New research explains why we cannot rule out that alien probes are already replicating in the Solar System. To identify them we must focus on technosignatures.
In 1949, the celebrated mathematician and physicist John von Neumann gave a series of lectures at the University of Illinois in which he introduced the idea of the “universal constructor” — a machine capable of self-replicating and, potentially, evolving in complexity like a biological organism. This hypothesis was then collected and published posthumously in the 1966 volume Theory of Self‑Reproducing Automataedited by AW Burks.
Neumann, in defining the self-reproducing machine, imagined a device that not only builds copies of itself, but also copies its description — just like the DNA molecule in living things. His model used the theoretical environment of “cellular automata” (a two-dimensional grid in which each cell changes state as a function of adjacent cells) and demonstrated that, under certain conditions, a “universal constructor” could replicate and potentially evolve.
The evolution of Seti. In the years that followed, scientists working on the SETI (Search for Extraterrestrial Intelligence) program took inspiration from these ideas to hypothesize that advanced civilizations could employ self-replicating probes — often called “Von Neumann probes” — to explore the galaxy. Theoretical studies indicate that a single probe, released from a fairly developed planet, could replicate, spread, and explore a large portion of the galaxy in a relatively short amount of time on a cosmic scale.
Now new research from Professor Alex Ellery of Carleton University even suggests that these probes may have already visited the Solar System — and that some may still be operational. In his article “Self-replicating probes are imminent – implications for SETI“, Ellery proposes that future research in the SETI field should focus not only on traditional radio signals, but also on technosignatures — technological signatures left by autonomous probes operating in the Solar System or its immediate vicinity.
Self-replicating probes. Ellery reconstructs the reasons that an advanced civilization might have for employing self-replicating probes. «First of all they could guarantee their own survival beyond the stable phase of their star», explains the researcher, «and therefore find threats (or alliances) in view of technological or civil development. Beyond that they could use exploration as a means of self-reproduction and diffusion. In practice, a probe that can replicate with local resources has a much higher efficiency than single long-term sendings.”
Ellery adds that these probes are not constrained by biological limits (nutrition, atmosphere, adapted gravity, etc.). They could tolerate accelerations well above (Earth’s gravity) and not require complex vital systems: potentially all the necessary material can be found during the journey or in the systems visited.
A six-step operating model. Ellery suggests that the activities of these self-replicating probes would follow a predictable trend, divided into six main phases:
1) locate asteroids, moons or bodies in the target system that are easy to access to extract raw materials.
2) Build sensing probes that scan the rest of the system for resource-rich environments.
3) Establish operational bases in strategic locations for self-replication.
4) Begin playing copies of the probe — both sentinels and scouts.
5) Initiate detailed long-term exploration of the target system.
6) Carry out specific instructions: for example build settlements, without necessarily altering potentially habitable planets (except in the more controversial hypothesis of direct panspermia).
Technofirms to identify. Ellery draws attention to some technological traces that we could look for within our Solar System. First, look for unusual accumulations of isotopes (for example, thorium-232, neodymium-144, or barium-137) that could indicate nuclear reactors built from self-replicating probes. So magnetic anomalies or unnatural structures on the Moon, in the Asteroid Belt or in the Kuiper Belt.
Other traces could be a concentration of nickel, cobalt, tungsten — elements that a probe could extract from rocky bodies and use as a “gift” for a civilization that begins to explore space. Ellery particularly suggests the Moon as a privileged site: a relatively nearby body, historic mission target, and potential base of operations for a self-replicating probe.
Paradigm shift for SETI. So far, the search for extraterrestrial civilizations has focused mainly on radio or optical signals. Ellery argues that we should broaden our scope: consider our Solar System not just as distant observatories, but as a potential ground for actively searching for technological signatures of interstellar probing. This approach also aligns with recommendations from Professor Gregory L. Matloff, who discussed interstellar transfer times and rational propulsion for Von Neumann probes.
