Interstellar Trash is Our Treasure

Avi Loeb
5 min readJun 7


Photo credit: Paramount Pictures/Lucasfilm

The detection rate of the first two interstellar meteors, IM1 and IM2, in NASA’s CNEOS catalog implies that meter-scale objects from interstellar space impact the Earth twice per decade. Over the lifetime of the Earth, a billion such impacts likely occurred. Can we recover materials from their crash sites?

The intelligence and defense agencies of the US Government are tasked with identifying objects falling from the sky, since some may represent spy balloons, drones or missiles sent by adversarial nations. It is therefore conceivable that the government acquired materials from crash sites of all of the above, including interstellar objects. Such occurrences lend credence to the report by the whistleblower David Grusch who served as a representative to the UAP Task Force and co-lead for UAP analysis. Grusch says recoveries of extraterrestrial objects of non-human origin have been ongoing for decades by the US Government, allies, and defense contractors.

The remaining question is how would the government know that a crash site involves an exotic origin. After all, foreign governments could test surprising technologies. Moreover, interstellar objects could originate from natural astrophysical environments that are very different from the solar system, such as the materials ejected from exploding stars or merging neutron stars — which are highly enriched in rare isotopes of heavy elements.

If the recovered materials involve a relic object which maintained some technological structure, then a natural astrophysical origin can be discarded. And if the equipment can be reverse-engineered to suggest that it represents technologies that exceed human capabilities, then the extraterrestrial technological origin would gain traction.

In the most likely scenario, crash sites would be associated with equipment that stopped functioning before impacting the Earth, namely interstellar space trash. A possible relevant example is the collision of the New Horizon spacecraft with an exoplanet a billion years from now.

Under such circumstances, the impact speed on our planet would be higher than the escape speed from Earth, 11 kilometers per seconds, implying an energy release per unit mass that is an order of magnitude higher than that of TNT. An object the size of a person would release as much energy as the Hiroshima atomic bomb. Natural rocks of this size impact the Earth from the solar system about once per year. Smaller size meteors typically burn up at an elevation of tens of kilometers in the atmosphere — often leading to a giant fireball as a result of their friction with air.

A crash site could leave a relic object behind, either if the initial object was large enough not to disintegrate completely into dust or if the object was technologically designed to withstand atmospheric entry.

The crater volume depends on the impactor energy, which scales as the impactor mass times the square of its impact speed. The best way to identify the interstellar origin of an object is by measuring its speed to be larger than the escape speed from the Sun, which is 42 kilometers per second at the Earth’s separation from the Sun. The speed cannot be inferred from craters and must be measured from the fireball before impact. For every interstellar object, Earth encounters hundreds of impacts by solar system rocks of the same size. Separating interstellar objects from the familiar solar system rocks is therefore a highly challenging task. In addition to this identification challenge, there is the possibility that some Oort cloud objects may have been exchanged with passing stars and could impact Earth.

The first interstellar object for which a speed beyond the value required to escape from the Solar system was measured is IM1, whose fireball was detected by the US Government on January 8, 2014. This half-meter-sized object was tougher in material strength than all other 272 meteors in the CNEOS catalog of NASA, and was formally recognized as having an interstellar origin at the 99.999% confidence in an official letter from the US Space Command to NASA on March 1, 2022. In my discovery paper of IM1 with Amir Siraj, we showed that this first recognized interstellar meteor was moving outside the solar system faster than 95% of all stars in the vicinity of the Sun. The possibility that IM1 benefited from technological propulsion early on, and the fact that it was tougher than all known space rocks, suggests that it may have been artificial in origin.

This summer, I will be leading an expedition of the Galileo Project to the Pacific Ocean to discover whether IM1 was a craft from an extraterrestrial civilization. Based on the IM1 fireball energy, I calculated in a paper with my students, Amory Tillinghast-Raby and Amir Siraj, that the object likely disintegrated into tiny spherules, which our search team hopes to find with a magnetic sled or a sluicing device. Once we recover the meteor materials, we plan to bring the sample back to the Harvard College Observatory, and analyze its composition with state-of-the-art diagnostic instruments.

In contrast to the storyline reported by David Gursch, the scientific findings of the Galileo Project will be open to the public. Any scientific knowledge about our cosmic environment should be shared by all humans because it does not adhere to national borders. All of us should know whether we have neighbors in order to adapt to the interstellar reality that surrounds us. Such knowledge is essential for guiding the long-term survival of humanity.

If indisputable evidence for a technological relic from an extraterrestrial civilization surfaces in 2024, this revelation should be included in President Biden’s State of the Union address for 2024 with the words: “My fellow earthlings, we are not alone.”


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".