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The Problem with Probes

I’ll wrap up this three-part series on ‘lurker’ probes and ways of finding them with Keith Cooper’s provocative take on the matter. A contributor to Centauri Dreams whose far-ranging ideas have fueled a number of dialogues here (see the archives), Keith is editor of Astronomy Now and the author of the upcoming book The Contact Paradox: Challenging Assumptions in the Search for Extraterrestrial Intelligence. I’ve read the manuscript and can tell you that you’re going to want this one on your shelves. Today, Keith takes us into the practical realm. If we were to find a Bracewell probe in our Solar System, what would we do with it? Who might discover it, who would claim its technologies, and what, under international law, would be its legal status? Plenty of material for science fiction plots here as we embark on the search to see what’s out there among Earth’s co-orbitals.

by Keith Cooper

It’s enough to keep me awake at night.

Suppose that an extraterrestrial probe is discovered in our Solar System, anchored to a co-orbiting near-Earth asteroid. It could potentially instigate one of the biggest crises in all of human history.

Consider this nightmare scenario: the alien probe would quite possibly be discovered by one of our probes. If we’re lucky, it will be one of our science missions, like Hayabusa2 or OSIRIS-REx. If we’re unlucky, it could be an autonomous asteroid-mining spacecraft, sent into space to chew up asteroids and refine their rocks for their precious minerals.

In that case, first contact could well end up with us destroying the alien probe along with the asteroid. Maybe the probe will defend itself and destroy the mining craft. Or, if the probe is passive, then maybe its last moments relayed back to its home civilisation will be of a human-built robot looming threateningly. Either way, it’s not the kind of first impression we’d really want to make.

Maybe that scenario is too far-fetched for you. Okay, let’s just go with the option of an alien probe being discovered during a science mission, or by an astronomical survey. We might try and contact it, but could we really resist the lure of advanced extraterrestrial technology just a few million kilometres from Earth? Of course not. Nations and private space companies will rush to try and capture the probe and to learn its secrets. Who, if anyone, would have the rights to claim it? It could lead to conflict between competitors, or maybe the probe would again try and defend itself, an act that we might deem to be hostile.

What we can learn from these scenarios, besides the importance of making a good first impression on behalf of humanity, is that there is a startling unpreparedness for any such discovery of a watching probe.

In his new paper (see A SETI Search of Earth’s Co-orbitals), Jim Benford has proposed searching asteroids in co-orbiting orbits – objects in a 1:1 gravitational resonance with Earth such that they orbit the Sun in exactly the same time as our planet, shadowing our world but on orbits that are a little more elliptical. Relative to Earth, these orbits trace out ‘horseshoe’- or ‘tadpole’-shaped paths. The co-orbiting objects include the asteroid Cruithne, which starred in Stephen Baxter’s novel Manifold: Time and gets as close as 12 million kilometres, and Earth’s first known Trojan asteroid, 2010 TK7, which comes as close as 19 million kilometres.

Benford recommends that Breakthrough Listen target these co-orbiting neighbours, since they would give an alien probe an ideal vantage point from which to watch us. It’s a great idea, and although I think there’s a very low probability of success, as with anything to do with SETI, we won’t know until we look. However, as per the scenarios above, the discovery of a probe could be fraught with danger.

If a probe is discovered, who has the right to claim its technology? In an ideal world I would say nobody, and that aside from trying to communicate with it, we should leave it be. However, we’re talking about human beings here, and the temptation to capture the probe and learn its secrets will be too hard to resist. But it could lead to one almighty free-for-all.

So I asked Frans von der Dunk, who is Professor of Space Law at the University of Nebraska-Lincoln, what the Outer Space Treaty says about extraterrestrial probes. Unsurprisingly, it doesn’t say anything. Instead, von der Dunk suggests that if we substitute ‘natural resources’ for ‘technology’ , then the best interpretation of the current law would be to treat the probe as any other celestial object, such as an asteroid, which can be mined or otherwise appropriated.

“In my view, [this] would indeed not make it illegal for states to unilaterally condone someone going for the technology and trying to appropriate it, if under an appropriate license and otherwise complying with whatever international space law dictates with respect to the use of outer space, as per Art. VI of the Outer Space Treaty,” he says.

However, von der Dunk accepts that rivals for the probe’s technology would be unlikely to accept this if it looks like someone else is going to get there first, leading to all kinds of diplomatic shenanigans, and potentially conflict.

There are other issues with the law. If the probe contains a sentient artificial intelligence, should it not be treated as a sentient being according to the law? The problem is, other species on Earth, such as dolphins, are also sentient but the law does not recognise them with the same rights as human beings.

Then there is the concern that the probe would defend itself against any action it deemed hostile. Given that we would not know its capabilities, nor the motivations of the civilisation that programmed it, this could be exceptionally risky on an existential scale. Should we destroy or capture the probe then we could incur the wrath of whoever sent it; if it defends itself, we cannot know what lengths it would go to before ceasing fire. There’s even a case for leaving the probe alone after discovery, and not attempting to communicate with it; the probe could be hibernating and unaware of our modern technological developments until we start poking and prodding it. As the saying goes, we might not want to wake the dragon. Visions of Fred Saberhagen’s berserker probes abound.

To be fair, I don’t necessarily agree with that assessment. If an alien probe is going to venture into our backyard, it would seem unreasonable to then not expect us to be curious. However, we do need to act accordingly, and sensibly. So far, little to no thought has been put into this. If we are going to embark on a search, as Benford encourages, then we need to start thinking about what the consequences will be and how we’ll manage them, and we need to start thinking about this with some haste. Should SETI discover a radio signal from another civilisation, it will have originated many light years away; sheer distance mitigates the danger. A probe, however, will be a cosmic stone’s throw from us, and any potential danger would be immediate.

So, this is what I recommend: any search must be in conjunction with educating space agencies and private space companies about the possibility, however small, of a probe being discovered. The asteroid mining companies of the future would especially have to bear this in mind, and survey their target asteroids thoroughly before mining, to make sure there are no probes there.

In the meantime, we should develop first contact protocols to be implemented if a probe is discovered, and we also need to update the law, such that if a probe is found, then it doesn’t result in a potentially violent mêlée as we race to learn its secrets before our rivals, and that whatever benefits can be gleaned from the probe are made available to the whole of humankind.

