Welcome to FreeAstroScience, dear readers. Today we’re chasing a provocative question: if advanced civilizations build self-replicating “von Neumann” probes, could some already be operating in our Solar System? You’ll learn what these probes are, why they make sense, and—crucially—what technosignatures to look for on the Moon and among asteroids. This article is written by FreeAstroScience only for you, so stick with us; by the end, you’ll have a practical checklist for the next wave of SETI.
What are self-replicating probes, and why would anyone build them?
In 1949, John von Neumann sketched the idea of a “universal constructor”—a machine that can build copies of itself. Decades of SETI thinking took that seed and asked a blunt question: if you can replicate, why not explore a galaxy quickly and cheaply? The logic is simple. You pay the cost to launch one smart factory. Each copy makes more copies. In time, probes can touch every star system.
Recent work by Alex Ellery (Carleton University) argues such probes are not just plausible—they’d leave detectable technosignatures in our own Solar System, especially on the Moon and in resource-rich asteroids. He also lays out concrete places and signals to check first . A popular write-up of Ellery’s study, published on November 6, 2025, frames the same take-home in plain terms: some probes could already be here, and we should start looking locally, not only with radio telescopes .
How do technosignatures help us cut through the Fermi paradox?
The Fermi paradox asks: Where is everybody? If civilizations arise and spread, shouldn’t the sky—or even our backyard—show their traces? Radio searches are one path. But technosignatures broaden the net to physical artifacts, industrial footprints, and energy waste.
Ellery offers a clean metric for civilization scale using the Kardashev index relating power (W) to a civilization’s “type”:
Formula 1: Kardashev Index
\( K = \frac{1}{10}\log_{10} W - 0.6 \)
Formula 1: Kardashev Index
K = (1/10) · log10(W) − 0.6
Large energy users—think planetary shells of satellites, exobelt traffic, or megastructures—emit waste heat, alter transit light curves, or reshape local materials. Even if we don’t find galaxy-scale projects, local, durable traces could persist far longer than fragile radio beacons .
If probes came here, what would they actually do?
Ellery’s mission profile is refreshingly practical. A rational probe that needs raw materials and safety will likely follow six steps. Here’s a scannable version you can keep:
| # | Activity | Why it Matters | Where to Look |
|---|---|---|---|
| 1 | Select asteroids & moons | Accessible metals, volatiles, and silicates | Asteroid Belt, lunar regolith |
| 2 | Build surveyors/sentinels | Map resources & biospheres, maintain awareness | Cislunar space, stable lunar orbits |
| 3 | Establish manufacturing bases | Secure steady inputs for replication | Permanently shadowed craters, lava tubes |
| 4 | Replicate | Exponential scaling of exploration | Near-resource nodes (nickel-iron zones) |
| 5 | Conduct long-term surveys | Detailed, patient system mapping | Surface/subsurface sensor networks |
| 6 | Execute tasks | Build habitat precursors, maybe seed life | Lunar industrial sites, selected asteroids |
This “industrial choreography” isn’t a fantasy list; it flows from resource economics and risk-aware exploration. If we look where a cautious engineer would set up shop, we’ll search smarter .
Why the Moon first? (And what, exactly, should we measure?)
The Moon is stable, close, and rich in the exact stuff machine factories love: silicates, nickel-iron, and trace metals. It’s also constantly peppered by asteroids, which deliver industrially interesting elements into the subsurface. Ellery argues it’s the perfect manufacturing hub for a visiting probe—and, crucially, a place where power systems might leave measurable isotopic fingerprints.
Power choice: compact, fuel-rich nuclear reactors—notably Magnox-style designs—could be built from lunar resources. That’s testable. Look for non-natural isotope ratios in thorium, neodymium, and barium near probable industrial zones:
- Th-232 / Nd-144
- Th-232 / Ba-137
Isotopic Ratios to Test (Lunar Sites)
- Th232 / Nd144
- Th232 / Ba137
Those ratios could flag reactor byproducts or fuel processing inconsistent with natural lunar geology. Ellery specifically singles out these lunar signatures as high-value technosignatures for the first generation of cislunar prospectors to measure . The ScienceAlert summary underscores the same “Moon-first” strategy for SETI, arguing it meshes nicely with NASA’s plans for sustained lunar operations in the 2020s–2030s—and beyond .
