Spacecraft Reaches Dwarf Planet With Unexplained Bright Spots

NASA's Dawn spacecraft made history at 7:39 a.m. Friday when it became the first to enter a dwarf planet's orbit. A signal reached mission control at NASA's Jet Propulsion Laboratory at 8:36 a.m. EST, confirming that Dawn had successfully reached Ceres, the biggest object in the asteroid belt between Mars and Jupiter.

"Since its discovery in 1801, Ceres was known as a planet, then an asteroid and later a dwarf planet," said Marc Rayman, Dawn's chief engineer and mission director at the JPL in Pasadena, California, in a press release. "Now, after a journey of 3.1 billion miles (4.9 billion kilometers) and 7.5 years, Dawn calls Ceres, home."

The spacecraft, which was about 38,000 miles from Ceres when it was captured by the dwarf planet's gravity, will spend more than a year in orbit, during which it will collect data and images. Dawn has already been sending back images of Ceres over the last few months, including one that showed a pair of bright spots on the dwarf planet's surface.

The spacecraft previously spent 14 months exploring the asteroid Vesta, the second biggest object in the asteroid belt, making it "the first mission to orbit two extraterrestrial targets."

Carol Raymond, deputy principal investigator at JPL, explained that "these bodies are samples of the building blocks that have formed Venus, Earth and Mars. Vesta-like bodies are believed to have contributed heavily to the core of our planet, and Ceres-like bodies may have provided our water."

As with missions like Rosetta—when the European Space Agency landed a probe on a comet for the first time—Dawn's journey is being documented on Twitter for the public to follow. And as the ESA did with Rosetta's probe, Philae, NASA has occasionally personified Dawn on the social media platform, so it appears as though the spacecraft is sharing its adventure live and in the first person.

"Studying Ceres allows us to do historical research in space, opening a window into the earliest chapter in the history of our solar system," Jim Green, director of NASA's Planetary Science Division in Washington, said in a previous release. "Data returned from Dawn could contribute significant breakthroughs in our understanding of how the solar system formed."