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Planet Venus | From the blog of Nicholas C. Rossis, author of science fiction, the Pearseus epic fantasy series and children's books

A hundred years ago, people thought there may be life on Mars. However, it turns out that moons like Europa and Titan are more likely candidates for life. Now, Venus is added to the list of possible life-bearing destinations on our doorstep.

As Popular Mechanics reports, researchers just discovered the molecule phosphine in the atmosphere of Venus. The molecule indicates that life may exist in the acidic clouds high above our sister planet. The discovery of phosphine in the Venusian atmosphere could signal a rejuvenated interest in the planet, which has long been ignored in favor of other locales in the solar system.

Planetary scientists have long speculated that Venus’s cloudy atmosphere could harbor life. The surface of Venus is inhospitable, with surface temperatures exceeding 800 degrees Fahrenheit. No probe sent to the planet—and there have been several—has survived for longer than a few hours. But the planet’s atmosphere, which is composed of plush layers of sulfuric acid clouds, may present a unique cradle for burgeoning lifeforms.

“We know that the molecule phosphine is a biomarker on Earth,” astronomer Jane Greave, of Cardiff University in Wales, said. “It’s been suggested that there are possible habitats in the cloud decks of Venus, so somewhere where little lifeforms could live.”

Phosphine

Phosphine (PH3) is usually generated by living things. It is composed of a single phosphorus atom that’s been stuck atop a trio of hydrogen atoms. “I like to think of phosphine as ammonia’s evil cousin,” Greaves said (ammonia is made up of a nitrogen atom surrounded by three hydrogen atoms).

Anaerobic microbes, which thrive in environments without oxygen here on Earth, also produce phosphine. However, they’ve got a completely different way of life from what we’re used to.

Scientists have discovered the molecule elsewhere in the solar system, in the cores of the planets Jupiter and Saturn. However, unlike Venus, there’s an explanation. The stifling heat and crushing pressure on these planets are powerful enough to slam atoms of hydrogen and phosphorus together. On Venus, however, there isn’t enough heat or pressure for phosphine to form this way.

The researchers, who published their findings today in the journals Nature Astronomy and Astrobiology, say the only explanations for the molecule are it’s either being produced by a living thing, or it’s generated through some chemical process currently unknown to science.

Conditions aren’t so bad 31 miles above the Venusian surface. High along the cloud decks that cloak the rocky planet, temperatures hover around 86 degrees Fahrenheit. The atmospheric pressure at this altitude is similar to what we experience at Earth’s surface. The only catch is the acidity; Venus’s clouds are filled with sulfuric acid and create an extremely caustic environment.

However, life on Earth thrives under these conditions. Scientists have discovered microbes in rocky crevices deep below the oceans and circle geothermal pools in places like Yellowstone and Iceland. The microorganisms that produce phosphine are even found in the guts of animals like penguins, deep-sea worms, and—you guessed it—humans.

The research was able to pinpoint a range of altitudes, between 32 and 37 miles above the surface, where the molecule was abundant. And it was abundant, indeed: The scientists discovered concentrations of phosphine ranging between 5 to 20 parts per billion—way more than the amount in Earth’s atmosphere, and way more than the team expected to find.

Life on Venus

That life could survive in the caustic clouds of Venus isn’t a new idea.

“The conditions in the lower clouds of Venus resemble those on Earth more than any other extraterrestrial environment now known,” astronomers Harold Morowitz and Carl Sagan wrote in the journal Nature in 1967.

NASA is currently in the process of reviewing two potential Discovery Program missions to Venus. One mission—Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy (VERITAS)—is designed to map the planet’s surface in order to unearth its many geologic secrets. The other mission, DAVINCI+, plans to study Venus’s atmosphere by plunging a probe down to the planet’s rocky surface. On the way down, it will collect samples of trace gases and snap pictures of both the volatile atmosphere and the rocky surface below.

With so many possibilities in our solar system alone, could life be far more ubiquitous than we expected?