High in the toxic atmosphere of Venus, astronomers on Earth have discovered signs of what might be life.
If the discovery is confirmed by additional telescope observations and future space missions, it could turn the gaze of scientists toward one of the brightest objects in the night sky. Venus roasts at temperatures of hundreds of degrees and is cloaked by clouds that contain droplets of corrosive sulfuric acid. Few have focused on the rocky planet as a habitat for something living.
Instead, scientists have sought signs of life elsewhere, usually peering outward to Mars and more recently at Europa, Enceladus and other icy moons of the giant planets.
The astronomers, who reported the finding Monday in a pair of papers, have not collected specimens of Venusian microbes nor have they snapped any pictures of them.
But with powerful telescopes, they have detected a chemical — phosphine — in the thick Venus atmosphere. After much analysis, the scientists assert that something now alive is the only explanation for the chemical’s source.
Some researchers question this hypothesis, and they suggest instead that the gas could result from unexplained atmospheric or geologic processes on a planet that remains mysterious.
But the finding will also encourage some planetary scientists to ask whether humanity has overlooked a planet that may have once been more Earthlike than any other world in our solar system.
“This is an astonishing and ‘out of the blue’ finding,” said Sara Seager, a planetary scientist at the Massachusetts Institute of Technology and an author of the papers (one published in Nature Astronomy and another submitted to the journal Astrobiology).
“It will definitely fuel more research into the possibilities for life in Venus’ atmosphere.”
Although the surface of Venus is like a blast furnace, a cloud layer just 31 miles below the top of its atmosphere may reach temperatures as low as 86 degrees Fahrenheit, and has a pressure similar to that at ground level on Earth.
Often called Earth’s twin, Venus is roughly the same mass. Many scientists think that Venus was once covered in water and possessed an atmosphere where life as we know it could have flourished.
It is hardly a place that makes visiting or research easy, although that doesn’t mean people haven’t tried. Space programs have tried dozens of robotic missions to Venus, many of them in the Soviet Union’s Venera series. But the planet eats metal, within minutes melting down and crushing spacecraft that have landed there. Of all those attempts, only two managed to directly capture images of the planet’s surface.
In a paper published in August, Seager and her colleagues suggested that microbes borne aloft on air currents called gravity waves could live, metabolize and reproduce inside droplets of sulfuric acid and water. Given the amount of gas being produced, the population of these microbes would be ample.
“We know that it is an extraordinary discovery,” said Clara Sousa-Silva, a Harvard molecular astrophysicist whose research has focused on phosphine and is another of the authors. “We may not know just how extraordinary without going back to Venus.”