The Extraterrestrial Search for Life - Exploring the Unknown

Tuesday - November 14 2023, 02:24 UTC - 1 year ago

Since the early 1990s, Astronomers have been able to observe thousands of planets located outside our own Solar System. These planets have been identified and studied by various space missions and Earth-based instruments with the aim of determining if any of them could potentially host life. To search for this possibility, scientists must capture the faint light from distant exoplanets and analyze the atmospheric chemicals that can signify aerobic respiration, indicating the possibility of life.

The quest to determine if anyone or anything is out there has gained greater scientific footing in the nearly half-century since that article’s publication. Back then, astronomers had yet to spot a single planet outside our solar system. Now we know the galaxy is teeming with a diversity of worlds. Our planet’s oceans were once considered exceptional, whereas evidence today suggests that numerous moons in the outer solar system host subsurface waters .

Our notion of the range of environments where life could exist has also expanded thanks to the discovery on Earth of extremophile organisms that can thrive in places far hotter, saltier, acidic, and more radioactive than previously thought possible, including creatures living around undersea hydrothermal vents. We’re now getting closer than ever before to learning how common living worlds like ours actually are .

New tools, including machine learning and artificial intelligence, could help scientists look past their preconceived notions of what constitutes life. Future instruments will sniff the atmospheres of distant planets and scan samples from our local solar system to see if they contain telltale chemicals in the right proportions for organisms to prosper. "I think within our lifetime we will be able to do it," says Ravi Kopparapu, a planetary scientist at NASA’s Goddard Space Flight Center in Maryland .

"We will be able to know if there is life on other planets." While humans have a long history of speculating about distant worlds, for much of that time actual evidence was in short supply. The first planets around other stars—known as exoplanets—were discovered in the early 1990s, but it took until the launch of NASA’s Kepler space telescope in 2009 for astronomers to understand how common they were .

Kepler carefully monitored hundreds of thousands of stars, looking for tiny dips in their brightness that could indicate planets passing in front of them. The mission helped the number of known exoplanets rise from a mere handful to over 5,500.Kepler was built to help determine the prevalence of Earth-like planets orbiting sun-like stars at the right distance to have liquid water on their surface (a region often nicknamed the Goldilocks zone) .

While not a single extraterrestrial world has been a perfect twin of our own so far, researchers can use the sheer quantity of discoveries to make educated guesses as to how many might be out there. The current best estimates suggest that anywhere between 10% and 50% of sun-like stars have planets like ours, leading to numbers that make astronomers’ heads swim. "If it’s 50%, that’s bonkers, right?" says Jessie Christiansen, an astrophysicist at Caltech in Pasadena, California .

"There are billions of sun-like stars in the galaxy, and if half of them have Earth-like planets, there could be billions of habitable rocky planets."Is there anybody home? Determining whether these planets actually contain organisms is no easy task. Researchers must capture the faint light from an exoplanet and spread it into its constituent wavelengths, scanning for signatures that indicate the presence and amount of different types of chemicals—such as oxygen and methane—in its atmosphere .