Historic asteroid sample reveals the ‘building blocks of life are in fact extraterrestrial in origin,’ scientists say

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Scientists have found organic compounds and minerals essential for life in the samples collected from the near-Earth asteroid Bennu, which supports the theory that asteroids may have brought the raw materials for life to our planet billions of years ago.

The samples are also giving us a glimpse of the chemical and biological processes that were already in progress as space rocks were careening wildly around during the early formation of our solar system.

The mixture consisted mainly of nitrogen and other organic materials, but the chemical composition of this organic material was largely unclear.

According to Dr. Daniel P. Glavin, a leading researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland, recent studies have discovered that the asteroid is composed of many of the essential chemical components of life, such as amino acids and the elements found in DNA.

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Discovered salts and minerals essential for life, some of which have not been found in asteroid samples before, within Bennu's rocks — as well as revealing the significance of ancient water's presence on the asteroid.

The results of both papers were revealed Wednesday at a NASA press conference, where Nicky Fox, associate administrator for NASA's Science Mission Directorate, called them a “groundbreaking scientific discovery.”

"These two studies complement each other to reveal that Bennu is a more intriguing and complex body than we likely believed even just six months ago," said Dr. Tim McCoy, co-author of the Nature study and curator of meteorites at the Smithsonian's National Museum of Natural History.

A close-up look at alien biology

Bennu is a rocky space object composed mainly of carbon. Scientists think that it broke away from a larger "parent" asteroid when it was hit by something. The pieces that flew off from this collision eventually came together, forming a weakly bonded pile of rocks held by gravity.

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The researchers diligently worked to retrieve the capsule and guarantee that the samples inside remained sealed and unaffected by Earth's atmosphere and environment, which could have altered or contaminated the extraterrestrial rocks and dust and compromised any analysis of its properties.

Scientists were excited to find that the capsule contained twice as much material as they had anticipated, which weighed about 120 grams, equivalent to a full bar of soap. Samples of this material were then split and distributed to researchers worldwide.

Glavin and his team discovered thousands of organic molecular compounds in the Bennu samples they analyzed, including 33 different amino acids. Amino acids are molecules that combine to create proteins, which are some of the fundamental building blocks of life.

The researchers discovered 14 of the 20 amino acids used in biology to build proteins, and 19 other amino acids that are not found in proteins, many of which are uncommon or do not exist in known biology, Dr. Glavin said.

The team also discovered adenine, guanine, cytosine, thymine, and uracil – all five biological building blocks that make up the genetic code in DNA and RNA.

These organic molecules were all identified in meteorites before. However, unlike meteorites, the Bennu samples have been preserved in their original state and weren't contaminated by Earth's atmosphere or heat when they entered it," Glavin said. "So we're now more confident than ever that these building blocks of life came from space and formed there, rather than being from Earth.

They also discovered compounds rich in nitrogen and ammonia in the samples, indicating that Bennu was once part of a bigger asteroid that formed roughly 4.5 billion years ago in one of the far-flung, icy regions of the solar system. Ammonia is a vital substance used in a wide range of biological processes, according to Glavin.

Ammonia ice stays more stable the farther it is from a heat source, like the sun. The researchers think that the ammonia-enriched ice inside the large parent asteroid body, which is estimated to be over 62 miles (100 kilometers) in diameter, melted, creating a liquid environment inside the rock that allowed complex organic molecules, like amino acids and nucleobases, to form.

After 35 years of studying meteorites, they contain the first half billion years of our solar system's history that was erased by tectonic activity, volcanic eruptions, and the water cycle on Earth, said Dr. McCoy. "I expected to learn about the earliest geological history of our solar system, but what we discovered was a wealth of information about the earliest biological history of our solar system, which is truly remarkable.

A "soup of the fundamental components"

The team led by McCoy found various salts and minerals when the water on Bennu and its parent asteroid evaporated. The minerals which were discovered include sodium phosphates, carbonates, chlorides, sulfates, and fluorides, many of which are crucial to the formation of life.

The team was surprised to discover the mineral trona, also referred to as sodium carbonate or soda ash, which has never been directly found in another asteroid or meteorite before. On Earth, it's commonly used in cleaning products and manufacturing glass.

The researchers think that underneath the surface of Bennu's parent asteroid, there were pockets or channels of water flowing. This asteroid likely resembled a massive ball of mud early on in the history of the solar system, said McCoy. Cracks and fractures in the asteroid allowed water to rise to the surface and evaporate, leaving behind a strong brine, or a "soup of the elements", in its wake.

This concentrated brine, similar to the salty crusts found on the dry lakebeds on Earth, is where salts and minerals come together and mix, possibly creating more complex structures that could be a starting point for the formation of organic compounds.

We now know from Bennu that the building blocks of life were coming together in complex ways on Bennu's precursor condition," McCoy said. "We've identified the next stage in the process that could lead to life. But we still don't know how far along that process could be supported by the environment there.

which also contains sodium carbonate.

Releasing the key to life's existence

The presence of water, minerals, salts, and amino acids indicates that it was conceivable that the building blocks of life were able to assemble in complex ways on Bennu, but further research is needed to uncover how organic compounds developed and changed there.

Many of the minerals contain tiny pockets of water within their crystal lattice, so researchers might gain insight into how the brine's composition evolved over time, which could shed light on what happened as the water evaporated, according to McCoy.

One of the enigmas presented by the samples is a combination of amino acids.

Amino acids have a property called handedness, meaning they can be identical twins, one with a left-handed molecule and the other with a right-handed one. On Earth, life produces left-handed amino acids, so Glavin anticipated that this trend would be evident in the Bennu samples - but they were surprised to find that the samples have a 50-50 split of both, suggesting that amino acids on Earth might have originated in both forms. Now, Glavin and his colleagues are trying to figure out why life on Earth ended up favoring the left-handed variety instead of the right-handed one.

The mixture of materials in the samples indicates that the chemical building blocks of life were abundant throughout the solar system, providing robust evidence that asteroids crashing into early Earth may have brought water and organic matter to its surface, Glavin observed.

That theory also brings up the question of whether the conditions were ever met on any other planet in our solar system, McCoy added. And there's another mystery to consider: if the necessary ingredients for life were already present, then why didn't life form inside Bennu itself, in the first place, Glavin noted.

It's possible that life on Earth got started before there was enough time for the more complex chemistry that's necessary for life when the salty liquids in our parent body evaporated," Glavin said. "Future missions to other worlds in our solar system will be crucial in helping us find the answers to how life evolved on Earth and where we might find life elsewhere.

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