The climactic end of a seven-year voyage comes Sunday (Monday in Manila) with the landing of a NASA capsule in the Utah desert, carrying to Earth the largest asteroid samples ever collected.

Scientists have high hopes for the sample, saying it will provide a better understanding of the formation of our solar system and how Earth became habitable.

The Osiris-Rex probe's final, fiery descent through Earth's atmosphere will be perilous, but the US space agency is hoping for a soft landing, around 9 a.m. local (15H00 GMT), in a military test range in northwestern Utah.

Four years after its 2016 launch, the probe landed on the asteroid Bennu and collected roughly nine ounces (250 grams) of dust from its rocky surface.

Even that small amount, NASA says, should "help us better understand the types of asteroids that could threaten Earth" and cast light "on the earliest history of our solar system," NASA Administrator Bill Nelson said.

"This sample return is really historic," NASA scientist Amy Simon told AFP. "This is going to be the biggest sample we've brought back since the Apollo moon rocks" were returned to Earth.

But the capsule's return will require "a dangerous maneuver," she acknowledged.

Osiris-Rex is set to release the capsule — from an altitude of more than 67,000 miles (108,000 kilometers) — some four hours before it lands.

The fiery passage through the atmosphere will come only in the last 13 minutes, as the capsule hurtles downward at a speed of more than 27,000 miles per hour, with temperatures of up to 5,000 Fahrenheit (2,760 Celsius).

Its rapid descent, monitored by army sensors, will be slowed by two successive parachutes. Should they fail to deploy correctly, a "hard landing" would follow. If it appears that the target zone (37 by 9 miles) might be missed, NASA controllers could decide at the last moment not to release the capsule.

The probe would then keep its cargo and make another orbit of the sun. Scientists would have to wait until 2025 before trying a new landing.

WITH AFP