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NASA’s Asteroid Bennu Sample Reveals Mix of Life’s Ingredients

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In this video frame, Jason Dworkin holds up a vial that contains part of the sample from asteroid Bennu delivered to Earth by NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security – Regolith Explorer) mission in 2023. Dworkin is the mission’s project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Credit: NASA/James Tralie

NASA’s Asteroid Bennu Sample Reveals Mix of Life’s Ingredients

Studies of rock and dust from asteroid Bennu delivered to Earth by NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification and Security–Regolith Explorer) spacecraft have revealed molecules that, on our planet, are key to life, as well as a history of saltwater that could have served as the “broth” for these compounds to interact and combine.

The findings do not show evidence for life itself, but they do suggest the conditions necessary for the emergence of life were widespread across the early solar system, increasing the odds life could have formed on other planets and moons.

“NASA’s OSIRIS-REx mission already is rewriting the textbook on what we understand about the beginnings of our solar system,” said Nicky Fox, associate administrator, Science Mission Directorate at NASA Headquarters in Washington. “Asteroids provide a time capsule into our home planet’s history, and Bennu’s samples are pivotal in our understanding of what ingredients in our solar system existed before life started on Earth.”

In research papers published Wednesday in the journals Nature and Nature Astronomy, scientists from NASA and other institutions shared results of the first in-depth analyses of the minerals and molecules in the Bennu samples, which OSIRIS-REx delivered to Earth in 2023.

Detailed in the Nature Astronomy paper, among the most compelling detections were amino acids – 14 of the 20 that life on Earth uses to make proteins – and all five nucleobases that life on Earth uses to store and transmit genetic instructions in more complex terrestrial biomolecules, such as DNA and RNA, including how to arrange amino acids into proteins.

Scientists also described exceptionally high abundances of ammonia in the Bennu samples. Ammonia is important to biology because it can react with formaldehyde, which also was detected in the samples, to form complex molecules, such as amino acids – given the right conditions. When amino acids link up into long chains, they make proteins, which go on to power nearly every biological function.

These building blocks for life detected in the Bennu samples have been found before in extraterrestrial rocks. However, identifying them in a pristine sample collected in space supports the idea that objects that formed far from the Sun could have been an important source of the raw precursor ingredients for life throughout the solar system.

“The clues we’re looking for are so minuscule and so easily destroyed or altered from exposure to Earth’s environment,” said Danny Glavin, a senior sample scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and co-lead author of the Nature Astronomy paper. “That’s why some of these new discoveries would not be possible without a sample-return mission, meticulous contamination-control measures, and careful curation and storage of this precious material from Bennu.”

While Glavin’s team analyzed the Bennu samples for hints of life-related compounds, their colleagues, led by Tim McCoy, curator of meteorites at the Smithsonian’s National Museum of Natural History in Washington, and Sara Russell, cosmic mineralogist at the Natural History Museum in London, looked for clues to the environment these molecules would have formed. Reporting in the journal Nature, scientists further describe evidence of an ancient environment well-suited to kickstart the chemistry of life.

Ranging from calcite to halite and sylvite, scientists identified traces of 11 minerals in the Bennu sample that form as water containing dissolved salts evaporates over long periods of time, leaving behind the salts as solid crystals.

Similar brines have been detected or suggested across the solar system, including at the dwarf planet Ceres and Saturn’s moon Enceladus.

Although scientists have previously detected several evaporites in meteorites that fall to Earth’s surface, they have never seen a complete set that preserves an evaporation process that could have lasted thousands of years or more. Some minerals found in Bennu, such as trona, were discovered for the first time in extraterrestrial samples.

“These papers really go hand in hand in trying to explain how life’s ingredients actually came together to make what we see on this aqueously altered asteroid,” said McCoy.

For all the answers the Bennu sample has provided, several questions remain. Many amino acids can be created in two mirror-image versions, like a pair of left and right hands. Life on Earth almost exclusively produces the left-handed variety, but the Bennu samples contain an equal mixture of both. This means that on early Earth, amino acids may have started out in an equal mixture, as well. The reason life “turned left” instead of right remains a mystery.

