The search for alien life is real science, and we’re getting close

To most people, extraterrestrial life is science fiction. However, research over the past 25 years has turned this topic into a real area of scientific inquiry. For the first time, scientists are optimistic that extraterrestrial life will be detected in the near future, probably within the next 20 to 30 years.

No, I am not talking about the possibility that we will be visited by humanoid aliens like those in the movies ET or Close Encounters of the Third Kind. Instead, I am talking about lower life forms similar to the most common and oldest organisms on Earth: bacteria. Although we tend to associate life with animals and plants, in fact much of the living biomass on Earth is in the form of microorganisms.

Humans need to consume water and breathe in oxygen, and we can only survive within a narrow range of temperatures. Bacteria are much more resilient. They can flourish in high temperatures, high acidity and extreme dryness. Bacteria have been found in the driest deserts of Chile, frozen lands of Antarctica, highly acidic water bodies, and hot thermal vents deep under the sea.

Right now, the only examples of life we have are on Earth. However, there is really nothing special about Earth. We are one of four rocky planets in our solar system, with a structure that is similar to those of our closest neighbours, Venus and Mars. The source of our energy is the Sun, an ordinary star – one of more than 100 billion stars in our Milky Way galaxy. In the past 20 years, astronomers have discovered several thousand other planets in our galaxy, and many of them are “Earth-like”. So the Earth is far from unique.

Watch: ‘Earth-like’ planet found just outside the solar system

We know from fossil records that life has been present on Earth for at least 3.7 billion years, but we are not sure exactly how it emerged. Life probably began in a “primordial soup” where suitable ingredients in a favourable environment gathered into self-replicating organisms. Until recently, many scientists believed that life developed on Earth in isolation, beginning with ingredients such as ammonia, methane and water. Over the past 20 years, we have learned that old stars produce complex organic compounds in abundance, and these products have been distributed all over the galaxy, including our early solar system. Between 4 and 4.5 billion years ago, our Earth was bombarded by debris from the early solar system. This brought heavy doses of organic matter, which probably facilitated the origin of life.