NASA's Dawn mission was launched in 2007 to orbit the large asteroid Vesta (left) and the dwarf planet Ceres (right). The two bodies have very different properties. By observing them with the same set of instruments, Dawn will uncover clues about the early Solar System.
Credit: NASA/JPL
SYDNEY: Modelling crater formation on Ceres and Vesta, the two largest objects in the asteroid belt, may help pinpoint the age of the gas giant Jupiter.
It will also aid our understanding of data collected by NASA's Dawn space mission when it visits these objects in 2011. Scientists hope the combined data will give clues to the evolution of the entire Solar System.
Ceres is a dwarf planet, the only one found in the Asteroid Belt. Vesta is the second largest object found there, with a diameter of over 500 km, and is classed as an asteroid.
Great uncertainty
Current estimates suggest that the Solar System began to form about 4.6 billion years ago. Measurements of cratering patterns on our own Moon tell us something about the age of the Earth, but because Jupiter has no solid surface we can't date it in a similar way.
"There is great uncertainty about the initial conditions and details of the formation process of giant planets. As a consequence, the only thing we know for sure about Jupiter's formation is that it was one of the earliest events in the history of the Solar System," said researcher Diego Turrini, with the Institute for Interplanetary Space Physics in Rome, Italy.
"The potential implications of this research for our comprehension of Jupiter's age and history are strong," he told Cosmos Online.
Push and pull
Planets form in protoplanetary nebulae; discs of gas and dust orbiting newly born stars. Gas giants such as Jupiter and Saturn initially grow by sweeping up nearby smaller bodies. The seed planet - around 10 to 15 times Earth's mass - then rapidly captures surrounding gases from the nebulae. This continues until the nebula disperses and the planet has reached its final mass.
These giants influence the evolution of the Solar System by their gravitational effects on smaller planets, planetesimals (the building blocks of planets) and other debris such as asteroids.
Turrini and researchers at the Italian National Institute for Astrophysics speculated that if Ceres and Vesta formed around the same time, as Jupiter, then their heavily cratered surfaces should contain a record of the planets birth. The Asteroid Belt they reside in is found between Jupiter and Mars.
To test this, the researchers wrote a computer program which simulates impacts on Vesta and Ceres at different stages of Jupiter's formation. This allowed him to predict what the cratering patterns on these planetoids should look like, depending on when they formed with respect to Jupiter.
