Bennu: the 4.5 billion-year-old asteroid that could reveal the origins of life on Earth

Samples of a 4.5 billion-year-old asteroid could reveal the origins of life on the planet as a teaspoon-sized specimen, taken from asteroid Bennu, is being examined by scientists at the Natural History Museum (NHM).

The black dust-like sample could help shed light on some of the biggest questions about how Earth formed and hold vital clues to the formation of the planets and our solar system, experts say.

Professor Sara Russell, senior research lead at the NHM said: “We’re really excited at the moment because we’ve just taken receipt of a tiny teaspoonful of black powder, but it’s actually come from space. We’re really excited to get a piece of asteroid Bennu because we believe that this asteroid dates from the very earliest times of the solar system, when the solar system and the sun and the planets were forming four and a half billion years ago.

She added: “It formed from a swirling disc of dust and gas, and we think that we might have components here of that time period.”

Prof Russell has already been examining the sample, which is contained in a nitrogen glovebox, so it is not being contaminated by being exposed to air, to preserve its natural state.

Explaining what the sample may contain, she said: “It also, we think, contains minerals like clays that trap loads of water, so it might contain loads of water and that could tell us how the Earth got to be a watery habitable planet.

“Also, we think that it might contain several per cent of carbon, which might be in the form of organic carbon, so we need to investigate that further. But it could be that asteroids like Bennu also provided the nutrients that were needed for life to flourish on Earth.”

Orbiting the Sun roughly 120,000,000 kilometres (74,564,543 miles) away, the asteroid is thought to be an "untouched time capsule from the beginning of the solar system", providing clues about the origin of Earth, according to the Natural History Museum, and in September, Nasa’s Osiris-Rex (Origins, Spectral Interpretation, Resource Identification and Security – Regolith Explorer), became the first US mission to collect a sample from an asteroid and return it to Earth.

Bennu is a carbon-rich asteroid, containing roughly 5% by mass, some of which is organic, and has the potential to harm Earth and is considered to be the most dangerous asteroid in the solar system.

Scientists at the NHM are among an international team who have received some of the sample to analyse.

The team also believe it could have extra-terrestrial water trapped within its minerals, and analysis of these minerals will help the team test the theory that asteroids delivered water to our planet 4.5 billion years ago.

Prof Russell said: “When the Earth formed it was probably formed really, really hot, and things like water would have just boiled up and escaped into space, it would have been very dry when it first formed.

“So the question is, how did we get to be on this beautiful blue planet that’s covered in oceans? And it’s likely that the answer is because water was brought to it by impact of asteroids and comets from the outer solar system.

“But we want to understand that process more. If we understand that then we might understand better how likely it is that we find habitable worlds around other stars as well.”

She added: “It will certainly help us understand the origin of life.”

Asked what her dream find would be, Prof Russell said: “It’s beyond my wildest dreams, just having the sample, but I think for me, I’m sort of looking forward to seeing if we can find grains in there that are not just old, but super old, formed before the asteroid formed, maybe even formed before our solar system formed.

“So they may be pre-solar grains that formed around stars that were ancestors to ours, and those would be really interesting, exciting to explore.”

Asteroid Bennu is thought to be similar in composition to the Winchcombe meteorite which fell to Earth in 2021 and although a quick collection of the Winchcombe meteorite made it relatively un-contaminated, it still interacted with our atmosphere.

But the Bennu samples, having been collected in space, remain uncontaminated, making them pristine time capsules from the earliest history of our solar system.

Ashley King, UKRI Future Leaders Fellow, Natural History Museum, said: “The Natural History Museum has one of the best meteorite collections in the world but for many of them we don’t know where they came from in the solar system.

“With this sample having been collected by Nasa from asteroid Bennu’s surface, we know its origins. This means our findings can be put into a greater context and can potentially help us to understand the origin of organics and water that may have led to life on Earth.”

The Museum is one of four UK institutes studying samples from Nasa, along with the Open University, Oxford University and the University of Manchester.