Does Alien Life Exist?

   

  It’s easy to proclaim that the existence of aliens is a crazy idea, until you consider these words from astrophysicist Stephen Hawking: “To my mathematical brain, the numbers alone make thinking about aliens perfectly rational. The real challenge is working out what aliens might actually be like.”

  

     Other scientists agree. But while the existence of alien life is mathematically probable, humans have not been able to prove that extraterrestrial life does exist. The quest to find that life has taken several forms. The Search for Extraterrestrial Intelligence (SETI) Institute, based in California, uses giant radio telescopes to try to detect radio signals sent by far-off, technically advanced life forms. NASA’s Kepler Space Telescope has found planets  within the Milky Way that could have the right conditions for life to develop. By one estimate, as many as 20 percent of the stars in the galaxy have such a suitable planet. A 2015 report highlighted one planet in particular, about 150 light-years away from Earth, that seemed like a possible candidate to support the development of alien life. It orbits a star called Epic 201367065, which is about half the size and mass of Earth’s Sun.

     While some people wonder about the complexity of possible alien life-forms, some scientists think it makes more sense to imagine “aliens” as simple microorganisms. Life on Earth started out as single cells, and life on other planets might still be at that stage of evolution. And as Hawking notes, Earth was lucky to avoid a cataclysmic collision with an asteroid or comet in the past 70 million years. Other planets could have had their early life-forms wiped out in such a cosmic crash.

     NASA research done in the 1990s found what scientists thought were signs of ancient bacteria on a meteorite from Mars that reached Earth in 1984. Other scientists, though, dismissed the claim, and no one has proved the existence of microbes on Mars, now or in the past. The possibility that the Red Planet once had water, however, was raised in 2014 after NASA scientists studied another meteorite from the planet that reached Earth. That same year, the NASA rovers, Curiosity and Opportunity, were able to capture high-resolution images of what are believed to be ancient riverbeds on the

surface of Mars. The presence of water raises the possibility of biological activity as well. So does the discovery of large amounts of methane, which Curiosity also detected. The methane, however, could be the product of geochemical processes, rather than biological.

     For now, scientists can feel confident in the odds that alien life does or did at some point m exist, but without any idea of its form. As for the possibility of intelligent alien life ever visiting us on planet Earth, Hawking had this insight: The arrival of aliens could turn out to be much like

Christopher Columbus’s arrival in the Americas—and be followed by a steady stream of conquistadors and explorers from another universe. And we all know how that turned out for the people already living there.