Chemical fingerprints could belong to a signature of life on distant planet

By Ashley Strickland, CNN

(CNN) — When astronomers search for evidence of life beyond Earth, what signs are they seeking?

Would clues be traced to microfossils trapped within ancient Martian rocks, swim in waters of an ocean world, or lead to an Earth-like twin thought of as Planet B? Or perhaps a technosignature, a signal that could be created by intelligent life, might point scientists in the right direction.

The scientific community has debated the question — as well as where the evidence of life may be found — for years.

This week, researchers shared a finding from an intriguing exoplanet that might represent the next step toward discovering whether life is possible on another world.

Other worlds

Using the James Webb Space Telescope, astronomers have found chemical fingerprints in the atmosphere of the distant planet K2-18b that could belong to molecules only created by life on Earth.

The molecules, dimethyl sulfide and potentially dimethyl disulfide, are typically made by marine phytoplankton on Earth.

Nikku Madhusudhan, professor of astrophysics and exoplanetary science at the University of Cambridge’s Institute of Astronomy, and his colleagues believe K2-18b, located 124 light-years from Earth, is a Hycean world, or a potentially habitable planet entirely covered in liquid water with a hydrogen-rich atmosphere.

“Given everything we know about this planet, a Hycean world with an ocean that is teeming with life is the scenario that best fits the data we have,” he said.

However, the study authors have not declared a definitive discovery of life beyond our planet — and experts remain skeptical about the idea of the molecules representing signs of biological activity.

Ocean secrets

An expedition seeking previously unknown marine life has revealed the first footage of a colossal squid, which resembles a “glass sculpture,” in its native deep-sea environment.

Defying gravity

This week, six female passengers, including singer Katy Perry and journalist Gayle King, went on a roughly 10-minute journey to space and back again aboard a Blue Origin New Shepard flight.

But how exactly do experts define where Earth ends and space begins during such a brief jaunt?

The capsule reached 346,802 feet (106 kilometers) above ground level and 350,449 feet above mean sea level (107 kilometers). New Shepard traveled well above the Kármán line, a point at 62 miles (100 kilometers) that’s often used to define the altitude at which airspace ends and outer space begins.

But throughout the history of its usage, the Kármán line has often been controversial.

Once upon a planet

Seismologist Deborah Kilb was the first to notice unusual tremors beneath the Sierra Nevada. They were occurring at a depth where Earth’s crust is typically too hot for quake activity, said Kilb of the Scripps Institution of Oceanography at the University of California, San Diego.

Now, Kilb and other researchers studying deep rock deformations beneath the Sierra Nevada have used an imaging technique to map Earth’s internal structure — and they detected the planet’s crust peeling away.

The phenomenon could shed light on how the continents formed and determine whether there are other parts of the planet where the crust is peeling.

Separately, the contents of a 4.6 billion-year-old rare type of meteorite could change how scientists understand Earth’s origin story and just how long water has been present on the planet.

Look up

Amateur astronomers discovered a new comet, known as C/2025 F2 (SWAN), at the end of March, but in recent days, the celestial object’s story has gained a new twist.

The latest observations of the comet suggest the object, made of ancient rock, frozen gases and dust, has disintegrated on its way to a close approach of the sun, which was anticipated to occur on May 1.

However, the comet’s remnant is still visible and will be for a few weeks, according to experts. Here’s everything you need to know about how and when to see it.

The wonder

NASA astronaut Don Pettit has ventured to space four times, and the veteran scientist is due to return to Earth on Saturday from his most recent stint aboard the International Space Station.

In addition to inventing the Zero-G coffee cup that allows astronauts to enjoy a hot beverage as they would on Earth, Pettit is also known for his stunning photography of the cosmos.

To celebrate his homecoming, here are some of Pettit’s awe-inspiring images from his seven-month stay on the orbiting laboratory, including long-exposure views of the colors that dance above the Earth.

Curiosities

These stories are worth a deep dive:

— Using a speck of mouse tissue, scientists created the first precise, 3D map of a mammal’s brain — and animations allow you to look right inside.

— Pollution from antianxiety medication is changing the ancient migration patterns of salmon by accumulating in their brains, and it could alter their lives in unforeseen ways.

— Venture into Uganda’s Bwindi Impenetrable Forest and watch how a wildlife veterinarian has dedicated her life’s work to protecting one of our closest genetic cousins, the mountain gorilla.

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