If we can meld the societal issues with the practical issues of the search, it would stand SETI in good stead. It would act as a precedent for that other area of controversy, the METI versus SETI debate, which revolves around the societal complications of instigating contact. And, if we could find and make contact with a probe, what a wonderful opportunity that would be, bypassing traditional SETI and providing instant contact. Since Jean-Luc Picard is only a fictional character, the question then becomes, who else should we nominate to speak to the probe on behalf of Earth?

But that’s a topic for another time.


Comments on this entry are closed.

  • Astronist March 27, 2019, 14:29

    This does sound to me rather like the Aztec Empire hoping to capture a shipload of Conquistadores and discover the secrets of gunpowder and ocean navigation. If hypothetical aliens can send a Bracewell probe to the Solar System, then they outclass us by a greater margin than that. But hopefully the probe’s data-gathering surrogates on Earth will enjoy your book?

    • Thomas Goodey March 28, 2019, 5:05

      Well, if the Aztec Empire had had the guts and the enterprise to try that, they might very well have succeeded. Mind you, if they had that level of enterprise, they wouldn’t have been so primitive in the first place.

      • Michael Spencer March 28, 2019, 8:46

        “if the Aztec Empire had had the guts and the enterprise”

        More to the point, the Aztecs lacked the necessary frame of mind, or indeed world view, that would have allowed them a more accurate sense of what was plainly in front of them. Did the Aztecs comprehend their level of peril? Indeed, *could* they have taken a more pragmatic view?

        We’ll never know, of course, the (possible) level of internal discourse within Aztec leadership. We *do* know that our world today would have become a very different place had they, so to speak, seen the light. In this quite limited sense, the Aztecs killed themselves by failing to initiate an action that they could have won, by simply throwing soldiers at the enemy in the manner of Omaha Beach, or indeed Masada (without throwing ourselves off a cliff, however).

        And what of us? Hampered as I am by my own world view, I have no clue.

      • ljk March 28, 2019, 9:14

        Have you studied the Aztec Empire, or any of the other civilizations that existed in the Americas before the Europeans arrived? Primitive is hardly what I would call them.


        Although there were many causes, diseases brought by the Europeans, which the Americans had no immunity to, were one big reason for their downfalls.

        • Michael Spencer March 28, 2019, 10:32

          No, of course you are right, and that’s not my intended message: the Aztecs were as you point out a very capable civilization. and there are direct parallels between the events faced by the Aztecs, and the discovery of an alien object in our solar system.

          And here I am going on memory, of the correspondence of Sr. Cortès in which he describes the internal bickering that characterized the Aztecs, at least as he saw them.

          The Aztecs couldn’t agree on what to do (an over-simplification for sure). Internal divisions played a key role in the downfall of a mighty civilization.

          What would we do? Coming across some sort of device, would we – the citizens of Earth – understand it to represent an existential crisis? And even if we did, could agree on a strategy? In the same way that the Spanish represented an entirely new class of events, so too the discovery of any kind of alien object. Would we know how to regard it?

          • ljk March 28, 2019, 11:35

            Here are a list of reasons why the Aztec Empire fell. Take away the specifics and they had many of the same issues that we have now which could also do us in if we mishandle an ETI encounter, or if they have less than friendly intentions for us:


            • Michael C. Fidler March 29, 2019, 10:20

              Well you are absolutely right, all they would have to do is imitate one of our gods, angels, devils or the other numerous deities and we would make fools of ourselves in no time. Horns are a common feature of animals, just imagine how common that may be in advanced ET’s, you see what I mean. }:-(

              • ljk March 29, 2019, 11:58

                Considering how many otherwise modern people have found unusually shaped knots in trees or stains on a wall that resemble a certain favorite deity of theirs and automatically assume it is a direct message from them, such a scenario is more than probable.

                That the scientists and other authorities would automatically denounce these “signs” as anything but messages or visitors from the beyond would only solidify their thoughts and positions on the subject.

                A clever ETI could make a fortune from the bipedal residents of this planet, if profit were their motive. Or devoted if non-discriminating followers if they liked such attention for various reasons.

              • Michael C. Fidler March 29, 2019, 18:21

                Interesting that horns are a trait of herbivores and may represent a much less aggressive and a more defensive ET. It would seem that we may end up being vegetarians if in the long run it would be a more stable diet. Would a omnivore or herbivore have a long term advantage over the aggressive carnivores when dealing with exterrestrial civilizations?

  • Norm Davison March 27, 2019, 15:08

    Somewhere, many years ago, I heard a very relevant statement. It was in the context of interstellar travel, but would apply well to “lurkers”. It ran roughly, “If ever we see someone coming in from the Deep, we would be well advised to be very, very polite.”

    I think the idea of us “capturing” a perhaps fully or even super-intelligent probe sent here using technologies and/or energies unimaginable to us is close to laughable unless preceded by a protracted period of very polite contact. Nevertheless, decisions would likely be made by politicians and the like, most of whom might well be totally without an appreciation of how dangerous such a “capture” scenario might be.

    The author is correct. The probability of contact during exploration or mining operations is quite low, but we need a protocol for what might be an existentially dangerous encounter.

  • Gary Wilson March 27, 2019, 15:34

    If we have sufficient money and resources to make the effort to look for various types of ET probes nearby I suggest we do as Keith Cooper says, and that is create the various rules and protocols needed to deal with finding one or more of these things. However knowing humans as well as I do, would we actually expect the finder to follow these rules given the chances of enormous wealth and advantage that would ensue from “capturing” the probe for personal/corporate/national use? No would be my answer. Whether the finder was American or Russian or Chinese or Japanese or Indian or European or any other nationality or federation allegiance I think the result would be the same. Immediately upon discovery communicate with home base and decide how best to appropriate the object for the country in question. Sorry to be so suspicious and cynical but I’ve seen some pretty selfish acts in my time courtesy of humans. It’s worth a try though Keith :).

  • Alex Tolley March 27, 2019, 15:53

    So, this is what I recommend: any search must be in conjunction with educating space agencies and private space companies about the possibility, however small, of a probe being discovered. The asteroid mining companies of the future would especially have to bear this in mind, and survey their target asteroids thoroughly before mining, to make sure there are no probes there.

