Flagstaff – March 8, 1998 – Astronomers at Northern Arizona University and the University of Oklahoma discovered a mystery at the edge of the solar system -comet-like bodies known as Kuiper Belt Objects have two distinct surfaces.

In the March 5 issue of the science journal Nature, Stephen Tegler, an

assistant professor in the NAU Physics and Astronomy department, and

William Romanishin, from the University of Oklahoma, report that the

objects exhibit neutral-colored surfaces and extraordinarily red surfaces.

"The reason for two distinct surfaces is a mystery. The resolution of the

mystery will likely provide scientist with a more complete picture of planet

formation and evolution in the outer solar system," Tegler said.

In 1992, astronomers David Jewitt and Jane Luu discovered the first

object in an ancient reservoir located beyond Neptune's orbit. Today

about 60 Kuiper Belt objects are known to exist and are orbiting the sun.

The objects are smaller than planets but larger than comets.

The discovery was revolutionary because it showed our solar system does

not end with Pluto. In fact, many astronomers now consider the tiny planet

Pluto to be the largest member of the Kuiper Belt.

"The discovery is exciting because many astronomers expected all Kuiper

Belt objects to have similar surface colors," Romanishin said.

Tegler said he and Romanishin have been engaged in this research for

about three years. They spent 40 nights making observations at Steward

Observatory, State of Arizona research facility on Kitt Peak, west of

Tucson, using a 2.3 meter (90-inch) diameter telescope.

"The actual observing of the belt was the tip of the iceberg. We spent

countless hours doing image processing with extremely sophisticated

computers and software which the NAU and Oklahoma physics and

astronomy departments obtained for us," Tegler said.

Objects in the Kuiper Belt are too far from the sun to experience

evaporation of their icy material. Tegler and Romanishin were able to

probe the surfaces of these objects without shrouds of evaporating gas

and dust surrounding the icy bodies. The known Kuiper Belt objects have

diameters similar to the width of Oklahoma.

Some comets that are visible to the unaided eye in the night sky are

escapees from the Kuiper Belt. These objects make their way into the

inner solar system where they are warmed by the sun and form visible

tails of evaporating gas and dust streaming away from the central icy

body. The central icy bodies of these more familiar comets have diameters

similar to the length of Manhattan Island, although the tails can stretch

millions of miles.

Since Kuiper Belt objects are more than one million times fainter than the

faintest stars visible to the unaided eye, the astronomers used a highly

sensitive electronic camera called a charge-coupled device (CCD) in

combination with the telescope.

Because Kuiper Belt objects are so small and far from the Earth,

astronomers cannot take actual pictures of the surfaces of the objects, but

they can measure the brightness of sunlight that reflects off the surfaces

of the objects.

The red Kuiper Belt comets may be the most intriguing objects for further

study since they may have carbon and nitrogen-rich compounds on their

surfaces and these compounds may represent the initial building blocks

of life in our solar system.

The idea that comet impacts on the primitive Earth delivered prebiotic

material important for the evolution of life on Earth has been around for

nearly a century. By virtue of their stable, circular orbits and great

distances from the sun, the present-day surfaces of Kuiper Belt comets

provides us with a window on the very young solar system. In the years

to come studies will be able to identify the types of compounds that likely

impacted the surface of the Earth, Tegler said.