What was the origin of the non-gravitational acceleration of the first recognized interstellar object `Oumuamua? The decline of the force with distance from the Sun was consistent with the inverse square law characterizing radiation pressure. There was also no evidence for a cometary tail that commonly flags the rocket effect. `Oumuamua had to lose a tenth of its mass in order to acquire the observed push.
In a set of publications, I suggested that `Oumuamua had a large surface area for its mass and was pushed by radiation pressure from the Sun, potentially indicating a technological origin. Three years later, the same Pan-STARRS telescope in Hawaii discovered another object, 2020 SO, with a non-gravitational acceleration consistent with a push by solar radiation pressure. A few weeks later, 2020 SO was identified as the upper stage used by NASA in September 1966 to launch the Surveyor 2 spacecraft to the Moon.
The mainstream of comet experts disagreed with my interpretation of `Oumuamua. They first suggested that `Oumuamua is a hydrogen iceberg, then a dust bunny, then a nitrogen iceberg and finally a water-hydrogen iceberg, with an invisible coma. The final attempt to shove `Oumuamua’s anomalies under the carpet of traditional thinking was made by a team of researchers led by Darryl Seligman, who published a paper in December 2024 in the prestigious journal Proceedings of the National Academy of Science (PNAS). This paper argued that `Oumuamua is a member of a population of Dark Comets, recently discovered near Earth. These objects show non-gravitational accelerations with no visible coma. The paper argued that they represent a weak version of `Oumuamua, with smaller sizes and weaker non-gravitational accelerations.
While studying this paper, it occurred to me that some of these so-called Dark Comets might have been space debris from the space age, as some orbits came close to Earth and Venus and resembled a population of lost spacecraft launched by the Soviet Union between 1961 and 1984 as part of the Venera program aiming to reach Venus.
Following this realization, I asked my excellent postdoc, Richard Cloete, to find the timing of the closest approach for these Dark Comets relative to Earth over the past century. Once Richard sent me the results, I searched archival records of spacecraft launched during the space age following Sputnik 1 in 1957. Within minutes, I found that one of these objects, 2005 VL1, was at closest approach to Earth in November 1965 when the Venera 2 spacecraft was launched by the Soviet Union to explore the planet Venus. The observed brightness of 2005 VL1 is indeed consistent with a high reflectance from the full surface of Venera 2 including its solar panels. As known for Venera 2, the orbit of 2005 VL1 implies that it arrived within a short distance from Venus at around February 1966, a highly improbable coincidence for the orbital phase of a natural comet that was not designed for a close encounter with Venus. Since the orbital period of Venus is 225 days, the chance of a random encounter of a near-Earth object with the precise orbital phase of Venus on the right date is less than one percent. 2005 VL1’s orbital parameters are very similar to the reported values for Venera 2. Given the area-to-mass ratio of Venera 2, I calculated that 2005 VL1’s non-gravitational acceleration and negligible transverse acceleration match the values expected from solar radiation pressure.
Consequently, I wrote a paper with Richard that summarizes our results. The publication of our paper was declined by the editor of PNAS, because shortly after our paper was posted online, two research notes, posted here and here, argued that the small differences between the orbital parameters of 2005 VL1 and Venera 2 imply that they are not the same object. In response, I wrote a brief research note, in which I explained that the small differences in orbital parameters between these objects could have been caused by gravitational deflection and unrecorded maneuvers during the flyby of Venera 2 near Venus. I submitted this note for publication in Research Notes of the American Astronomical Society (RNAAS), where the other two notes were immediately accepted for publication. The RNAAS editor wrote back: “The recently published Research Notes by McDowell and Spada make, between them, several arguments against the identification of 2005 VL1 with Venera-2. In addition to the failure to match the orbits, and in particular the inclination, they both comment that 2005 VL1 was not near Earth at the appropriate period.” As a result, the only publications regarding the possible association of Dark Comets with the Venera spacecraft are authored by the critics of my note and paper. The calculations to which the critics responded were declined from publication.
Today, a new detailed paper was posted online by Adam Hibberd with the title “Study of Venera Spacecraft Trajectories and Wider Implications.” The abstract reads: “Historically, there is no doubt that the early years of the USSR space program put them way ahead of the competition (the USA). Nonetheless, although this was not what the Russians wished to present to the world, the interplanetary campaign, centered around missions to the planet Venus (the Venera program) was also beset with difficulties. Many of the early Venera probes failed, despite making it to a heliocentric orbit, but naturally the success rate improved with time. The result is that there are now many Venera probes in heliocentric orbits, either completely intact, or the main bus after a successful deployment of the lander; together with the associated Blok-L upper stages. This paper is a response to some previous quite contentious research proposing that a certain member of a new class of objects, designated 2005 V L1 may in fact be the Venera-2 probe. In this paper we look into the invariance of the Earth Tisserand parameter in an attempt to establish if there are indeed any members of this class which could be Venera probes. It is found, with extremely small probability, that compared to a sample of randomly chosen Near Earth Objects, members of the class of Dark Comet have an Earth Tisserand unusually close to 3, a property shared by the Venera missions. Furthermore, there are particular associations of 3 Dark Comets with 3 of these probes, the most significant being 2010 RF12 with the Venera-12 mission.”
This gives me hope that scientific progress cannot be hindered by traditional thinking. As Galileo Galilei stated: “In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.”
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.
