Reasons Why Scientists Think There Is Life on Other Planets

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Extremophiles on Earth

Extremophiles are organisms that can survive in extreme conditions of heat and cold, environments dramatically different than those that sustain us. Humans have found creatures that are able to live without oxygen around vents in volcanoes at the bottom of the sea, in the unforgiving desert, in ice-covered lakes in the Arctic, and even in space — those creatures are called tardigrades and can exist in a vacuum. Scientists have had to reassess the requirements for extraterrestrial life following the discoveries of extremophiles.

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Evidence of chemical forerunners to life elsewhere

The precursors to life on Earth were organic compounds such as nucleic acids, proteins, and lipids in the atmosphere and in the ocean. These created chemical reactions that led to cellular membranes and an early version of DNA. Scientists have found evidence of these forerunners of life in other worlds.

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More planets like ours

Over the last decade astronomers have found hundreds of so-called exoplanets beyond our solar system, many of them with gaseous environments like Jupiter. Scientists have been able to detect smaller, rocky planets similar to ours as well as other planets in what is known as the “Goldilocks zone.” These planets orbit their stars at a distance that allows for temperatures similar to those on Earth.

In 2015, scientists found an Earth-like planet orbiting a star similar to our sun, which NASA scientists dubbed “Earth’s bigger, older cousin.” Planet hunters who had been searching for planets similar to ours named it Kepler 452b.

Two years ago, scientists announced that the Trappist-1 star, just 39 light years away, has seven Earth-sized planets orbiting it. Scientists said the solar system there looked similar to ours, and possibly contained three planets located in a zone that might be hospitable to liquid water.

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Water on Mars

Some evidence has shown that water once flowed on Mars or still does, well beneath the surface or frozen in its polar ice caps. Evidence for water on Mars first appeared in 2000, when NASA satellite Mars Global Surveyor sent back images of gullies that appeared to have been formed by flowing water. A recent study said that if liquid water exists under Mars’ southern polar ice cap, it is because of volcanic activity.

The obstacles to life on Mars began billions of years ago. During the annual Mars Society meeting in 2016, Jennifer Eigenbrode, a biogeochemist and geologist at NASA Goddard Space Flight Center in Maryland, said for reasons not known, Mars lost its magnetic field, and with nothing to shield the planet from the solar wind, the planet’s atmosphere disintegrated.

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Jupiter’s moons

Scientists believe Jupiter’s moon Europa has a massive ocean. Astronomers using data gathered by NASA’s Galileo probe believe the amount of water beneath the icy surface of Europa is possibly two to three times more in terms of volume than Earth. Pictures and data collected by Galileo indicate Europa has a layered structure similar to Earth: a core with iron, a rocky layer, and an overlay of ice. François Poulet from the Institute of Space Astrophysics at the Université Paris-Sud in France said Europa’s surface resembles Antarctica’s sea ice. Other Jupiter moons Callisto and Ganymede might also have water.