Is There Life Beyond Earth?

Are there living beings on other planets? Scientists have wondered about this fascinating question for many years, and they still have not found a definite answer. Over the past century, new technologies have helped scientists to learn more about other planets in our solar system and have discovered that those planets are very different from Earth. For example, Mars, Earth’s red-colored neighbor, has a typical temperature of −80° F. That is even colder than the average temperature of Antarctica, the coldest place on Earth!

Because other planets are so unlike Earth, scientists predict that extraterrestrial life, or life beyond Earth, might look completely different from the plants, animals, and humans we are used to seeing on our planet. One form of life that could survive and even thrive on planets with extreme conditions is extremophilic microbes. These are microscopic living beings that love crazy conditions like super-hot or super-cold temperatures, high levels of acidity, or low amounts of oxygen [1]. As scientists learn more about these extreme-habitat-loving microorganisms, they are coming to believe that understanding extremophilic microbes could be essential to our search for extraterrestrial life.

Mars And Its Copycats On Earth

Many scientists think that Mars is one of the planets most likely to house life. Scientists have found clues that Mars once had the necessary components for life: liquid water and organic molecules, which are chains of carbon and other atoms that make up the building blocks of all living things. Pictures taken of the surface of Mars show gullies, which are carvings on the surface that look like they were made by running water (Figure 1). Scientists also discovered that Martian soil has similar elements to the soil found on early Earth, including carbon and other organic molecules [2].

Because Mars has a relatively high chance of having life on it, scientists are trying to learn more about the planet. However, it is difficult to travel to Mars because it is hundreds of millions of miles away. We have sent some unmanned rovers, or machines that we control from Earth, that roam around the surface of Mars. We have also sent spacecrafts to orbit around Mars. All of these missions are very expensive and time-consuming. Sending humans to Mars is an exciting possibility, but it could still be many years before this dream becomes a reality.

The next best thing to being on Mars is finding environments on Earth that are similar to Mars, which are called analogue environments. These Martian copycats are easier to access for experimentation and exploration. Scientists have already identified some Mars analogue environments like the dry, dusty plains of Tibet, China and the icy cold climate of Antarctica [3]. Mars analogous environments can also be created in the lab, where scientists can simulate the harsh conditions of the planet.

Experimenting With Extremophilic Microbes On Earth

To test whether extremophilic microbes could survive on Mars, a team of European scientists collected samples of extremophilic microbes living in analogue environments. Buttiauxella and Salinisphaera shabanensis are strains of bacteria that thrive in extreme conditions and are part of the extremophilic microbe family. Buttiauxella was isolated in Southern Germany from cold springs with limited oxygen and Salinisphaera shabanensis came from the salty Red Sea.

The scientists allowed these bacteria to grow in the lab and then placed these samples in an artificial environment that was similar to the environment on Mars. The scientists first dried out these extremophilic microbes and decreased the oxygen levels to mimic the dry, low-oxygen atmosphere on Mars. After three months, the scientists checked on the microbes in the Mars-like environment. Their observations showed that a sizable fraction of both extremophilic microbe samples survived over the three months! The scientists also mixed the two species of bacteria and allowed them to grow together. When mixed, the extremophilic microbes actually experienced higher rates of survival in the artificial Mars conditions.

Then, the scientists added in other Mars-like factors. They exposed the extremophilic microbes to Martian levels of ultraviolet light, the amount of high-energy radiation that Mars gets from the Sun. UV levels are much higher on Mars compared to Earth because Mars has a thinner atmosphere, without protective gas like Earth to block UV rays [3]. They also put in low-moisture soil from Earth that is similar to the dry soil on Mars, which we call Martian regolith (Figure 2). The extremophilic microbes continued to survive under these conditions. In fact, adding the soil actually increased the survival rates of the microbes. Scientists predicted that this happened because the dry soil protected the extremophilic microbes from the higher UV levels.

What Does This Tell Us About Life On Mars?

The results of this experiment are exciting because they provide evidence that Mars could be a habitat for life. If these extremophilic microbes can withstand the conditions the scientists created in their experiment, they could also survive on Mars! The survival of Salinisphaera shabanensis and Buttiauxella in a Mars-like environment also confirms that extremophilic microbes are likely to be the forms of life we would encounter beyond Earth because other organisms would not be able to tolerate these extreme conditions.

Looking to the future, the scientists hope Salinisphaera shabanensis and Buttiauxella are chosen for the project called Mars EXposed Extremophiles Mixture (MEXEM) which is supposed to happen in 2025. The MEXEM project will choose some extremophilic microbes and bring them to the International Space Station, which is floating in orbit above Earth, to run more experiments on them over three months. Though the scientists learned a lot from the experiments they did on Earth, studying these extremophilic microbes in space will allow them to fill in some gaps in their knowledge about the survival of extreme-habitat-loving microbes on Mars.

Though humans continue to explore the possibility of finding living beings beyond Earth, we now have an exciting direction for our search. Learning more about extremophilic microbes like Salinisphaera shabanensis and Buttiauxella could be one of the most important clues for solving the mystery of extraterrestrial life on Mars and beyond.

Glossary

Extraterrestrial Life: ↑ Any life that exists outside of Earth.

Extremophilic Microbes: ↑ Micro-organisms that thrive in extreme conditions, such as high/low temperatures, acidic pH levels, high levels of salt, and limited oxygen.

Organic Molecules: ↑ Chains of carbon and other atoms that form chemical compounds. Organic molecules are the building blocks of all living things.

Unmanned Rovers: ↑ Machines we control from Earth that can explore other planets and collect information that can teach us about the Martian climate and terrain. Unmanned rovers on Mars include Perseverance and Curiosity.

Analogue Environments: ↑ Places on Earth that may have conditions similar to those present on Mars now or in the past.

Martian Regolith: ↑ Dry, dusty soil that covers the surface of Mars.

Mars EXposed Extremophiles Mixture: ↑ A 2025 project where selected organisms will be sent to the International Space Station for experimentation.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.