Where are the Spherules of IM1?

Avi Loeb
3 min readJun 20


Diary of an Interstellar Voyage: Part 17 (June 20, 2023)

The treasure hunt for anomalous particles captured by the sled magnets in Run 9 on June 20, 2023. From right: the expedition funder, Charles Hoskinson, next to Avi Loeb and J.J. Siler. All team members will co-author the scientific papers that will result from the expedition.

Any qualified detective knows when the time comes to pause, summarize the evidence and choose the best path for resolving the mystery. This approach enhances the efficiency of the search for answers, which otherwise requires much more time and resources. Since our time and resources on Silver Star are limited, I reevaluated where we should go next based on our experience and asked Art Wright to follow this path.

The Department of Defense (DoD) reported the location of the first recognized interstellar meteor, IM1, to within one significant digit after the decimal point in longitude and latitude. We therefore considered the localization uncertainty to be 0.1 degrees and used additional seismometer data to reduce the localization uncertainty.

However, it occurred to me today that out of the 9 lines we surveyed so far in the lower half of the DoD box, the most successful one in collecting anomalous steel shards was Run 6, which passed through the middle of the error box. It is therefore possible that the fireball occurred exactly at the center of the DoD box. I therefore suggested that Run 10 will pass through this center. Finding a concentration of shards at the box center would strengthen the case that the shards may be related to IM1, since it is unlikely that an unrelated process would concentrate them there.

The different lines surveyed by the expedition’s sled within the DoD box. Line 6 provided the largest crop of steel shards and passed through the box center. The orange region is the path favored by seismometer data.
Retrieval of the magnetic sled in Run 9. The materials retrieved by Runs 8 & 9 in the lower part of the DoD box did not deliver any steel shards.

The fireballs of solar system meteors often produce magnetic spherules of melted droplets that are shaped by surface tension and friction with air. Where are IM1’s spherules?

Examples of impact spherules. Although mostly spherical, some spherules are dumbbell, tear-drop, and oval shaped.

A careful inspection of the particles in our samples showed a special class of nearly-spherical magnetic particles. However, imaging through our electronic microscopes revealed that they are biological in origin. Jeff Wynn who imaged them, informed me that they are likely plankton encrusted with magnetite. He asked whether I am interested in biology. I told him that I am interested in biology but not from planet Earth.

Microscope image of a nearly-spherical magnetic particle which was identified as a plankton sphere encrusted with magnetite.

So far, we had not retrieved any spherules from IM1. This may either imply that they were rare, non-magnetic, or that we visited the wrong locations.

Later this week, we are planning to use a sluicing device to separate non-magnetic particles based on their high density. If the sluicing device would retrieve any gold from sunken ships, we would throw it back to the ocean. After all, our treasure is valued in interstellar currency.


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".