    Nice thought, but the rewards for unilateral action are just too great for this to happen. We might think we are past the atrocities and law breaking of the colonial era, but we are seeing these same actions today. Corporations and bribed government officials are already abrogating laws to get what they want. In recent years, with the possibility of asteroid mining, the Outer Space Treaty is being circumvented to allow profits to be made. If a probe is discovered, I cannot see how we could possibly constrain all parties to leave it alone. Some agency, whether national or private will attempt to capture whatever advantage they can. It is just human nature coupled with the extreme rewards greed brings.

    • ljk March 27, 2019, 17:39

      The Space Review article from 2015 goes into the “legal implications of an encounter with extraterrestrial intelligence”:


      Robert Freitas covered the subject as well:


      I have a feeling the scenario would go pretty much as you describe it. Not entirely certain what the UN could do to stop the offending parties, other than send a strongly-worded letter of protest.

  • ljk March 27, 2019, 17:31


    A direct communication proposal to test the Zoo Hypothesis

    Joao Pedro de Magalhaes

    (Submitted on 8 Sep 2015 (v1), last revised 28 Jan 2017 (this version, v2))

    Whether we are alone in the universe is one of the greatest mysteries facing humankind. Given the >100 billion stars in our galaxy, many have argued that it is statistically unlikely that life, including intelligent life, has not emerged anywhere else. The lack of any sign of extraterrestrial intelligence, even though on a cosmic timescale extraterrestrial civilizations would have enough time to cross the galaxy, is known as Fermi’s Paradox.

    One possible explanation for Fermi’s Paradox is the Zoo Hypothesis which states that one or more extraterrestrial civilizations know of our existence and can reach us, but have chosen not to disturb us or even make their existence known to us.

    I propose here a proactive test of the Zoo Hypothesis. Specifically, I propose to send a message using television and radio channels to any extraterrestrial civilization(s) that might be listening and inviting them to respond.

    Even though I accept this is unlikely to be successful in the sense of resulting in a response from extraterrestrial intelligences, the possibility that extraterrestrial civilizations are monitoring us cannot be dismissed and my proposal is consistent with current scientific knowledge.

    Besides, issuing an invitation is technically feasible, cheap and safe, and few would deny the profound importance of establishing contact with one or more extraterrestrial intelligences.

    A website has been set up (this http URL) to encourage discussion of this proposal and for drafting the invitation message.

    Comments: 16 pages

    Subjects: Popular Physics (physics.pop-ph); Earth and Planetary Astrophysics (astro-ph.EP)

    Journal reference: Space Policy (2016) 38:22-26

    DOI: 10.1016/j.spacepol.2016.06.001

    Cite as: arXiv:1509.03652 [physics.pop-ph]
    (or arXiv:1509.03652v2 [physics.pop-ph] for this version)

    Submission history

    From: Joao Pedro De Magalhaes [view email]

    [v1] Tue, 8 Sep 2015 10:06:43 UTC (70 KB)
    [v2] Sat, 28 Jan 2017 17:30:25 UTC (68 KB)


    • ljk March 27, 2019, 17:32

      The URL mentioned above in the article abstract:


    • Paul451 March 28, 2019, 19:25

      The reasoning seems weird. Older civilisation does a thing for billions of years, let’s deliberately go against what they are doing, that will make them respect us.

      Wouldn’t it make more sense, since we’re still rapidly learning about the neighbourhood, to keep learning about our neighbourhood until we have a list of worlds with life, worlds with advanced life, and worlds with apparently technological civilisation. And then, and only then, pick the nearest world-with-technological-civilisations and send them a direct message.

      Instead of shouting in a dark, silent forest, “Look at me! I’m important!”, we quietly learn about our place until we can approach a single person “Excuse me, I’m new here, can you recommend any good hotels?”

      • Kamal Ali April 1, 2019, 18:10

        I dont get why people think we would be announcing ourselves. If there are galaxy-spanning civilizations , their probes would already know lots about us, maybe hi-def videos of battles on Earth occuring thousands of years ago, Toba explosion of 70K years ago etc.
        Less advanced civs may have capability of telescopes that round-robin over the 10^11 systems in our galaxy, focusing on biospheres. Especially if such civs longevity is in the millions of years, they might have a handy catalogue of all biospheres in the galaxy and which ones have macrofauna, which ones are technical or near-technical etc.
        They will discover us before we discover them.

        • Paul451 April 4, 2019, 0:51

          Then why is METI needed? If they know about us, and yet they aren’t contacting us, what would METI achieve?

          And don’t say “They are waiting for us to say hello”, a) that’s retarded. And b) Drake &co already broadcast a Hello message back in 1974. The Voyagers contain Hello messages. What does METI add that a Zoo-Hypothesis alien federation would consider different?

          Critically, why is METI so important now? (By amazing coincidence, within the lifetimes of the advocates.) Why is it so hard to conceive of waiting until we know more about life out there?

  • John walker March 27, 2019, 17:32

    Perhaps it sounds silly to some, but as Dawn approached Ceres, now 4 years ago, and the peculiar whitish conglomeration in Occator crater was slowly resolving itself, I admit to having fantasized, no hoped, that it may turn out to be an….outpost. Sigh. I am usually more interested in basic science, but I wouldn’t be here if I didn’t share the sort of dreams that most of you have in one way or another of eti.

    That said, on the topic of nearby alien Earth observation there a few critical points I want to make.

    The first is the arbitrary nature of positing that a “co-orbital” station be a preferred location for an observer(unit). I see little logic here. In my opinion the preferred location would surely be in closest physical proximity to the object of study. ie Here on Earth. Landed. This improves and simplifies analysis immeasurably. And should the unit land on a planet as in our case in an era of some degree of technological development, appropriate steps to hide the observer may be selected. Cloak. Submerge. Whatever. An eti with interstellar travel capacities will also possess the capability to avoid detection from a, in our case, technologically highly inferior species.
    Second choice for an observation platform location would be in planetary orbit. Third choice on an orbiting moon. The Earth’s moon offers a fulsome range of advantages over any Trojan or NEO. It’s high gravity is likely the greatest drawback. A more distant outpost will have only more and greater disadvantages save the reduced chance of unwanted detection. However, detection under a certain physical size and radiative signature is virtually certain, as I believe, in much greater proximity. No need for co orbitals.

