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Avi Loeb — Interstellar Meteors, Spherules, and Alien Origins

Interstellar: The Search for Extraterrestrial Life and Our Future in the Stars (book cover)

Did Harvard astronomer Avi Loeb discover the remnants of an interstellar meteor in the form of spherules on the ocean floor? Could they be of alien origin?

In today’s special edition of The Michael Shermer Show the guest, Harvard astrophysicist Dr. Avi Loeb announces that he has discovered material from a large interstellar object from the bottom of the Pacific Ocean near Papua New Guinea in an expedition he led over the summer. The object, which he labels IM1—Interstellar Meteor 1—collided with Earth nearly a decade ago and was tracked by U.S. government satellites, which gave Loeb and his team coordinates of where to look (more on this below). Most of the meteor burned up in the atmosphere but tiny spherules remained on the ocean bottom, which Loeb retrieved and had analyzed in labs at Harvard, UC Berkeley, and the Broker Corporation. These spherules are tiny—smaller than a grain of sand—and there are literally trillions of them around the world of both terrestrial and extraterrestrial origin, so whether or not these particular spherules are Interstellar in origin remains to be seen, despite Loeb’s confidence that they are. Here is what he announced today in a press release:

The Interstellar Expedition of June 2023–led by the expedition’s Chief Scientist, Harvard University Astrophysicist Avi Loeb and coordinated by Expedition Leader Rob McCallum of EYOS Expeditions retrieved hundreds of metallic spheres thought to be unmatched to any existing alloys in our solar system from the seafloor in the Pacific Ocean near Papua New Guinea. Early analysis shows that some spherules from the meteor path contain extremely high abundances of Beryllium, Lanthanum and Uranium, labeled as a never-seen-before “BeLaU” composition. These spherules also exhibit iron isotope ratios unlike those found on Earth, the Moon and Mars, altogether implying an interstellar origin. The loss of volatile elements is consistent with IM1’s airburst in the Earth’s atmosphere. “The “BeLaU” composition is tantalizingly different by factors of hundreds from solar system materials, with beryllium production through spallation of heavier nuclei by cosmic-rays flagging interstellar travel,” says Avi Loeb.

The press release of August 29, 2023 was timed with the publication date of Dr. Loeb’s new book, Interstellar, whose subtitle hints at the scientist’s larger ambitions: The Search for Extraterrestrial Life and Our Future in the Stars.

Dr. Loeb’s co-authored paper has not been peer reviewed. In fact, none of the world’s leading experts on spherules from space have even seen any of Dr. Loeb’s evidence. So in preparation for this episode, I contacted Peter Brown, an astronomer at Western University, Ontario, who specializes in the physics of meteors, and he directed me to the five leading experts in the world on spherules. These include: George Flynn, SUNY, Plattsburgh; Don Brownlee, University of Washington; John Bradley, University of Hawaii; Michael Zolensky, NASA; and Matthew Genge, Imperial College, London. I also consulted Steven Desch, from Arizona State University, as he has been quoted elsewhere as a critic of Avi Loeb’s research. All expressed their skepticism about Dr. Loeb’s findings, which I read on air to Avi to get his response (see the show notes below). Listen to the experts and Dr. Loeb’s response to their skepticism in this episode. (Note: Steven Desch’s initial statement, included in the show notes, was so negative that I chose not to read it on air, but include it here for full disclosure of what he thinks about this research. I also included Dr. Desch’s additional comments on why many scientists are skeptical of the U.S. government data on the meteor’s trajectory and impact site.)

I should note that I am a member of the Galileo Project team, which organized this expedition, and I consider Avi a friend and colleague who always welcomes my skepticism in our weekly team meetings. To that end let me emphasize that he is not claiming to have discovered alien technology, only the remnants of an interstellar object. Unfortunately, the media coverage surrounding the Galileo Project in general and this expedition in particular is only interested in whether or not we have made contact with ET. We have not, and Avi is not claiming that we have. But here is an example, which I tweeted out recently, of what Avi is claiming and what the media reports:

Tweet by Michael Shermer

No matter the scientific find is, the media reports it as aliens, aliens, and aliens. Alas.

