By Jonny Lupsha, Wondrium Staff Writer
For the first time in 30 years, NASA has announced a mission to Venus. By 2030, two probes will visit Earth’s sister planet to study its geology, atmosphere, and whether it had an ocean. Could it ever have supported any form of life?
Despite being the planet that gets physically closest to Earth, much of Venus remains a mystery to us. We know that it’s incredibly hot, masked by cloud cover, and suffers from sulfuric acid rain. After that, the details get scarcer. However, NASA hopes to help change that, as it has announced that two missions to the “hothouse planet”—dubbed DAVINCI+ and VERITAS—will bring back more information. DAVINCI+ will measure the planet’s atmosphere and drop down for a one-way trip of gathering high-resolution images of its geology, while VERITAS will map its surface from orbit.
There is no life on Venus, whether intelligent or basic, but did the planet ever have conditions that could have supported it? In his video series Life in Our Universe, Dr. Laird Close, Professor of Astronomy and Astrophysics at The University of Arizona, said that if you travel back in time four billion years, it looks possible.
Venus, before the Heat
These days, Venus’s surface temperature is close to 900 degrees Fahrenheit. One of the purposes of NASA’s upcoming Venusian missions is to figure out what happened to cause this. Additionally, Dr. Close said, there’s so little water in the whole Venusian system that even its mantle is made of relative dry rock.
“Perhaps if we go back some four billion years ago, Venus may not have been so hellish as it is today,” Dr. Close said. “Surface temperature might have been more conducive for life: The young Sun was a bit cooler than it is now and so Venus might have been, as well.”
However, over time, Venus heated up and developed a “runaway greenhouse” effect, leading to its current state. Meanwhile, Mars went the opposite way: It lost its atmosphere, cooled off, and became too cold for life. Dr. Close mentioned that this leads to the intriguing possibility that billions of years ago, before Venus and Mars reached such extreme temperatures, simple life could have existed on all three planets, simultaneously.
Additionally, it shows clear evidence that planets can be either too hot or too cold to support surface water and thus surface life, which is why there is no life on Mars or Venus, right now. A sweet spot in the middle range of temperatures, which scientists call a “habitable zone,” is needed, where atmospheric and temperature conditions mesh to provide a life-sustaining environment.
“We can even estimate how wide this zone is by using very simple arguments,” Dr. Close said. “We know that to have liquid water at one atmosphere of pressure requires temperatures in the range of about 0 degrees to 100 degrees Celsius. We can understand where the habitable zone is in our own solar system—it is about 0.8 to 1.1 Astronomical Units.”
An Astronomical Unit (AU) is the average distance between the Earth and the Sun, which is 93 million miles. According to Dr. Close, Venus is about 0.72 AU from the Sun and Mars is 1.5 AU, excluding both from the habitable zone.