The asteroid Ryugu, which orbits the sun between Earth and Mars, contains many of the building blocks for life, a new analysis finds.
The study, published February 23 in the journal Science (opens in a new tab)one of the first glimpses of samples from Ryugu was returned by Japan’s Hayabusa2 spacecraft in 2020. The mission is only the second time a spacecraft has successfully returned a sample from a spacecraft an asteroid; In 2010, the first Hayabusa mission brought back dust from the asteroid Itokawa, but that sample was only micrograms in size due to a failure of the collection system. Hayabusa2, for comparison, returned more than 0.17 oz (opens in a new tab) (5 grams) to Earth from the space rock officially known as 162173 Ryugu.
Analysis of a small portion of this sample revealed that the carbon-rich asteroid contains molecules vital to all known life, including 15 amino acids, the building blocks of proteins. These molecules themselves are not alive, but because they are found in all life, scientists call them “prebiotic”. Researchers knew from previous studies of detritus found on Earth that space rocks could contain prebiotic molecules, but that rocks that fell through Earth’s atmosphere could harbor such compounds due to contamination. It was also unclear whether these molecules could survive on the surface of an asteroid or deep within an asteroid’s body. In this case, the molecules came from surface dust.
“The presence of prebiotic molecules on the asteroid surface despite its harsh environment caused by solar heating and ultraviolet irradiation, as well as cosmic ray irradiation under high vacuum conditions, indicates that Ryugu’s upper surface grains have the ability to protect organic molecules. ,” study leader Hiroshi Naraoka (opens in a new tab) Kyushu University in Japan said in a statement (opens in a new tab). That means asteroids could spread the building blocks of life throughout the solar system.
And according to the second study, which was also published in Science (opens in a new tab), the organic materials may have existed on Ryugu even before the formation of the solar system itself, and instead formed in a primordial cloud of interstellar dust that eventually coalesced into Ryugu’s parent body. In other words, many of the ingredients for life may have been baked into the solar system from the start.
To capture an asteroid
Ryugu is a carbonaceous asteroid, a type that makes up 75% of the asteroids found in the solar system, according to NASA (opens in a new tab). Essentially, these asteroids are the fragments left behind when the solar system formed, making them a fascinating window into the molecules that existed 4.5 billion years ago. As part of a collaboration with the Japanese space agency, NASA received about 10% of the Hayabusa2 sample for testing, and additional research was also conducted in Europe.
Naraoka and a large international team of molecules extracted just 30 micrograms (0.000001 oz) of a sample using various solvents and analyzed the organic matter. They found thousands of combinations containing carbon, hydrogen, nitrogen, oxygen, and/or sulfur, including the 15 amino acids. Other compounds included amines, which contain nitrogen, and carboxylic acids, which have a specific structure including carbon, oxygen and hydrogen. The compounds found were broadly consistent with what is seen in carbonaceous meteorites exposed to water in space and found on Earth, study co-author Jason Dworkin (opens in a new tab)astrobiologist at NASA’s Goddard Space Flight Center, said in the statement.
However, the researchers did not find sugars or nucleobases, the main components of DNA and RNA.
“These compounds may be present in asteroid Ryugu but are below our analytical detection limits due to the relatively small sample mass available for study,” study co-author Daniel Glavin (opens in a new tab)also an astrobiologist at NASA Goddard, said in the statement.
Researchers have only begun to analyze Ryugu’s samples, and soon plan to compare them with samples from other asteroids. In September, NASA’s OSIRIS-REx mission is scheduled to return to Earth samples from 101955 Bennu, another carbonaceous asteroid.
“OSIRIS-REx is expected to return a much larger sample mass from Bennu and provide another important opportunity to look for the organic building blocks of life in a carbon-rich asteroid,” said Dworkin.