My own view is that aliens are very likely out there somewhere—given the astronomical numbers of hundreds of billions of galaxies, each of which has hundreds of billions of stars, each of which has planets it seems highly unlikely that we’re alone in the cosmos—but that they have very likely not come here in any shape or form—nonhuman biologics or extraterrestrial metalogics (my own neologism echoing government whistleblower David Grusch’s ridiculous description of alien pilots as “nonhuman biologics” in his Congressional testimony). The universe is vast and consists of mostly empty space. The odds are very long indeed that anyone could find us, much less leave traces for us to evaluate. But in keeping with Cromwell’s Rule in Bayesian reasoning (never assign a 0 or 1 probability to anything because, as Oliver Cromwell famously said, “I beseech you in the bowels of Christ you might be mistaken”), we should keep an open mind and keep looking. That is why I support the SETI program and am on the Galileo Project team. The odds are long but the payoff would be spectacular if we ever did discover extraterrestrial intelligence or the technological artifacts of an extraterrestrial civilization.

Abraham (Avi) Loeb is the Frank B. Baird, Jr., Professor of Science at Harvard University, the longest-serving chair of Harvard’s Department of Astronomy, the founding director of Harvard’s Black Hole Initiative, and the current director of the Institute for Theory and Computation (ITC) within the Harvard-Smithsonian Center for Astrophysics. He also heads the Galileo Project, chairs the Advisory Committee for the Breakthrough Starshot Initiative, and is former chair of the Board on Physics and Astronomy of the National Academies. Author of eight books and more than a thousand scientific papers, Loeb is an elected fellow of the American Academy of Arts and Sciences, the American Physical Society, and the International Academy of Astronautics. In 2012, Time selected Loeb as one of the 25 most influential people in space. He lives near Boston, Massachusetts.

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Show Notes

Peter Brown, Western University, Ontario, gave me the names of the top experts in the world on spherules (tiny fragments of meteors that strike earth and/or industrial debris from manufacturing), whom I queried about Avi Blum’s findings. Here are their responses:

Michael Zolensky, NASA

Yes, I know all about this, but I would rather withhold any question or statement until I see what he actually has. I’m sure you understand.

Matthew Genge, Imperial College, London

Sure… I’d be interested to see the paper too. I am guessing it won’t be in Science or Nature. However, I do think pushing the envelope is necessary as a scientist, as is being provocative, but at the end of the day, the more dramatic the conclusion, the stronger the evidence has to be. However, I haven’t seen the data, thus I can’t give a proper opinion, only an impression on what has been reported in the media.

My question to Avi Loeb would be this:

“The only evidence universally accepted by scientists for an origin beyond our solar system is an isotopic composition significantly outside the range of materials within our solar system. What isotopes have you analysed in the materials you have recovered? What is their range as a ratio to maximum solar system values?”

I suspect his answer will be to dismiss the requirement and instead to point to dynamic evidence (e.g. entry velocity from meteor observations). If he tries to claim this add:

“Considering radar observations are highly uncertain how can you be certain that this meteor was interstellar? Many meteor scientists claim there still has never been an unequivocal interstellar meteor.”

It might, however, be easier to put me on the same podcast with him so we can talk. I even agree with him on some things…for example, the compositions I’ve seen reported seem to be artificial, I agree they are not interplanetary dust from our solar system, however, I would suggest they are much more likely to be terrestrial and anthropogenic. I also have some suggestions by which he might be able to distinguish between terrestrial and extraterrestrial materials.


“If you heat Ti-rich metal in an oxygen-rich atmosphere, it reacts to form titanium oxides. It is difficult to say, since the results havent yet been published, but if your particles are made of titanium-rich metal, then they haven’t experienced atmospheric entry.”

I do, however, agree with Avi. If an alien civilization has ever visited Earth, now or in the distant past, they may have left tiny pieces of evidence on our planet in the form of droplets formed by their atmospheric entry. The evidence, however, must be exceedingly strong. For example, several years ago we found iron-manganese oxide spherules in 100-million year old sea floor rocks, and it crossed our minds that these materials are used in spacecraft alloys, however, it turned out that ordinary interplanetary dust is transformed during its time on the seafloor by replacement of nickel by manganese. Geology is a complicated business since we still dont know all the processes that operate in the natural environment.

