At my freshman seminar at Harvard University last semester, I mentioned that the nearest star to the sun, Centaurus near star, mainly emits infrared radiation. There is a planet near star B in its livable area. As a challenge to the students, I asked: “suppose there are creatures crawling on the surface of Proxima B? What will their infrared sensitive eyes look like?” the smartest student in the class gave the image of mantis shrimp with infrared vision in a few seconds. The shrimp’s eyes look like two table tennis balls, connected to his head with a rope. “It looks like an alien,” she whispered.
When we try to imagine what we have never seen before, we often default to what we have seen. Therefore, in our search for extraterrestrial life, we are usually looking for life we know. But is there a way to expand our imagination to life we don’t know?
In physics, a similar path has been established a century ago and has been successful in many cases. It includes carrying out laboratory experiments to reveal the basic laws of physics, which is then applicable to the whole universe. For example, around the same time that neutrons were discovered in James Chadwick’s laboratory in 1932, Lev Landau proposed that there might be stars composed of neutrons. Astronomers then realized that, in fact, there are about 100 million neutron stars in our Milky Way alone, while there are more than 1 billion times more neutron stars in the observable universe. Recently, LIGO experiment detected the gravitational wave signal generated by the collision of neutron stars in the cosmic distance. It is now believed that the precious gold produced by this collision was forged into a wedding ring. The moral of this story is that physicists can imagine new things in the universe and look for them in the sky according to the insights obtained from Earth laboratory experiments.
A similar approach can be used to find extraterrestrial life. By creating synthetic life from a bowl of chemical soup in the laboratory in various ways, we may be able to imagine a new environment where the occurrence of life may be different from that on earth. This is similar to writing a recipe with recipes for baking different types of cakes. In order to write a rich recipe book, we need to experiment with a variety of chemicals. Moreover, as I pointed out in a paper with Manasvi lingam, this experiment may use liquids other than water, which is considered necessary for life as we know it
One of my Harvard colleagues, Nobel laureate Jack Szostak, is approaching the creation of synthetic life in his laboratory. Any success of a single formula may mean changes with multiple results, which will be compiled into our synthetic life formula. By determining the appropriate environmental conditions from our laboratory experiments, we can later find real systems to realize them in the sky, just as in the case of neutron stars.
In following this policy, we should be as cautious as developing nuclear energy. As imagined in Frankenstein’s story, the artificial changes that create life in our laboratory will bring the risk of environmental disaster. Such experiments must be carried out in an isolated environment, so that the life accidents we don’t know won’t endanger the life we know.
Although the surfaces of planets and asteroids can be remotely detected for biological characteristics, extraterrestrial life may be the most abundant below the surface. Habitable conditions may exist in the ocean under thick ice, not only in satellites such as Saturn’s encladus or Jupiter’s Europa, but also in free floating objects in interstellar space. In other lingam studies, we found that the number of living objects in the habitable area around stars may exceed the number of rocky planets by many orders of magnitude.
Life’s adaptation to extreme environments can take strange forms. Extreme microorganisms on earth are an example. For example, it has recently been found that frozen micro animals can survive 24000 years in Siberian permafrost, while microbial life can survive 100 million years on the seabed. These microbes were born during the warm Cretaceous period, when dinosaurs ruled the earth.
In the solar system, the conditions closest to the earth are realized on its nearest neighbors Venus and Mars. NASA recently selected two new missions to study Venus. Its Mars rover perseverance is looking for traces of life on Mars. If extraterrestrial life is found, the key follow-up question is whether it is “the life we know”. If not, we will realize that there are many chemical ways of natural life. But if we find evidence that life on Mars or Venus is similar to life on earth, it may indicate that we have a special preference for “life we know”. Alternatively, life may be transported through a process called “embryo”, through rocks moving between planets. My student Amir silagi and I wrote a paper suggesting that the transfer of life may be mediated by planetary predatory asteroids. We should also remember a very distant possibility that life is sown inside the solar system by an “extrasolar gardener”, that is, through “directional embryo“.
The most vivid memory of my childhood is the conversation at dinner, in which the adults in the room pretended to know much more than they actually knew. There is no doubt that this is a kind of “intellectual makeup”. They improve their appearance through makeup. If I ask a question that these impostors don’t have a ready answer, they will think it doesn’t matter and ignore it. As a senior scientist, my experience is no exception, especially when I ask such a question: “are we the smartest children in the universe?”
Science provides the privilege of maintaining our childhood curiosity. It is unstoppable to improve scientific knowledge through experiments. I hope we can find the formula of artificial life and let us imagine something smarter than the natural life we currently encounter. It will be a humbling experience. But even if we can’t find this supreme intelligence in the laboratory, its by-products may appear in our sky, just like emails from distant communities in the Milky way. We will look for it through the recently announced Galileo telescope.