So, Venus might have life! But how do we find out for sure?! We need to GO there.
Here’s a recap of the Venusian Life story thus far:
On September 14, the discovery of phosphine gas in the Venusian clouds was announced by a team of scientists led by Jane Greaves of Cardiff University.
In light of the phosphine detection, a 103 page research paper entitled “Phosphine on Venus Cannot be Explained by Conventional Processes”, co-authored by some of the original scientists on the phosphine detection research team including William Bains, Janusz J. Petkowski, and Sara Seager, was submitted to Astrobiology Magazine. After examining “gas reactions, geochemical reactions, (and), photochemistry” as potential producers of the phosphine the paper concluded that:
None of these potential phosphine production pathways are sufficient to explain the presence of ppb (parts per billion) phosphine on Venus.
Bains et al 2020
We do know of one way that phosphine is created, however… by life. On Earth, the paper reiterates, “phosphine is exclusively associated with anthropogenic (human activity) and biological sources.”
Do the clouds of Venus harbour life? c. NASA
Two days after the phosphine announcement, Mansavi Lingam and Abraham Loeb confirmed that the concentrations of phosphine in the Venusian atmosphere could plausibly be generated by microbes residing in the clouds. Had the phosphine concentrations been much higher, the gas may yet be the result of an unknown chemical or geological process. But even biomass orders of magnitude lower than what we find in our own aerial biosphere on Earth could theoretically generate the 20 ppb phosphine concentrations we’ve observed.
Wow…so we are living in a time where we’re seriously discussing extant life on another world in our Solar System. Certainly, the entire astrobiology community (and the rest of us as well) wants a biosignature – a potential marker for life like phosphine – to actually be life. However, because of scientific discipline, we don’t want to simply jump to the conclusion that it’s aliens. We need to return to the clouds themselves to discover the true nature of the phosphine detection.
Back to Venus:
I say “return” because Earth has sent missions to the clouds of Venus in the past. In 1986, the Russian Vega mission (a combination of the Russian Words Venera and Gallilei – Venus and Halley) used a balloon probe to understand Venusian meteorology. The mission had two objectives, first to take advantage of Comet Halley’s pass through the solar system that year capturing images of the comet, and then continued to Venus.
Vega Mission Diagram – Public Domain
Vega consisted of a lander and also a balloon that remained at cloud altitudes around 53.6km. The balloon itself was 3.4m in diameter with total a total mass of 21kg. The instrumentation package connected to the balloon measured meteorological conditions of Venus over a 46 hour period transmitting data back to Earth at 2kb/s (2 kilobits per second….not far off from my first dial-up connection.) At this altitude above the Venusian surface, temperature and pressure are similar to those on Earth…they also correspond to the altitudes where phosphine has been detected.
Vega balloon probe on display at the Udvar-Hazy Center of the Smithsonian Institution. Photo by Geoffrey A. Landis. CC by SA 4.0
Since Vega, other possible missions with their respective devices have been explored. In 2010, Aeronautical Engineer Graham Dorrington compiled a review of various engineering solutions for the exploration of Venus’ clouds. The solutions included paragliders, kites, fold out wing gliders, solar powered aircraft, and airships. Large scale versions of these solutions have even been suggested for future colonization of Venus in cloud-based habitats. Dorrington concluded, based on the results of the Vega program, that continuing to use balloon-based designs seemed to be the “most favored platform.” So, with the recent phosphine detection at the altitudes Vega operated, and past research of the efficacy of balloons, a new proposed life-seeking balloon mission was developed by a team including Mansavi Lingam; co-author of the theoretical required biomass for the phosphine signature. While Vega was a meteorological study of Venus, these balloons would be launched with life-detection as their primary mission. As the research team states: “The most unambiguous method…is to send spacecraft to Venus to carry out on-site measurements and experiments of its cloud layers.”
Artist rendition of balloon/blimp technology which in the future may be used fore future colonization of Venus as well as exploration – c. NASA
This new Venus balloon mission would have 4 key objectives. 3 of these would be primary life-seeking objectives with one fourth side-quest meteorological objective. The 3 primaries are:
1) Collect aerosol and dust samples to search for microscopic life. Past research by MIT planetary scientist Sara Seager suggested that microbes could live in aerosols within the Venusian clouds that would alter between states of hydration and desiccation as they precipitated to lower and hotter altitudes. In addition to the phosphine detections, a curious absorption of UV light has also been observed in the clouds of Venus. It’s been suggested that UV light is being absorbed for photosynthetic processes by microbes in the cloud layers. If either such life-form exists, the balloon would be able to find them using tiny collection plates, petri dishes, and small cameras operating as microscopes.