    The second point I wanted to address is the question of timing. Our galaxy in slightly smaller form was already 6 billion years old as the first planetesmals that would soon become the Earth collided for the first time. When considering alien visitors many often lose sight of the vast expanses of time that preceded the present day. It is vastly more likely that the Earth was evaluated perhaps visited by eti even multiple times in the remotely distant past than in the few centuries since, say, we discovered the basic reality of worlds beyond our own. Does this trivial fact lessen the chances of finding an observer unit nearby? No. I find the prospect of discovering million or billion year old units even if defunct or derelect even more evokative. That’s the romantic in me. I just think that the chances of discovering recent even centuries old additions goes against the simple math I have described multiple times elseware on this blog. But, let’s keep.an eye out.

    • Paul451 March 28, 2019, 19:29

      “The first is the arbitrary nature of positing that a “co-orbital” station be a preferred location for an observer(unit). I see little logic here. In my opinion the preferred location would surely be in closest physical proximity to the object of study. ie Here on Earth. Landed. This improves and simplifies analysis immeasurably.”

      The reasoning is a space-faring civilisation looking to contact other space-faring civilisations. The probe is, in essence, a comms relay. It just uses a local AI to reduce the speed-of-light lag.

    • ljk March 29, 2019, 9:15

      If that were a base on Ceres, they certainly were not trying very hard to conceal themselves. Brilliant white against a uniformly gray surface.

      Imagine if the ETI held so little concern for our existence that they did not even taking hiding from us as a consideration.

      Plus if we did become what they considered to be a problem, dwelling in the Main Planetoid Belt gives one plenty of ammunition to choose from. Just aim a few space rocks at Earth, just big enough to get our attention but not take us out, and that should be enough of a message to us to leave them alone. All they would need is a rocket motor and guidance system to turn a space rock into a weapon.

  • Law Wong March 27, 2019, 20:09

    Yes, intergovernmental contingency plans for first contact should be drawn up for first contact scenarios. However, considering the existence of such probes so likely as to warrant dedicated pre mining surveys seems to me as outlandish as surveying for lurker probes before terrestrial excavation operations or during trawls. Surely there is some chance an alien reentry probe might have been buried in the silt of the Ganges floodplain or sunk into the depths of the North Sea.

    • Kamal Ali April 1, 2019, 18:17

      If there’s no galactic UN, if we are in the “wild west” or nascent days of the galaxy, one could well imagine contact by multiple civs over the last billions of years. Some could be just starting interstellar exploration and their probes may crash into Earth. Other more advanced ones may be very efficient at hiding their exploration of Earth (I’m assuming they choose to hide because if they did not, they would have already shown themselves to us). I don’t necessarily subscribe to the notion that just because the galaxy predates Earth by billions of years, that that necessarily means there must be civs billions of years more advanced than us. The first generation of stars was metal-poor and maybe only now are we getting stars making planets with enough of the right chemicals, materials to support technical civilizations. Or maybe machines inevitably have faults and break down and cannot support a relentless spread between systems at the galactic scale.

  • Harold Daughety March 27, 2019, 23:29

    When we were young children, my older sister told me about “shortcuts” between our house and relatives we seldom visited in the mid to late 1940’s. She explained that one could find the paths by stepping “sideways.” I have always had a fondness to sci-fi involving “strange new worlds” but I have known ever since I was old enough to shave that it is fantasy. There is no theoretical basis to warp drives or any other FTL space flight technology, and the distance between stars preclude any star-faring civilizations, or the planting of probes in other star systems. ET, I firmly believe, is “out there:” and we may find some hint of radio broadcast that might be from ET. But for now there are far more serious concerns for humanity and better ways to spend our meager resources.

  • Andrew Palfreyman March 28, 2019, 0:15

    As an engineer, my first instinct would be to pop it quickly into a double Faraday cage. As a human, my first instinct would be to keep it away from the major powers, most especially the USA.

    • ljk March 28, 2019, 9:17

      And how would that be done? Who would be guarding it that they too would not want to use whatever the probe has to offer for themselves?

      All this assumes such a device would be catchable and containable in the first place.

  • torque_xtr March 28, 2019, 2:23

    I think almost any reasonable strategy for ETI sending Lurkers would take into account a great range of possible actions from host civilisation.

    Imagine the reverse: It’s 2150, and we send an advanced automatic lab to some closest system with a real Earth analog with complex biosignatures (but not advanced technosignatures). Humanity is basically the same as now, only more technologically advanced, and it’s time for real exploration. How would we program the lab? In 2220, it arrives. How would we respond to various actions of indigenous civilisation if it is there and does something to our lab?

    How the answers change if it was an alternative history? If Nazi Germany won in 1945, and it is their descendants who send the probe? If it is the Soviets? Or if some other human society which differs ideologically from the one who are currently most capable for space exploration?

    My thought is that for ventures this deep into Great Unknown, the basic answers and strategy won’t differ radically, and we can rely upon them to some extent when preparing for METI in our own Solar system. But it’s worth studying.

    • Kamal Ali April 1, 2019, 18:26

      Excellent thinking torque: imagine Aztecs or Romans etc having made it to interstellar stage: each of their contact modalities would be quite different than those allowed by our morality today. Now multiply those possibilities thousand-fold: the motives, means for interstellar civs would be a thousand-fold more varied than what is in our history. There could be vastly different types of contact as imagined in sci-fi: benevolent, commercial, enslavement etc. If the civ is a few thousand years different than us, there could be commerce or warfare etc. But if they are millions/billions years ahead, I can’t imagine them wanting to trade. Nor can I imagine they would want to exploit us for food or some special chemical found on Earth etc, or to fight us. At that level of technical difference, especially if they are automatons, it becomes very difficult to imagine their motives and needs and thus the type of contact they would want to have with us (if any). Maybe they’ve already seen our story many times and it’s not particularly interesting for them to talk about wealth or sex or even science.

  • Ken Wisian March 28, 2019, 10:42

    On the call for developing first contact protocols see https://www.centauri-dreams.org/2016/05/13/extraterrestrial-first-contact-in-space-protocols/ for a coarse starting point.
    I and others are putting together a working group on first contact protocols during TVIW 2019 – please think about participating.

