Many space scientists have stopped wondering whether there is life elsewhere in the universe.
The question they ask is: When will we find it?
Many are optimistic that we will discover signs of life on a distant world within our lifetime, perhaps in the next few years.
One scientist leading a mission to Jupiter goes so far as to say that it would be “surprising” if there was no life on one of Jupiter’s icy moons.
NASA’s James Webb Space Telescope recently discovered puzzling signs of the possibility of life on a planet outside our solar system.
Many of the missions currently underway or those that will begin soon represent a new space race for the greatest scientific discovery ever.
“We live in an infinite universe, with an infinite number of stars and planets,” says Professor Catherine Heymans, an honorary Scottish astronomer. “It is clear to many of us that we cannot be the only intelligent life out there.”
She adds: “We now have the technology and ability to answer the question of whether we are alone in the universe.”
Planets in the “Goldilocks Zone”
NASA Artwork: Planet K2-18 b orbits a cool dwarf star that appears red and is at a distance sufficient for a temperature to permit life.
Telescopes can now analyze the atmospheres of planets orbiting distant stars, looking for chemicals that, on Earth at least, can only be produced by living organisms.
The first flash of such a discovery was found earlier this month. A possible sign of a gas produced by marine organisms on Earth was discovered in the atmosphere of a planet called K2-18b, which is eight times larger than Earth and 120 light-years away from us.
The planet is located in what space scientists call the “goldilocks zone,” which is the appropriate distance away from its star so that its surface temperature is neither too hot nor too cold, but it is perfectly suitable for the presence of liquid water, which is necessary for life.
The team expects to know within a year from now whether these puzzling signals they saw have been confirmed or have disappeared.
Professor Nico Madhusudan, from the University of Cambridge’s Institute of Astronomy, who led the study, said that if these signals were confirmed, “it would radically change the way we think about searching for life.”
He continued: “If we find signs of life on the first planet we are studying, this will increase the possibility that life is common in the universe.”
If his team doesn’t find signs of life on K2-18b, they have a list of 10 other planets to study, and perhaps many more after that. Not finding anything would also “provide important insights into the possibility of life on such planets,” he says.
His project is just one of many ongoing or planned in the coming years to search for signs of life in the universe. Some search for planets in our solar system and others search much further, in deep space.
Although NASA’s James Webb Space Telescope is powerful, its capabilities are limited.
The size of planet Earth and its proximity to the sun are factors that allow life on it. But the James Webb Space Telescope will not be able to detect small distant planets like Earth, or planets close to their parent stars, because of the glare.
Therefore, NASA is planning to create an Observatory of Habitable Worlds, scheduled to launch in the 2030s.
Using a high-tech sunshade, it reduces the light of the star around which the planet orbits. Which means that it will be able to discover and sample the atmospheres of planets similar to ours.
Later this decade, a giant telescope will also be available on the ground in the Chilean desert to look at the clear sky. It has the largest mirror of any instrument ever built, at 39 meters in diameter, and can therefore see much more detail than its predecessors.
These three telescopes are used to analyze the atmosphere, a technique that chemists have used for hundreds of years to distinguish the chemicals present within materials through the light they emit.
Its power is so high that it can detect this through a tiny pinprick of light from the atmosphere of a planet orbiting a star, hundreds of light-years away.
NASA’s “tiger stripes” on Europa, caused by cracks on its icy surface
Search near the ground
While some look to distant planets, others focus their search in our planet’s backyard, the planets of our solar system.
The most likely home for life is one of Jupiter’s icy moons, Europa. It is a beautiful world with fissures resembling tiger stripes on its surface. Europa has an ocean beneath its icy surface, from which plumes of water vapor shoot out into space.
NASA’s Clipper mission and ESA’s Jupiter Icy Moons Explorer (JUS) mission will arrive there in the early 2030s.
Shortly after the Goss mission was approved in 2012, BBC News asked Professor Michelle Doherty, the lead scientist on the European mission, whether she thought there was a chance of finding life. “It would be surprising if there was no life on one of Jupiter’s icy moons,” she replied.
NASA is also sending a spacecraft called Dragonfly to land on one of Saturn’s moons, Titan. It is a strange world with lakes and clouds made up of carbon-rich chemicals that give the planet a strange orange haze. These chemicals, along with water, are believed to be a necessary element for life.
Mars is currently considered very inhospitable to living organisms, but astrobiologists believe the planet was once fertile, with a thick atmosphere and oceans and was capable of hosting life.
NASA’s Perseverance rover is currently collecting samples from a crater that was thought to have been an ancient river delta. A separate mission in the 2030s will bring those rocks back to Earth to analyze them for possible microfossils of simple life forms that have long since disappeared.
Attempted contact from aliens?
Some scientists consider this question to be from the realm of science fiction and far from reality, but the search for radio signals from alien worlds has continued for decades, not least by the Institute for the Search for Extraterrestrial Intelligence (SETI).
The vast expanse of space is a large place to search, so searches have been random until now.
But the ability of telescopes, such as the James Webb Space Telescope, to pinpoint where alien civilizations are most likely to exist, means that SETI can now focus its search.
This has injected new momentum into SETI’s study of life in the universe, according to Dr. Natalie Cabrol, director of the Carl Sagan Center.
The institute has upgraded its array of telescopes and now uses instruments to search for communications from powerful laser pulses from distant planets.
As a highly qualified astrobiologist, Dr Cabrol understands why some scientists are skeptical about SETI’s search for signals.
But she says that chemical signatures from distant atmospheres, interesting readings from lunar flybys, and even microfossils from Mars are all open to interpretation.
She adds that searching for a signal “may seem like the most distant goal possible compared to all the different ways to find signs of life. But it will also be the most obvious and can be achieved at any time.”
“Imagine getting a signal that we can actually understand,” Dr. Cabrol says.
Thirty years ago, we had no evidence of planets orbiting other stars. Now more than 5 thousand of them have been discovered, which astronomers and astrobiologists can study in unprecedented detail.
All the elements are there for a discovery that will be more than just a stunning scientific achievement, according to Dr. Subhajit Sarker of Cardiff University, a member of the team studying K2-18b.
He added: “If we find signs of life, it will be a revolution in science, and it will also be a huge change in the way humanity views itself and its place in the universe.”
