In 2007 NASA launched its Dawn spacecraft on a mission to the solar system’s second biggest asteroid – Vesta. Vesta is located in the main Asteroid Belt and is approximately 117 million miles (188 million kilometres) from Earth. It has a circumference of 329 miles.
Dawn reached its destination last Saturday July 16. It transmitted information to confirm it entered Vesta’s orbit, but the exact time this milestone took place is not known. The time of Dawn’s capture depended on Vesta’s mass and gravity, which could only be estimated until this historic visit. The asteroid’s mass determines the strength of its gravitational pull. If Vesta is bigger than expected, its gravity is stronger, and consequentially it pulled the spacecraft into orbit quicker. If the asteroid is smaller than expected, its gravity is weaker and it would have taken Dawn longer to arrive at the orbit. With the spacecraft now in orbit, the researchers will be able to take more accurate readings of Vesta’s gravity and gather more accurate timeline information.
Dawn navigated toward the asteroid belt, a space rock-rich zone between the orbits of Mars and Jupiter, using gravitational energy from Mars and by firing its ion-powered thrusters.
Down spacecraft is the first human object to visit the asteroid. It is also the first spacecraft to orbit two solar system destinations beyond Earth. Dawn will hover about 9,900 miles above Vesta’s surface for a year and use two different cameras, a gamma-ray detector and a neutron detector to study the object. Next July, Dawn’s ion thrusters will fire up and slowly propel the spacecraft toward the dwarf planet Ceres – the largest object in the Asteroid Belt.
Dawn’s observations of Vesta will help scientists understand the earliest chapter of our solar system’s history. The findings will also be used for planning future manned missions to the Asteroid Belt.
Planetary scientists know very little about either Vesta or Ceres, but they suspect each has planet-like qualities. Vesta may have once had a molten core that oozes lava before going cold after a few million years. Ceres, meanwhile, may have an icy mantle and active mud volcanoes.
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[Images - NASA]
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