Let’s start our discussion by asking a simple question. Is there another Earth-like planet? The answer is yes, and it is relatively close, by galactic standards. In my book, Unraveling the Universes Mysteries (2012), I mentioned the first Earth-like planet discovered, Kepler 22b. Kepler 22b is, to the best of our scientific measurements, Earth-like. Perhaps when our grandchildren’s grandchildren read this book or one like it, it will be old hat. We will have discovered countless Earth-like planets, and perhaps our grandchildren’s grandchildren will be living on one of them.

If it is Earth-like, will it have life on it? The odds are it will. Hard to believe? It will become more believable if we examine how life spreads around in the universe. To understand this phenomenon, we will start with our own planet, which we know had life on it when the dinosaurs became extinct 65 million years ago.

From the fossil record, the extinction of the dinosaurs most likely occurred when an asteroid, approximately 10 km in diameter (about six miles wide), and weighing more than a trillion tons, hit Earth. The impact killed all surface life in its vicinity, and covered the Earth with super-heated ash clouds. Eventually, those clouds spelled doom for most life on the Earth’s surface. However, this sounds like the end of life, not the beginning. It was the end of life for numerous species on Earth, like the dinosaurs. However, the asteroid impact did one other incredible thing. It ejected billions of tons of earth and water into space. Locked within the earth and water—was life. The asteroid’s impact launched life-bearing material into space. Consider this a form of cosmic seeding, similar to the way winds on Earth carry seeds to other locations to spread life.

Where did all this life-bearing earth and water go? A scientific paper from Tetsuya Hara and colleagues, Kyoto Sangyo University in Japan, (Transfer of Life-Bearing Meteorites from Earth to Other Planets, Journal of Cosmology, 2010, Vol 7, 1731-1742), provide an insightful answer to our question. Their estimate is that the ejected material spread throughout a significant portion of the galaxy. Of course, a substantial amount of material is going to end up on the Moon, Mars, and other planets close to us. However, the surprising part is that they calculate that a significant portion of the material landed on the Jovian moon Europa, the Saturnian moon Enceladus, and even Earth-like exoplanets. It is even possible that a portion of the ejected material landed on a comet, which in turn took it for a cosmic ride throughout the galaxy. If any life forms within the material survived the relatively short journey to any of the moons and planets in our own solar system, the survivors would have had over 64 million years to germinate and evolve.

Would the life forms survive an interstellar journey? No one knows. Here, though, are incredible facts about seeds. The United States National Center for Genetic Resources Preservation has stored seeds, dry and frozen, for over forty years. They claim that the seeds are still viable, and will germinate under the right conditions. The temperature in space, absent a heat source like a star, is extremely cold. Let me be clear on this point. Space itself has no temperature. Objects in space have a temperature due to their proximity to an energy source. The cosmic microwave background, the farthest-away entity we can see in space, is about 3 degrees Kelvin. The Kelvin temperature scale is often used in science, since 0 degrees Kelvin represents the total absence of heat energy. The Kelvin temperature scale can be converted to the more familiar Fahrenheit temperature scale, as illustrated in the following. An isolated thermometer, light years from the cosmic microwave background, would likely cool to a couple of degrees above Kelvin. Water freezes at 273 degrees Kelvin, which, for reference, is equivalent to 32 degrees Fahrenheit. Once the material escapes our solar system, expect it to become cold to the point of freezing. If the material landed on a comet, the life forms could have gone into hibernation, at whatever temperature exists on the comet. If an object in space passes close to radiation (such as sunlight), its temperature can soar hundreds of degrees Kelvin. Water boils at 373 degrees Kelvin, which is equivalent to 212 degrees Fahrenheit. We have no idea how long life-bearing material could survive in such conditions. However, our study of life in Earth’s most extreme environments demonstrates that life, like Pompeii worms that live at temperatures 176 degrees Fahrenheit, is highly adaptable. We know that forms of life, lichens, found in Earth’s most extreme environments, are capable of surviving on Mars. This was experimentally proven by using the Mars Simulation Laboratory (MSL) maintained by the German Aerospace Center. It is even possible that the Earth itself was seeded via interstellar material from another planet. Our galaxy is ten billion years old. Dr. Hara and colleagues estimate that if life formed on a planet in our galaxy when it was extremely young, an asteroid’s impact on such a planet could have seeded the Earth about 4.6 billion years ago.

Would any of the life-bearing material be able to reach Kepler 22b? The trip to Kepler 22b would have taken an Earth meteorite about 30 million years to reach it. However, the amount of material reaching Kepler 22b would likely be small, due to dispersion. To understand dispersion, consider a flashlight. If you shine the light on a nearby wall, you will see a bright spot on the wall. This is due to the high number of photons that concentrate on the wall to form the bright spot. However, if you move farther away from the wall, the bright spot becomes larger and dimmer. The photons are spreading over a larger area, and are not as concentrated. If you move back far enough, the bright spot will eventually fade, and only a faint glow will be seen on the wall. This phenomenon is called dispersion. The photons being emitted from the flashlight spread apart and become less dense the farther they travel from the flashlight. This same phenomenon occurred when the dinosaur-killing asteroid ejected material from the Earth. As it traveled farther from the Earth, the ejected material began to spread further apart (disperse). Even if a portion of life-bearing material made it to Kepler 22b, the smaller meteorites may have simply burned up in its atmosphere. This is what happens on Earth. Since Kepler 22b is twice the diameter of Earth, it is likely to have a dense atmosphere. Yet, the possibility of seeding Kepler 22b with Earth’s life-bearing material is still possible. If it happened, the life forms would have had 35 million years to evolve.

This is essentially a new way of thinking about the origin of life on Earth, and on other planets. This process of spreading life between planets is known as the panspermia theory of life. Once life forms on a planet, it appears that the cosmos itself takes care of spreading it throughout the galaxy. Therefore, you may begin to conclude that life on other planets would look a lot like life on Earth. That would be unlikely, unless the planet closely resembled Earth. As we see when we study life in extreme environments on Earth, life adapts to the environment. Therefore, on a large planet where gravity might be three times greater than on Earth, the life forms would have evolved to accommodate the increased gravity. Perhaps they would be closer to the ground, and have larger legs or even no legs, like snakes. Perhaps they have larger eyes if the planet has low light. Perhaps they have no eyes, like worms, if the planet is in darkness. Science fiction writers do an excellent job of conjuring up extraterrestrial life based on the planet from which the life forms originate. You can use your imagination to draw your own conclusions on what they might look like, based on their planet of origin.