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Life Signs
A Space Daily column

Life Signs

Nature and earth science

Life Signs is where Space Daily looks down instead of up. Animals, ecosystems, and Earth science, with a bias for peer-reviewed studies over press-release hype. The living world turns out to be at least as strange as anything in orbit.

Marsdaily

In April 2026, scientists reported that Curiosity had detected the first nitrogen heterocycle on the Martian surface — a class of organic molecule that on Earth forms part of the chemical pathway toward RNA and DNA. It isn’t evidence of life, but it shows that ancient Mars possessed surprisingly complex prebiotic chemistry.

Curiosity's first possible nitrogen heterocycle is chemically relevant to pathways toward RNA and DNA, but the instrument's imperfect match and reactive reagent keep the result well short of evidence for life.

Venusian Heat

Scientists reported phosphine in Venus’s clouds in 2020, then watched the finding come under fierce attack. But years of follow-up observations have repeatedly recovered the signal with far more data, while no known non-biological process has yet been shown to produce the claimed amounts.

New JCMT-Venus observations have recovered the candidate phosphine signal with far more data, but overlapping teams, instrumental systematics and unknown chemistry keep the result contested.

Science

In 1976, Carl Sagan and astrophysicist Edwin Salpeter published a peer-reviewed paper proposing that Jupiter’s atmosphere might support an entire aerial ecosystem — sinking microorganisms, buoyant “floaters” potentially kilometres across, and mobile “hunters” that preyed on them — living their entire lives in a world with no solid surface below.

Sagan and Salpeter's 1976 Jovian ecology was a calculation, not a claim of discovery: could airborne organisms grow, reproduce and control buoyancy before fatal descent?

Human Behaviour

On the Japanese island of Okinawa, a cluster of villages produced so many people who lived past 100 that researchers spent decades studying their diet and eventually traced part of the effect to a purple sweet potato that supplied roughly 60 percent of daily calories through the first half of the twentieth century

For most of the twentieth century, the purple sweet potato supplied roughly 60 percent of daily calories in Okinawan villages that produced the world's densest cluster of centenarians. What the data can and cannot tell us about why.

Science

Sea otters have the densest fur of any mammal on Earth, up to one million hairs per square inch, because unlike whales and seals they carry no insulating blubber and would freeze to death in the North Pacific without a coat that traps a layer of air against their skin

Sea otters carry up to one million hairs per square inch — the densest fur of any mammal on Earth — because they have no blubber and would die in North Pacific water without a coat that traps a permanent layer of air against their skin.

White Out

We tend to think of Antarctica as the coldest place on Earth, but the actual record was set on the East Antarctic Plateau where satellites measured a surface temperature of minus 98 degrees Celsius, cold enough that breathing it unprotected would injure the airway long before the air reached the lungs

The coldest temperature ever measured on Earth — minus 98 degrees Celsius, detected by satellite over the East Antarctic Plateau — is so far below biological tolerance that a single unprotected breath would freeze moisture inside the human lung.

Science

When the young Earth was a molten inferno, much of its water may not have escaped to space at all. A 2025 Science study found that as the planet cooled, the mineral bridgmanite could have locked as much as an ocean’s worth of water deep inside the mantle — and some of that primordial reservoir may still survive there today.

High-pressure experiments show that bridgmanite retained more water at magma-ocean temperatures than expected, but the ocean-sized figure is a wide modelled range.