Celebrating the Ten-Year Anniversary of the First Identified Interstellar Meteor
January 8, 2024 marks the ten-year anniversary for the discovery of the fastest-moving meteor relative to the Sun. The fireball it generated as a result of its friction with air was detected by US government satellites. The high speed implied that the object was unbound to the Sun’s gravitational potential and this interstellar origin was double-checked by the US Space Command. Outside the solar system, the object was moving at about 60 kilometers per second relative to the Local Standard of Rest, faster than 95% of the stars in the vicinity of the Sun. Its high speed and the fact that it exploded in the lower atmosphere less than 20 kilometers above the Pacific Ocean, implied that its material was strong enough to sustain a higher ram-pressure than all 272 other bolides in the CNEOS catalog of NASA.
On June 14–28, 2023, we travelled to the Pacific Ocean in search of the materials of this meteor, labeled IM1 as an abbreviation for “Interstellar Meteor 1”. The mission took a year to plan, including the recruitment of an exceptional engineering and navigation team led by Rob McCallum and Art Wright, generous donations of funds to the Galileo Project by Charles Hoskinson and Eugene Jhong, the design and construction of a magnetic sled and non-magnetic sluicing device by Rob Milsap’s team, lending of an X-ray fluorescence analyzer by Frank Laukien and Roald Tagle from the Bruker Corporation which was operated by Ryan Weed and Jeff Wynn, and the preparation of the perfect ship for the task — fittingly named “Silver Star”.
Despite all odds, the expedition was remarkably successful. The team of nearly thirty members worked collaboratively around the clock on the ship. As chief scientist I did not sleep for more than a few hours between runs, as we had to scoop the magnets whenever the sled was brought back on deck, rain or shine, day or night. Altogether, we surveyed the ocean floor at a depth of roughly two kilometers across a region measuring tens of kilometers in length around the meteor site. We searched for tiny droplets that melted off the surface of IM1 when it was exposed to the immense heat from the fireball it generated. The airburst deposited a few percent of the Hiroshima atomic bomb energy into half a ton of material, most of which evaporated. Altogether, our magnetic sled retrieved 850 tiny spherules in the size range of 0.05–1.3 millimeters, comparable in diameter to grains of sand. We posted our preliminary results for 57 spherules after the first couple of months of analysis.
By now, six months after returning from sea, we were able to examine carefully and methodically our entire harvest of spherules. A micro X-ray fluorescence analysis was led by Dr. Roald Tagle at the Bruker Corporation’s laboratories in Berlin, Germany. This study was complemented by detailed electron microprobe imaging and ICP mass spectroscopy of 60 elements from the periodic table for a select group of spherules, led by the world-renowned geochemist, Professor Stein Jacobsen, and his Cosmochemistry research group at Harvard University. This heroic research effort employed the best instruments in the world. What did it reveal so far?
Our team identified 78% of the spherules as primitive, in that their composition had not been affected by planetary differentiation of elements. We divided these into four groups corresponding to previously described cosmic spherule groups. The remaining 22% appear to all reflect planetary igneous differentiation and are all different from previously described spherules in the scientific literature. We call these D-type spherules. A small portion of the D-spherules show an excess of Be, La and U, by up to three orders of magnitude relative to the solar system standard of CI chondrites. These “BeLaU”-type spherules, never seen before, clearly appear to be derived from material formed by planetary igneous fractionation. Their chemical composition is unlike any known solar system material, the KREEP component of the lunar crust being closest. Tidal disruption and melting of rocky planets near dwarf stars, could eject objects with “BeLaU”-type composition to interstellar space at 60 kilometers per second, as observed for IM1.
We are currently working on the completion of our analysis and plan to summarize the detailed results within a future publication in a peer-reviewed scientific journal.
For now, we regard the “BeLaU”-type spherules as birthday decorations in our celebration of the discovery of IM1 on January 8, 2014. Impacts by interstellar meteors of IM1’s mass and speed are rare, occurring roughly once per decade. The surface of IM1 was mostly vaporized and only a small fraction of it survived as spherules. This is clear from our “BeLaU”-type spherule harvest. Altogether, our meter-scale sled surveyed a region that was a thousand times smaller than the likely debris field of IM1. The survey retrieved a total mass in “BeLaU”-type spherules that is less than one part in ten million of the estimated mass of IM1, implying that the debris field contains at most a part in ten thousand of IM1’s mass in “BeLaU”-type spherules. However, if IM1 was larger than half a meter in size, large pieces from its core could have survived the fireball and settled on the ocean floor. Our next expedition will aim to search for such pieces in the region where we found the “BeLaU”-type spherules.
Our team is currently starting to plan the tools for our next expedition. If we are successful at finding a large piece of IM1’s core, I promised to bring it for display at the Museum of Modern Art in New York City if it was made by aliens or the Smithsonian Museum in Washington DC if it is of natural origin.
Any new knowledge about what lies outside the solar system will be shared with all humans, as commonly done in science. IM1 was discovered serendipitously by the US government employees, whose day job is to monitor objects manufactured by humans on Earth. Once the government officials realized that IM1 is of pure scientific value and has no national security implications, they released the data to scientists. I am grateful for their generosity because my day job as a scientist complements theirs. I am leading the Galileo Project which aims to find out what exists beyond the solar system and whether any interstellar object might have been an ark manufactured by a cosmic neighbor.
A few days ago, I met the brilliant fiction writer, Dror Burstein, in Israel, and reviewed the findings from IM1’s expedition to him. Dror smiled and noted calmly: “It is inspiring to watch you as a theoretical physicist, Avi, pioneering an exciting expedition to the Pacific Ocean in search of interstellar materials. A fictional character who paralleled your experience in space-archaeology is Indiana Jones in the film `Raiders of the Lost Ark’.” I corrected Dror by pointing out a subtle difference: “Gladly, I do not have to deal with Nazis.”
Well, we should be careful of wishful thinking. Given the rise of antisemitism, I have to watch out that Nazi characters not show up on the Harvard campus.
ABOUT THE AUTHOR
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”, was published in August 2023.