George Flynn, SUNY, Plattsburgh

Cosmic spherules have been recovered from the ocean floor since the Challenger Expedition in the 19th century. Since the Challenger Expedition recovered these spherules they have also been recovered from lakes, and even the Polar Ices. A good summary of the history is given in this paper. So I guess the most important question is how do the spherules Loeb recovered differ from the ones routinely collected and identified over the past century and a half, and what specific characteristic(s) distinguish them from the spherules of likely Solar System origin that have been studied in detail over that time.

I think the important point is that extraterrestrial metallic spheres have been collected from the seafloor in numerous locations in the Pacific Ocean (and other places around the world) since the 1880s. Finding these spherules in a location where Loeb expects ablation debris from a specific object does not demonstrate they are from that object. He should expect to find these spheres pretty much everywhere. So, to claim they are interstellar he must demonstrate that there is some specific feature that indicates they are not ablation products from Solar System meteors that enter the atmosphere all the time.

Don Brownlee, University of Washington

If something is found from outside the solar system, it will have a different isotopic composition than Earthly materials. This property has been used to identify thousands of small presolar grains in meteorites and interplanetary dust. These grains are usually a micron or smaller and they formed around other stars but were preserved inside the asteroids that generate meteorites. With the right equipment, these rare grains can be proven to have formed around other stars. It should be simple to ID interstellar material and it is done routinely for the rare presolar grains. As Carl Sagan famously said – extraordinary claims require extraordinary proof. Isotopic composition or age older than the Sun would be proof.

My thoughts are that most interstellar solids entering the solar system in sizes of microns to kilometers were probably made during the peak of star formation in the Galaxy and are over 10 billion years old. These objects have typically spent billions of years in interstellar space at near zero temperature- no heat for Capt. Kirk or semiconductors. The first interstellar solids entering the solar system on unbound orbits were found by dust detectors on the Ulysses and Galileo spacecraft.

If an object is ET made, it surely will not be made of transparent aluminum or any other fantasy material. It would be made of materials that could be used to make spacecraft. The materials that we use to make spacecraft are exotic materials that never would be expect to be found in natural planetary materials, Such exotics are metallic Al, metallic Ti, carbon fiber, kapton sheet with metal coating, gold connectors, high strength steel, teflon, copper wire, epoxy and a vast array of engineered materials that would never have existed without human or ET production.

John Bradley, University of Hawaii

Dismay does not begin to describe my sentiments about Loeb’s scientific shenanigans. To assert that cosmic spherules (i.e., melted micrometeorites) that litter the seafloor are parts of an alien spacecraft defies common sense, unless of course alien spacecraft are actually made of rocks. This sort of nonsense may explain why so many in the public at large harbor an abiding antipathy towards science. Academic freedom, like (past) Presidential powers, is not without its limits.

Steven Desch, Arizona State

I have sparred with Loeb on matters from ‘Oumuamua, to the Chicxulub impactor, and now to the 2014-01-08 bolide. Regarding the interstellar meteor, I have engaged in my own research, much of which I presented at the June 2023 Asteroids, Comets & Meteors conference in Flagstaff. Peter Brown of University of Western Ontario also presented his research as well. Below I summarize the science case as it stands now.

Everyone agrees that if the meteor entered at the speed (45 km/s) and vector reported in the CNEOS database, it would be interstellar; but no scientist trusts those numbers, and it’s VERY likely this meteor came from our solar system.

  • Previous attempts to verify the CNEOS database numbers (using those also observed from the ground) shows they are wildly in error in about 1/3 of cases; sometimes the reported vectors are 90 degrees off. (Devilleux et al. )
  • Peter Brown demonstrated that the uncertainties in speeds for high-speed meteors are especially large; for this one they’re probably ±20 km/s. The 2014-01-08 bolide probably came in at 25 km/s (which would be more consistent with other aspects of its light curve), and therefore wasn’t interstellar. (Brown et al. 2023 )
  • I’m working with Maria Hajdukova in Slovakia, who is an expert on meteors, and in work in preparation, they show that all the fast meteors in the CNEOS database have one velocity component that’s really funky (i.e., 45 km/s is probably measurement error).

