Diplomat and author Michael Michaud returns to Centauri Dreams with a look at interstellar probes and how we might use them. Drawn from a presentation originally intended for the 100 Year Starship Symposium in Houston, the essay asks what effect our exploring another stellar system would have on its possible inhabitants. And beyond that, what effect would it have on us, as we weigh ethical issues and ponder the potential — and dangers — of highly intelligent artifacts going out into the galaxy? Michaud is the author of the indispensable Contact with Alien Civilizations: Our Hopes and Fears about Encountering Extraterrestrials (Springer, 2007). Among his numerous other works are many on space exploration. He was a U.S. Foreign Service Officer for 32 years, serving as Counselor for Science, Technology and Environment at the U.S. embassies in Paris and Tokyo, and Director of the State Department’s Office of Advanced Technology. He has also been chairman of working groups at the International Academy of Astronautics on SETI issues.

by Michael A. G. Michaud

Although the planets may belong to organic life, the real masters of the universe may be machines. We creatures of flesh and blood are transitional forms.

— Arthur C. Clarke

A Paradigm Reversed


For the past forty years, nearly all published work about the impact of contact with an extraterrestrial civilization has foreseen that it will be one way, from the aliens to us. These scenarios have rested on an assumption that any alien civilization detectable by its technological activity must be more scientifically and technologically advanced than we are.

The 100 Year Starship Study is bringing this paradigm into question, because of an anticipated change in human capabilities. We are talking about sending our own machines to visit nearby star and planet systems. This is the beginning of a role reversal.

We could be the first technological civilization to begin expanding its presence into this region of the galaxy. The impact of contact, whether intended or not, might flow from us to others.

If there are alien forms of intelligence in any of the target systems, they may be less scientifically and technologically advanced than we are. If those other sapient beings live in pre-industrial societies, they may not be detectable before our probe arrives.

On Earth, practical ethics imply that we should try to anticipate the effects of our actions. Our plans for our probe’s arrival in an alien system should have an ethical dimension.

Sending Out a Mind

Our first interstellar probe may include the most autonomous artificial intelligence we have built up to that time. While much of its behavior will be pre-programmed, the probe’s actions may not be determined solely by the instructions it receives from its makers. That probe must be able to adapt to unforeseen circumstances, in some cases to make its own decisions. How independent should that intelligence be?

During its long journey, such a machine might evolve by connecting data in new ways. The artificial intelligence could be mutated by the effects of radiation generated when the probe collides with interstellar matter.

An altered machine might make choices different from those its senders intended. Like the HAL 9000 in 2001: A Space Odyssey, the probe might override its programming, making its own choices about which actions it will take.

It may take years for our new instructions to reach the probe. It would take more years to know if the probe has obeyed those instructions.

Robot Warriors

We are seeing a preview of this issue in the military use of robots. Articles in Scientific American have warned of a threat from semiautonomous machines over which humans retain nothing more than last-ditch veto power. Some systems are only a software upgrade away from fully self-sufficient operation.

According to articles in The Economist, humans will increasingly monitor military robots rather than fully control them. Some robot weapons already operate without human supervision to save precious seconds. Defense planners are considering whether a drone aircraft should be able to fire a weapon based on its own analysis.

As autonomous machines become smarter and more widespread, they are bound to end up making life or death decisions in unpredictable situations, thus assuming – or at least appearing to assume – moral agency.

The Singularity

We have heard much about a Singularity predicted for less than twenty years in our future. At that time, human intelligences would be uploaded into machines, eventually becoming independent of biology.

Our interstellar probes could be the most advanced forms of such an uploaded intelligence. Sending out such intelligent machines could be a first step toward a post-biological galaxy.

A Second Singularity may begin when we lose control of the probe. The good news is that we would be sending our creation very far away, where it would pose the least potential risk to Humankind.


Recognizing Evidence

We commonly assume that our probe will give priority attention to whatever planet in the target system is most like Earth. What will our probe look for? High on that list will be evidence of life.

With a limited payload, interstellar probe designers will have to make choices among instruments. Those choices will rest on assumptions about the nature of life that prevail at that time.

Will the probe recognize evidence of life forms very different from the ones we know on Earth? What if the probe reports ambiguous evidence? What if we are not sure whether the phenomenon we discover is life or non-life, because it is so different from the life we know?

Even if forms of life exist on that far off world, the probe’s sensors might not detect them. A report that there are no signs of biology could clear the way for an eventual human colonizing mission.

Will the probe also look for evidence of intelligence? Will it recognize such evidence in a society that does not emit electromagnetic signals and does not pollute its atmosphere with the by-products of industry?

