NASA on Wednesday gave the public a first glimpse of what scientists found inside a tightly sealed capsule that was returned to Earth last month carrying a carbon-rich soil sample scooped from the surface of an asteroid, including water molecules locked inside clay-like minerals.

A small portion of the material collected by the OSIRIS-REx spacecraft three years ago from the near-Earth asteroid Bennu was unveiled in an auditorium at NASA's Johnson Space Center in Houston, a little more than two weeks after it was parachuted into the Utah desert.

The landing of the return capsule capped a seven-year joint mission of the U.S. space agency and the University of Arizona. It was only the third asteroid sample, and by far the biggest, ever returned to Earth for analysis, following two similar missions by Japan's space agency ending in 2010 and 2020.

"It's days like this that continue to amaze me," NASA chief Bill Nelson said from the stage as he introduced the first picture of material retrieved from Bennu on a viewing screen.

The image showed a loose cluster of small charcoal-colored rocks, pebbles and dust found to have been left in the bottom of the sample-collection assembly and lid when the asteroid's soil was sucked into the spacecraft's storage canister.

Bennu, a small, carbon-rich body discovered in 1999, appears to be made up of a loose collection of rocks, like a rubble pile, according to scientists. It measures about three-tenths of a mile (500 meters) across, making it slightly wider than the Empire State Building is tall but tiny compared with the Chicxulub asteroid that struck Earth some 66 million years ago, wiping out the dinosaurs.

Technicians are still in the process of methodically disassembling hardware surrounding the inner canister, which remains unopened and contains the bulk of the specimen.

But the "bonus" sample of overflow material was immediately examined with electron microscopes and X-ray instruments, said Dante Lauretta, principal mission investigator at the University of Arizona.

What they found was material high in carbon, nearly 5% by weight of an element that is the foundation of life on Earth, as well as water molecules crystallized in clay fibers, Lauretta said. Lauretta said scientists achieved their goal of keeping the entire sample pristine and free of terrestrial contamination.

Daniel Glavin, a senior sample scientist at NASA's Goddard Space Flight Center, said early analysis found the material seems to be "loaded with organics."

The preliminary findings point to a likelihood of further discoveries buttressing the hypothesis that celestial objects such as comets, asteroids and meteorites that bombarded early Earth seeded the young planet with the primordial ingredients for life.

Like other asteroids, Bennu is a relic of the early solar system. Because its present-day chemistry and mineralogy are virtually unchanged since forming some 4.5 billion years ago, it holds clues to the origins and development of rocky planets such as Earth.

The capsule was initially inspected at the Utah Test and Training range near the landing site, then was flown to Houston for closer examination in a specially built "clean room" inside an astromaterials curation facility at the Johnson Space Center.

In the months ahead, the overall asteroid sample is to be parceled into smaller specimens promised to some 200 scientists in 60 laboratories around the world.

At the time it landed, the Bennu sample was estimated to weigh about 250 grams (8.8 ounces), well above the minimum amount of 60 grams (2 ounces) scientists had hoped to collect. A more precise measurement will be made once the canister has been fully opened.

OSIRIS-REx launched in 2016 and reached Bennu in 2018, then spent nearly two years orbiting the asteroid before venturing close enough to snatch a sample of the loose surface material with its robotic arm on Oct. 20, 2020.

NASA is due to launch a separate mission on Thursday to a more distant asteroid called Psyche, a metal-rich body believed to be the remnant core of a protoplanet and the largest known metallic object in the solar system.

(Reporting by Steve Gorman in Los Angeles; Editing by Will Dunham)