At first glance, the arithmetic looks absurd. Three asteroid sample-return missions, years of engineering, multiple launches, international recovery teams, ultra-clean laboratories and well over a billion dollars have brought back an amount of asteroid material that would fit in the palm of a hand.
Japan’s Hayabusa returned microscopic grains from Itokawa in 2010. Hayabusa2 returned about 5.4 grams from Ryugu in 2020. NASA’s OSIRIS-REx returned 121.6 grams from Bennu in 2023. Add them together and the total is roughly 127 grams, less than a small apple.
That comparison is not an argument that the missions were wasteful. It is a reminder that sample return is not mining. These missions were not built to bring back useful bulk material. They were built to bring back context, chemistry, history and contamination-controlled pieces of bodies that formed near the beginning of the Solar System.
A 2026 review paper, The science from asteroid sample return missions, summarises the state of the field: so far, three samples from near-Earth asteroids have been delivered to Earth by Hayabusa, Hayabusa2 and OSIRIS-REx. The paper frames the value of those samples in terms of planetary formation, the delivery of organics and water to early Earth, and the nature of potentially hazardous asteroids.
The first grains were almost nothing, and still mattered
Hayabusa was the first mission to return material from an asteroid. It reached the small S-type asteroid Itokawa in 2005 and returned its sample capsule to Earth in 2010. The mission did not go smoothly. Its sampling mechanism did not work as intended, and for a time there was real uncertainty about whether the capsule held asteroid material at all.
JAXA’s Hayabusa mission page describes the spacecraft as a sample-return mission to Itokawa, and later analysis confirmed that the capsule contained more than 1,500 tiny particles from the asteroid. The mass was not measured in grams in the way the later missions were. It was dust, grains and fragments small enough to require careful microscopy.
That tiny return still changed planetary science. It showed that asteroid material could be collected, preserved, returned through Earth’s atmosphere, curated and distributed for laboratory study. It linked Itokawa to ordinary chondritic meteorites and helped confirm that some meteorites on Earth really are fragments of asteroid parent bodies. It also proved that a damaged, imperfect mission could still deliver scientifically valuable material.
The mass was minute. The lesson was large. Hayabusa demonstrated the method.
Hayabusa2 made the return larger and cleaner
Hayabusa2 was designed as a successor, with a different target and a more reliable sampling strategy. It went to Ryugu, a carbon-rich C-type asteroid, and collected material during two touchdowns in 2019. JAXA’s Hayabusa2 mission page records the return of the sample capsule to Earth on Dec. 6, 2020, after the spacecraft had collected samples during two touchdowns.
The returned mass, about 5.4 grams including gas samples, was still tiny by everyday standards. It is about a teaspoon’s worth of dark asteroid material. But compared with Hayabusa’s microscopic grains, it was a major increase. It allowed broader allocation, multiple teams, and a much richer set of chemical, mineralogical and isotopic analyses.
Ryugu mattered because it is chemically primitive. Its material is rich in carbon-bearing compounds and water-related minerals, making it a laboratory sample of the kinds of small bodies that may have delivered volatiles and organic material to the early Earth. Meteorites can answer some of those questions, but they pass through Earth’s atmosphere, experience heating, sit on the ground, and can be altered by terrestrial water and biology.
Sample return avoids much of that uncertainty. The chain of custody is known. The geological context is measured by the spacecraft. The sample container is curated from the moment it is opened. Five grams can therefore carry more scientific information than kilograms of poorly contextualised material.
OSIRIS-REx changed the scale, but only slightly
OSIRIS-REx was the first United States mission to return a sample from an asteroid. It reached Bennu, mapped its unexpectedly rough surface, performed a touch-and-go sample collection in 2020, and dropped its capsule in Utah in September 2023.
NASA’s final mass measurement for the Bennu sample was 121.6 grams. That was more than twice the mission’s original requirement, and it became the largest asteroid sample ever returned beyond the Moon. A 2024 paper on Bennu in the laboratory describes the returned material as roughly 120 grams of carbonaceous regolith, with particles ranging from sub-micron dust to a stone about 3.5 centimetres long.
By asteroid sample-return standards, OSIRIS-REx brought back a lot. By ordinary standards, it brought back less than half a cup of gravel and dust. Combined with Ryugu and the Itokawa grains, the total still sits around 127 grams.