Aren’t asteroids an even bigger clue factory?
Asteroids are a materials buffet: iron-nickel-cobalt, silicates, carbon, sulfur, nitrogen, and plenty of water locked in minerals and ice. They’re perfect for feedstock and thermal processing (solar concentrators can hit ~1500 °C). The catch? Mining debris fields, dust, and thermal signatures can look frustratingly like natural collisional processes. That makes “asteroids alone” a trickier technosignature target, at least initially .
So, a good early-stage search plan is:
- Prioritize the Moon for isotope anomalies and subsurface magnetic oddities near metal-rich impacts or lava tubes.
- Map asteroid surfaces/subsurfaces for localized slag, unusual alloy phases, or repeat-pattern excavation geometries that don’t match standard cratering statistics.
- Correlate any asteroid anomalies with lunar findings to see if there’s a system-wide industrial pattern rather than isolated oddities .
What simple physics can guide the search?
Two compact relations help visualize targets you’ll see discussed in technosignature papers:
- Clarke Exobelt radius (where geostationary artifacts could cluster around an exoplanet):
Formula 2: Clarke Exobelt Radius
r = [ (G · mp · P2) / (4π2) ]1/3
- Waste-heat peak from megastructures around stars (Dyson-like constructs radiating at 200–400 K):
<p><b>Rule of Thumb: Waste-Heat Peak</b></p>
<p>λ<sub>peak</sub> ≈ 10–20 μm (mid-IR), consistent with 200–400 K emitters.</p>
While these are astronomical technosignatures, Ellery’s main point is a pivot to Solar-System archaeology—the Moon and nearby small bodies first—because artifacts here would be closer, cheaper to test, and more definitive if found .
Could “berserker” replicators run amok? How would engineers prevent that?
Science fiction loves the runaway swarm. Engineers don’t. Ellery discusses limiting replication counts, error-correction, and calibration regimes—all standard control ideas scaled to space factories—to avoid mutation cascades and population explosions. In other words, sensible design can keep a probe family boringly well-behaved—exactly what you’d want in shared, resource-scarce environments . The ScienceAlert piece highlights this “safety-rails” angle as well .
So…what should we do next?
Here’s a minimal, evidence-first campaign that fits ongoing lunar and asteroid work:
| Action | Measurement | Instrument/Platform | Decision Trigger |
|---|---|---|---|
| Lunar isotope survey | Th232/Nd144, Th232/Ba137 | Drill cores, in-situ MS, return samples | Ratios outside natural ranges → focused excavation |
| Subsurface magnetic mapping | Localized anomalies, linear/rectilinear patterns | Lunar rover arrays, cubesats, orbital magnetometers | Artificial-looking geometry → ground-truthing |
| Asteroid morphology & petrology | Slag textures, alloy phases, repeated excavation motifs | Proximity radars, hyperspectral imagers, micro-landers | Non-impact morphologies → micro-sampling |
| Networked sentinels check | Quiet, long-lived beacons or dormant hardware | Permanently shadowed crater surveys, lava-tube scouting | Any hardware → contamination controls, secure lab study |
The “aha” here is pragmatic: we don’t need to “see aliens.” We only need to measure the right rocks and map the right craters. If factories once hummed on the Moon, the chemistry and magnetism will carry that memory.
Conclusion: What if the first proof isn’t in the stars, but in the regolith?
We’ve lived with the Fermi paradox for 70+ years. Maybe we’ve over-weighted distant radio while under-scanning our own backyard. A Moon-first technosignature survey, paired with targeted asteroid checks, gives us the cheapest, most decisive path forward. If humanity is about to industrialize cislunar space, we should add technosignature assays to the packing list. Worst case, we learn more lunar geology. Best case, we find proof that intelligence has been here before—and perhaps left a gift for when we became ready to use it .
— Written for you by FreeAstroScience.com, which explains complex science simply to spark curiosity—because the sleep of reason breeds monsters.
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