  • Gary Wilson March 28, 2019, 12:37

    I had also been thinking about how we might design our own Lurker probes. It’s a very interesting question torque. What would the key attributes of a human Lurker be? How would we design it to react to investigation/damage either accidental or purposeful from an alien species? Would we design it to respond with force? To self-destruct after communicating the event? To respond with an attempt at communication or a revelation of some of what the human race represent ala the Voyager Golden Record?

    • ljk March 29, 2019, 12:03

      All deep space vessels made and sent by us need to contain an information package describing ourselves and our world.

      As we have seen here in this thread, to not make some kind of an attempt at communicating the peaceful or at least neutral intentions of our own such probes – especially the ones that get sent into the wider Milky Way galaxy inert – might only heighten any concerns the recipients may have about an unknown and alien object entering their system.

      The Voyager Interstellar Record is a good template for future information package designs.


      • Gary Wilson March 29, 2019, 14:34

        I’m fairly certain the Golden Record doesn’t include any indications of our warlike, aggressive side. I assume we’re not going to mention that to any alien species so should we assume they would mention it about themselves? How do we deal with this in both directions? Misleading a possible first contact species would immediately alert them to our more disingenuous nature. It’s an interesting problem and possibly we should start think about it.

        • Gary Wilson March 29, 2019, 14:35

          Sorry, that should read start to think about it.

          • ljk April 1, 2019, 9:22

            The makes of the Voyager Interstellar Record purposely did not put in any content that might seem aggressive or a threat, even if it would be considered a puny one to a species that can conduct interstellar travel. This is understandable such a detonated nuclear bomb mushroom cloud.

            Others have shown our flaws with their information packages and I am sure that this trend will only continue as it becomes easier to loft satellites into space. This was the case with The Last Pictures art project, sent into geosynchronous orbit in 2012:


  • PW March 28, 2019, 13:57

    I am happy to read a good SciFi story about intelligent aliens any time! And I’ve read shelves of them. Yes, there is certainly life out there…somewhere. And no telling how far away “somewhere” might be.
    Apparently, NASA is not able to commit funds these days to anything that doesn’t have a very high likelihood of success and a payoff. This even extends to looking for habitable planets at Alpha Centauri.
    Not imagining they will spring for the search for alien probes. While I am all for developing base technology to explore the solar system, the probes from the deep are not likely at all. If they are discovered while we are there doing something else, fantastic!
    The galaxy remains for now an incredible creation that is just too big for us, and likely for most anyone else struggling to stay alive. If it ever is confirmed that FTL travel is even possible, then we should give it more thought. Meanwhile, discovering a probe is a trillion to one shot.

    • Robin Datta March 28, 2019, 23:21

      Unfortunately the price of a ticket is much higher than in lotteries.

    • ljk March 29, 2019, 9:31

      NASA is planning a mission to Alpha Centauri in 2069, but you can decide just how serious they are:


      Quoting from your comment:

      “Meanwhile, discovering a probe is a trillion to one shot.”

      I bet that is what a lot of astronomers used to think before Oumuamua came along.

  • Robin Datta March 28, 2019, 16:18

    Perhaps some post-biologic sentient intelligence, so minimally disruptive to matter-energy as to be undetectable to our present technology, had initiated panspermia billions of years ago as a lurker technology? Did/do they/it consider biological systems to be a “primitive” basis for sentience? And does it/they deem unacceptable the constraints by the physical limits of individual units and the limits of their interactions (Spock’s mind-meld notwithstanding)?

  • J. Jason Wentworth March 28, 2019, 17:00

    Finding an alien probe in our Solar System would be–in most respects–a *good* problem to have! If it was still functioning (which might not be easy to discover, if it appeared to be passive–sufficiently good shielding could mask internal electrical activity, especially if it was DC rather than AC), it would be a good idea–not knowing–to just leave it alone and observe it for a while. What other countries, companies, or even individuals would do (or be inclined to do) if they were the first to discover the probe would probably vary quite a lot (although my list of “villains” is somewhat different from Andrew Palfreyman’s). But:

    If a ^functioning^ probe was discovered, I suspect that any discoverer, regardless of his or her dreams about technologically leap-frogging terrestrial rivals by reverse-engineering the probe’s technologies, would also realize that damaging, destroying, or dismantling the probe could easily be seen as being a hostile or even warlike act by the probe’s makers, who would obviously have the ability to “reach out and touch us” (and not kindly!) if they so chose. Also:

    Legally, the probe could and should (unless it initiated purposefully [not accidentally] destructive or harmful action) be considered a remote diplomat, and its “body” would enjoy the same freedom from harm, and protection by the local government, as a foreign nation’s embassy, consulates, and diplomatic and consular personnel. This is not just my idea, either. Chris Boyce’s thoughtful and insightful non-fiction 1979 book, “Extraterrestrial Encounter: A Personal Perspective” (see: http://www.abebooks.com/servlet/SearchResults?sts=t&cm_sp=SearchF-_-home-_-Results&an=Boyce%2C+Chris&tn=Extraterrestrial+Encounter&kn=&isbn= ) discusses this very issue. He also “war-gamed” a similar one, regarding what we would do if we discovered a crippled but inhabited alien starship in orbit around Jupiter. He concluded (and he provided historical terrestrial analogs) that over time, the disabled alien vessel would acquire the legal status of an embassy, to which terrestrial diplomats, scientists, and even industrialists would go in order to carry on diplomatic relations, joint scientific research and scientific/cultural information exchange, and trade relations with the starship’s home civilization. As well:

    Chris Boyce was a believer in, and advocate of, Von Neumann-type (self-replicating) Bracewell probes with what we now call AI (Artificial Intelligence), and he considered them almost quasi-life forms. (I don’t say that such self-replicating machines and probes are impossible, for the history of science & technology shows that “impossible” is a very dangerous word to use. We may one day develop such machines. But for us–at this time–such devices ARE impossible.) However:

