Radar imaging at NASA's Goldstone Solar System Radar on June 12 and 14, 2009, revealed that near-Earth asteroid 1994 CC is a triple system. Credit: NASA/JPL/GSSR

New radar observations have revealed that a near-Earth asteroid is actually three rocks.

The system, asteroid 1994 CC, was imaged by NASA's Goldstone Solar System Radar on June 12 and 14. The results were released this week.

While most asteroids roam in a belt between Mars and Jupiter, some are kicked or drawn inward and cross our orbital path around the sun. Some 15 percent of these near-Earth asteroids are binaries. Even fewer, a mere one percent, are triples.

1994 CC, which came within 1.56 million miles (2.52 million km) of Earth on June 10 (about six times farther away than our moon), is only the second triple system known in the near-Earth population.

The three-rock setup consists of a central object about 2,300 feet (700 meters) in diameter that has two smaller moons revolving around it. Preliminary analysis suggests that the satellites are at least 164 feet (50 m) in diameter.

Asteroids are often loose rubble piles rather than solid objects, and pairs are common. In a 2008 study, scientists found that binaries can be created when energy from sunlight, over long periods of time, splits a loose asteroid in two.

Radar observations at Arecibo Observatory in Puerto Rico, led by the center's director Mike Nolan, also detected all three objects, and the combined observations from Goldstone and Arecibo will be used by JPL scientists and their colleagues to study 1994 CC's orbital and physical properties.