Should our probe send signals to whatever planets it observes? Would local intelligences be able to receive such messages, or understand them?

It is conceivable, though not probable, that our astronomers will remotely detect signs of intelligent life in a nearby system before we launch a probe. Should we send a probe to that destination, or avoid it?

The Consequences of Contact: A Mirror Image

What would be the impact on intelligent beings who detected our probe? How would they react? This could be seen as a mirror image of the debate among humans about the consequences of contact for us.

What if the extraterrestrials had believed that they were the universe’s only intelligent beings, as most humans have believed about themselves? What if an alien technological civilization had used astronomical instruments to survey planets around other stars as we are doing now, and had found no evidence of the kind of biochemistry they know? They might have concluded that they were alone.

Even if they had imagined life and intelligence on faraway planets, they may not have thought of interstellar exploration. They may not have anticipated direct contact. Our probe’s arrival in their system could be a startling surprise.

Detecting evidence of an alien technology in their system would tell them that at least one civilization had achieved interstellar flight. They would know that contact could be direct.

To extraterrestrials, we would be the powerful and mysterious aliens, whose character and purposes are unknown. Suddenly, they might feel vulnerable.

Alien impressions of Humankind would be determined by their understanding of our probe. What would they see as our motivation in sending it? Would they think that the detected probe was only one of many, part of a grand scheme of relentless interstellar colonization?

Consider what now seems the most likely form of such an encounter: a fly-through of the alien system. The probe’s high velocity would make the event brief. Our machine might not be detected. If it were, the extraterrestrial equivalent of skeptical scientists might say that a one-time sighting is not proof.

Arthur Clarke described such a scenario in his novel Rendezvous with Rama, in which a giant alien spacecraft flies through our solar system without stopping or communicating. The implied message was deflating: Humankind was not only technologically inferior, but also irrelevant.

Imposing Ethics on a Machine

We humans have set a precedent for regulating our behavior toward possible alien life during our interplanetary explorations. Protocols are in place to avoid contaminating other solar system bodies, and to prevent back-contamination of the Earth.

Implicitly, we have accepted a principle of non-interference with alien biology. Such rules may be extended to an interstellar probe, suggesting that our machine should not enter the atmosphere or land on the surface of a planet suspected to have life.

What should be our probe’s rules of engagement if it encounters intelligent life? Will our machine be able to make ethical choices? Can we give our probe a conscience? Should our probe obey Star Trek‘s often violated Prime Directive, observing the other civilization while keeping our presence secret?

Before Star Trek, Stephen Dole and Isaac Asimov argued that contacts with alien intelligence should be made most circumspectly, not only as insurance against unknown factors but also to avoid any disruptive effects on the local population produced by encountering a vastly different cultural system. After prolonged study, a decision would have to be made whether to make overt contact or to depart without giving the inhabitants any evidence of our visit.


Image: The Hubble view in the direction of Sagittarius, looking toward the center of the Milky Way. The discovery of life around distant worlds raises huge questions of ethics and even self-preservation as we ponder what kinds of future probes we might send. What should a program of galactic expansion look like? Credit: NASA, ESA, K. Sahu (STScI) and the SWEEPS science team.

Future Behavior

Some of those involved in the extraterrestrial intelligence debate have assumed that a program of sending probes, once begun, would continue until all the Galaxy had been explored, perhaps by having probes reproduce themselves. This model has been used to dismiss the idea of extrasolar intelligences; if we don’t see their machines, they must not exist.

This model flies in the face of the only behavioral data base we humans have: our own history. No human expansion has continued unchecked. No technological program continues indefinitely.

Newman-and Sagan argued that self-reproducing probes will never be built because they constitute a potential threat to their builders as well as to other sentient species that encounter them. Wise civilizations would not create potential Berserkers.

What if we send several probes, and none finds a habitable planet? Would our interstellar probe program be abandoned like the Apollo manned missions to the Moon? Sending our first probes might be a technological catharsis, not to be repeated.


You who plan to build starships may be initiating a new phase in Galactic history. If we expand our presence beyond our Solar System through our probes, our role in the galaxy will begin to change.

We cannot foresee all the powers that our machines will have a century in our future, any more than people in 1913 could foresee what powers our machines have now.

We should think through the implications of succeeding ourselves with artificial Intelligence. What motivations should we instill in our intelligent machines? What limits on their behavior can we impose?

For those who would design artificially intelligent probes, I offer a warning. Be careful of what you loose upon the galaxy. Above all, do not give those machines the ability to reproduce themselves.

Someday, Humankind may praise or condemn what interstellar advocates and their successors actually do. Choose wisely.