Might an Iron Peanut or Bean Be Worth Ten Thousand Spherules or Nothing at All?

Avi Loeb
4 min readJun 26


Diary of an Interstellar Voyage, Report 31

(June 26, 2023)

Avi Loeb holds the 10-gram iron peanut that he retrieved from the sled magnet in Run 15 on June 23, 2023.

By now we have gotten used to the idea of finding tiny spherules, each measuring a quarter of a millimeter in size. We already have 38 of them. After seeing several of them, my older daughter, Klil, texted me the message: “They are so beautiful! Can I have one on a necklace?”

An Earth-miniature spherule from Run 14 has a mass that is 31 orders of magnitude smaller than that of Earth. Its location indicates that it likely came from the fireball of the first recognized interstellar meteor, IM1 (June 26, 2023).

But finding beauty on the ocean floor was not the goal of the Interstellar Expedition. Instead, the exceptional team members gathered on the deck of the ship Silver Star to figure out the nature of the first recognized interstellar meteor, IM1. Our ability to measure the elements and radioactive isotopes that constituted IM1 before it exploded 18 kilometers above the Pacific Ocean surface, depends mainly on the total mass of the sample of relics that we recover from it.

Sorting spherule candidates under a microscope on the upper level of Silver Star.

“Our signal-to-noise ratio is all about the total mass and not the number of spherules,” I explained to Rob McCallum at our team meeting today. Admittedly, the 25 milligrams of material we collected so far in 38 spherules is not a lot of mass. It is merely a part in twenty million of the total mass that was entrained in IM1’s fireball on January 8, 2014.

The latest spherule count is 38 (June 26, 2023), adding up to 30 milligrams of material.

But in Run 15 on June 23 I found a brown magnetic object from the sled and in Run 19 on June 25 I found another one in the shape of a kidney bean. When I separated the first object from the magnet, I realized that it has the shape of a peanut (or a seashell) of width 0.8 centimeters and length 2.5 centimeters. With a mass of 10 grams, it is equivalent to ten thousand spherules, each with a radius of 300 microns and a mass of about a milligram. The iron bean has similar properties.

Since we collected 38 such spherules in about a week, it would have taken us 10 years to collect twenty thousand of them at the same efficiency. And here comes the sled with its delivery of the iron peanut and the iron bean stuck to one of its magnets, allowing us to reach the same signal-to-noise ratio with our gamma-ray spectrometer right now as we would have achieved after collecting sub-millimeter spherules for a decade. When I informed Art Wright about the discovery of the iron peanut and bean, he asked: “Did we just win the lottery twice?”

My take was probably not. Winning the mass budget by four orders of magnitude twice is a very low probability event and so I was skeptical about the connection of the iron peanut and bean to IM1.

Tonight, we used the X-ray Fluorescence analyzer and measured that the composition of the iron peanut and bean is dominated by iron (85%) and Silicon (10%). It is different from the spherules and could be geological in origin. Surface contamination by the environment is possible, but we plan to conclusively rule out a common origin for the spherules and the iron peanut or iron bean with the sensitive diagnostics available to us once we return to the US.

But the good news is that total mass is not everything. The numerous spherules are important in tracing the trajectory of IM1 and leading us to any large relic left from it on the ocean floor in our next expedition. They resemble the way a trail of blood drops helps us find a wounded cat.

My former postdoc Girish Kulkarni wrote to me: “I am grateful to have people like you in my life, Avi… I have been reading your reports from the Pacific Ocean. Every one of them fills me with enthusiasm and optimism.” Frankly, I derive this optimism from the gifts of mother nature. Among these gifts are the 38 beautiful spherules that we recovered so far. Unfortunately, they are too small to be threaded on a necklace.


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".