    Older societies elsewhere in the Galaxy (or even beyond it) may have developed Von Neumann-type Bracewell probes, so it would be folly on our part to *not* consider the possibility–and ramifications–of discovering, or being discovered by, such a probe, just because ^we^ can’t build such spacecraft. Even a “primitive,” non-replicating Bracewell probe might be difficult or impossible for us to capture, especially if it was advanced enough to slow down and enter orbit around our Sun (although it could have been braked by a now-spent [or jettisoned] retro-propulsion rocket stage, sail, E-sail, etc), and:

    It might evade capture, self-destruct, or destroy approaching spacecraft with other types of weapons, depending on its purposes, which in turn depends on its makers’ purposes and psychology–we just can’t know. The U.S. government’s loose plan for dealing with an overt landing on Earth by one or more living extraterrestrials (the Department of Agriculture would quarantine the alien(s) at a “hard” bio-hazard facility they have, NEST–the Nuclear Emergency Search Team, formed after a false but seemingly credible terrorist atomic bomb threat in the 1970s–would examine the spacecraft, assuming it was nuclear-powered if it produced no detectable exhaust, etc.) is laughable (although they deserve credit for at least considering the possibility). Any race that could cross interstellar space could easily avoid or nullify our primitive–by comparison–capabilities, and alien interstellar probes could be similarly well-able to take care of themselves.

    While the ideal such probe contact would be with a friendly probe sent by a non-belligerent race engaging in peaceful exploration (an older, more advanced society–but not *too* advanced for us to “leap the intellectual, cultural, and technological abyss” separating us from them–that could and would mentor us could be ideal for us), can we expect to be this lucky? Even a non-belligerent but cold (to us) contact, with a probe (or signal, or even expedition) from a god-like race too advanced for us to comprehend, or with a not-so-advanced (although still more than us) race that regards human beings as merely interesting creatures to be studied, not to engage with intellectually, could be stultifying or even devastating to human society. The only prudent course of action is to be willing to meet anything, because we just don’t know what or who we might find–or be found by.

    • Keith Cooper March 29, 2019, 7:57

      Huh, I actually I have that Chris Boyce book on my bookshelf, I just never got around to reading it. Might have to push it to the top of the read pile.

      Great post, by the way. There’s currently a discussion in the planetary science community about what level of forward contamination on Mars, or any world we are exploring, is acceptable. Brent Sherwood at JPL has written a paper about the ethical implications of forward contamination – that is, terrestrial bugs hitching a ride on our spacecraft – and calls for a scientific and societal discussion about these ethics (https://www.astrobio.net/news-exclusive/putting-the-ethics-into-planetary-protection/). Are the current rules too strict? Does society in general even care if we contaminate Mars or Europa with Earthly bugs that then go on to destroy or interrupt any established biospheres there? I can imagine a civilisation sending out lurker or explorer probes having the same kinds of ethical discussions: do they care whether their probes interfere with or destroy some primitive species that’s barely mastered space travel? Are we just the equivalent of Martian microbes to them?

      While reading through the posts here another point occurred to me. We’re making the big assumption that a lurker probe would come here just to study us. There’s an entire Solar System out there, and just as we explore it, they might explore it too, and they can’t very well do that from Earth, or the Moon, or even co-orbiting asteroids. If we begin with the premise that there could be a probe in the Solar System, I don’t think we can assume it will necessarily be in any particular location. Not finding a probe near Earth doesn’t mean there’s not one lurking over Europa instead.

      This entire discussion about lurker probes is very much a ‘what if’ discussion. Personally I think the chances of finding a probe are low, but although some people have dismissed all this talk of probes, I think it’s a good discussion to have, not least because it provides another angle on the topic of contact and how it might play out.

    • Paul451 March 29, 2019, 11:09

      “If it was still functioning (which might not be easy to discover, if it appeared to be passive […]
      damaging, destroying, or dismantling the probe could easily be seen as being a hostile or even warlike act by the probe’s makers,”

      Then they would be wrong. Any newly space-faring civilisation discovering an ancient alien artefact in their (relative) backyard would want to examine it. It’s as natural a reaction as anything you could imagine. If the senders consider the probe to be off-limits, but place in such a place, they are being hostile even warlike.

      (Also, “diplomats” don’t get to sneak in and hide in a secret watch-house outside the city, they are required to present themselves to the receiving nation’s leaders.)

      This is not to say that a Lurker won’t be a spy-probe (although that’s not the actual concept being discussed), or that it won’t be designed to attack or self-destruct to prevent examination. But that won’t be us doing something wrong, it will be them.

  • Paul451 March 28, 2019, 19:40

    Re: Alien probe responding to our approach as a threat.

    I would think that such a scenario would play out many times over galactic history, and so would be an accepted part of the process of contacting a new space-faring civilisations. They are going to dismantle your probe. It’s a fact of life. Accept it and move on. Hence the technology of the probe becomes part of the “gift”, along with the information contained. Anything you don’t want them to have, you dump into the sun long before they’ve evolved.

    Designing the probe to “defend itself” would be crazy. And I’d be deeply suspicious of any civilisation that was sending out armed Lurkers. Those are the bad guys.

    • ljk March 29, 2019, 9:26

      Put a self-destruct system on the probe if you do not want anyone getting ahold of it whom you do not trust. It could be made relatively simple so that something akin to hitting a trip wire set off an explosive device.

      Sad that we even have to consider such things, but I agree with those here who have described how humanity would probably react to an actual alien probe in our cosmic neighborhood. Many governments alone would want it for the advanced technologies it might have.

      We assume the ETI would be cautious and even suspicious of what they would deem to be potentially hostile natives, but they could have very different mindsets on the subject. Humanity evolved in a world where life preyed upon life and higher beings had to form groups and communities to protect their species from others who were not their kind. We often assume ETI evolved in a similar manner but we just do not know.

      • Michael C. Fidler March 29, 2019, 19:29

        Two problems that would change the scenario:
        1.Any probe may be sent by a large group of independent exterrestrial civilizations, that have a long history of dealing with new civilizations.
        2. We are already looking at quantum level technology and the question would be what would a probe at this level look like? Would it be a plasma ball like ball lightning? Something like this could be used for close surveillance and would disintegrate after use, like a miniature proximity fuze.