This is where the apple comparison is useful. It forces the scale into view. The combined material from three historic asteroid sample-return missions weighs less than something people eat without thinking. But that is also why the comparison can mislead. The value is not in mass. It is in what the mass preserves.
Why grams can be enough
Modern laboratory instruments do not always need much material. A particle can be cut, polished, scanned, dissolved, vaporised, imaged, dated or analysed atom by atom. Some instruments work on grains smaller than a human hair. Others can read isotopic ratios in tiny fragments and compare them with meteorites, solar material and other returned samples.
A gram of asteroid material can be divided many times. It can be stored for future techniques that do not yet exist. It can be compared with spacecraft observations of the original surface. It can be kept away from Earth’s atmosphere and biology in ways meteorites cannot.
That last point is central. Meteorites are natural sample returns, but they are uncontrolled. They arrive through a hot entry, fall somewhere on Earth, then wait to be found. Some are recovered quickly. Others sit in deserts, ice fields or soil for long periods. By the time scientists analyse them, they may carry terrestrial alteration along with their original chemistry.
Returned asteroid samples are different. The mission knows where the material came from. It knows the target body’s shape, orbit, surface properties and sampling site. The return capsule is handled as a scientific object from landing onward. That makes each grain more meaningful.
The cost per gram is the wrong metric, but not a useless one
If the missions are judged only by dollars per gram, the numbers become theatrical. Public estimates put OSIRIS-REx alone near a billion dollars, with Hayabusa and Hayabusa2 adding hundreds of millions more depending on accounting method and exchange rate. Dividing that total by 127 grams creates a figure that sounds ridiculous.
But dollars per gram is not how the science works. The missions did not purchase raw material. They purchased launch vehicles, spacecraft, navigation, instruments, sample mechanisms, communication time, recovery operations, clean-room curation, engineering experience, and observations of three different asteroids before any sample reached Earth.
The returned material is only one output. Hayabusa mapped Itokawa and proved a difficult technology. Hayabusa2 deployed small surface robots, created an artificial crater, sampled Ryugu and continued into an extended mission. OSIRIS-REx mapped Bennu in detail, measured its thermal behaviour and refined understanding of the Yarkovsky effect, which matters for predicting asteroid orbits.
Still, the cost-per-gram view is useful if handled carefully. It makes clear how hard it is to touch a small body, collect material in microgravity, keep that material clean, and bring it home intact. Asteroid sample return is not expensive because the rocks are rare in the abstract. It is expensive because obtaining known, uncontaminated, geologically contextualised material from a specific asteroid is a difficult engineering problem.
The small apple is a serious scientific archive
The combined 127 grams will not be consumed in a few years. Sample curation is deliberately conservative. Only part of the material is allocated for early study. Some is held back for future scientists, future instruments and future questions. Apollo lunar samples still produce new results decades after they were collected, because laboratory methods keep improving.
The same logic applies here. A few milligrams of Bennu or Ryugu may answer a question that could not be asked when the mission launched. The chemistry of organics, the movement of water through parent bodies, the relationship between meteorites and asteroids, and the physical behaviour of rubble-pile worlds all depend on careful analysis of small quantities.
There is also a planetary-defence dimension. Bennu and Ryugu are not just museum specimens. They are examples of near-Earth asteroids, the class of objects whose orbits and structures matter if humanity ever needs to predict, deflect or understand an impact threat. Knowing how such bodies are built is not a decorative science question. It affects how they respond to sunlight, impacts and spacecraft contact.
A handful from the early Solar System
The number remains striking. More than a billion dollars, three missions, three asteroids, and about 127 grams of returned material. Less than a small apple.
But a small apple is the wrong kind of object. It is ordinary, replaceable and known. These grains are not. They are selected pieces of worlds that formed from the early Solar System’s leftover building material, collected from bodies whose surfaces had never been touched by Earth, and brought back under controlled conditions.
That is why the smallness is not an embarrassment. It is part of the achievement. The missions did not bring back much. They brought back the right little pieces, from the right places, with enough context for laboratories on Earth to ask questions no telescope or meteorite fall could answer in the same way.
