NASA’s Dawn mission has been orbiting Vesta since mid-July. Vesta is the second most massive asteroid in orbit around the Sun. The asteroid’s southern hemisphere, imaged in false colors above, has one of the largest mountains in the Solar System. Other results show Vesta’s surface is diverse in its composition, much rougher than most asteroids in the main asteroid belt. Crater ages suggest areas in the south are 1-2 billion years old, much younger than areas in the north. The findings were presented October 12 at the annual meeting of the Geological Society of America in Minneapolis. A report was also given to the Europlanet Research Infrastructure meeting October 3.
More results of these Science Reports are below⬇
The Dawn scientists have identified two impact basins at the south polar region. Here they are marked with circles. One is older evidenced by a smoother terrain from effects of the debris from the more recent impact crater complex. The newer one has been named Rheasilvia. The centers of these two craters appear to coincide with the grooved structures found around the equatorial region. There are two grooved regions of different ages. The older grooves are related to the older impact basin and the newer ones are related to Rheasilvia. Some grooves are over 350 km long and about 30 km wide.
A cross section diagram shows the changes in elevation across Rheasilvia.
Scientists have used previous images to model and create an oblique side view of the central peak in the center of the image above. The perspective is as viewed from the left side of the image. The foreground feature in this gray scale image is the central peak, one of the highest in the solar system. It is larger than the big island of Hawaii, the largest mountain on Earth, as measured from the ocean floor. It is almost as high as the highest mountain in the solar system, the shield volcano Olympus Mons on Mars. The peak rises about 13 miles (22 kilometers) above the average height of the surrounding terrain. The distant feature is a cliff, or scarp, probably due to a landslide and visible in the color image just right of center.
If you have a pair of Red-Blue 3-D glasses, you can view this anaglyph image which creates the perception of height and depth of this same central peak on Vesta. Put the Red filter in front of the left eye and Blue in front of the right eye. I suggest you get some good ones and spend time viewing NASA's large stereo imaging collections.
|Here is an anaglyph of the scarp which is the other prominent feature in the south polar region.|
“We are learning many amazing things about Vesta, which we call the smallest terrestrial planet,” said Chris Russell, the Dawn Principal Investigator. “Like Earth, Mars, Venus and Mercury, Vesta has ancient basaltic lava flows on the surface and a large iron core. It has tectonic features, troughs, ridges, cliffs, hills and a giant mountain. ”
“We completed that (survey at 2700 km) phase at the beginning of September and since then have been moving the spacecraft to its next mapping orbit, the High Altitude Mapping Orbit at 680 km altitude, which it reached on the weekend. Over the coming month it will return complete coverage of the sunlit surface with a resolution of 60 meters,” said Carol Raymond, Dawn’s Deputy Principal Investigator.
Dawn's framing camera, built and operated by the Max-Planck Institute for Solar System Research (MPS), in cooperation with DLR, Berlin and the Technical University of Braunschweig, provides much more information than the black and white images. It is equipped with seven color filters in order to collect spectral information. Features can be highlighted in false color maps not visible to the naked eye. These false color variations are indicative of different surface materials. The color variations are particularly strong around craters. Where the clear filter images show bright and dark features, the color data show these are also comprised of different materials, particle sizes, and ages likely excavated by the impacts.
“One of the most prominent colour features on Vesta’s surface is associated with a 40 km diameter crater near Vesta’s equator. It shows a spectacular red ejecta blanket to the south. We believe that this eject blanket, which covers only a half-circle, has been created by an impactor hitting the surface on a trajectory of oblique incidence,” said Andreas Nathues of MPS.
What Is Ahead For Dawn?
Dawn's mapping of Vesta from an altitude of about 680 kilometers (420 miles) is going very smoothly. It has completed its first cycle of 10 orbits in which the principal objective was to acquire images looking straight down. The spacecraft will begin a new cycle of observing the surface at an angle to provide images scientists will use to create topographic maps and stereo images. In December, there will be another science report of this phase.
Dawn will then descend to low orbit gathering higher resolution imaging and data from the other instruments. Reports on that phase are likely in March 2012.
In July 2012, Dawn will leave orbit around Vesta and proceed to the largest asteroid, Ceres, for a similar orbiting and mapping mission.
I will try to keep you posted as things happen.