Morphology of Fragments Recovered from the Crash Site of the Interstellar Meteor IM1
On June 14–28, 2023, I led an expedition to retrieve materials from the crash site of the interstellar meteor, IM1 (CNEOS 2014–01–08) in the Pacific Ocean. Using a sled covered with neodymium magnets, we found close to 850 fragments. Of the samples collected from the expedition site, roughly 20% were found to deviate from the typical chemical compositions of the primitive material that made the solar system (chondrites). These fragments were classified by our team as differentiated, or “D-type”, in terms of their composition which indicated elevated abundances for some elements from the periodic table. These D-type particles were demonstrated to be distinct in their degree of chemical differentiation from known samples of solar system materials. Among the sub-class of D-type particles, “BeLaU” spherules were named for their elevated abundances in highly incompatible elements such as beryllium (Be), Lanthanum (La), and Uranium (U). Their discovery from an unknown origin was reported in our extensive analysis publication. One BeLaU spherule, whose polished cross-section was analyzed, exhibited a magnetite rim and quench features, suggestive of an extraterrestrial origin.
This week, in a new second paper accepted for publication in the prestigious journal Chemical Geology, our analysis team led by Eugenia Hyung from Stein Jacobsen’s laboratory, studied correlations between morphology and chemical composition of the recovered fragments as another diagnostic of their origins. Backscattered electron microscope images were obtained on polished cross-sections of the fragments to observe their inner features, and elemental analyses were performed to determine the compositions of the various features. This new study aimed to flag fragments of possible extraterrestrial origins.
Among the 850 samples from the expedition, about 160 were classified as D-type spherules. 37 out of the 160 particles were studied through backscattered electron images in a scanning electron microscope, which were used to define the particle morphology.
We studied the D-type fragments with the goal of comparing their various morphological features to their chemical compositional groupings. Four morphological classifications were considered: “scoriaceous,” “stubby,” “blocky,” and “vesicular.” The specimens from the “scoriaceous” and “stubby” groups exhibited a spinel magnetite rim in at least one instance, characteristic of atmospheric entry from an extraterrestrial origin. The particles exhibiting “blocky” and “vesicular” textures are likely terrestrial in origin, with no obvious quench features or signs of ablation. The D-type particles identified and characterized in this study have a spectrum of terrestrial and extraterrestrial origins and about half of them were considered to be BeLaU-type in our previous paper.
We have found that the morphologies and compositional sub-classes of D-type fragments correlate. This is not surprising since the morphologies and compositions of the fragments are indicative of their origins and recent thermal history. The unusually high iron content of the D-type fragments, along with their highly differentiated nature suggest that these particles could have originated from rocky exoplanets, as suggested in a paper I published a year ago with my postdoc, Morgan MacLeod.
To find out more about the nature of IM1, we are currently planning a second expedition to IM1’s crash site in summer 2025. IM1 arrived from outside the solar system at a speed of about 60 kilometers per second, faster than 95% of all stars in the vicinity of the Sun. It also exhibited material strength tougher than all meteors documented by NASA, and so our research team would like to check whether it was technologically manufactured by retrieving large pieces of it. To achieve this goal, we reserved a ship which is equipped with a Remotely Operated Vehicle (ROV) that can pick up large pieces from the ocean floor based on a video feed to our engineers on the ship. An analogous study of an interstellar object that did not collide with Earth would have cost billions of dollars, a thousand times more than this planned expedition. The year 2025 is promising to be exciting.
I mentioned the latest findings and plans in a special Science Discovery Lecture at Clemson University today and told the audience and my generous hosts, Marco Ajello and Dieter Hartmann, that I feel privileged to be defined by my future rather than my past research — as is commonly the case in academia. In that sense, I did not change much from my early life as a curious kid trying to figure out the world I was born into. My mother told me that shortly after being born, my eyes were looking around with wonder and trying to make sense of the delivery room. Sixty-three years later, I expanded this task to my cosmic delivery space in the Milky-Way galaxy.
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 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. The paperback edition of his new book, titled “Interstellar”, was published in August 2024.