        Two great inventions that were very advanced for their time and are at the same level as the atomic bomb in deciding the outcome of WWII was the cavity magnetron and the doppler proximity fuze. Both have little public credit or knowledge of and reflect a cooperative and concentrated effort by the British and the USA to develop the technology. The British had major breakthroughs in these two fields in early 1940 and this was given to the USA for the development in late 1940. The cavity magnetron was the first light weight high power microwave freqs radar device and the doppler proximity fuze used constructive and destructive interference to detect its target. Both were a scientific and creative breakthrus for their time.

        “The Allied fuze used constructive and destructive interference to detect its target. The design had four tubes. One tube was an oscillator connected to an antenna; it functioned as both a transmitter and an autodyne detector (receiver). When the target was far away, it would reflect little of the oscillator’s energy back to the fuze and have almost no effect on the circuit. When a target was nearby, it would reflect a significant portion of the oscillator’s signal back to the fuze. The amplitude of the reflected signal indicated the closeness of the target. This reflected signal would affect the oscillator depending on the round trip distance from the fuze to the target. If the reflected signal were in phase, the oscillator amplitude would increase and the oscillator’s plate current would also increase. If the reflected signal were out of phase, then the plate current would decrease.

        The distance between the fuze and the target is not constant but rather constantly changing due to the high speed of the fuze and any motion of the target. When the distance between the fuze and the target changes rapidly, then the phase relationship also changes rapidly. The signals are in-phase one instant and out-of-phase a few hundred microseconds later. The result is a heterodyne beat frequency that indicates the velocity difference. Viewed another way, the received signal frequency is doppler shifted from the oscillator frequency by the relative motion of the fuze and target. Consequently, a low frequency signal corresponding to the frequency difference develops at the oscillator’s plate terminal. Two additional amplifiers detected and filtered this low frequency signal. If the amplified beat frequency signal is large enough (indicating a nearby object), then it triggers the 4th tube (a gas-filled thyratron); the thyratron conducts a large current that sets off the electrical detonator. There were many shock hardening techniques including planar electrodes and packing the components in wax and oil to equalize the stresses.”


      • Alex Tolley March 30, 2019, 12:37

        There is also the assumption that any probe AI will have a cognition that reflects that of their creators. We cannot assume that either. Indeed, much of our current AI development clearly does not reflect human cognition at all.

        If self-destruction on discovery is wired into the probe, I would hope that it is done with some sort of safe destruction that does not create any explosions or other perceivable threats. That is how we should design our probes if that is a desired outcome.

  • Marshall Eubanks March 28, 2019, 22:25

    I worried about this in the context of 1I/’Oumuamua. Suppose we sent a probe to 1I? How would we find out about its composition? A logical approach would be to hit it with a small sub-probe (or probes) and look at the impact light in the EUV for spectral lines.

    The issue here is that the probe would do this 0.5 light day or further away from Earth, and it wouldn’t be able to see 1I well until at most 1 day out, so we here on Earth would no nothing about the details of 1I until after the entire encounter was over. In other words, if 1I was an interstellar probe, we wouldn’t know it until _after_ we shot it with hypervelocity bullets, which might not go over well.

    • ljk March 29, 2019, 9:18

      I only wish we had an actual probe going there to have that issue to contend with in the first place.

      Perhaps a soft lander would be a safer compromise?

  • Curious March 28, 2019, 22:38

    There is an assumption in here that the “lurker” probe is large – I think its more logically the opposite. Physics still matters even for advanced civilization, and the smaller the probe the faster it can be sent, and more cheaply – allowing many to be sent to cover more targets. Consider how our electronics have advanced in the last 100 years and now imagine what another 100 years will bring. If such a probe was sent here, say Oumuamua was its spent light sail, then perhaps it is only as big as a pea maybe even less if it where a nanomachine. If it were designed to seek advanced civilizations like say at least at our level, then it seems logical that it would seek out the source of greatest RF transmission, and then find local power resources to use to power the signal it sends back, maybe using local power grid and data infrastructures to both harvest data and as a “software defined” transmitting antenna from existing transmitters. Physically you would likely never find it, so might be best to listen for unknown signal bursts going outbound from Earth.

  • ljk March 29, 2019, 10:22

    The 1997 SF film Contact, based on the 1985 novel of the same name by Carl Sagan, gives an idea of how at least certain segments of humanity would respond to a First Contact:


  • Gary Wilson March 29, 2019, 13:05

    I see the NASA budget for 2019 looks very good at around 21.9 billion. They are very concerned about more cost overruns for JWST which they should be. Another 2.2 billion added on I hear. That is completely out of control. Surely a head or two must roll for that peccadillo of a project. What is the total cost projected to be now? I think it’s up to 8.8 billion now.

    • ljk March 29, 2019, 13:48

      Have you seen what it will take to get JWST to deploy in space – by itself? One slip-up and the whole mission could be doomed. Oh, and they did not provide a way for in-orbit repair because JWST will be so far from Earth.

      See here:


      • Gary Wilson March 29, 2019, 22:32

        I may be wrong but I think it’s madness to sink so much money into one project, even one like JWST. But surely it can’t be cancelled now, with so much money already spent can it? It should provide lessons for funding decisions on future missions though. The lack of an ability to repair it seems very shortsighted as well. Possibly it could be reached using SLS? I know it’s going to be a long way out but surely that is the type of mission SLS is intended for? Mars is a long way out too.

        • Keith Cooper March 31, 2019, 10:19

          They’re not just choosing to send JWST to L2 at random – there’s a reason for it, which is to keep the Earth and the Sun behind its sun-shield so that it it can keep its instruments cool enough to perform the sensitive infrared observations that it will be making. Also, since the retirement of the space shuttle, there’s not really any means by which NASA could service an instrument in orbit anyway – remember the space shuttle had a cargo bay and a robotic arm to grab the HST, the SLS is going to be launching capsules that won’t have that capability.

          • Gary Wilson March 31, 2019, 13:48

            Thank you. That makes sense Keith. However I don’t think that the space shuttle took the Hubble into its bay to repair it. The astronauts worked on it in situ didn’t they? And I assume the same could be done by SLS astronauts. Aren’t they intending to travel to asteroids using SLS and Mars? They will have to be versatile at those locations as well. If the JWST cannot be repaired because it cannot be reached at L2 then we really aren’t growing in capability are we?

