By DPA
Washington : Its journey will last eight years, but when the Dawn spacecraft leaves Earth it will take scientists on an even longer trip, offering insights into the beginning of the universe.
If the weather cooperates, Dawn will take off Monday for a 5 billion km journey to the asteroid belt between Mars and Jupiter, where scientists say some of the greatest mysteries of our solar system are hidden. Poor weather conditions have delayed the launch several times.
The 1.6-metre long, 747 kg craft is headed for the dwarf planet Ceres and the asteroid Vesta, which are both significantly smaller than our moon.
The rocky objects date to the time when planets were forming in the solar system and could be an especially rich source of information for scientists.
About 4.5 billion years ago, the time when the asteroid belt was formed, there were no planets, but scientists believe the asteroids contain the ingredients that later formed the rest of our solar system.
"The asteroid belt is really fascinating because it's kind of like the bone-yard of material that's left over from forming all these planets," said Carol Raymond of NASA's Jet Propulsion Laboratory in Pasadena, California.
"It's fragments of explosions of planetary embryos, perhaps during collisions or material that's come in from other parts of the solar system and been captured into this orbit of the asteroid belt," he added.
Vesta and Ceres were discovered more than 200 years ago and NASA chose them for their completely different characteristics.
Dawn will first survey Vesta, reaching there in October 2011. Vesta is about 500 km in diameter and is the brightest asteroid in the solar system. It can be seen from Earth as a small point of light above the Scorpius constellation.
The heavenly body is hot and dry and there are remnants of volcanoes.
Six months later, Dawn will leave the heat for icy Ceres. The dwarf planet is 950 km in diameter and its coat of ice is believed to be 100 km thick.
Ceres was the first asteroid to be discovered in our solar system in 1801.
"Ceres likely has a rocky core and a very thick ice mantle," Raymond said. "There's even the possibility that there's liquid water under the surface of Ceres."
Dawn's launch is the culmination of five years of hopes and fears. NASA at one time scrapped the $449 million robotic expedition because of high costs and technical problems, before reviving the project last March.
Dawn is also the first US mission for which primary components were brought from Europe. Two multi-spectral cameras that allow the craft to capture images were made in Germany and the Italian space agency provided the craft's spectrometer.