“OSIRIS-REx has been a highly successful mission,” said Jason Dworkin, OSIRIS-REx project scientist at NASA Goddard and co-lead author on the Nature Astronomy paper. “Data from OSIRIS-REx adds major brushstrokes to a picture of a solar system teeming with the potential for life. Why we, so far, only see life on Earth and not elsewhere, that’s the truly tantalizing question.”

NASA Goddard provided overall mission management, systems engineering, and the safety and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator. The university leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space in Littleton, Colorado, built the spacecraft and provided flight operations. NASA Goddard and KinetX Aerospace were responsible for navigating the OSIRIS-REx spacecraft. Curation for OSIRIS-REx takes place at NASA’s Johnson Space Center in Houston. International partnerships on this mission include the OSIRIS-REx Laser Altimeter instrument from CSA (Canadian Space Agency) and asteroid sample science collaboration with JAXA’s (Japan Aerospace Exploration Agency) Hayabusa2 mission. OSIRIS-REx is the third mission in NASA’s New Frontiers Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington.

Bibliographic information:

Glavin, D.P., Dworkin, J.P., Alexander, C.M.O. et al. Abundant ammonia and nitrogen-rich soluble organic matter in samples from asteroid (101955) Bennu, Nat Astron (2025), DOI: https://doi.org/10.1038/s41550-024-02472-9

In this video frame, Jason Dworkin holds up a vial that contains part of the sample from asteroid Bennu delivered to Earth by NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security – Regolith Explorer) mission in 2023. Dworkin is the mission’s project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.Credit: NASA/James Tralie
In this video frame, Jason Dworkin holds up a vial that contains part of the sample from asteroid Bennu delivered to Earth by NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security – Regolith Explorer) mission in 2023. Dworkin is the mission’s project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Credit: NASA/James Tralie

Press release from NASA

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Hubble goes hunting for small main-belt asteroids

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This graph plots the size of asteroids versus their abundance, based on a Hubble Space Telescope archival survey that found 1701 mostly previously undetected asteroids lying between the orbits of Mars and Jupiter. The vertical axis lists the number of objects from zero to 70. The horizontal axis lists size, from zero kilometres on the left, to 2 kilometres on the right. The graph slopes up such that the most abundant asteroids detected by Hubble in the survey are 0.5 kilometres across in size.

Hubble goes hunting for small main-belt asteroids

Astronomers recently used a trove of archived images taken by the NASA/ESA Hubble Space Telescope to visually snag a largely unseen population of smaller asteroids in their tracks. The treasure hunt required pursuing 37 000 Hubble images spanning 19 years. The payoff was finding 1701 asteroid trails, with 1031 of those asteroids uncatalogued. About 400 of these uncatalogued asteroids are about below a kilometre in size.

Annotated image of barred spiral galaxy UGC 12158 against the black background of space, with compass arrows, a scale bar, and colour key for reference. The galaxy has a pinwheel shape made up of bright blue stars wound around a yellow-white hub of central stars. The galaxy is tilted face-on to our view from Earth. A slightly S-shaped white line across the top is the Hubble image of an asteroid streaking across Hubble’s view. Indicated filters are expressed as: “F475W” in blue, “F606W” in green, and “F814W” in red. At the bottom left corner is a scale bar labelled “60,000 light-years” over “30 arcseconds.” At the bottom right corner, the “E” compass arrow points towards the 2 o’clock position. The “N” compass arrow points towards the 5 o’clock position.
This is an annotated NASA/ESA Hubble Space Telescope image of the barred spiral galaxy UGC 12158, with compass arrows, a scale bar, and colour key for reference. It looks like someone took a white marking pen to it. In reality it is a combination of time exposures of a foreground asteroid moving through Hubble’s field of view, photobombing the observation of the galaxy. Several exposures of the galaxy were taken, which is evidenced by the dashed pattern.
The asteroid appears as a curved trail as a result of parallax: Hubble is not stationary, but orbiting Earth, and this gives the illusion that the faint asteroid is swimming along a curved trajectory. The uncharted asteroid is inside the asteroid belt in our Solar System, and hence is 10 trillion times closer to Hubble than the background galaxy.
Rather than being a nuisance, this type of data is useful to astronomers for doing a census of the asteroid population in our Solar System.
Credit: NASA, ESA, P. G. Martín (Autonomous University of Madrid), J. DePasquale (STScI).
Acknowledgment: A. Filippenko (University of California, Berkeley)

Volunteers from around the world known as ‘citizen scientists’ contributed to the identification of this asteroid bounty. Professional scientists combined the volunteers’ efforts with machine learning algorithms to identify the asteroids. This represents a new approach to finding asteroids in astronomical archives spanning decades, and it may be effectively applied to other datasets, say the researchers.

