Starting the Analysis of Spherules from the Interstellar Expedition

Avi Loeb
8 min readJul 7


Follow-up on an Interstellar Voyage, Report 36

(July 7, 2023)

Avi Loeb holding a vial with a spherule from the site of the first recognized interstellar meteor in a NewsNation interview with Chris Cuomo on July 6, 2023. This spherule arrived on Earth on January 8, 2014 and stayed for almost a decade at a depth of 2 kilometers on the Pacific Ocean floor, before it was picked-up by a magnet on a sled that delivered it to the deck of the ship Silver Star on June 20, 2023. Subsequently, it was scraped from the magnet together with volcanic ash, and eventually separated with tweezers into the vial shown here.

Upon our return to San Francisco airport, we boarded a car headed to UC Berkeley, where we conducted preliminary imaging and composition analysis of a few tiny marbles, each half a millimeter in size and a milligram in mass. These spherules are a subset of the 50 that we retrieved in our expedition to the Pacific Ocean, aiming to find relics of the first recognized interstellar meteor, IM1. The microscope on our ship, Silver Star, revealed these spherules as beautiful metallic marbles, colored gold, black, blue and brown. Reassuringly, most of them were concentrated around the expected path of IM1 — about 85 kilometers off the coast of Manus Island in Papua New Guinea.

The electron-microscope images were tantalizing, showing surface dendrites as expected for molten droplets from an explosive event that heated the meteor’s surface to extreme temperatures. The interior structure of one of the spherules included spheres within spheres down to the scale of hundreds of atoms, organized like nested matryoshka dolls. A possible explanation for this arrangement is that after the smallest droplets solidified, they were engulfed by molten iron that glued them together within a larger droplet that solidified and then was captured by yet a bigger droplet. The hierarchical merging was evident already on the ship when we found an ellipsoidal composite of multiple spherules which solidified prematurely before turning into a spherical merger product.

This nested spherule structure provides a metaphor to the way scientific knowledge solidifies. It is seeded by small clues which are glued together within a grander scheme. The scientific process is not revealed through press conferences in which scientists lecture to the public about their results, clean of any doubts or mistakes. Instead, the final realization is acquired through trial and error, following correction of doubts and missteps. This makes science an imperfect human activity. Scientists often hide the intermediate steps out of fear that exposing them would lower their prestige and risk future funding of scientific research. But ironically, the classroom approach of presenting final products creates distrust by the public when mistakes are exposed for some results after they were announced with confidence in press conferences. The premature solidification of ideas resembles the mergers of droplets, which solidify prematurely before acquiring a perfectly spherical exterior. A better approach, inspired by the electron microscope images of spherules, is to expose the scientific process in which clues are glued together iteratively in an effort to gain a more comprehensive understanding. Millions of readers of my 35 diary reports from the expedition were excited by witnessing science in action. Apparently, science is particularly exciting to the public when it resembles a detective story rather than a classroom. Moreover, science will likely receive more funding if it resonates with the public’s interests, and is driven by raw curiosity instead of a sense of intellectual privilege or a status symbol.

A few days after returning back home, FedEx delivered a black plastic suitcase with the expedition materials to my front door. This was a historic moment, as I realized that for the first time in history, humans are in possession of materials from a meter-size object that came from outside the solar system, IM1. FedEx was the last step in a journey that this package made over billions of years through interstellar space before reaching my doorstep. The spherules arrived on Earth on January 8, 2014 and stayed for almost a decade at a depth of 2 kilometers on the Pacific Ocean floor, before they were picked-up by a magnet on a sled that delivered them to the deck of the ship Silver Star the second half of June 2023. Subsequently, they were scraped from the magnets together with volcanic ash, and eventually separated with tweezers into vials.

I estimate that there are about a million objects like IM1 right now within the orbit of the Earth around the Sun, but they do not reflect enough sunlight to be detectable with our best telescopes on Earth. Only a small fraction of them are detected as meteors after colliding with Earth and burning up in a fireball of atomic bomb proportions as a result of their friction with the air. The Earth scoops meter-scale interstellar objects about once per decade.

