The next obvious step is sending a robotic probe to take a closer look. NASA and its Russian counterpart seem interested in this. The US space agency was already considering conducting two different Venus missions, one or both of which could potentially be modified to look for phosphine or attempt more direct detection of alien organisms.
Russia now has a long history of sending robotic spaceships there, and last week the head of Roscosmos, the country’s space agency, named Venus a “Russian planet”
But both agencies could also be drawn. The day after the news broadcast, a privately funded organization backed by Russian billionaire Yuri Milner called Breakthrough Initiatives announced that it had hired a team of top scientists to investigate opportunities for a short-term Venus exploration mission.
“We just want to do something small, quick, and focused,” said Sara Seager, MIT astrophysicist who leads the breakthrough study and co-author of the Nature Astronomy article that announced the detection of phosphine.
“Can we send a microscope and look straight for life?” She asked. It’s possible, she said. “Of course we’d love to see little microbes swimming around.”
Like other scientists, Seager knows that any claim of discovery of extraterrestrial life would require enormously convincing evidence. Finding phosphine is not the same as finding hard evidence of life.
On earth, the molecule can be made by the metabolic processes of life as we know it and by industrial manufacture. The scientists who reported the discovery of phosphine on Venus said they could think of no natural explanation other than the presence of life for the abundance of the molecule. And they discovered it in that part of the Venusian atmosphere that was believed to be the most comfortable for life.
“We can only say that we can reliably detect phosphine gas at an amount of 20 parts per billion from a distance of 50 to 60 kilometers from the surface, where the temperatures are not too hot, not too cold, but just right for life” said Seager.
What a life? Nobody knows. The Venusians might have some truly alien biochemistry adapted to one of the harshest environments in the solar system.
Venus is so hot – roughly 900 degrees Fahrenheit – that the rocks literally glow on the surface. However, this has not always been the case.
Venus, Earth, and Mars all formed more than 4 billion years ago, and for much of their early history they had many similarities, including moderate temperatures that allowed water to become liquid on the surface. It is conceivable that life existed on all three planets a few billion years ago.
But Venus’ location near the Sun proved disastrous. As the young sun got older, it got hotter. The oceans of Venus eventually boiled away. That flooded the atmosphere with carbon dioxide that had previously largely been dissolved in the ocean. The result was a runaway greenhouse effect.
Astrobiologist David Grinspoon of the Planetary Science Institute in Tucson notes that the reflectivity of Venus’ thick cloud cover makes the planet so bright in our night sky. The clouds are the result of prolonged volcanic activity, he said.
“With your naked eye, you can confirm the presence of volcanic activity on our twin planet,” Grinspoon said in an email. “It’s hot enough on the surface to melt lead and zinc and some aluminum alloys. The Soviets sent a metallic bust of Lenin to one of their early countries that must have quickly turned into a puddle. “
But higher in the atmosphere the temperature is milder. In 1967 the astronomer Carl Sagan speculated that microbes could survive in the Venusian clouds. However, since the clouds are shot through with sulfuric acid, these microbes likely need a protective cover.
The Soviet Union had a particular fascination for Venus and sent pioneering space probes there as part of its Venera program from the 1960s. The Soviets eventually managed to land six spaceships on Venus, and they sent back images of a barren, rocky landscape.
“The romance of Venus was gone by the late 1960s,” said Sanjay Limaye, a planetary researcher at the University of Wisconsin in Madison who, like Grinspoon, is a long-time proponent of the Venusian life hypothesis.
Another proponent of Venus is Darby Dyar, a planetary scientist at Mount Holyoke College and chairman of NASA’s Venus Advisory Committee. She knows that her favorite planet is overshadowed by Mars and estimates the number of Venus specialists to be no more than a tenth of those on Mars. There has been no major mission to explore Venus in a quarter of a century, she said.
But Venus, she argues, is wrongly overlooked, and the budget for planetary science should be more balanced, also because new research suggests Venus likely had a congenial environment for billions of years.
In fact, she said, Venus probably had oceans in front of Earth. It had a lot of time for life to develop – possibly into complex organisms. It’s not out of the question that the rocks of Venus may have fossils, she said.
“The likelihood that there was ever life on Venus has skyrocketed,” Dyar said, referring to studies on the longevity of the Venusian oceans. “There are atmospheric models that show that Venus had as much water as Earth and that it actually had it earlier.”
Dyar is one of the scientists pushing for a mission called Veritas that would send a probe to Venus to map its surface. It is one of four proposed planetary missions competing for funding from NASA under the agency’s Discovery program, which supports relatively inexpensive robotic explorations of the solar system.
“At the moment we know the topography of Pluto” – the dwarf planet on the outskirts of the solar system – “better than we know the topography of Venus,” she said.
Another planned mission, DaVinci +, currently under development at NASA’s Goddard Space Flight Center in Greenbelt, Md., Would send a probe through Venus’ atmosphere and to the surface to understand the history of water on the planet . According to NASA, the mission’s instruments would be “encapsulated in a specially built descent sphere to protect them from the intense environment of Venus.” The mission would send back images from the surface.
The other two planetary missions competing for dollars are Trident, which would be a probe used to study Neptune’s large, icy moon Triton – which may have an underground ocean – and the Io Volcano Observer (IVO) which would examine one of the four large moons from Jupiter.
NASA is expected to make its selection next April. The agency’s response to the phosphine announcement has been particularly cautious. Its administrator, Jim Bridenstine, posted a description of the many NASA-supported astrobiology programs on his blog, but made no promises of special treatment for Venus.
A separate statement from the agency was similarly ambiguous, but mentioned one of the attractive features of Venus as an exploration target: it is “a planetary target that we can accomplish with smaller missions.”
In other words, proximity is a cosmological virtue.