How to Search for Life as We Don't Know It

Last semester, during my Harvard freshman seminar, I mentioned that Proxima Centauri is the closest star to the sun and emits a lot of infrared radiation. It also has a planet called Proxima B in its habitable zone. I challenged the students to a question: What if there were creatures crawling on Proxima Centauri's surface? I asked the class to imagine what their infrared-sensitive eye would look like. The brightest student responded in seconds with an image showing the mantis shrimp which has infrared vision. Its eyes look like two ping pong balls attached to its head. She whispered that it looked like an alien.
We often fall back to what we've seen when trying to imagine something that we haven't seen. In our quest for extraterrestrial existence, we often look for the same life that we already know. Is there a way to expand our imagination and live a life that is not what we know?

A century ago, physics had an analogous path that was successful in many situations. This involves performing laboratory experiments to reveal the fundamental laws of physics that apply to all things. Lev Landau, for example, suggested that stars might be made of neutrons at the same time as the discovery of the neutron in James Chadwick's laboratory in 1932. Astronomers discovered that there are actually about 100 million neutron stars within the Milky Way galaxy and a billion more throughout the universe. The LIGO experiment recently detected gravitational waves from neutron star collisions at cosmological distances. Now it is believed that these collisions create the precious metal that is used to make wedding bands. This story demonstrates that physicists can see the future and find it by using the insights from Earth-based laboratory experiments.

Similar methods can be used to search for extraterrestrial human life. We might be able create synthetic life from chemicals in the laboratory in a variety of ways. This could allow us to envision new environments in which life might exist differently than it does on Earth. This is similar to creating a recipe book that contains recipes for different kinds of cakes. To create a rich recipe book we must experiment with different types of chemicals. As I mentioned in a paper by Manasvi Lingam, some of this experimentation might use fluids other then water. This is essential for the existence of life as we know.

Jack Szostak (Nobel laureate) is close to creating synthetic biology in his Harvard laboratory. A single success may lead to variations, which could produce many outcomes. These will be added into our recipe book for synthetic living. We can identify the right environment conditions in our laboratory experiments and then search for them in the sky. This is just like the case with neutron stars.

This approach should be followed with the same care as when tapping nuclear energy. As Frankenstein explains, creating artificial life forms in our labs can lead to an environmental catastrophe. This experimentation should be done in isolated settings so that any mishaps with the life we know will not cause harm to our lives.

Extraterrestrial life may be more abundant below the surface of planets and asteroids, even though they can be remotely scanned for biological signatures. Habitable conditions may exist under thick icy oceans, which could be found not only on moons such as Saturns Enceladus and Jupiters Europa but also in free-floating objects within interstellar space. Lingam and I also discovered that the number life-bearing planets could be greater than the number of stars in the habitable zone.

Extremophiles are an example of how life can adapt to extreme environments. Recent research has shown that frozen microscopic animals can survive for up to 24,000 years in Siberian permafrost. Microbial life is also found to exist 100 million years below the seafloor. These microbes were created during the warm Cretaceous period, when dinosaurs ruled the Earth.

The closest conditions to Earth in the solar system were found on Venus and Mars, its closest neighbors. NASA has recently chosen two new missions to study Venus. The Perseverance Rover is looking for signs of life on Mars. The key question to ask if extraterrestrial life has been found is whether it is the same as our own. If so, then we will discover that there are many chemical pathways to natural living. If we find evidence of life on Mars or Venus that is similar to terrestrial life, this could indicate that life was transported between the planets by rocks called panspermia. Amir Siraj, my student, and I wrote a paper that suggested that planet-grazing asteroids could have mediated the transfer of life. It is possible that life was planted in the inner solar system via directed panspermia, but this possibility is very unlikely.

One of my most vivid childhood memories is dinner conversations at which adults pretended to know more than they did. They used this form of intellectual makeup to enhance their appearance. They would not answer a question I asked, even if they had an unanswered one. As a senior scientist, my experience is the same. Especially when I ask the question: Are you the smartest child on the cosmic block?"

Science gives us the opportunity to keep our childhood curiosity alive. It is impossible to stop scientific discovery through experimentation. We are hopeful that artificial life will be possible. It will be an incredibly rewarding experience. Even if we don't discover this superintelligence in our laboratories, its byproducts could just appear in our skies as mail from faraway places in the Milky Way. We will be looking for it through the telescopes of Galileo Project.

This article is an opinion/analysis article. Scientific American does not necessarily endorse the views expressed in it.