“We are getting deeper into seeing the smaller population of main-belt asteroids. We were surprised to see such a large number of candidate objects,” said lead author Pablo García Martín of the Autonomous University of Madrid, Spain. “There was some hint that this population existed, but now we are confirming it with a random asteroid population sample obtained using the whole Hubble archive. This is important for providing insights into the evolutionary models of our Solar System.”

The large, random sample offers new insights into the formation and evolution of the asteroid belt. Finding a lot of small asteroids favours the idea that they are fragments of larger asteroids that have collided and broken apart, like smashed pottery. This is a grinding-down process spanning billions of years.

This graph plots the size of asteroids versus their abundance, based on a Hubble Space Telescope archival survey that found 1701 mostly previously undetected asteroids lying between the orbits of Mars and Jupiter. The vertical axis lists the number of objects from zero to 70. The horizontal axis lists size, from zero kilometres on the left, to 2 kilometres on the right. The graph slopes up such that the most abundant asteroids detected by Hubble in the survey are 0.5 kilometres across in size.
This graph is based on Hubble Space Telescope archival data that were used to identify a largely unseen population of very small asteroids. The asteroids were not the intended targets, but instead photobombed background stars and galaxies in Hubble images. The comprehensive treasure hunt required perusing 37 000 Hubble images spanning 19 years. This was accomplished by using ‘citizen science’ volunteers and artificial intelligence algorithms. The payoff was finding 1701 trails of previously undetected asteroids.
Credit: NASA, ESA, P. G. Martín (Autonomous University of Madrid), E. Wheatley (STScI)

An alternative theory for the existence of smaller fragments is that they formed that way billions of years ago. But there is no conceivable mechanism that would keep them from snowballing up to larger sizes as they agglomerate dust from the planet-forming circumstellar disc around our Sun. “Collisions would have a certain signature that we can use to test the current main belt population,” said co-author Bruno Merín of the European Space Astronomy Centre in Madrid, Spain.

Because of Hubble’s fast orbit around Earth, it can capture wandering asteroids through their telltale trails in the Hubble exposures. As viewed from an Earth-based telescope, an asteroid leaves a streak across the picture. Asteroids ‘photobomb’ Hubble exposures by appearing as unmistakable, curved trails in Hubble photographs.

As Hubble moves around Earth, it changes its point of view while observing an asteroid, which also moves along its own orbit. By knowing Hubble’s position during the observation and measuring the curvature of the streaks, scientists can determine the distances to the asteroids and estimate the shapes of their orbits.

The asteroids snagged mostly dwell in the main belt, which lies between the orbits of Mars and Jupiter. Their brightness is measured by Hubble’s sensitive cameras, and comparing their brightness to their distance allows for a size estimate. The faintest asteroids in the survey are roughly one forty-millionth the brightness of the faintest star that can be seen by the human eye.

“Asteroid positions change with time, and therefore you cannot find them just by entering coordinates, because at different times they might not be there,” said Merín. “As astronomers we don’t have time to go looking through all the asteroid images. So we got the idea to collaborate with more than 10 000 citizen-science volunteers to peruse the huge Hubble archives.”

In 2019 an international group of astronomers launched the Hubble Asteroid Hunter, a citizen-science project to identify asteroids in archival Hubble data. The initiative was developed by researchers and engineers at the European Science and Technology Centre (ESTEC) and the European Space Astronomy Centre’s science data centre (ESDC), in collaboration with the Zooniverse platform, the world’s largest and most popular citizen-science platform, and Google.

A total of 11 482 citizen-science volunteers, who provided nearly two million identifications, were then given a training set for an automated algorithm to identify asteroids based on artificial intelligence. This pioneering approach may be effectively applied to other datasets.

