Venus has long played the second violin to her younger, younger and more distant brother. Given how inhospitable we have learned to be on Venus, we have spent most of the last century thinking about some of our greatest hopes of finding signs of extraterrestrial life on Mars.
That all changed this week.
On Monday it was announced that a particular gas called phosphine he had been seen in the clouds above Venus. The gas is produced by microbes here on Earth, and after most of the known non-biological processes have been discarded, the discovery has renewed hope that there will be life on Venus. Now we need to know for sure.
“To really get to the heart of this question, we need to go to Venus,” says Paul Byrne, planetary scientist at North Carolina State University and self-proclaimed “evangelical Venus”. In fact, it might be time to think not right on what should be the next mission on Venus, but what would be a new era of Venus exploration: a fleet of multiple missions exploring Venus in concert as we currently do with Mars.
There is, after all, only so much you can do with ground tools. “Venus is very bright, and many of the large terrestrial telescopes can’t observe it correctly,” says Sara Seager, an MIT astronomer and one of the co-authors of the new phosphine study. This luminosity, caused by the intense reflection of the sun from its thick clouds and highlighted by its proximity to the Earth, basically blinds our instruments to making detailed observations of the planet. It’s like trying to look at the road while the high beams of another car are pointing in your direction. Space-based telescopes may be better, but Seager says it’s still too early to know if they will suffer from the same problem.
And while terrestrial telescopes can detect traces of phosphine and other gases of interest, there is no way to wonder if they are produced by life or by some other exotic chemical, such as volcanism. While Seager and his team have well discarded known natural causes for phosphine in Venus, the planet could very well host geochemistry that we never thought possible. Answering these questions and completely excluding natural explanations means that we need to approach them.
Then let’s go to Venus!
Of course, it’s easier said than done. Surface temperatures reach 464 ° C, and pressures are 89 times higher than on Earth. Only the Soviet Union landed successfully on the Venusian surface – its Venus 13 lander ran for 127 minutes before giving in to the elements in 1982. It’s not easy to justify spending hundreds of millions or even billions of dollars. on a mission that could end in a matter of hours and not give us what we need.
So an orbiter is the most sensible principle. Unlike terrestrial observations, orbits can be seen in the atmosphere and will have a better time observing how phosphine or other potential biosignatures change over time or on which regions they are most concentrated in. Men have experience with such missions. Venus’ last major orbiter was ESA’s Venus Express, which studied Venus for eight years until engineers lost contact with it, probably because it lacked fuel. Currently, the only spacecraft exploring Venus is Japan’s Akatsuki orbiter, which arrived in 2015 to study the planet’s climate and climate. It makes good science, but it doesn’t have tools that could probe atmospheric chemistry and look for signs of organic life.
An orbiter also presents the opportunity to pull off more daring projects and venture directly into the clouds. A return mission champion it could be possible, in which a spacecraft flies into the atmosphere and bottles some gas to be returned to Earth for laboratory analysis. Byrne notes that many proponents over the years have asked to drop something into the atmosphere itself to look for more biosignatures or even organic matter. To keep such a platform in the air for as long as possible (potentially weeks or months at a time), engineers have proposed slowing down their descent using balloons or rotors.
Trying to find life on another planet, however, is not just a walk from point A to point B. No mission on Venus will be able to pull out all the work needed to answer the question. NASA already has two prospective Venus missions in operation. DAVINCI + is a probe that would flash directly into the atmosphere of Venus and study its chemical composition using multiple spectrometers over the course of a 63-minute descent. VERITAS is an orbiter that uses a combination of radar and near-infrared spectroscopy to look beyond the thick clouds of the planet and help you understand surface geology and topography. Past research suggests that the planet may have active volcanism and may have once been home to shallow oceans, but the inability to optically map the surface has made it impossible to verify these theories so far.
Each mission might find interesting new clues that bring us closer to determining if there is life, but neither one nor the other could answer this question alone. When it comes to phosphine, for example, DAVINCI + might be lucky enough to determine in which part of the atmosphere this gas is concentrated. But if it is produced on the surface, the probe does not necessarily have the tools to identify the location. VERITAS might find the site of geochemistry strange, but without actually sampling phosphine directly in the clouds, there would not be enough evidence to connect the two mysteries.
Byrne is bullish about wanting to see a full-fledged exploration program for Venus similar to what we’ve already seen for Mars. On that planet, there are orbiters that imagine the landscape, measure atmospheric leakage and chemistry, and look at the climate. There are rovers tasked with understanding the organics on the ground and looking for signs of life. There are landers that look at internal geology and measure the seismic activity of the planet.
Imagine a similar program on Venus, with more missions running at the same time. Under such a program, VERITAS and DAVINCI + are working alongside other missions to isolate biosignatures such as phosphine and really see if they are evidence of existing life or not. “I hate having to pick one over the other,” Byrne says. “But even if we both have it, I’ll still push for more missions.”
These two missions (plus two others) are in the running to get the green light from NASA next April. Throwing windows at Venus (when the planet is closest to Earth) comes every 19 months. If one is chosen, it will not launch before 2026 and it would take at least a few months to make the trip.
Other missions could definitely happen — and sooner. The Indian space agency is discussing the launch in 2023 of a Venusian orbiter called Shukrayaan-1 to study atmospheric chemistry. The New Zealand-based Rocket Lab wants to launch a small satellite called Photon for a Venus flyby as early as 2023. This mission would throw a small probe in the Venusian atmosphere to collect data, even if it could carry only one instrument, limiting the scope of any resulting research. Byrne points out that it might be worth looking into building a program out of several cheaper missions like Photon rather than a few very expensive ones like DAVINCI + and VERITAS. Seager says his immediate plans are to “lead a mission concept study for an affordable, low-cost mission,” in collaboration with Advanced Initiatives (led by Russian billionaire Yuri Milner).
And even though surface missions are hard to pull off, there has always been a steady stream of proposals on how to improve spacecraft engineering to make any landings last longer. One launched by NASA scientists, called Long-Lived In-situ Solar System Exploration, calls for building electronics and hardware that can withstand Venus ’punitive environment for up to 60 days. This type of landing will probably not be ready until the next decade.
Although we find no signs of life on Venus, it is also interesting: it would mean that Venus and Earth were two planets that started out very similar and ended up with radically different destinations. “This always raises deep questions that need to be answered,” Byrne says. “But to answer that, we need a program to study the planet.”