The Count is Up to 360 Spherules!

Avi Loeb
4 min readJul 21


Diary of an Interstellar Voyage, Report 41

(July 21, 2023)

A beautiful image of one of our spherules, taken at Harvard University using the electron microprobe in Professor Stein Jacobsen’s laboratory. The spherule looks like a soccer ball.

In an email two weeks ago, my summer intern student, Sophie Bergstrom, told me that she is determined to pursue a career in science journalism but will also be delighted to help with the search for spherules. I arranged for Sophie to access the microscope and tweezers in Professor Stein Jacobsen’s laboratory at Harvard University and she was delighted to go through the expedition samples. Within a few days, Sophie broke the team’s record by finding 190 new spherules from the survey lines pursued by the expedition ship Silver Star. I assigned her the prestigious title of the expedition’s official “Spherule Hunter!”

Our total spherule count is now at 360, seven times more than the initial spherule sample we isolated on Silver Star. One of the spherules which was imaged by Stein’s electron microprobe looks like a soccer ball, very timely for celebrating FIFA Women’s World Cup which is taking place right now.

And there is another thread of soccer running through our research adventure. Before engaging in the expedition, we initiated an official research collaboration with the University of Technology at Papua New Guinea, established through an official letter from their Vice Chancellor. Tomorrow, Dr. Jim Lem, head of the Mining Engineering department at that University, is scheduled to visit Harvard University and participate in our analysis of the expedition’s findings. Jim is currently on his way to Harvard, as such a trip takes a few days. I will meet him upon his arrival, and we both plan to play the same evening, along with Sophie, in the annual soccer match of students versus faculty & postdocs of Harvard’s Institute for Theory and Computation, for which I serve as director.

We are still in the early stages of analyzing our expedition samples at Harvard, UC Berkeley and the Bruker laboratories in Germany. Currently, we are comparing the composition and morphology of spherules along the meteor path to those in control regions far away. The distant spherules should represent a background from either a geological origin on Earth or other meteorites from space. We can separate these two classes because spherules that pass through the atmosphere encounter isotopic mass fractionation, where some isotopes are lost during evaporation of the spherules when exposed to the immense heat from the fireball. The morphology of the two types is also expected to be different. This is why we plan a thorough study of morphology and composition of all spherules.

As the expedition’s chief scientist, I assigned the analysis of the samples to independent state-of-the-art laboratories and agnostic world experts in geology and meteoritic studies. This is the best way to arrive at fully rigorous and unbiased scientific conclusions. We plan to summarize our results in a future paper, to be submitted to a peer-reviewed journal.

Composition image of a spherule, obtained by Misha Pataev in Stein Jacobsen’s laboratory at Harvard. Color scheme in Red:Green:Blue reflects the abundance of Fe:Si:Al.

By now, Sophie has a unique first-hand experience of how science is done, which will serve her well in publishing her first article as a science journalist about the expedition.

Science is all about seeking evidence based on quantitative measurements by state-of-the-art scientific instruments. Here’s hoping for a future where all scientists would adhere to this methodology rather than express strong opinions as to why all interstellar objects must be stones. I define this phase as the “stone age” of science.

We must liberate our minds to notice the grander picture or else we would never be recognized as an intelligent species by those who are looking at us from interstellar space. For more details, check out my new book, Interstellar, available now for pre-orders a month before its publication date.


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".