The sample, ancient black dust and chunks, was collected from the carbon-rich asteroid named Bennu, almost 60 million miles away.

It is the largest ever returned to Earth.

NASA's Osiris-Rex spacecraft collected the samples three years ago and then dropped them off sealed in a capsule during a flyby of Earth last month.

Scientists hope it can shed light on the origin of the solar system and of life on Earth.

An Osiris-Rex sample analyst, Daniel Glavin, said during a news conference to reveal the material that the sample was "loaded with organics".

"This is just incredible material," he said.

"This stuff is an astrobiologist's dream, I just can't wait to get at it."

The scientists have been investigating whether asteroids like Bennu seeded the Earth with pre-biotic chemicals.

Mr Glavin said: "We're going to learn so much about the origin of the solar system, the evolution and potentially how even life started here on Earth."

Dante Lauretta, Osiris-Rex principal investigator, said the different-sized stones contained in the sample would provide invaluable information for scientists.

'Something from space we have never seen in our laboratories'

"Something like that would not make it to the surface of the Earth as a meteorite," he said.

"So to have something from space that we have never seen in our laboratories, there is nothing more exciting."

Bennu is considered the most dangerous asteroid in the Solar System - although NASA has estimated its chances of actually hitting Earth in 2182 are remote, at just one in 2,700, or 0.037%.

Lori Glaze, director of the agency's planetary science division, explained how the latest sample could help protect our planet from a catastrophic impact with a space object.

She said the mission allowed NASA to measure a small force created by the sun's heat and an asteroid's rotation - explaining this force was "really important for helping us to predict when a particular asteroid might be dangerous".

"What we really want to know is if an asteroid is going to cross over Earth's orbit at the same time that we are in that place, and we want to not be in that place when an asteroid comes by," she said.

Administrator Bill Nelson explained the discovery was unprecedented.

"At nearly 5% carbon by weight, carbon being the central element of life, far exceeding our goal of 60g, this is the biggest carbon-rich asteroid sample ever returned to Earth," he said.

Carbon and water molecules are "exactly the kind of material that we wanted to find", Mr Nelson added.

"They are going to help us determine the origin of elements that could have led to life."