At 1 A.M. Eastern time on July 16, NASA's Dawn spacecraft will become the first man-made probe to enter orbit around a so-called main-belt asteroid. The spherical body, Vesta, circles the sun in a stretch of asteroids known as the Asteroid Belt located between the orbits of Mars and Jupiter.

As Dawn approaches Vesta, it is taking detailed photographs, such as the July 9 image shown here at a distance of about 42,000 kilometers with a resolution of 3.8 kilometers per pixel. Vesta is large for an asteroid, leading to its classification as a "protoplanet," a celestial body that, it is thought, could have developed into a planet.

NASA's Jet Propulsion Laboratory in Pasadena, Calif., supervises the Dawn mission, which launched from Cape Canaveral Air Force Station in September 2007 and flrst flew by Mars for a gravity boost.

After circling Vesta for about a year, Dawn will depart for Ceres, which is larger than Vesta, and the only dwarf planet in the Asteroid Belt; it will enter orbit there in 2015.

—Sophie Bushwick