The Wow! signal and extraterrestrial life

Are there extraterrestrials on Earth or elsewhere in outer space? The Wow! signal, the strongest candidate for an alien radio transmission ever detected, was a strong narrowband radio signal (in radio communications, narrowband describes a channel in which the bandwidth of the message does not significantly exceed the channel’s coherence bandwidth) received on August 15, 1977, by Ohio State University’s Big Ear radio telescope in the United States of America, then used to support the search for extraterrestrial intelligence.

The Ohio State University Radio Observatory was a Kraus-type radio telescope located on the grounds of the Perkins Observatory at Ohio Wesleyan University from 1963 to 1998. Known as Big Ear, the observatory was part of The Ohio State University’s Search for Extraterrestrial Intelligence (SETI) project. Construction of the Big Ear began in 1956 and was completed in 1961, and it was finally turned on for the first time in 1963.

The Wow! signal

The signal appeared to come from the constellation Sagittarius and bore the expected hallmarks of extraterrestrial origin. Astronomer Jerry R. Ehman discovered the anomaly a few days later while reviewing the recorded data. He was so impressed by the result that he circled the reading on the computer printout and wrote the comment Wow! on its side, leading to the event’s widely used name. The entire signal sequence lasted for the full 72-second window during which Big Ear was able to observe it, but has not been detected since, despite several subsequent attempts by Ehman and others. Many hypotheses have been advanced on the origin of the emission, including natural and man-made sources, but none of them adequately explains the result.

In a 1959 paper, Cornell University physicists Philip Morrison and Giuseppe Cocconi had speculated that any extraterrestrial civilization attempting to communicate via radio signals might do so using a frequency of 1420 megahertz (21 centimetres), which is naturally emitted by hydrogen, the most common element in the universe and therefore likely familiar to all technologically advanced civilizations. By 1977, Ehman was working at the SETI project as a volunteer; his job involved analysing by hand large amounts of data processed by an IBM 1130 computer and recorded on line printer paper. While perusing data collected on August 15, he spotted a series of values of signal intensity and frequency that left him and his colleagues astonished.

Determining a precise location of the signal in the sky is complicated because the Big Ear telescope used two feed horns to look for signals, each pointing to a slightly different direction. The signal has been detected in only one of these two horns and the data has been processed in such a way that it is impossible to determine in which of the two horns the signal has entered. There are therefore two possible right ascension values.

Are extraterrestrials among us?

From the Renaissance, myths fed the collective imagination. It became popular with the conquest of outer space in the 1960s, and the proliferation of science-fictional stories. Extraterrestrials would have already visited the Earth, established a secret colony to spy on us, and leave us in peace while we grow.

Difficult, however, to cross and identify us in a universe as vast and old as ours. While the planet is four and a half billion years old, we have been able to receive and emit signals for only a hundred years. One of the most famous program concerning extraterrestrial life is SETI. The search for extraterrestrial intelligence (SETI) is a collective term for scientific searches for intelligent extraterrestrial life, for example, monitoring electromagnetic radiation for signs of transmissions from civilizations on other planets. Scientific investigation began shortly after the advent of radio in the early 1900s, and focused international efforts have been going on since the 1980s. Have we ever managed to make contact with them? Given the number of exoplanets and galaxies, could there be, at least, other forms of intelligent and more evolved lives?

For the French astrophysicist Jean Duprat, the extraterrestrials are a priori not among us. “If they ever were among us, if we ever had signs, we would talk about it among scientists, we would observe that, it would not be a secret”. “But for the moment we have absolutely no sign of not only an extraterrestrial life on Earth that would be among us, but even an extraterrestrial life elsewhere”. Is extraterrestrial life other than on Earth plausible? “It’s quite a scientific question, given the number of stars that there is”. “There is no reason that life only developed on Earth”. “The Milky Way contains two hundred to four hundred billion stars, and we know that most of these stars are surrounded by planets, so that’s about one hundred billion planets. Among all these planets, there must be some who are likely to have conditions for life to develop. Now the question is: did life develop in extraterrestrial environments? For the moment, we do not know, since the only life we know is on Earth”.

Are there any clues that would suggest that this extraterrestrial life exists? “The elementary bricks of life must exist on other planets”. Why weren’t we found by extraterrestrials? “The planet is four and a half billion years old, and our species appeared about one hundred thousand years ago”. “Our species is able to look at space only since the recently”. “During most of its life, Earth was inhabited mainly by bacteria, unicellular organisms, small algae in the ocean; life on our planet was not looking towards outer space and we couldn’t then emit any signals”. Are we more likely to find a technologically advanced extraterrestrial life? “We have absolutely no indication that a technological life can appear elsewhere. The other very important point with this, in relation to extraterrestrial life, is how long this technological life can hold”.

Could we be extraterrestrials? “Our matter is extraterrestrial, it comes from outer space. Our atoms, our nuclei… it all comes from outer space. But then, the human species appeared on Earth only very recently; our species is clearly a part of an evolution of a great apes branch. We are the result of an evolution which happened on Earth”.

Space Law and extraterrestriality

The founding text concerning Space Law and extraterrestriality is found in Article IX of the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies (entered into force on October 10, 1967) which states that “In the exploration and use of outer space, including the Moon and other celestial bodies, States Parties to the Treaty shall be guided by the principle of cooperation and mutual assistance and shall conduct all their activities in outer space, including the Moon and other celestial bodies, with due regard to the corresponding interests of all other States Parties to the Treaty. States Parties to the Treaty shall pursue studies of outer space, including the Moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter and, where necessary, shall adopt appropriate measures for this purpose. If a State Party to the Treaty has reason to believe that an activity or experiment planned by it or its nationals in outer space, including the Moon and other celestial bodies, would cause potentially harmful interference with activities of other States Parties in the peaceful exploration and use of outer space, including the Moon and other celestial bodies, it shall undertake appropriate international consultations before proceeding with any such activity or experiment. A State Party to the Treaty which has reason to believe that an activity or experiment planned by another State Party in outer space, including the Moon and other celestial bodies, would cause potentially harmful interference with activities in the peaceful exploration and use of outer space, including the Moon and other celestial bodies, may request consultation concerning the activity or experiment”.

The 1967 Outer Space Treaty and the 1979 Moon Agreement both use the terms extraterrestrial matter or extraterrestrial materials: “to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter”, “does not apply to extraterrestrial materials which reach the surface of the Earth by natural means”, and “avoid harmfully affecting the environment of the Earth through the introduction of extraterrestrial matter or otherwise”. In Space Law, we call this concept “Planetary Protection”.

Planetary protection is a field concerned with keeping actual or possible zones of life pure and unspoiled. A planet’s biosphere is its complete zone of life, its global ecological system, and includes all its living organisms as well as all organic matter that has not yet decomposed. Planetary protection, which mainly focuses on microbial life and on potentially invasive species, is essential for several reasons: to preserve our ability to study other worlds as they exist in their natural states; to avoid contamination that would obscure our ability to find life elsewhere – if it exists; and to ensure that we take prudent precautions to protect Earth’s biosphere in case it does.

Typically, planetary protection is divided into two major components, two types of interplanetary contamination (biological contamination of a planetary body by a space probe or spacecraft, either deliberate or unintentional). Forward contamination is the transfer of viable organisms from Earth to another celestial body; it is prevented primarily by sterilizing the spacecraft. Back contamination is the transfer of extraterrestrial organisms, if such exist, back to the Earth’s biosphere. Non-biological forms of contamination have also been considered (objects left on the Moon or Moon Junk). Current space missions are governed by the Outer Space Treaty and the COSPAR guidelines for planetary protection.