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One way that astronomers and astrobiologists search for life in the galaxy is observation of rocky planets orbiting other stars. Such planets may contain an atmosphere, liquid water, and other ingredients that are required for biological life on Earth. Once a number of these potentially inhabited planets have been identified, the next logical step in exploration is to send remote exploratory probes to make direct observations of these planets. Present-day study of other planetary systems is so far limited to remote observation with telescopes, but future plans for exploration include the design and deployment of small robotic exploratory spacecraft toward other star systems.

If intelligent, technological extraterrestrial life exists in the galaxy, then it is conceivable that such a civilization might embark on a similar exploration strategy. Extraterrestrial intelligent (ETI) civilizations may choose to pursue astronomy and search for planets orbiting other star systems and may also choose to follow-up on some of these targets by deploying their own remote exploratory spacecraft. If nearby ETI have observed the Solar System and decided to pursue further exploration, then evidence of ETI technology may be present in the form of such exploratory probes. We refer to this ETI technology as “non-terrestrial artifacts”, in part to distinguish these plausible exploratory spacecraft from the flying saucers of science fiction.

In a recent paper titled “On the likelihood of non-terrestrial artifacts in the Solar System”, published in the journal Acta Astronautica, myself and co-author Ravi Kopparapu discuss the likelihood that human exploration of the Solar System would have uncovered any non-terrestrial artifacts. Exploratory probes destined for another star system are likely to be relatively small (less than ten meters in diameter), so any non-terrestrial artifacts present in the Solar System have probably remained undetected. The surface and atmosphere of Earth are probably the most comprehensively searched volumes in the Solar System and can probably be considered absent of non-terrestrial artifacts. Likewise, the surface of the moon and portions of Mars have been searched at a sufficient resolution to have uncovered any non-terrestrial artifacts that could have been present. However, the deep oceans of Earth and the subsurface of the Moon are largely unexplored territory, while regions such as the asteroid belt, the Kuiper belt, and stable orbits around other Solar System planets could also contain non-terrestrial artifacts that have so far escaped human observation. Because of this plenitude of nearby unexplored territory, it would be premature to conclude that the Solar System is absent of non-terrestrial artifacts.

Although the chances of finding non-terrestrial artifacts might be low, the discovery of ETI technology, even if broken and non-functioning, would provide evidence that ETI exist elsewhere in the galaxy and have a profound impact on humankind. We do not argue that the search for non-terrestrial technology should be given priority over other astronomical missions; however, as human exploration into the Solar System continues, we may as well keep our eyes open for ETI technology, just in case.

One possibility for communicating across the vast distances of space is the use of radio or other electromagnetic waves. Human civilization already posses the technology to broadcast and receive signals at many wavelengths. If other extraterrestrial civilizations exist in the galaxy, then it is possible that they could develop similar capabilities. Based on this premise, the search for extraterrestrial intelligence (SETI) has scanned the sky for over fifty years now to look for any such signals. Along similar lines, a handful of attempts at messaging to extraterrestrial intelligence (METI) have been undertaken in recent years, with hopes of being picked up by an extraterrestrial listener. The content of these messages has increased in complexity and content, though, which may produce cryptic messages that are disorganized or difficult to decipher.

In a recent paper published in the journal Space Policy, my co-authors Dimitra Atri and Julia DeMarines and I propose the development of a METI protocol in order to guide the construction and transmission of messages to extraterrestrials. A METI protocol would include technical considerations such as the method of signal encoding, message length, and transmission strategy. This protocol would also provide guidelines for the content of messages, which includes limits on culturally-dependent, anthropocentric, or sense-dependent information. This will help ensure that a message into space is more representative of Earth as a whole and may also increase the likelihood that the message is understood by potential listeners.

As a way of testing messages and promoting educational outreach, we will implement an interactive website in which users can attempt to submit or decrypt messages according to a METI protocol. This will allow messages to be tested across cultural borders, which arguably is a minimum requirement for a message that would be sent to unknown extraterrestrial listeners. Such an exchange will also help users of the website to gain insight into cultures other than their own by discovering success or failure at effectively communicating a message to unknown receivers on Earth.

Humans have yet to encounter any extraterrestrial beings, and, although speculations abound in Hollywood and in science fiction, we really have no idea what contact with aliens would be like. In one scenario, a population of aggressive and malevolent extraterrestrials invade Earth in order to enslave us or eat us as part of their conquest of the galaxy. Still another hypothetical extraterrestrial civilization might welcome us with open arms into peaceful communication and help us solve many of our global problems. With such a wide range of possibilities for an as yet unknown encounter, can we say anything at all regarding the risk of contact with extraterrestrials?

We explore this question in a recently published article titled “Would contact with extraterrestrials benefit or harm humanity? A scenario analysis“. This article was written by Seth Baum, Shawn-Domagal Goldman, and myself and appears in the current issue of Acta Astronautica. Rather than focusing on one particular outcome of alien contact, we take a broad approach of categorizing a wide range of contact scenarios as either beneficial, neutral, or harmful to humanity. In doing so, we draw on scientific as well as ethical analysis to demonstrate that there are a wide range of responses to contact with extraterrestrials, which may depend at least in part on human actions in the near and distant future.

Our television and radio signals have been leaking away from our planet for decades now, detectable by any nearby extraterrestrials willing to listen. The light from our planet, too, shows not only signs of biological life but also signs of rapid warming and climate change. Although we cannot be certain that any of our behaviors will necessarily invoke the wrath–or solicit the aid–of advanced extraterrestrials, perhaps it would behoove us to give thought and care to our future trajectory, just in case someone is watching.

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Voting is open until April 20, and each person is allowed one vote per day, so you can vote often. First place gets a cash award and an internship with Scientific Blogging, so I’m crossing my fingers!

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