Approach image of Vesta contrasting southern hemisphere (lower right) with northern hemisphere (upper left).
Shape model of southern hemisphere of Vesta showing complex structures, including the large south polar mountain, sinuous grooves, steep scarps and slumps.
NASA’s Dawn mission has been orbiting asteroid Vesta since mid-July – and scientists are overjoyed with what they are seeing!
For instance, the southern hemisphere of the asteroid boasts one of the largest mountains in the Solar System.
Other results show that Vesta’s surface, viewed at different wavelengths, has striking diversity in its composition particularly around craters. The surface appears to be much rougher than most asteroids in the main asteroid belt.
Preliminary results from crater age dates indicate that areas in the southern hemisphere are as young as 1-2 billion years old, much younger than areas in the north.
These and other findings were presented today at the European Planetary Science Congress (EPSC) and the American Astronomical Society’s Division of Planetary Sciences (DPS) – a joint meeting being held in Nantes, France.
Striking diversity
“We are learning many amazing things about Vesta, which we call the smallest terrestrial planet,” said Chris Russell, the Dawn Principal Investigator. “The south polar mountain 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 Dawn framing camera was built and is being operated by the Max-Planck Institute for Solar System Research (MPS), in cooperation with DLR, Berlin and the Technical University of Braunschweig.
That camera yields more information than black and white images suggest. The framing camera is equipped with seven color filters in order to collect spectral information. This makes it possible to highlight certain spectral features in false color maps that would not be visible to the naked eye.
The surface of Vesta has striking diversity when viewed in false colors that are ratios of light intensity at different wavelengths. Where the clear filter images show bright and dark features, the color data show these are also comprised of different materials, likely excavated by the impacts.
Unexpected result
Here’s a surprise. The difference in the number of craters between the two hemispheres is striking.
By counting the number of craters per unit area in different terrains, the relative ages of these different terrains can be obtained.
Preliminary results of these crater age dates indicate much younger ages for areas in the south versus the north, as young as 1-2 billion years old. So far, the oldest ages, in the northern hemisphere, are younger than 4 billion years old, which is an unexpected result given that meteorites from Vesta have ages of 4 billion years.
However, the crater counts will be refined with the more detailed data to be collected, and the assumptions about how the impact flux decays with time will be evaluated, so the absolute ages are preliminary.
“Vesta’s surface has a surprisingly complex set of structural features, including the massive south polar mountain, steep slopes, deep troughs, and sets of curved lineations that appear in some cases to be associated with slumps, or landslides,” explained Carol Raymond, Dawn’s Deputy Principal Investigator at NASA’s Jet Propulsion Laboratory in Pasadena, California.
Following a year at Vesta, Dawn will depart in July 2012 for asteroid Ceres, where it will arrive in 2015.
By Leonard David