            • Keith Cooper March 31, 2019, 17:12

              The shuttle would grab Hubble using the robotic arm that protrudes from its cargo bay. So while the telescope wasn’t dragged into the cargo bay, it was held in place by the arm so that the astronauts could get to it – it wasn’t free-floating while they worked on it. I suppose you could modify a capsule to move alongside the JWST and grab it with an arm, but development on the JWST began at the turn of the century, pre-Columbia disaster, when the space shuttle was very much the primary means of getting into space, and the shuttle could not travel to L2. (Back then, NASA budgeted JWST at less than a billion dollars!) So it just wasn’t designed to be serviced simply because that option was not on the menu at the time. If it was being designed today, it might be designed very differently in that regard.

        • Paul451 April 5, 2019, 12:08

          “JWST. But surely it can’t be cancelled now, with so much money already spent can it?”

          The definition of the Sunk Cost Fallacy.

          “It should provide lessons for funding decisions on future missions though.”

          Which is why I believe it should be cancelled. Nothing will be learned if JWST is successful. The people involved have to suffer in order for the lesson to matter. “Too big to fail” cannot be used to defend incompetence.

          • david lewis May 6, 2019, 22:02

            There’s another expression – cutting of your nose to spite your face. It’s to be expected that the first of it kind of anything will run into over costs. By cancelling the JWST we would be either turning our backs on extending our knowledge of the cosmos, or be starting a new project, only with the more exact price tag of 8.8 billion dollars. Either we want that knowledge, or we don’t. Either we’re willing to pay the price, or we aren’t.

            Consider that the combined GDP of the US/Canada/European Union is around 40 T. Over ten years, which is how long the JWST is hoped to last, that’s 400 T dollars. 8.8 billion is around 0.0022 percent of that figure. Is 0.0022 percent too much to extend our knowledge of how the universe began, in finding our if there are other biospheres out there, …

            And it’s not as if all that money was for a one time space telescope. Future projects will also be able to make use of the technological knowledge gained from the JWST’s development, and the expertise gained from its deployment.

            Those technologies will also have applications here on Earth.

            To me it says something about our species when we’re willing to spend trillions on war, yet people get the vapours at billions for expanding our understanding of the cosmos.

  • Gary Wilson March 29, 2019, 13:06

    That should read 21.5 billion. Sorry for the inaccuracy.

    • Bruce D. Mayfield March 30, 2019, 13:32

      What’s a mere $400 mil amongst friends Gary? Odds are the way things are going that your mistake will even be exceeded when the final talley for JWST is added up.

      • Gary Wilson April 1, 2019, 12:58

        And when the Vice President of the United States doesn’t get the name of the chief NASA administrator correct (he called him Jim Bridenstiner in a recent speech) that can’t be a good sign either Bruce. Thank you again for your comments Keith. I just think flexibility in design and repair should always be taken into consideration. These programs are so far off budget now that there probably wasn’t even any point in making the early estimates. A truly gloomy outlook for American manned space exploration.

  • Adam March 30, 2019, 9:20

    Nice to see someone has invoked the shade of Chris Boyce. His ET Presence, the sequel to “ET Encounter” which he started on-line in the late 90s, has this intriguing perspective on the presence of von Neumann probes or machines in our system:

    As things stand we have no evidence of contact between humanity and vN. Logic does dictate that if ET societies exist vN are virtually certain to be in the Solar System, perhaps with a presence here on Earth or close by. In this event they are leaving it up to us to find them and make up our own minds as to whether or not we wish to knock on their door.

    Over the next few centuries we may seek them out, perhaps find them and try to communicate. Or we may simply go our own way and choose to ignore their presence.

    But whether we do or not – they are real and they are here.

    Thus all our discussions are likely irrelevant to the reality and the vN presence will go on ignoring us – except they’re likely to be monitoring our discussions, if they exist. It’s not the first time someone has raised that possibility, but no ETIs have made themselves known so far. If they’re nearby then we may need to knock. Carefully.

    • ljk April 1, 2019, 9:33

      Can you imagine the poor ETI who is assigned to sift through our species’ verbal diarrhea such as Twitter? They are not trying to contact us because they are too busy demanding a transfer to another less barbaric planet.

      • Gary Wilson April 1, 2019, 13:02

        Yes ljk we are a very chaotic species with a great deal to say about very little and very little sensible to say about things of far greater importance such as human caused climate change.

        • ljk April 2, 2019, 9:56

          I think Walter M. Miller summed up humanity pretty well in his great SF novel A Canticle for Leibowitz:

          “There were spaceships again in that century, and the ships were manned by fuzzy impossibilities that walked on two legs and sprouted tufts of hair in unlikely anatomical regions. They were a garrulous kind. They belonged to a race quite capable of admiring its own image in a mirror, and equally capable of cutting its own throat before the altar of some tribal god, such as the deity of Daily Shaving. It was a species which often considered itself to be, basically, a race of divinely inspired toolmakers; any intelligent entity from Arcturus would instantly have perceived them to be, basically, a race of impassioned after-dinner speech-makers.”


        • Michael C. Fidler April 2, 2019, 10:06

          We’ll make our own KT boundry from plastic waste and something better will come along!

          • Gary Wilson April 2, 2019, 12:35

            A wonderful quote from Miller ljk. I loved the novel. One of the truly great SF works. I just finished reading Stewart’s Earth Abides again and it was as amazing as I remembered it to be.

  • Kamal Ali April 1, 2019, 18:04

    I imagine the more advanced civilization will be the one that calls the shots on how/when/why/if the contact will occur. If they are advanced enough and have plenty of resources, each probe may be a fully functioning autonomous AI with advanced propulsion, defense/attack and decision-making capabilities. If it does not want to get discovered, it will not – if it sees the humans get too close, it could leave our system if it does not want to get discovered.

  • Gary Wilson April 1, 2019, 21:43

    We are a relatively short lived species and therefore very impatient. I think it could take hundreds of years just to learn about our galactic neighborhood properly. Put a 1000 light year bubble around us, determine how many planets around how many stars, determine how many planets with any life we can detect and confirm, and determine if any have what we would refer to as ET. Are any of these ET sending out probes? Do we detect outgoing ships either robotic or otherwise from any of these places? Are we a target? And so on. What a wonderful adventure in learning it will be!