The project will next explore the streaks of previously unknown asteroids to characterise their orbits and study their properties, such as rotation periods. Because most of these asteroid streaks were captured by Hubble many years ago, it is not possible to follow them up now to determine their orbits.

The findings are published in the journal Astronomy and Astrophysics.

This is a Hubble Space Telescope image of the barred spiral galaxy UGC 12158. The majestic galaxy has a pinwheel shape made up of bright blue stars wound around a yellow-white hub of central stars. The hub has a slash of stars across it, called a bar. The galaxy is tilted face-on to our view from Earth. A slightly S-shaped white line across the top is the Hubble image of an asteroid streaking across Hubble’s view. It looks dashed because the image is a combination of several exposures of the asteroid flying by like a race car.
This NASA/ESA Hubble Space Telescope image of the barred spiral galaxy UGC 12158 looks like someone took a white marking pen to it. In reality it is a combination of time exposures of a foreground asteroid moving through Hubble’s field of view, photobombing the observation of the galaxy. Several exposures of the galaxy were taken, which is evidenced by the dashed pattern.
The asteroid appears as a curved trail as a result of parallax: Hubble is not stationary, but orbiting Earth, and this gives the illusion that the faint asteroid is swimming along a curved trajectory. The uncharted asteroid is inside the asteroid belt in our Solar System, and hence is 10 trillion times closer to Hubble than the background galaxy.
Rather than being a nuisance, this type of data is useful to astronomers for doing a census of the asteroid population in our Solar System.
Credit: NASA, ESA, P. G. Martín (Autonomous University of Madrid), J. DePasquale (STScI).
Acknowledgment: A. Filippenko (University of California, Berkeley)

Press release from ESA Hubble

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Hubble sees boulders escaping from asteroid Dimorphos

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Hubble boulders Dimorphos The bright white object at lower left is the asteroid Dimorphos. It has a blue dust tail extending diagonally to the upper right. A cluster of blue dots surrounds the asteroid. These are boulders that were knocked off the asteroid when, on 26 September 2022, NASA deliberately slammed the half-tonne DART impactor spacecraft into the asteroid as a test of what it would take to deflect some future asteroid from hitting Earth. Hubble photographed the slow-moving boulders in December 2022

Hubble sees boulders escaping from asteroid Dimorphos

Astronomers using the NASA/ESA/ Hubble Space Telescope’s extraordinary sensitivity have discovered a swarm of boulders that were possibly shaken off the asteroid Dimorphos when NASA deliberately slammed the half-tonne DART impactor spacecraft into Dimorphos at approximately 22 500 kilometres per hour. DART intentionally impacted Dimorphos on 26 September 2022, slightly changing the trajectory of its orbit around the larger asteroid Didymos.

Hubble boulders Dimorphos The bright white object at lower left is the asteroid Dimorphos. It has a blue dust tail extending diagonally to the upper right. A cluster of blue dots surrounds the asteroid. These are boulders that were knocked off the asteroid when, on 26 September 2022, NASA deliberately slammed the half-tonne DART impactor spacecraft into the asteroid as a test of what it would take to deflect some future asteroid from hitting Earth. Hubble photographed the slow-moving boulders in December 2022
This NASA/ESA Hubble Space Telescope image of the asteroid Dimorphos was taken on 19 December 2022, nearly four months after the asteroid was impacted by NASA’s DART (Double Asteroid Redirection Test) mission. Hubble’s sensitivity reveals a few dozen boulders knocked off the asteroid by the force of the collision. These are among the faintest objects Hubble has ever photographed inside the Solar System. The ejected boulders range in size from 1 metre to 6.7 metres across, based on Hubble photometry. They are drifting away from the asteroid at around a kilometre per hour. The discovery yields invaluable insights into the behaviour of a small asteroid when it is hit by a projectile for the purpose of altering its trajectory.
Credit: NASA, ESA, D. Jewitt (UCLA)

The 37 ejected boulders range in size from 1 metre to 6.7 metres across, based on Hubble photometry. They are drifting away from the asteroid at around one kilometre per hour. The total mass in these detected boulders is about 0.1% the mass of Dimorphos. The boulders are some of the faintest objects ever imaged in the Solar System.

