low-cost solutions to ...

Cadavers beat computers for learning anatomy

14 minutes ago

Despite the growing popularity of using computer simulation to help teach college anatomy, students learn much better through the traditional use of human cadavers, according to new research that has implications ...

Cell architecture: Finding common ground

37 minutes ago

When it comes to cellular architecture, function follows form. Plant cells contain a dynamic cytoskeleton which is responsible for directing cell growth, development, movement, and division. So over time, changes in the cytoskeleton ...

Recommended for you

New window on the early Universe

17 hours ago

Scientists at the Universities of Bonn and Cardiff see good times approaching for astrophysicists after hatching a new observational strategy to distill detailed information from galaxies at the edge of ...

Chandra's archives come to life

19 hours ago

Every year, NASA's Chandra X-ray Observatory looks at hundreds of objects throughout space to help expand our understanding of the Universe. Ultimately, these data are stored in the Chandra Data Archive, ...

New robotic telescope revolutionizes the study of stars

20 hours ago

In the last 8 months a fully robotic telescope in Tenerife has been carrying out high-precision observations of the motion of stellar surfaces. The telescope is the first in the SONG telescope network and ...

User comments : 0