Mars is all the rage right now for future space travelers both human and robotic. But there’s an argument to be made that Venus should be higher on the list of priorities. Despite the planet’s thick atmosphere, temperatures that would melt lead and tendency to snow metal, researchers say that exploration of Venus may reveal how our own planet was able to foster life.
“Venus and Earth are, superficially, the two most similar planets in the solar system,” Colin Wilson, of Oxford University, told Robin McKie at The Guardian. “They are almost exactly the same size while their orbits both lie in a relatively warm habitable zone round the sun. Yet one of these worlds is balmy and pleasant while the other has turned out to be utterly inhospitable. The question is: why?”
A desire to answer that question has led to a "flurry of new proposals to send unmanned spacecraft to our closest planetary neighbor," reports McKie. NASA is working on an idea that would set floating cities in Venus’ atmosphere as bases for astronauts.
Venus has received comparatively little attention from space agencies on Earth. There were the initial bouts of surveillance in the 1970s and 80s and a few flybys in the 90s and 00s. The European Space Agency’s Venus Express orbiter was the most recent dedicated Venus probe, but it ran out of fuel and took a planned dive into the planet’s atmosphere in November 2014. However, those missions did offer some ideas as to why Earth has life and Venus does not.
NASA’s Magellan spacecraft used a specialized form of radar to look through the planet’s clouds and find lava plains below, McKie reports. The lava plains were unmarred by craters from meteorites, indicating that the eruption or eruptions that created them took place recently — around the time life was evolving on Earth. The planet-wide lava flows could have stopped life from emerging on Venus, but researchers aren’t sure if the planet still harbors volcanic activity. If it does, that may tell researchers why the atmosphere is so thick and persistent.
The new mission proposals, two from NASA, called Raven and Veritas, would include updated versions of Magellan's specialized radar to get more detailed maps of the lava fields. ESA is also interested and their mission is called EnVision. All these proposals are for robotic probes.
Yet another mystery is why Venus has no water. “The atmosphere on early Earth was made of water vapor and carbon dioxide,” Wilson told McKie. “Various processes, including the appearances of living organisms, led to a decrease in carbon dioxide and an increase in oxygen. That never happened on Venus though we suspect its early atmosphere was also made of water vapor and carbon dioxide.”
Filling in the details on Venus will also help scientists looking for potentially habitable planets in other solar systems narrow their search. It’s not enough to be a planet orbiting the right distance from its star — a number of other factors must be just right to give rise to life.