A sample of material collected from the surface of the near-Earth asteroid Bennu has been found to contain abundant water and carbon, the US space agency NASA said, offering more evidence for a theory that life on Earth was seeded from outer space. The findings were announced on Wednesday as NASA gave the public a first glimpse of what scientists found inside a sealed capsule that was returned to Earth last month after carrying material scooped from the 4.5-billion-year-old asteroid's surface by the OSIRIS-REx spacecraft. "This is the biggest carbon-rich asteroid sample ever returned to Earth," NASA administrator Bill Nelson said at a press event at the Johnson Space Center in Houston, where the first images of black dust and pebbles were revealed. Carbon accounted for almost 5 percent of the sample's total weight, and was present in both organic and mineral form, while the water was locked inside the crystal structure of clay minerals, Nelson said. The findings were made through a preliminary analysis involving scanning the sample with electron microscopy, X-ray computed tomography and more.