With a surface hot enough to melt lead, crushing atmospheric pressure and clouds of sulphuric acid, Venus might not sound like the most enticing destination for human exploration.
But a group of experts are advocating that our other nearest neighbour, rather than Mars, should be the initial target for a crewed mission to another planet.
There are notable downsides. Walking on the surface would be an unsurvivable experience, so astronauts would have to gaze down at the planet from the safety of their spacecraft in a flyby mission.
In its favour, however, Venus is significantly closer, making a return mission doable in a year, compared with a potentially three-year roundtrip to Mars. A flyby would be scientifically valuable and could provide crucial experience of a lengthy deep-space mission as a precursor to visiting Mars, according to a report presented at the International Astronautical Congress (IAC) in Paris last week.
“Venus gets a bad rap because it’s got such a difficult surface environment,” said Dr Noam Izenberg of the Johns Hopkins University Applied Physics Laboratory and one of the proponents of the Venus flyby.
“The current Nasa paradigm is moon-to-Mars. We’re trying to make the case for Venus as an additional target on that pathway,” he said.
Izenberg said there were practical arguments for incorporating a Venus flyby into the crewed Mars landing that Nasa hopes to achieve by the late 2030s. Although the planet is in the “wrong” direction, performing a slingshot around Venus – known as a gravity assist - could reduce the travel time and the fuel required to get to the red planet. That would make a crewed flyby trip to Venus a natural stepping stone towards Nasa’s ultimate goal.
“You’d be learning about how people work in deep space, without committing yourself to a full Mars mission,” he said. “And it’s not just going out into the middle of nowhere – it would have a bit of cachet as you’d be visiting another planet for the first time.”
“We need to understand how we can get out of the cradle and move into the universe,” he added.
There is also renewed scientific interest in Venus. The discovery of thousands of exoplanets raises the question of how many might be habitable, and scientists want to understand how and why Venus, a planet so similar to our own in size, mass and distance from the sun, ended up with infernal surface conditions.
Izenberg said a Venus flyby “doesn’t yet have traction” in the broader space travel community, although there are advocates within Nasa, including its chief economist, Alexander Macdonald, who led the IAC session.
The pair recently co-edited a report entitled Meeting with the Goddess that makes the case for the hypothetical mission, suggesting that astronauts could deploy tele-operated rovers, drones and balloons to observe Venus’s active volcanoes and search for signs of past water and ancient life.
“There is every reason to believe that Venus will be an endless wonderland of beguiling and mysterious vistas and formations,” the report says.
Not everyone, however, is convinced by the concept. “It’s really not a nice place to go. It’s a hellish environment and the thermal challenges for a human mission would be quite considerable,” said Prof Andrew Coates, a space scientist at UCL’s Mullard space science laboratory.
He said Venus was rightly a focus of scientific exploration, but that “a human flyby really wouldn’t add very much”.
