The IM1 Spherules from the Pacific Ocean Have Extrasolar Composition

Avi Loeb
11 min readAug 29, 2023


Diary of an Interstellar Voyage, Report 45

(August 29, 2023)

The expedition team on the deck of the ship “Silver Star” (June 27, 2023). The large A-frame in the background directed a long cable from the ship to the magnetic sled on the ocean floor at a depth of 2 kilometers. The sled retrieved about 700 submillimeter-sized spherules through 26 Runs which criss-crossed a 10-kilometer region around the fireball location of the first recognized interstellar meteor, IM1.

Wonderful news! For the first time in history, scientists analyzed materials from a meter-size object that originated from outside the solar system. The object lit up the sky over the Pacific Ocean nearly a decade ago and its bright fireball was tracked by US government satellites.

It has been my great fortune to shepherd this analysis. The interstellar expedition team of the Galileo Project just completed the early analysis of 57 spherules from the crash site of the first recognized interstellar meteor, IM1. Five of these millimeter-size marbles originated as molten droplets from the surface of IM1 when it was exposed to the immense heat from the fireball generated by its friction on air on January 8, 2014.

Altogether, about 700 spherules were collected by the expedition I led to the Pacific Ocean on June 14–28, 2023. Below I overview our main findings. Technical details and supporting information can be found in our scientific paper, accessible here, which was submitted for publication in a prestigious peer-reviewed journal. A detailed day-by-day description of the journey can be found in my previous 44 diary reports, accessible here.

The success of the expedition was not a chance coincidence. We were blessed with exceptional team members who worked selflessly to accomplish this outcome. Our collective experience feels like a soccer team after a winning game. All team members contributed professionally and constructively.

Vacuum cleaning and scraping of the sled’s magnets by team members J.J. Siler (left) and Avi Loeb (right).

The interstellar origin of IM1 was established at the 99.999% confidence based on velocity measurements by US government satellites, as confirmed in a formal letter from the US Space Command to NASA. The fireball light curve showed three flares, separated by a tenth of a second from each other. Prior to entering the solar system, IM1 was moving at a speed of 60 kilometers per second relative to the Local Standard of Rest of the Milky-Way galaxy, faster than 95% of all stars in the vicinity of the Sun. Based on the fact that it maintained its integrity at an impact speed on Earth of 45 kilometers per second down to an elevation of 17 kilometers above the Pacific Ocean, its material strength must have been tougher than all 272 space rocks documented by NASA in the CNEOS meteor catalog, including the 5% minority of them which are iron meteorites.

The retrieved spherules are being analyzed by the best instruments in the world within four laboratories at: Harvard University, UC Berkeley, the Bruker Corporation, and the University of Technology in Papua New Guinea — whose Vice Chancellor signed a Memorandum of Understanding with Harvard University for partnership on the expedition research.

Collected material from the magnetic sled at IM1’s site, showing a 0.4-millimeter diameter iron-rich spherule (white arrow) amongst a background of shell hash and other debris.

The collection of spherules by the expedition had a yield per background mass that increased significantly the count of spherules near IM1’s path. The heatmaps below show that the spherules collection had three high-yield regions, colored in yellow, relative to the control regions colored in purple, potentially reflecting the three flares from IM1’s light curve.

Heatmap of spherule density (count per mass of material analyzed in grams). Assuming that the first flare of the fireball light curve was located at the start of Run 4, we placed three stars for the locations of the three flares. The color bar maximum is clipped at 0.35 in this visualization. Each colored pixel in the heatmap is 0.555 kilometer on a side.
Zoom on the region sampled around the predicted IM1 path (orange box) and the DoD error region (red box). For reference, the dots represent the GPS recordings of the ship track in different numbered runs.

The heatmap was derived from the spherule detection statistics by my postdoc, Laura Domine. It greatly benefitted from the 622 spherules that were discovered by my summer intern student, Sophie Bergstrom. The extensive composition analysis of the spherules was performed by Stein Jacobsen and his cosmochemistry laboratory team at Harvard University.

Remarkably, Stein’s conservative analysis revealed that five unique spherules from the high-yield (yellow) regions near IM1’s path and not anywhere else, showed a composition pattern of elements from outside the solar system, never seen before. This result was obtained after the heatmap was generated and provided an independent confirmation that IM1 is responsible for the excess spherules in the yellow regions.

From right: Stein Jacobsen, Avi Loeb and Sophie Bergstrom, behind the mass spectrometer in Jacobsen’s laboratory at Harvard University (July 31, 2023).

The electron microprobe images from Stein’s laboratory were also fascinating. An example of a large (1.3 mm in maximum diameter) spherule in the high-yield (yellow) region near IM1’s path is S21 from run 14. This lopsided spherule, shown in the image below, is a composite of three spherules that solidified shortly after merger, too late for the merger product to become spherical.

