SPACE ROCKS: Asteroid Bennu contains building blocks of early life on Earth, Nasa reveals

Nasa revealed a pristine asteroid sample which may be a time capsule from the formation of our solar system, with probable building blocks of life in the space agency's new discovery.

According to Nasa administrator Bill Nelson, the rocks and dust are rich in carbon and contain significant amounts of water, indicating that asteroids like Bennu may have brought the necessary ingredients for life to Earth. Nearly 5% of the sample's weight is carbon.

“Far exceeding our goal of 60 grams, this is the biggest carbon-rich asteroid sample ever returned to Earth,” Nelson said. “The carbon and water molecules are exactly the kinds of material that we wanted to find. They’re crucial elements in the formation of our own planet. And they’re going to help us determine the origin of elements that could have led to life.”

On September 24, a capsule carrying the sample, which Nasa's OSIRIS-REx mission had taken in October 2020 from the 4.5 billion-year-old near-Earth asteroid Bennu, fell from the spacecraft and landed in the Utah desert.

Since that time, researchers have been working diligently to do an initial analysis of the abundance of material that is located just within the top of the canister, which is more than they had anticipated. 

On Wednesday, the first look at the sample and the findings of that research were presented during a live Nasa broadcast from Houston's Johnson Space Centre. The largest asteroid sample yet to be brought back to Earth.

The team hasn't yet opened the bulk sample because there was so much "bonus" material when the scientists opened the canister.

A ‘treasure chest of extraterrestrial material’

The science team examined some of the rocks and dust over the course of the previous two weeks using a scanning electron microscope, infrared measurements, and chemical element analyses. 

According to OSIRIS-REx principal investigator Dante Lauretta, they also utilised X-rays to generate a 3D model of one of the particles to determine its composition, revealing a "scientific treasure" of carbon and water content.

“The first analysis shows samples that contain abundant water in the form of hydrated clay minerals, and they contain carbon as both minerals and organic molecules,” Nelson said.

The water-bearing clay minerals could be seen in the fine-grained photos of the particles that the researchers released.

“That is how we think water got to Earth,” Lauretta said. “The reason that Earth is a habitable world, that we have oceans and lakes and rivers and rain, is because these clay minerals landed on Earth 4 billion years ago to 4 and a half billion years ago, making our world habitable. So we’re seeing the way that water got incorporated into the solid material.”

The investigation also uncovered iron oxide minerals called magnetite that react to magnetic fields, sulphide minerals, "a critical element for planetary evolution and biology," and other minerals that could be significant for biological evolution, according to Lauretta.

According to Dr Daniel Glavin, a senior scientist at Nasa's Goddard Space Flight Centre in Greenbelt, Maryland, and an analyst of the OSIRIS-REx sample, the science team was thrilled to find organic materials and an abundance of carbon, which is crucial for all life.

“We’re just beginning here, but we picked the right asteroid, and not only that, we brought back the right sample,” Glavin said. “This stuff is an astrobiologist’s dream.”

Going forward, the team will look to see just how much chemistry evolved on Bennu to determine whether the building blocks of life created peptides, or chains of amino acids that form proteins, Glavin said.

Meanwhile, still waiting inside the canister is “a whole treasure chest of extraterrestrial material,” Lauretta said.

What the sample could reveal

Three years ago, the OSIRIS-REx spacecraft made a close approach to Bennu, at which point it extended a TAGSAM head—a Touch-and-Go Sample Acquisition Mechanism—and shot a blast of nitrogen gas at the asteroid. Rocks and dust were raised by the gas explosion all the way from 19 inches (50 centimetres) underneath the surface of the space rock. The TAGSAM head was filled with the detritus.

24 surface contact pads on the TAGSAM also made contact with the asteroid, trapping fine-grained debris.

Bennu's internal and exterior dust and rocks, taken together, may be able to shed light on the asteroid's formation and evolution over time. These discoveries will also shed light on the space rock's general makeup, allowing Nasa to better predict how it can divert an asteroid that may one day strike Earth.

From the launch of the OSIRIS-REx mission in 2016 to the capsule landing last month, it has taken seven years to finally make the eagerly awaited announcement. Some have anticipated this time for even longer. Lauretta has waited almost 20 years to view the sample and learn what it might reveal about our solar system. She assisted in the mission's early development.

“Our labs were ready for whatever Bennu had in store for us,” said Vanessa Wyche, director of Nasa’s Johnson Space Center. “We’ve had scientists and engineers working side-by-side for years to develop specialised gloveboxes and tools to keep the asteroid material pristine and to curate the samples so researchers now and decades from now can study this precious gift from the cosmos.”

In a specialised clean room at Johnson Space Centre, researchers will examine the rocks and soil over the following two years. Additionally, the sample will be split up and distributed to other research facilities across the world, including collaborators in the OSIRIS-REx mission at the Canadian Space Agency and the Japanese Aerospace Exploration Agency. In order for future generations with improved technology to learn even more than what is currently attainable, about 70% of the sample will remain undamaged in storage.

“Rocks tell you a story,” Lauretta said. “The greatest mystery that we’re facing right now is, how do you go from a ball of mud to something that’s alive? When do you make that transition? The deepest desire is that we’re going to make some progress in trying to figure out why is it that we’re here in this universe.”