LOS ANGELES Jan 8, 2006 — Comets have long lit up the sky and the imaginations of scientists. Now these icy bodies from the beginnings of the solar system are finally ready for their close-up.

Six months after NASA scientists first peeked inside one comet from afar, they're bringing pieces of another to Earth for study under the microscope.

This weekend, the Stardust spacecraft will jettison a 100-pound capsule holding comet dust. It will nosedive through the Earth's atmosphere and if all goes well make a soft landing in the Utah desert.

The searing plunge is expected to generate a pinkish glow as bright as Venus that should be visible without a telescope across much of the West.

Comets which astronomers consider to be among the solar system's leftover building blocks have been scrutinized for centuries. But only in recent years have scientists had the technology to learn firsthand their ingredients.

Last July, the Deep Impact spacecraft released a probe that carved a crater in a comet, exposing its interior to NASA telescopes. The Stardust mission went a step further by retrieving the first samples from a comet named Wild 2, which was about 500 million miles from Earth when Stardust launched in 1999.

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But the capsule isn't home yet.

First it faces a blistering descent, piercing the atmosphere at a record-breaking 29,000 mph the fastest re-entry of any man-made probe.

Its target is Dugway Proving Ground, a Rhode Island-sized Army base southwest of Salt Lake City where in 2004 the ill-fated Genesis probe crashed on live television after its parachute failed to open. Despite that crash, scientists recovered enough solar wind atoms for study.