A geological map of minor planet Vesta has been released by NASA, revealing a body riddled by the impact of countless impacts, taking place over billions of years.
Vesta has a mean diameter of around 325 miles, roughly the size of the state of Arizona. This rocky body revolves around the Sun, between the orbits of Mars and Jupiter, once every 1,325 days.
The topographical and geological map was developed from images collected by the Dawn spacecraft, operated by NASA. That vehicle launched on September 27, 2007, on a mission to explore the minor planets Vesta and Ceres. The spacecraft examined Vesta between June 2011 and September 2012, and is expected to rendezvous with Ceres in April 2015. The 3D maps allowed researchers to develop a time scales, comparing impacts on the asteroid to those seen on the Moon and other celestial bodies.
Investigation of the maps reveal Vesta was occasionally impacted by large objects, which left behind sizable craters. Rheasilvia and Veneneia were formed soon after the formation of the asteroid, while the crater Marcia was the result of a later impact.
Astronomers develop geological histories of rocky bodies by carefully studying features in the surface. However, placing an age to certain markings on the minor body remains elusive. The few samples of Vesta available to scientists do not contain the mineral compound howardite-eucrite-diogenite (HED), which would have allowed for reliable dating.
"So figuring out an actual date in years is a step-by-step-by-step process. We work with rock samples from the moon, mostly from Apollo missions decades ago. These give actual dates for large lunar impacts," David Williams of the School of Earth and Space Exploration division at Arizona State University, said.
This method required researchers to develop a process to connect the age of impacts on Vesta to those on the Moon. This was estimated using a pair of processes, which generated radically different ages for the impact sites on Vesta.
The map is color-coded to differentiate major varieties of landscapes. The Veneneia impact, created eons ago through collision with a large object, is seen in purple. The youngest surface features are seen in green and yellow, while the oldest surfaces are marked in brown.
Comets developed during the formation of the solar system, and most have remained largely unchanged for over four billion years. Astronomers believe study of these ancient bodies may help answer questions about the formation of terrestrial planets of the solar system, including the Earth.
Vesta can occasionally be seen from the Earth without the aid of a telescope or binoculars.
"Dawn uses ion propulsion in spiraling trajectories to travel from Earth to Vesta, orbit Vesta and then continue on to orbit the dwarf planet Ceres. Ion engines use very small amounts of onboard fuel, enabling a mission that would be unaffordable or impossible without them," Jet Propulsion Laboratory reported.
Development of the unique map of Vesta was detailed in the journal Icarus.