With the recent discovery of a possible sign of life on Venus, it’s possible we could see a new surge of missions headed to the cloudy world in the future. Those next-generation robotic explorers may need to take extra precautions than Venusian explorers of the past.
Numerous missions to Venus have been proposed throughout the years, but few have actually manifested over the last three decades. That could change now, with perhaps the most compelling reason to visit the planet again. Astronomers found a gas, phosphine, in the sulfuric acid clouds of the planet, and they can’t really explain why it’s there. It’s possible that phosphine is being produced by some tiny lifeforms since we know that it’s produced by microbes here on Earth, or it’s some strange new type of chemistry we have never seen before.
Either scenario is intriguing, and NASA officials have already hinted that some proposed missions to the Venusian clouds could get the green light soon. If those missions do manifest, planetary scientists may need to take extra care to avoid any potential biological contamination of the system. If the goal is to determine if alien life does — or doesn’t — exist on Venus, then we’ll want to be extra sure any potential life we might find there didn’t just hitch a ride from Earth. Venus’ extreme environment could make those planetary protection efforts tricky.
“I think it’s gonna be interesting if someone does propose a long-term aerial platform that just sort of hovers above the clouds,” Rakesh Mogul, a biological chemist at California State Polytechnic University, tells The Verge. Mogul’s research focuses on extreme microbial life, and he has proposed a way for life to survive on Venus. “How do you prevent that from contaminating the environment? Is there a potential for that? Is there no potential for that?” Mogul says.
The timing of this phosphine announcement is pretty fortuitous because NASA is about to pick new planetary missions to fund as part of its Discovery Program — an initiative to send small robotic spacecraft to explore various parts of the Solar System. In February, NASA selected four mission concepts as finalists for the program to be considered for the latest round of funding.
Two of the finalists — called DAVINCI+ and VERITAS — propose missions to Venus. VERITAS would send a probe to orbit Venus and map its surface, while DAVINCI+ would send a probe down through the planet’s atmosphere. That probe would take samples of the air on the way down, potentially telling us more about what is lingering in the clouds. “I would bet that they will make sure they have the capability of looking for the presence of this newly announced material. phosphine,” Jim Zimbelman, a planetary geologist at the National Air and Space Museum, focusing on Mars and Venus, tells The Verge.
There are no guarantees that NASA will pick the Venus spacecraft as finalists, but top NASA officials have indicated that they’re paying attention to the news. “It’s time to prioritize Venus,” NASA administrator Jim Bridenstine wrote in a tweet about the phosphine discovery. However, Bridenstine later clarified that the final missions for the Discovery Program have not yet been decided. “There is no doubt that NASA’s Science Mission Directorate will have a tough time evaluating and selecting from among these very compelling targets and missions, but I know the process will be fair and unbiased,” he wrote in a blog post.
Even if one or both of the Venus missions moves forward, they may not be enough to truly determine where the phosphine detection is coming from. More ambitious missions have also been proposed — notably, a Venus flagship mission concept that conceives of sending three orbiters, a lander, and a balloon to float in the upper atmosphere to better characterize the chemicals that are present. That mission idea, designed even before the phosphine detection, could potentially provide long-term details about the atmosphere and what is behind these mysterious gases. “If you want to understand the clouds, you’ve got to hang out in the clouds,” Martha Gilmore, a planetary geologist at Wesleyan University, who led the study on the most recent Venus flagship mission, tells The Verge. “And the balloon on our mission survives 60 days.”
If someone were to send balloons into the Venusian clouds, that opens up another question: what kind of precautions need to be taken? When it comes to exploring the Solar System, NASA and other space agencies abide by a concept known as planetary protection — the idea of avoiding cross-contamination of the worlds in our cosmic neighborhood. Don’t bring Earth life to other planets, and don’t bring life from other planets (if they exist) to Earth. Under planetary protection guidelines, planets are placed in different categories, relating to the amount of cleaning and precautions scientists must take if they want to send spacecraft there. Currently, missions that would go to Venus are considered Category II, which means there’s only a remote chance that a spacecraft could contaminate the planet and compromise future investigations.
However, Mogul thinks this discovery may mean it’s time to take some extra precautions for future missions to the planet. Up until now, researchers have mostly agreed that whatever hitchhiking spores we send from Earth probably couldn’t survive the descent to Venus, where temperatures on the surface soar to nearly 900 degrees Fahrenheit, and the sulfuric acid clouds are billions of times more acidic than any environment on Earth.
With the phosphine discovery, those assessments of any tiny hitchhikers’ durability could change. “Can they survive an acid wash? I think they probably could,” Mogul says. “And then once they found a habitable zone, let’s say somewhere in the lower middle clouds, could they then become a vegetative cell and then become active? In my opinion, yeah. If we’re going to go look for habitability, then we should be considering the potential to contaminate the environment.”
However, it’s probably going to be a while before NASA sends a large robotic mission to Venus. “Flagship missions are big and expensive,” says Zimbelman. “They are in the billions of dollars range, and NASA is lucky to do one of those a decade.” For this decade, NASA is already working on two major planetary science missions: a rover called Perseverance that’s on its way to Mars, and a spacecraft that will launch in the mid-2020s to explore Jupiter’s icy moon Europa.
NASA ultimately picks its biggest missions based on a comprehensive report that comes out every decade known as the Decadal Survey. It’s an incredibly lengthy document, written by planetary science experts throughout the world, who come up with a wish list of missions they think are the most important for NASA to fund. Gilmore and her team submitted their idea for the Venus flagship mission late last year, estimating that the price tag for the concept would be around $3.7 billion. In the coming months and years, the scientists who craft the Decadal Survey will go over all of the different submissions and design concepts, as well as listen to members of the community to hear their thoughts on what should be the biggest priorities. It’s possible that the phosphine discovery could elevate Gilmore and her team’s work during those considerations.
“Our goal with the Venus Flagship was to have it rise to the top of the Decadal as the recommendation for the flagship,” says Gilmore. “One of NASA’s biggest quests is to find life in the Solar System. And the phosphine detection puts Venus in the realm of planets that we must consider to be habitable or even inhabited.”
The Decadal process will take a long time, and more information could come out that sways scientific opinion in another direction. In the meantime, work is still being done to confirm this phosphine detection, research that doesn’t require a fancy new NASA mission. Breakthrough Initiatives is investigating where the phosphine might be coming from and devising ways to explore Venus to find out more about the gas’s origins. Other Venus missions are already in the works from both India and Russia. And US-based company Rocket Lab has been very vocal about sending a spacecraft to Venus in 2023, even before the phosphine was found. Now, the head of the company says its Venus mission can be designed to look for signs of life there, too.
With all of the excitement and planning, it’s clear that, for now, all eyes are on Venus. And no matter what, we’re about to get a much clearer look at the planet next door.