There’s nothing obviously unnatural about this bolide.

Assuming anyway the 2014-01-08 bolide was moving at 45 km/s, Siraj & Loeb (2022, ApJ) have implied it couldn’t have been a natural material because it broke up at a ram pressure of 200–250 MPa, whereas they cite a paper and claim iron meteorites can’t withstand pressures greater than 50 MPa. In fact they completely misquoted the papers they cite, which show iron meteorites can withstand pressures up to 700 MPa.

If the meteor did come in at 45 km/s, nothing would have survived.

  • In a preprint on arXiv, Tillinghast-Raby (a poor student), Loeb & Siraj claim that 10% of the meteor would have survived entry, but they falsely assumed the bolide exploded with every piece moving outward at 41 km/s (so that backward-moving material sees its forward motion almost completley cancelled). Actually, meteors disintegrate and all that material keeps moving forward at 45 km/s.
  • The formulas for how much material survives are in the meteor literature and are pretty well established once you define the ‘ablation parameter’. For any non-exotic material, < 0.0001% of this meteor would have survived if it were moving at 45 km/s. We’re talking milligrams.

There is no way to pin down the location of the material to better than tens of square kilometers.

  • In a preprint on arXiv, Siraj & Loeb tried to pin down the location using seismometry, but this preprint has many mathematical errors (a figure even shows the bolide moving east to west, instead of west to east!), and tries to attribute a signal to the bolide that is probably the signal of a passing truck or something on the island. It’s a hot mess. The uncertainty in where it fell is > 10 km.
  • In my ACM talk, we showed that in the minutes it takes spherules to sink to the ocean floor, the currents there would have distributed spherules across many kilometers east-to-west.

At no point did Loeb seem to recognize that the ocean floor is littered with metallic spherules from a variety of sources.

  • Micrometeorites have been purposefully collected from the seafloor using magnets for at least 50 years (ask Don Brownlee, PI of the Stardust mission), and were recognized for almost a century before that. Loeb cited NONE of this literature. As my oceanography colleague Hilairy Hartnett puts it, there are “squillions” of such spherules almost anywhere you can put a magnet on the seafloor.
  • Metallic spherules come from micrometeorites, but also from volcanic activity, and human industrial processes. Loeb presented no plan ahead of time for how he would distinguish these.
  • I’m not an expert on what variety of materials can be found on the seafloor, but I understand there are many industrial byproducts, and all of these would have to be ruled out to make any claims at all.

About the Book

In the New York Times bestseller Extraterrestrial, Avi Loeb, the longest serving Chair of Harvard’s Astronomy Department, presented a theory that shook the scientific community: our solar system, Loeb claimed, had likely been visited by a piece of advanced alien technology from a distant star. This provocative and persuasive argument opened millions of minds internationally to the vast possibilities of our universe and the existence of intelligent life beyond Earth. But a crucial question remained: now that we are aware of the existence of extraterrestrial life, what do we do next? How do we prepare ourselves for interaction with interstellar extraterrestrial civilization? How can our species become interstellar?

Now Loeb tackles these questions in a revelatory, powerful call to arms that reimagines the idea of contact with extraterrestrial civilizations. Dismantling our science-fiction fueled visions of a human and alien life encounter, Interstellar provides a realistic and practical blueprint for how such an interaction might actually occur, resetting our cultural understanding and expectation of what it means to identify an extraterrestrial object. From awe-inspiring searches for extraterrestrial technology, to the heated debate of the existence of Unidentified Aerial Phenomena, Loeb provides a thrilling, front-row view of the monumental progress in science and technology currently preparing us for contact. He also lays out the profound implications of becoming—or not becoming—interstellar; in an urgent, eloquent appeal for more proactive engagement with the world beyond ours, he powerfully contends why we must seek out other life forms, and in the process, choose who and what we are within the universe.

Combining cutting edge science, physics, and philosophy, Interstellar revolutionizes the approach to our search for extraterrestrial life and our preparation for its discovery. In this eye-opening, necessary look at our future, Avi Loeb artfully and expertly raises some of the most important questions facing us as humans, and proves, once again, that scientific curiosity is the key to our survival.

This episode was released on August 29, 2023.

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