Electron microprobe image of S21 from Run 14 in the high yield region of IM1’s path.

The emergence of this composite spherule S21 through mergers of smaller droplets in the initial fireball volume has a simple quantitative explanation. Naturally, Stein chose this large spherule first for composition analysis with his state-of-art mass-spectrometer. The results were tantalizing.

The “BeLaU” composition template measured by the Harvard mass spectrometer. Plotted are the elemental abundances throughout the entire mass of the massive spherule S21 normalized to the solar system standard of CI chondrites (represented by a value of unity on the vertical axis).

As shown in the above figure, S21 was heavily enriched by factors of hundreds in Beryllium (Be), Lanthanum (La), and Uranium (U), relative to the solar-system standard composition of CI chondrites. This led Stein to label this unique abundance pattern: “BeLaU”.

The “BeLaU” abundance pattern of elements in spherule S21 and four other spherules in the high-yield (yellow) regions from runs 4, 13 and 14 near IM1’s path, also displays the loss of volatile elements, as expected from the airburst of a non-terrestrial object.

The measured abundances of heavy elements beyond lanthanum are consistently well beyond those of the solar system standard of CI chondrites, suggesting that “BeLaU”-spherules originated from outside the solar system. The source had a very low content of elements with affinity to iron, such as Rhenium (Re). The birth site of IM1 could have been a differentiated crust of an exo-planet with an iron core and a magma ocean. The lack of volatile elements is most likely due to evaporative losses during IM1’s passage through the Earth’s lower atmosphere.

Altogether, a significant fraction of the spherules from the runs near IM1’s high-yield (yellow) regions have “BeLaU” abundances, but no such spherules are found in control regions far from IM1’s path. The excess is consistent with IM1 doubling the number of spherules per unit area in the yellow regions. Detailed analysis shows that the discrepancies between the “BeLaU” abundance pattern and solar system environments could not have originated from the magma oceans of the Earth, the Moon or Mars.

The “BeLaU” abundance pattern for five spherules near IM’1 path as a function of the volatility of elements, namely their ability to be lost by evaporation during IM1’s airburst.

An independent test of whether “BeLaU” spherules originated from an extraterrestrial source is offered by iron isotope ratios. Indeed, the giant “BeLaU” spherule S21 from run 14 deviates considerably from various solar system environments in terms of its Iron-57 versus Iron-56 abundances. Given that this spherule was collected from the high-yield (yellow) region around IM1’s path, this is consistent with an interstellar origin for IM1.

The large “BeLaU” spherule S21 from Run 14 deviates considerably from various solar system environments in terms of its Iron-57 versus Iron-56 isotopic abundances. Given that this spherule was collected from the high-yield region around IM1’s path, this result suggests an interstellar origin for IM1 unlike those found in known solar system environments.
Ryan Weed’s team performing SEM/EDS measurements of IM1 spherules at the Department of Nuclear Engineering in UC Berkeley.

At Ryan Weed’s laboratory in UC Berkeley, Scanning Electron Microscope and Energy Dispersive X-Ray Spectroscopy (SEM-EDS) measurements were conducted on an initial inventory of spherule samples. The electron microscope images show “Russian-doll” structures of spheres within spheres embedded in a matrix with dendritic structure and indicating rapid cooling during an airburst.

Spherule S4 from Run 8, showing interior structure of spheres within spheres, with the smallest micro-spherules of approximately 5–10 microns in diameter.

Altogether, the highlights of our findings are twofold:

(i) The magnetic sled survey retrieved about 700 spherules of diameter 0.05–1.3 millimeters through 26 runs covering a survey area measuring a quarter of a square kilometer in total.

(ii) Mass spectrometry shows unique spherules from the high-yield regions near IM1’s path, having a high enrichment of Be, La and U, as well as a very low content of elements with high affinity to iron, like Re. Volatile elements were lost by evaporation during IM1’s passage through the Earth’s atmosphere.

Spherules with the “BeLaU” abundances were found only along IM1’s path and not in control regions. The “BeLaU” elemental abundance pattern does not match terrestrial alloys, fallout from nuclear explosions, magma ocean abundances of Earth or its Moon or Mars, or other natural meteorites in the solar system. This supports the interstellar origin of IM1, independently of the measurement of its high speed as reported in the CNEOS catalog and confirmed in an official letter to NASA from the US Space Command.

Since IM1’s spherules melted off the surface of the object, the enhanced Be abundance may represent a flag for cosmic-ray spallation on IM1’s surface along an extended interstellar journey through the Milky-Way galaxy. This constitutes a fourth indicator of an interstellar origin for IM1, in addition to its high speed, its heavy element composition and its iron isotope ratios. Some of these indicators can be used to identify an interstellar origin of historic meteorites for which no information is available about their orbital velocity relative to the Sun.

Ryan Weed (left) vacuuming the sled’s magnet while wearing the “Interstellar Expedition Team” T-shirt.

