Even though Venus is the closest planet to Earth, there's still a lot we don't know about it, especially when it comes to its galactic-scale history. Was it once habitable? Did it ever have water? Was the atmosphere ever different than the toxic cocktail of carbon dioxide and sulphuric acid that swirls around its blazing surface today? Could it be a cautionary tale for Earth? To find out, astronomers have proposed using the James Webb Space Telescope to look at five exoplanets that exist in the Venus Zone.
First put forward in 2014 by University of California, Riverside (UCR) astrophysicist Stephen Kane, the Venus Zone is the region around a star where it's too hot for a planet to have any remaining water, but not so hot that it has lost its atmosphere. It's similar to the idea of a Goldilocks Zone where astronomers regularly train their instruments to find planets that still retain liquid water and therefore might have the "just right" conditions for life to form.
Looking at exoplanets in the Venus Zone could help astronomers get a better understanding of our own planetary neighbor. For example, if an exoplanet was found in the Venus Zone that emitted gases such as methane or nitrous oxide, it could indicate the presence of life.
“Detecting those molecules on an exoVenus would show that habitable worlds can exist in the Venus Zone and strengthen the possibility of a temperate period in Venus’ past,” said Colby Ostberg, a UCR Ph.D student.
Osterberg led a study to identify five Venus-like planets from a list of 300 that would be ideal candidates for further investigation. In whittling down the list, Osterberg and her colleagues looked at criteria including size, mass, density, orbital paths and distance from their stars. The researchers are suggesting that the James Webb Space Telescope look at these planets in 2024 as part of its ongoing exploration of the galaxy in which it recently spotted its first expolanet. For this reason, they also looked for planets that were orbiting relatively bright stars to give Webb the best light in which to view them.
Something else scientists hope to discover is whether the recent volcanic activity spotted on Venus is normal and whether its lack of tectonic activity is typical.
The data gathered by the Webb observations will be added to the findings from two upcoming NASA Venus-exploration missions: DAVINCI, which will analyze the Venusian atmosphere, and VERITAS, which will map the landscape in 3-D. The result of all of this new information could help astronomers understand just why Earth and its nearest neighbor have such contrasting conditions, and if the hellish atmosphere on Venus poses something for us Earthlings to worry about.
Or, as Kane put it: "Is Earth weird or is Venus the weird one?”
“It could be that one or the other evolved in an unusual way, but it’s hard to answer that when we only have two planets to analyze in our solar system, Venus and Earth," he added. "The exoplanet explorations will give us the statistical power to explain the differences we see.”
If the exploration reveals that all planets in the Venus Zone go the way of our fiery planetary neighbor, Kane says it could indeed be a cause for concern.
“That would be a warning for us here on Earth because the danger is real," he said. "We need to understand what happened there to make sure it doesn’t happen here.”
The study has been published in The Astronomical Journal.