This opens up a new dimension for studying the aftermath of the DART experiment using the European Space Agency’s upcoming Hera mission, which is due to launch in 2024. The spacecraft will perform a detailed post-impact survey of the target asteroid Dimorphos. Hera will turn the grand-scale experiment into a well-understood and repeatable planetary defence technique that might one day be used for real [1].

The boulders are most likely not shattered pieces of the diminutive asteroid caused by the impact. They were already scattered across the asteroid’s surface, as evident in the last close-up picture taken by the DART spacecraft just two seconds before collision, when it was only 11 kilometres above the surface.

The science team that observed these boulders with Hubble estimates that the impact shook off two percent of the boulders on the asteroid’s surface. While the boulder observations by Hubble also give an estimate for the size of the DART impact crater, Hera will eventually determine the actual crater size.

Long ago, Dimorphos may have formed from material shed into space by the larger asteroid Didymos. The parent body may have spun up too quickly or could have lost material after a glancing collision with another object, among other scenarios. The ejected material formed a ring that gravitationally coalesced to form Dimorphos. This would make it a flying rubble pile of rocky debris loosely held together by the relatively weak pull of its gravity. Therefore, the interior is probably not solid, but has a structure more like a bunch of grapes.

It’s not clear how the boulders were lifted off the asteroid’s surface. They could be part of an ejecta plume that was photographed by Hubble and other observatories. Or a seismic wave from the impact may have rattled through the asteroid — like hitting a bell with a hammer — shaking loose the surface rubble.

The DART and LICIACube (Light Italian CubeSat for Imaging of Asteroids) teams have also been studying boulders detected in images taken by LICIACube’s LUKE (LICIACube Unit Key Explorer) camera in the minutes immediately following DART’s kinetic impact.

Notes

[1] Just like Hubble and the NASA/ESA/CSA James Webb Space Telescope, NASA’s DART and ESA’s Hera missions are great examples of what international collaboration can achieve; the two missions are supported by the same teams of scientists and astronomers, and operate via an international collaboration called AIDA — the Asteroid Impact and Deflection Assessment.

NASA and ESA worked together in the early 2000s to develop asteroid monitoring systems, but recognised there was a missing link in the chain between asteroid threat identification and ways of addressing that threat. In response NASA oversaw the DART mission while ESA developed the Hera mission to gather additional data on DART’s impact. With the Hera mission, ESA is assuming even greater responsibility for protecting our planet and ensuring that Europe plays a leading role in the common effort to tackle asteroid risks. As Europe’s flagship planetary defender, Hera is supported through the Agency’s Space Safety programme, part of the Operations Directorate.

The bright white object at lower left is the asteroid Dimorphos. It has a blue dust tail extending diagonally to the upper right. A cluster of blue dots surrounds the asteroid. These are boulders that were knocked off the asteroid when, on 26 September 2022, NASA deliberately slammed the half-tonne DART impactor spacecraft into the asteroid as a test of what it would take to deflect some future asteroid from hitting Earth. Hubble photographed the slow-moving boulders in December 2022
Hubble sees boulders escaping from asteroid Dimorphos: this NASA/ESA Hubble Space Telescope image of the asteroid Dimorphos was taken on 19 December 2022, nearly four months after the asteroid was impacted by NASA’s DART (Double Asteroid Redirection Test) mission. Hubble’s sensitivity reveals a few dozen boulders knocked off the asteroid by the force of the collision. These are among the faintest objects Hubble has ever photographed inside the Solar System. The ejected boulders range in size from 1 metre to 6.7 metres across, based on Hubble photometry. They are drifting away from the asteroid at around a kilometre per hour. The discovery yields invaluable insights into the behaviour of a small asteroid when it is hit by a projectile for the purpose of altering its trajectory.
Credit: NASA, ESA, D. Jewitt (UCLA)

Press release from ESA Hubble

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Hubble captures movie of DART asteroid impact debris

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Hubble captures DART asteroid impact debris

Hubble captures movie of DART asteroid impact debris

The NASA/ESA Hubble Space Telescope captured a series of photos of rapid changes to the asteroid Dimorphos when it was deliberately hit by a 545-kilogram spacecraft on 26 September 2022. The primary objective of the NASA mission, called DART (Double Asteroid Redirection Test), was to test our ability to alter the asteroid’s trajectory as it orbits its larger companion asteroid, Didymos. Though Dimorphos poses no threat to Earth, data from the mission could help inform researchers how to potentially change an asteroid’s path away from Earth, if ever necessary.