There are up to a thousand times more asteroids from the solar system within the Earth’s orbit around the Sun than interstellar objects of the same size. Consequently, it is difficult to isolate an interstellar object without knowing its velocity prior to impact. It is possible that some interstellar objects were confused for members of a rare class of solar system meteorites in the past. One way to figure this out is by studying the spherules of meteors like IM1, where velocity measurements are available.

Some interstellar objects are trapped by the gravitational fishing net of the Jupiter-Sun system. In a recent paper, we calculated the abundance of trapped interstellar objects near Earth. If a trapped interstellar object is identified near Earth, we could send a probe that would land on it and explore it, similarly to the study of the asteroid Bennu by OSIRIS-REx. Such a space mission would cost a thousand times more than the expedition to retrieve the remnants of IM1 in the Pacific Ocean.

TV interview of Avi Loeb with Chris Cuomo (left), shortly after the spherules were delivered by FedEx. The images in the middle show the sled bringing the spherules to the deck of Silver Star, where they were separated from the sled’s magnets.

An hour after the spherules were placed in my home office, I was interviewed by Chris Cuomo on NewsNation who asked to see them. As I showed one of the vials, I cautioned that the millimeter-scale marble is probably not resolved by the camera. Subsequently, I informed Lou Dobbs in his podcast “The Great America Show”, that the expedition validated the meteor measurements by the Department of Defense. A year after the US Space Command put their reputation on the line by checking their data and issuing a formal letter to NASA confirming the interstellar origin of IM1 at the 99.999% confidence, two astronomers published a paper in The Astrophysical Journal , stating that the government data must be wrong. Since their model for solar system rocks could not fit the government’s data, they concluded that the meteor speed was much smaller and it could not have been made of iron. Early in my career, my mentors taught me that if a model does not fit the data then the model should be revised. This is a trademark of modesty, and also of common sense after an expedition retrieves spherules from the meteor being modeled, and these spherules are found to be made mostly of iron!

The following day, I brought the black suitcase with the spherules to my office at Harvard University, where I met with Professor Stein Jacobsen and his research group to plan the analysis of the spherules with state-of-the-art instruments.

As I opened the wrappings around the vials, my finger got dirty with ocean mud. One of the students offered me a napkin and I politely declined because “there may be a spherule embedded in this dirt so I would rather clean my finger into a vial.”

After the completion of the planning session, I escorted Stein down the elevator to the ground floor. As we came out of the elevator door, a CBS reporter with a TV camera was waiting for me. I showed him the vials inside the black suitcase and explained what they mean while he was filming the scene. As Stein walked away with the suitcase, I asked him to take good care of the babies delivered by the interstellar expedition. A maintenance person who was working in the same corridor approached me to ask: “Is this the material from the famous expedition that I keep hearing about?”

The expedition team held its first online meeting to plan ahead and start putting together the content of the scientific paper that summarizes our findings. We hope to complete the preliminary analysis of the spherules through three laboratories in UC Berkeley, Harvard and the Bruker Corporation in Germany, and incorporate the results into a paper that will be submitted for publication in a peer-reviewed journal within the coming month. The fundamental question we will address is whether the elements and radioactive isotopes in the spherules have different abundances than solar system materials. If so, we would also check for any anomalies that might indicate a technological origin. For example, the melted material of semiconductors would include rare elements at a much higher abundance than found in nature.

Subsequently, I received an email from our team geologist, Jeff Wynn, who reported: “Interest in the Interstellar Expedition extended to the humble man who came by to fix my sprinkler system this morning — he was aware of it! Before I could say much, he voiced the idea of “…what human arrogance to think that we are alone and unique in the universe.” I rest my case.

Our findings open a new frontier in astronomy of studying what lies outside the solar system through microscopes rather than telescopes.

Art Wright (left) and Avi Loeb discussing the next expedition to find larger pieces of IM1, following a champagne toast on Silver Star (June 27, 2023).


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".