A few years ago, a survey of 2,000 people revealed their top scientific question: Are we alone in the universe?
Until now, we have had absolutely no evidence of life beyond Earth. But wait, ET might not just be a Hollywood movie.
What appears to be a potential breakthrough in the search for extraterrestrial life, a team of researchers has claimed compelling evidence of biological activity on K2-18b, an extrasolar planet 120 light years from Earth.
One light year is the distance light travels in a vacuum over the course of an Earth year. In everyday language, the distance roughly comes to about 9.4 trillion kilometres.
“This is a revolutionary moment,” said Dr Nikku Madhusudhan, the astrophysicist and professor at the University of Cambridge who led the team of researchers that made the discovery.
“It’s the first time humanity has seen potential biosignatures on a habitable planet,” he said.
“Still, the best explanation for our observations is that K2-18b is covered with a warm ocean, brimming with life,” he said.
Proof of life
The team of researchers analysed data from the James Webb Space Telescope (JWST), the largest telescope in space fitted with high-resolution instruments, which allow researchers to view objects that are too old, distant, or faint using infrared waves.
What the researchers found in the atmosphere of K2-18b was a strong presence of dimethyl sulfide, a compound made of sulfur, carbon, and hydrogen.
On Earth, dimethyl sulfide is exclusively produced by living organisms. For example, certain ocean algae generate this compound, which rises into the air and contributes to the sea’s characteristic smell.
The Astrophysical Journal Letters published Madhusudhan’s study on April 16. Its findings are being hailed as the strongest indication yet of life beyond our solar system.
Many researchers called it an exciting, thought-provoking first step towards making sense of what’s on K2-18b.
Yet many were reluctant to draw grand conclusions.
“It’s not nothing,” said Stephen Schmidt, a planetary scientist at Johns Hopkins University. “It’s a hint. But we cannot conclude it’s habitable yet.”
Scientists will now conduct lab experiments to interpret the new study by, for example, replicating sub-Neptune conditions to determine if dimethyl sulfide behaves similarly to how it does on Earth.
K2-18b is classified as a sub-Neptune, which means it’s much bigger than the rocky planets in our inner solar system with shorter orbits, but smaller than Neptune and other gas-dominated planets of the outer solar system.
“I’m not screaming, ‘aliens!’” said Nikole Lewis, an exoplanetary scientist at Cornell University. “But I always reserve my right to scream ‘aliens!’”
NASA’s latest asteroid samples reveal that key ingredients for life likely arrived from space billions of years ago, hinting at the possibility of extraterrestrial life.
‘Where’s everybody?’
Physicist Enrico Fermi had once famously asked the question: “Where is everybody?”
That came to be known as the Fermi paradox, a puzzling yet simple question of why we haven’t seen or heard from intelligent alien life, despite the universe being so vast and old.
Think of the galaxy as a spread-out neighbourhood with billions of stars, with many orbiting planets.
Our default assumption would be that some of these planets should have conditions for life, and given the universe’s age — 13.8 billion years — intelligent civilisations should have had plenty of time to develop, spread, or send signals we could detect.
After all, scientists estimate there could be 20 billion Earth-like planets in our galaxy alone. Advanced civilisations on a handful of these planets might have built megastructures or broadcast radio waves we’d notice, no?
The possible explanations that scientists have come up with for the universe's eerie silence include: Earth might be a fluke, intelligent life is even rarer, or civilisations self-destruct before they can reach out.
Or maybe aliens are out there, but too far away, their signals are too weak, or we’re just not looking in the right way.
As the scientific community gets ready to carry forward the latest study, Madhusudhan has urged restraint. “It is in no one’s interest to claim prematurely that we have detected life.”
After all, many previous studies had also offered different theories about the possible presence of alien life.
But the world is still grappling with the question: Where is everybody?
