NASA's Dawn spacecraft, illustrated in this artist's concept, is propelled by ion engines. Image credit:
NASA's Dawn spacecraft, illustrated in this artist's concept, is propelled by ion engines. Image credit: NASA

NASA spacecraft Dawn entered into an orbit around asteroid Vesta on Saturday. It will study Vesta until July 2012. Then, it will travel to and study nearby dwarf planet Ceres in 2015.

Today, we celebrate an incredible exploration milestone, said NASA Administrator Charles Bolden on Saturday.

Dawn's orbit of Vesta is historic for several reasons.

It's the first orbit of a celestial body in the asteroid belt between Mars and Jupiter. It's the first spacecraft to orbit a celestial body and then fly to orbit a second destination. It's also the first spacecraft to be powered by ion propulsion rather than chemical propulsion.

The ion propulsion, which relies on electric charges, is what gives Dawn the longevity to embark on a two-celestial body and multi-year assignment.

Bolden said the information gathered by Dawn will be used to send humans to an asteroid by 2025 in accordance with President Barack Obama's directive.

Scientists are interested in Vesta because it's believed to be a remnant of a protoplane as its core is differentiated. Other asteroids on the asteroid belt, contrastingly, do not have this property likely because Jupiter's gravitational pull and tidal effects prevent the formation of dense celestial bodies.

Scientists hope to study Vesta to better understand the formation of planets like the earth.

We can't wait for Dawn to peel back the layers of time and reveal the early history of our solar system, said Christopher Russell, Dawn principal investigator, at UCLA.

Vesta also happens to a significant source of meteorites that fall to the earth.

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