Deep beneath the public galleries of the Natural History Museum, in a labyrinth of corridors lined with wooden drawers containing specimens from Robert Scott’s expeditions to Antarctica, are even rarer treasures that can only be handled within a sealed nitrogen-filled box.
Scott’s artefacts may have travelled 10,000 miles to be here, but these fragments of dust and rock have voyaged 20,000 times further, brought back from an asteroid 200 million miles from Earth.
The Bennu asteroid is described as the most dangerous rock in the solar system due to the small chance its orbit could bring it on a collision course with Earth. Fragments scooped from its surface have now been distributed to scientists around the globe, including in London, Manchester and Oxford.
The sample is now being bombarded with x-rays, stripped with lasers and scanned with electron microscopes to teach scientists what the asteroid is made of. It is hoped the research will provide insight into what our solar system looked like in its infancy 4.5 billion years ago, before the formation of the planets.
Analysis has already revealed the presence of carbon-rich “nano-globules of organic material”, lending weight to the theory that asteroid strikes may have delivered to Earth some of the ingredients for life.
Also trapped within the space dust could be particles that date back even further to before our sun was born. These grains would carry the signature of long-dead stars and ancient clouds of dust that came into being billions of years earlier, providing the materials from which our solar system would ultimately form.
“One of the really exciting things we will be looking for are ‘pre-solar’ grains,” Professor Sara Russell said when The Times visited the laboratories where the samples are being analysed. She said the isotopic composition of these particles, measuring less than a micron in diameter, will belong to their extinct “parent star” rather than our own sun.
The Natural History Museum has been analysing space rock “for 200 years longer than Nasa”, Russell boasted, dating to when the museum acquired its first meteorite from an institution in Russia in 1776.
The largest space rock in their collection is the five-tonne Cranbourne meteorite, but the sample from Bennu weighs just 100 milligrams. Even the largest fragments are just tiny grains, but Russell said that “this is actually loads” to work with.
The most celebrated extraterrestrial material to arrive in Britain in recent years was the Winchcombe meteorite that fell on a driveway in Gloucestershire in 2021, but the asteroid sample arrived in Britain not via shooting star but via a FedEx delivery from the United States, sealed in a nitrogen flask.
Its journey to the US was rather more remarkable. It was scooped up in 2020 by the Osiris-Rex spacecraft from the surface of an asteroid 200 million miles away and dropped off into the Earth’s atmosphere to land in the Utah desert in September this year as the probe whizzed past our planet on its way to chase down another asteroid.
In a small room beneath the museum is a sealed “nitrogen box” accessed via thick black gloves. Inside plastic Tupperware-like boxes containing pebble-sized fragments from the Winchcombe meteorite are clear plastic bags and slides holding tiny specks of black dust.
The clay-rich material from the asteroid readily sucks up moisture from surrounding air, so the dust is stored in pure nitrogen to avoid contamination.
Russell is examining her sample looking for minerals such as olivine and pyroxene, which are “primordial dust grains”. “By analysing the components, we can learn about what the solar system was like before the planets were around”, she said. It will enable researchers to understand “how the solar system went from [a disk of] dust to a planetary system and how long that takes”.
In a laboratory down the corridor, a device bombards a sample of space dust with x-rays as it spins, capturing the diffracted rays to analyse the shape of the crystals within the rock.
They are also using scanning electron microscopes and a process called laser ablation to unlock every secret within the 100mg sample, at least until Nasa funding ends in September 2025.
The James Webb Space Telescope is discovering infant solar systems across the galaxy whose planets are still forming. Russell said this makes it a “really exciting time” to have a sample from an asteroid that could provide a glimpse of what our own solar system was like at this stage.
Teams around the globe are analysing their samples looking for resources that could be mined from asteroids. Meanwhile others are examining Bennu’s composition to help develop defence systems to avert asteroid strikes should one be found on a collision course with Earth. The results of preliminary analyses will be presented at a meeting of the American Geophysical Union in San Francisco this month.