Hubble’s resulting time-lapse movie of the aftermath of the collision reveals surprising and remarkable changes as dust and chunks of debris were flung into space from the wounded asteroid. Smashing head-on into the asteroid at 21 000 kilometres per hour, the DART impactor blasted over 900 000 kilograms of dust off of the asteroid.

The Hubble movie provides invaluable new clues into how the debris was dispersed into a complex pattern in the days following the impact.

The movie shows three overlapping stages of the aftermath of the crash: the formation of an ejecta cone, the spiral swirl of debris caught up along the asteroid’s orbit about its companion asteroid, and the tail swept behind the asteroid by the pressure of sunlight.

The Hubble movie starts at 1.3 hours before impact. In this view both Didymos and Dimorphos are within the central bright spot; even Hubble can’t resolve the two asteroids separately. The thin, straight spikes projecting away from the centre (and seen in later images) are artefacts of Hubble’s optics. The first post-impact snapshot is two hours after the event. Debris flies away from the asteroid, moving in with a range of speeds faster than four miles per hour (fast enough to escape the asteroid’s gravitational pull, so it does not fall back onto the asteroid). The ejecta forms a largely hollow cone with long, stringy filaments.

At about 17 hours after the collision the debris pattern entered a second stage. The dynamic interaction within the binary system started to distort the cone shape of the ejecta pattern. The most prominent structures are rotating, pinwheel-shaped features. The pinwheel is tied to the gravitational pull of the companion asteroid, Didymos.

Hubble next captures the debris being swept back into a comet-like tail by the pressure of sunlight on the tiny dust particles. This stretches out into a debris train where the lightest particles travel the fastest and farthest from the asteroid. Hubble also recorded the tail splitting in two for a few days.

Due to launch in October 2024, ESA’s Hera mission will perform a detailed post-impact survey of the target asteroid Dimorphos. Hera will turn the grand-scale experiment into a well-understood and repeatable planetary defence technique that might one day be used for real.

Just like Hubble and the NASA/ESA/CSA James Webb Space Telescope, NASA’s DART and ESA’s Hera missions are great examples of what international collaboration can achieve; the two missions are supported by the same teams of scientists and astronomers, and operate via an international collaboration called AIDA — the Asteroid Impact and Deflection Assessment.

NASA and ESA worked together in the early 2000s to develop asteroid monitoring systems, but recognised there was a missing link in the chain between asteroid threat identification and ways of addressing that threat. In response NASA oversaw the DART mission while ESA developed the Hera mission to gather additional data on DART’s impact. With the Hera mission, ESA is assuming even greater responsibility for protecting our planet and ensuring that Europe plays a leading role in the common effort to tackle asteroid risks. As Europe’s flagship planetary defender, Hera is supported through the Agency’s Space Safety programme, part of the Operations Directorate.

 

Press release from ESA Hubble

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Webb Detects Extremely Small Main-Belt Asteroid

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Webb Detects Extremely Small Main-Belt Asteroid

A previously unknown 100–200-metre asteroid — roughly the size of Rome’s Colosseum — has been detected by an international team of European astronomers using the NASA/ESA/CSA James Webb Space Telescope. Their project used data from the calibration of the Mid-InfraRed Instrument (MIRI), in which the team serendipitously detected an interloping asteroid. The object is likely the smallest observed to date by Webb and may be an example of an object measuring under 1 kilometer in length within the main asteroid belt, located between Mars and Jupiter. More observations are needed to better characterize this object’s nature and properties.