The enhanced abundances of heavy elements may explain the high material strength inferred for IM1 based on the high ram-pressure it was able to sustain before disintegrating.

The high material strength inferred for IM1 can potentially be tested experimentally by assembling a material mix based on the “BeLaU” composition, with proper compensation for lost volatile elements.

The “BeLaU” abundance pattern could potentially be explained if IM1 originated from a highly differentiated crust of an exoplanet with an iron core. In that case, IM1’s high speed of ~60 kilometers per second in the Local Standard of Rest of the Milky-Way galaxy and the extremely large number of similar objects per star, 10 to the power of 23, inferred statistically for the population of meter-size interstellar objects , are challenging to explain by common dynamical processes.

The “BeLaU” overabundance of heavy elements could have instead originated from so-called “r-process” enrichment and fragmentation of ejecta from core-collapse supernovae or neutron star mergers. However, the “BeLaU” pattern also displays a so-called “s-process” enrichment which must have originated from an independent origin, such as Asymptotic Giant Branch (AGB) stars. A more exotic possibility is that this unfamiliar abundance pattern, with uranium being nearly a thousand time more abundant than the standard solar system value, may reflect an extraterrestrial technological origin. These interpretations will be considered critically along with additional results from spherule analysis in future work.

Irrespective of the interpretation, this is a historic discovery because it represents the first time that scientists analyze materials from a large object that arrived to Earth from outside the solar system.

Avi Loeb’s hands opening the suitcase containing the spherules from the site of the first recognized interstellar meteor, IM1. The content was delivered by FedEx within days, but likely took billions of years to be delivered to Earth prior to that.

The “Interstellar Expedition” was risky. There were many potential failure points, such as: not securing the needed funding of 1.5 million dollars, not recruiting qualified expedition engineers and navigators, not building the proper machinery to accomplish the task, not getting the sled to stay on the ocean floor because of the lift exerted by the cable connecting it to the ship, not finding magnetic spherules from IM1 on the ocean floor, not having enough spherules from IM1 to find them within the surveyed area, not noticing the spherules among the background volcanic ash, and not having access to a state-of-the-art mass spectrometer that enabled a reliable discovery of the unprecedented “BeLaU” abundance pattern.

Inspecting the magnetic sled harvest on a rainy night. From left: Avi Loeb, Charles Hoskinson — who generously funded the expedition at $1.5M, Ryan Weed and Jeff Wynn. Behind the sled, Josh Saltzman is filming the event for a documentary.

But long before all of that, I could have decided not to pursue this project because of the extreme pushback from “experts” on space rocks who were “sick about hearing Avi Loeb’s wild claims”, according to a New-York Times article and a New-York Times Magazine profile.

I wish these astronomers happiness and prosperity. Now that we discovered spherules with an extra-solar composition near IM1’s path, they better retract their published claim that the US Space Command overestimated IM1’s speed by a large factor and that IM1 was a stony meteorite from the solar system. We now know that IM1 was interstellar. Instead of rejecting the data, they would be better off revising their model.

The success of the expedition illustrates the value of taking risks in science despite all odds as an opportunity for discovering new knowledge. The discovered “BeLaU” spherules provide a wake-up call from afar, urging astronomers to be more curious and open-minded.

The expedition’s party chief, Art Wright, and chief scientist, Avi Loeb, contemplating the next expedition at sunset (June 27, 2023).

My initial fascination with another interstellar object, `Oumuamua, in October 2017, was triggered by the realization that its mere detection was in conflict with my expectation for a much lower abundance of interstellar objects in a 2009 paper, based on what was known about the solar system. Mistakes offer an opportunity to learn something new. My subsequent engagement with IM1 followed a radio interview with John Catsimatidis in January 2019 about the Kamchatka meteor which exploded a few weeks earlier and led me to wonder whether the CNEOS catalog contains interstellar objects like `Oumuamua.

The name we assigned to IM1 sounds like: “I am one”, fittingly labeling the first recognized interstellar meteor, but also — a member of a large population of similar objects. The second interstellar meteor, IM2, sounds like “I am too.” Finding the first and second ants in a kitchen is alarming because it implies many more ants out there. A random detection rate of once per decade for meter-size interstellar objects implies that a few million such objects reside within the orbit of the Earth around the Sun at any given time. Some of them may represent technological space trash from other civilizations.

During my routine jog at sunrise on the deck of Silver Star, I was asked: “Are you running away from something or towards something?” My answer was: “Both. I am running away from colleagues who have strong opinions without seeking evidence, and I am running towards a higher intelligence in interstellar space.”


Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He chairs the advisory board for the Breakthrough Starshot project, and is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. His new book, titled “Interstellar”, is scheduled for publication in August 2023.



Avi Loeb

Avi Loeb is the Baird Professor of Science and Institute director at Harvard University and the bestselling author of “Extraterrestrial” and "Interstellar".