Why Mars? Why Not Life on Venus?
Is there life on Mars? Nobody knows. Why not look for life on Venus? There could be microbes in the clouds. Learn more.
Hard as it is to believe, it's been almost four years since David Bowie passed away. When I downloaded his final album, Blackstar, I was moved to go back through his catalogue, searching for gems.
I knew some of his early work, but most of my experience with Bowie came from his comeback in the early 80s on the albums Scary Monsters and Let's Dance. One of those gems is playing in my head today.
It's his 1971 hit, Is There Life on Mars? It's an odd song lyrically. It has absolutely nothing to do with space exploration. The words to the song briefly portray a bored young woman going to the movies by herself. They read like a prose poem from Baudelaire.
Planetary exploration is on my mind
Even so, planetary exploration is on my mind as I write this. News from an international team of scientists led by Sanjay Limaye of the University of Wisconsin has me thinking about life beyond Earth. Like David Bowie, when we think about the possibility of life in our solar system, our minds leap straight to Mars.
Mars is nearby, it's earth-like in many ways, and NASA has done lots of exploring there. They haven't found any final proof of living organisms, but there does seem to be subsurface water. Most scientists are convinced that life doesn't exist anywhere without water.
Some of the other places in the solar system that have captured the public's imagination include moons orbiting our two nearest gas giant neighbours, Jupiter and Saturn. Three of Jupiter's moons, Europa, Ganymede and Callisto, are strong candidates for study. So are Titan and Enceladus, which are satellites of Saturn.
Venus never seems to come to mind anymore
One place in the solar system that never seems to come to mind anymore is Venus. Venus is enveloped by thick clouds that are heavy in carbon dioxide and sulphuric acid. Temperatures there average 462˚ Celsius. So, the general consensus has been to use Venus as a cautionary tale about global warming and look elsewhere
Professor Limaye and his team aren't so quick to write Venus off. In a research paper published in the journal Astrobiology, they argue that there could be microbial life, not on the surface of Venus, but suspended in its atmosphere. This isn't a new idea. It was raised in 1967 by Carl Sagan and Harold Morowitz, but it hasn't grabbed the public's attention.
Scientists have run models trying to understand the history of Venus' climate. Some of these models suggest that Venus used to be a reasonably hospitable place. Venus would have had liquid surface water for up to two billion years. That's far longer than the length of time scientists believe there was surface water on Mars. We'll probably never know for sure, though. Lava flows have wiped out any evidence of what the surface of Venus used to be like.
Bacteria floating in Earth's atmosphere 40 kilometres above us
One of the co-authors of the study is David J. Smith from NASA. He points out that balloons can detect bacteria floating in Earth's atmosphere over 40 kilometres above sea level. Scientists have found microorganisms in very hostile conditions. For instance, they live in the hot springs of Yellowstone, deep-sea thermal vents, toxic sludge and even in so-called "dead" acidic lakes
Professor Rakesh Mogul is from California State Polytechnic University, Pomona. He's also on the research team. He reminds us that, "On Earth, we know that life can thrive in very acidic conditions, can feed on carbon dioxide, and produce sulphuric acid." The atmosphere of Venus consists mainly of carbon dioxide and suspended drops of water mixed with sulphuric acid.
This work was inspired, in part, when team member Grzegorz Słowik of the University of Zielona Góra in Poland, told Professor Limaye about bacteria on Earth that absorb light. These bacteria might be similar to strange particles that cause dark patches to appear in the cloudy atmosphere of Venus.
Dark patches appear in the cloudy atmosphere of Venus
Astronomers first noticed these patches a century ago, and probes have explored them, but we still haven't explained what they are or why they form. They are amorphous, changing shape and density as they float around for a few days and then fade out. As readers might expect, they contain high concentrations of sulphuric acid. The particles are about the same size as a bacterium.
Professor Limaye told Oded Carmeli of Haaretz what inspired him to reconsider these dark clouds on Venus. "In the summer of 2016, I went on a scientific expedition in the Ladakh region in northern India…While we were walking along the shore, I noticed the powdery remnants of desulfurizing bacteria on the leaf of a weed. Suddenly a gust of wind simply carried the powder – together with the bacteria, of course – into the air. For me, it was a eureka moment."
One way that we may able to confirm this hypothesis is a mission concept from aerospace companies Northrop Grumman and LGarde. It's called the Venus Atmospheric Movable Platform (VAMP). It involves a vehicle that looks like a cross between an airliner and a blimp.
A vehicle that looks like a cross between an airliner and a blimp
The VAMP would be powered by solar arrays and batteries. It could float and maneuver around in the atmosphere of Venus for up to a year, taking measurements from the clouds it passes through. The mission is still at the drawing board stage right now. We're not likely to see this take flight until the late 2020s at the earliest. Even so, it's fun to think about it.
There's an urban legend that a newspaper once asked a noted astronomer to write 100 words on whether there was life on other planets. Frustrated by how short they wanted his answer, he wrote back, "nobody knows" 50 times.
Even so, we've all gazed in wonder at the night sky and asked ourselves who or what is out there. Turning our attention to the planet Venus and seeking life in its cloudy, acid-laden atmosphere may help us find a more meaningful answer to this age old question.
Venus' Spectral Signatures and the Potential for Life in the Clouds
Is There Life on Mars? (song)
Astrobiology: 3 Questions We Need to Answer
Tagged Atmosphere, David J. Smith, Grzegorz Slowik, Haaretz, Mars, Rakesh Mogul, Sanjay Limaye, VAMP, Venus, Venus Atmospheric Movable Platform
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