Scientists have solved the mystery of how the building blocks of life formed on a 4.6-billion-year-old asteroid, and it could rewrite our own origin story.
In 2023, NASA's OSIRIS-REx mission recovered 121.6 grams of material from the asteroid Bennu as it drifted through the solar system.
This rocky rubble was found to contain molecules called amino acids, which combine to make proteins that form the basis of all biological life.
How these molecules formed on a freezing rock 105 million miles (168 million kilometres) from the sun was a total mystery - until now.
Previously, scientists thought that amino acids could only form through a process involving liquid water and relatively warm conditions.
However, scientists from Pennsylvania State University discovered that these amino acids actually formed in the cold, radioactive environment of the early universe.
This discovery hints that the basic ingredients of life on Earth could have been delivered by a frozen asteroid just like Bennu.
Co-lead author Dr Allison Baczynski says: 'It now looks like there are many conditions where these building blocks of life can form, not just when there's warm liquid water.'
After NASA's mission returned with material from Bennu, tiny samples of this precious dust were distributed to research centres around the world.
Shockingly, scientists soon discovered that this ancient space rock was carrying a wide array of organic molecules.
Scientists found sugars essential for life, a mysterious 'gum-like' substance, and a collection of amino acids.
At Pennsylvania State University, scientists focused on the molecule glycine - the simplest of all the amino acids with just two linked carbon molecules.
These tiny molecules can be combined to make more complex amino acids, which are then combined to make proteins and eventually the earliest forms of life.
This is why glycine is considered an important sign of the chemical reactions that eventually led to life on Earth
According to some scientists, the fact that glycine has been found in asteroids and comets suggests life's fundamental ingredients might have formed in space before coming to Earth.
Previously, the main theory for how glycine formed was something called Strecker synthesis, in which chemicals like ammonia and hydrogen cyanide react in the presence of water.
In 2023, NASA's OSIRIS-REx mission recovered 121.6 grams of material from the asteroid Bennu (pictured) and found that it contained chemicals called amino acids that are essential for life
Asteroid Bennu: Key facts
- Age: 4.6 billion years
- Diameter: 500 metres
- Surface temperatures: -73°C to 116°C
- Average distance form the sun: 105 million miles (168 million kilometres)
- Orbital period: 1.2 years
- Composition: Largely clay materials like those found on mid-ocean ridges on Earth
However, that doesn't seem to have been the case for the molecules found inside Bennu.
The researchers used specialised equipment to look for subtle differences in the weight of atoms, called isotopes.
These tiny atomic differences can give scientists information about where a chemical came from, the conditions that created it, and the kinds of reactions that took place.
The researchers compared their measurements from Bennu with amino acids from the Murchison meteorite, a carbon-rich space rock that landed in Australia in 1969.
Co-lead author Dr Ophélie McIntosh says: 'What's a real surprise is that the amino acids in Bennu show a much different isotopic pattern than those in Murchison.
'These results suggest that Bennu and Murchison's parent bodies likely originated in chemically distinct regions of the solar system.'
The chemicals on the Murchison meteorite likely formed via Strecker synthesis under warm, wet conditions that can also be found on Earth.
Those on Bennu, by contrast, likely formed via a very different set of processes.
The researchers looked at differences in the weight of atoms, known as isotopes, and found that these amino acids likely formed in the icy cold, radioactive environment of the early solar system
The researchers suggest these amino acids formed as primordial ice was bombarded with radiation in the very earliest days of the solar system.
This suggests that there might be more ways for amino acids to form than had previously been thought, increasing the chances that these vital chemicals formed in space.
Dr Baczynski says: 'Our results flip the script on how we have typically thought amino acids formed in asteroids.'
'There's much more diversity in the pathways and conditions in which these amino acids can be formed.'
In the future, the researchers want to look at even more samples from different asteroids and see what kinds of amino acids they might contain.
Dr Baczynski adds: 'We want to know if they continue to look like Murchison and Bennu, or maybe there is even more diversity in the conditions and pathways that can create the building blocks of life.'