2) Search for signs of macroscopic life. Macroscopic life could potentially be observed simply by using a camera on board the balloon. The proposal suggests a unit similar to the 250g megapixel camera aboard the Curiosity Rover on Mars which has produced incredible images from the surface of the Red Planet. Aerial macroscopic life isn’t out of the realm of possibility for a world like Venus. In 1976, Carl Sagan and Edwin Salpeter hypothesized an aerial ecology in the clouds of Jupiter. They envisioned “sinkers and floaters” throughout the Jovian atmosphere – a combination of organisms resembling photosynthetic plankton being fed upon by creatures using “float bladders” to stay aloft in the clouds. If there is any such macroscopic ecology in the clouds of Venus, a camera should be able to detect it.
3) Look for building block materials of life. These would include complex organic compounds, polymers, amino acids, and nucleotides. This mission would require the installation of a miniature mass spectrometer within the balloon’s instrumentation package. A mass spectrometer would be the heaviest and most power demanding of the instruments aboard the balloon.
4) Meteorological studies of the Venusian clouds. This objective is similar to the previous Vega mission which would require outfitting the balloon with atmospheric sensors. The is the side-quest mission.
Artist’s rendition of a theoretical balloon probe in Venus Clouds c. T.Balint ESA
As with anything you send into space, your mission is constrained by weight and power. You can do more things in space with more stuff…but getting stuff up there, and giving it power, gets more difficult with more stuff. It’s physics! The team proposed two architecture variants of the balloons. The category 1 variant is lighter weight and only carries equipment to complete mission objectives 1 and 2. Objective 3 is the heaviest necessitating the mass spectrometer and objective 4 is still a side mission. Each category 1 balloon would weigh a total of 1.7kg (amazing when you think about all it needs to accomplish with that weight) and would operate for an estimated 48 hours – similar to the Vega operating window. In that 48 hours, a single balloon could send 20MB of data back to Earth which would include a total of 140 images. Given the previous estimates for biomass density a single balloon could theoretically sequester as many as 1700 microbes from the atmosphere in the same time frame. Even if the biodensity estimates are way off, by orders of magnitude, the research team concludes “it seems conceivable that each (category) 1 probe may stumble across a microbe.” At least one. Theoretically the balloon could operate at under 5W of power.
The category 2 probes are bulkier and carry room for the mass spectrometer allowing completion of mission objective 3 and possibly 4. They are an order of magnitude more massive at 16.1kg but that affords higher data transmission rates allowing 108MB total for a 48 hour period which includes 715 images. Power requirements would be higher – probably around 15W or more (still less than a typical LED bulb in your house).
Fig 1. from Bains et al 2020 showing the temperate zone in the Venusian Clouds where life may be possible and where Phosphine has been detected. (figure modified from (Seager et al. 2021))
Both balloon designs use “off-the-shelf” technology that is presently available meaning that the mission could be launched within the next 2-3 years. While the category 2 probe could do more research on Venus, the higher payload means you can send far fewer of the balloons at once. At some point there are diminishing returns. So, the authors outline a plausible mission using the category 1 balloons. A mission based on the category 1 architecture could send a vehicle to Venus carrying 11 of the balloons for about 20 million dollars. You know, discovering life on another world within the next 3 years for 20 million seems like a worthwhile investment to me.
As I was writing this article, I had goosebumps. We’re possibly discussing one of the greatest discoveries of all time unfolding before us. That unfolding is important too! That’s the science – it’s how science works! We won’t just have suddenly put balloons on Venus and found life. What we’re seeing is one discovery – phosphine, built on previous research which leads to more study – ruling out geology/chemistry, leading to more research – biodensity calculations, leading to mission design proposals. Each of these steps involves more scientists, researchers, engineers, and the collaboration of them all to make discovery possible. That process is sometimes excluded with the big scientific announcements. But these individual steps, and being able to look back at the journey, is why we can be certain of the discoveries we have made. Now we have to wait and see if anyone picks up this mission design proposal for implementation. In the meantime, let’s keep our heads in the clouds – you never know what you may find there.
More to Explore:
Originating Paper: A Precursor Mission for Venusian Astrobiology – Hein et al 2020
Universe Today – Did Scientists Just Find Signs of Life on Venus?
Universe Today – How Much Life Would be Required to Create the Phosphine Signal on Venus?
Universe Today – Colonizing Venus with Floating Cities
Phosphine on Venus Cannot be Explained by Conventional Processes – Astrobiology – Bains et al 2020
(UV Absorption in Venus) Astrobiology and Venus exploration – Grinspoon and Bullocks 2007
Particles, environments, and possible ecologies in the Jovian atmosphere – Sagan and Salpeter 1976
Venus atmospheric platform options revisited – Dorrington 2010
On The Biomass Required To Produce Phosphine Detected In The Cloud Decks Of Venus – Lingam and Loeb 2020