An international team of researchers has performed a detailed analysis on a binary pair of �asteroids� near Jupiter�s obit, and found that the bodies are mostly water ice covered in a layer of dust. This finding suggests the objects originated from the Kuiper Belt � a region beyond Neptune�s orbit where around 100 million icy objects lie.

The objects, named Patroclus and Menoetius, are estimated to be about 122 and 112 kilometers wide, respectively. They lie in one of Jupiter�s Lagrange points � positions where the gravitational forces of the Sun and Jupiter are perfectly balanced. One Lagrange point lies in front and the other behind Jupiter in its orbit. Material tends to build up in these stable positions, and the larger bodies are known as Trojans. The researchers believe the objects formed in the Kuiper Belt when the Solar System was only 650 million years old.

If confirmed, this would suggest that more of the thousands of so-called Trojans that sit in the Lagrange points could be more like comets than asteroids

The objects are small and dim, and difficult to observe with ground-based telescopes. A new technique that uses sodium lasers and image-correcting technology called Laser Guide Star Adaptive Optics (LGS-AO) is helping scientists study Trojens more easily than before. Scientists used the LGS-AO system with the Keck II telescope in Hawaii, to remove the blurring effects caused by the Earth�s atmosphere.

"Space telescopes are tremendous tools for observing remote Solar System targets, but large ground-based telescopes equipped with Laser Guide Star Adaptive Optics systems provide both the power to collect more light and the ability to study objects with even more detail," said David Le Mignant, lead team member for LGS-AO at the W. M. Keck Observatory.

"With LGS-AO, we observe a different population of Solar System targets: fainter and smaller objects like Patroclus and more distant ones like the object beyond Pluto. This should lead us to many new discoveries," added Le Mignant.

The findings were published in the 2 February edition of Nature.