Asteroid dust collected by a Japanese space probe contains organic material that shows some of the building blocks of life on Earth may have been formed in space, scientists said Friday.

Pristine material from the asteroid Ryugu was brought back to Earth in 2020 after a six-year mission to the celestial body around 300 million kilometers away.

But scientists are only just beginning to discover its secrets in the first studies on small portions of the 5.4 grams (0.2 ounces) of dust and dark, tiny rocks.

In one paper published Friday, a group of researchers led by Okayama University in western Japan said they had discovered "amino acids and other organic matter that could give clues to the origin of life on Earth".

"The discovery of protein-forming amino acids is important, because Ryugu has not been exposed to the Earth's biosphere, like meteorites

The team said they found 23 different types of amino acid while examining the sample collected by Japan's Hayabusa-2 probe in 2019.

The dust and rocks were stirred up when the fridge-sized spacecraft fired an "impactor" into the asteroid.

The Ryugu sample has the most primitive characteristics of any natural sample available to mankind, including meteorites," the Japan Aerospace Exploration Agency (JAXA) said in a statement.