When it comes to searching for life elsewhere in the solar system, astronomers typically fixate on Mars or the handful of ice-encrusted moons around Jupiter and Saturn. But according to a new study, to find extraterrestrial life, we may only need to look to our nearest neighbor — Venus.
In a
paper published March 30 in the journal
Astrobiology, an international team of researchers suggests that the thick and acidic atmosphere of Venus may actually serve as a potential safe haven for microbial life. In the hypothesis paper, they not only present multiple lines of evidence showing the venusian clouds could harbor extreme forms of life, but also show that airborne life on Venus would help explain the fluctuating appearance of the planet’s clouds — a mystery that has plagued astronomers for nearly a century.
Although scientists have debated the habitability of Venus’ atmosphere for many decades — Carl Sagan co-authored a
paper on the topic in 1963 — our sister world is often still ignored as a target for astrobiological research. This is primarily because the surface of Venus is now almost undoubtedly inhospitable to life, sporting temperatures of over 860 degrees Fahrenheit (450 Celsius) and surface pressures about 90 times greater than those found on Earth. However, despite the fact that Venus is now a hellish landscape (largely due to a run-away greenhouse effect), at one point, the planet looked a lot more like Earth does today.
“Venus had plenty of time to evolve life on its own,” said lead author Sanjay Limaye, a planetary scientist at the University of Wisconsin-Madison’s Space Science and Engineering Center, in a
press release. In fact,
previous research suggests that Venus could have once maintained a habitable climate with liquid water on its surface for as long as 2 billion years. “That’s much longer than is believed to have occurred on Mars,” he said.
This would have allowed life to initially form on the surface of Venus (when the toxic planet looked more like present-day Earth) before eventually migrating up into the venusian clouds. Although this scenario may seem unlikely, on Earth, microorganisms such as bacteria can (and do) get swept high up into the atmosphere. According to co-author David Smith of NASA’s Ames Research Center, by using specialized research balloons, scientists have even found such
high-altitude microorganisms surviving up to 25 miles (41 kilometers) above the Earth’s surface.
Furthermore, as the new paper points out, a series of space probes sent to Venus between 1962 and 1978 showed that, though the surface of Venus is not conducive to life, the venusian atmosphere very well could be. At altitudes between 25 and 37 miles (40 and 60 kilometers), the atmospheric temperature of Venus ranges between about 90°F and 160°F (30°C to 70°C), and the pressure is almost the same as you would find at sea level on our own planet. On the other hand, the acidic, sulfur-laden venusian air is rather toxic — that is, at least to most forms of life.
Over the years, though, scientists have compiled a large catalog of microbes that are known to survive and thrive in incredibly harsh environments here on Earth. One such organism is the humble
tardigrade — a microscopic animal (often called a “water bear”) that can survive even the most extreme conditions. These hardy critters have been found almost everywhere on the planet, ranging from the driest deserts to the tallest mountaintops. In 2007, researchers even found that Tardigrades could survive up to 10 days in the irradiated vacuum of space.