small asteroid Webb
Webb Detects Extremely Small Main-Belt Asteroid. A previously unknown 100–200-metre asteroid — roughly the size of Rome’s Colosseum — has been detected by an international team of European astronomers using the NASA/ESA/CSA James Webb Space Telescope. Their project used data from the calibration of the Mid-InfraRed Instrument (MIRI), in which the team serendipitously detected an interloping asteroid. The object is likely the smallest observed to date by Webb and may be an example of an object measuring under 1 kilometer in length within the main asteroid belt, located between Mars and Jupiter. More observations are needed to better characterize this object’s nature and properties. Credits: N. Bartmann (ESA/Webb), ESO/M. Kornmesser and S. Brunier, N. Risinger (skysurvey.org)

The Solar System is teeming with asteroids and small rocky bodies — astronomers currently know of more than 1.1 million of these rocky remnants of the early days of the Solar System. The NASA/ESA/CSA James Webb Space Telescope’s ability to explore these objects at infrared wavelengths is expected to lead to groundbreaking new science, but a team of scientists have shown that Webb also has an unpredicted aptitude for serendipitously detecting small and previously unknown objects.

“We — completely unexpectedly — detected a small asteroid in publicly available MIRI calibration observations,” explained Thomas Müller, an astronomer at the Max Planck Institute for Extraterrestrial Physics in Germany. “The measurements are some of the first MIRI measurements targeting the ecliptic plane and our work suggests that many, new objects will be detected with this instrument.”

The Webb observations which revealed this small asteroid were not originally designed to hunt for new asteroids — in fact, they were calibration images of the main-belt asteroid (10920) 1998 BC1, which astronomers discovered in 1998 [1], but the calibration team considered them to have failed for technical reasons due to the brightness of the target and an offset telescope pointing. Despite this, the data on asteroid 10920 were used by the team to establish and test a new technique to constrain an object’s orbit and to estimate its size. The validity of the method was demonstrated for asteroid 10920 using the MIRI observations combined with data from ground-based telescopes and ESA’s Gaia mission [2].

In the course of the analysis of the MIRI data, the team found the smaller and previously unknown interloper in the same field of view. The team’s results suggest the object measures 100–200 meters, occupies a very low-inclination orbit, and was located in the inner main-belt region at the time of the Webb observations.

“Our results show that even ‘failed’ Webb observations can be scientifically useful, if you have the right mindset and a little bit of luck,” elaborated Müller. “Our detection lies in the main asteroid belt, but Webb’s incredible sensitivity made it possible to see this roughly 100-metre object at a distance of more than 100 million kilometres.”

The detection of this asteroid — which the team suspects to be the smallest observed to date by Webb and one of the smallest detected in the main-belt — would, if confirmed as a new asteroid discovery, have important implications for our understanding of the formation and evolution of the solar system. Current models predict the occurrence of asteroids down to very small sizes, but small asteroids have been studied in less detail than their larger counterparts owing to the difficulty of observing these objects. Future dedicated Webb observations will allow astronomers to study asteroids smaller than 1 kilometer in size, providing the necessary data to refine our models of the solar system’s formation.

What’s more, this result suggests that Webb will also be able to serendipitously contribute to the detection of new asteroids. The team suspect that even short MIRI observations close to the plane of the Solar System will always include a few asteroids, most of which will be unknown objects.

In order to confirm that the object detected is a newly discovered asteroid, more position data relative to background stars is required from follow-up studies to constrain the object’s orbit.

“This is a fantastic result which highlights the capabilities of MIRI to serendipitously detect a previously undetectable size of asteroid in the main belt,” concluded Bryan Holler, Webb support scientist at the Space Telescope Science Institute in Baltimore, USA. “Repeats of these observations are in the process of being scheduled, and we are fully expecting new asteroid interlopers in those images!”

Notes

[1] The main asteroid belt is a doughnut-shaped region which contains the majority of the Solar System’s asteroids. It lies roughly between the orbits of the planets Mars and Jupiter, and is closely aligned with the ecliptic plane, the plane of the Earth’s orbit around the Sun, which is also the rough plane in which the other planets of the Solar System lie.

[2] ESA’s Gaia mission is in the process of precisely measuring the positions of astronomical objects to build up an extraordinarily precise three-dimensional map of more than a thousand million stars.

Press release from ESA Webb on the small asteroid detected by the James Webb Space Telescope.

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