"Intriguing" discovery in the atmosphere of Venus 1:09
Editor's Note:
Sara Seager is a professor of planetary science, physics, and aerospace engineering at the Massachusetts Institute of Technology.
The opinions expressed here are yours.
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(CNN) -
Venus is the brightest object in the night sky after the Moon and has intrigued humans for thousands of years.
The discovery of phosphine gas in the atmosphere of Venus has just added to the planet's appeal.
I was a member of the multinational research team that announced the finding in Nature Astronomy on Monday, and my conclusion is that it indicates that something very unusual is happening to produce phosphine, be it a completely unknown chemistry or possibly some kind of microbial-like life.
Each explanation, somehow, seems equally crazy.
Phosphine is a gas made up of one phosphorus atom and three hydrogen atoms.
Phosphine is toxic to any life on Earth that uses oxygen, including humans.
It was used as a chemical warfare agent in World War I and is associated only with human industry (eg pesticides) or life in oxygen-free environments.
Phosphine is found in swamps, marshes, and muds.
It is also found in the guts and excrement of animals;
for example, in relatively high concentrations in penguin colonies.
Phosphine has also been measured in the laboratory to come from complex mixtures of bacteria.
LOOK: Gas finding suggests the existence of life on Venus
The finding is so amazing because phosphine shouldn't be present in Venus's atmosphere.
Phosphine needs a lot of hydrogen and the right temperatures and pressures to form, conditions found on Jupiter and Saturn, but not on Venus.
My team at MIT searched extensively for all known chemistry and found no way to easily produce phosphine gas on Venus.
Planetary processes including volcanoes, lightning, and meteorites entering Venus's atmosphere are also "forbidden," as some may produce the least amount of phosphine, but not enough to match the observations.
Does this mean that Venus has extraterrestrial life in its atmosphere that produces phosphine gas?
Not necessarily.
Venus is a very hostile place for any kind of life as we know it.
The surface is very hot, too hot for the complex molecules necessary to form life.
High above the surface, the atmosphere is getting colder and colder.
On Venus there is a sweet spot 48 to 60 km (30 to 37 miles) above the surface, in the clouds, where the temperature is not too hot or too cold, but just right for life.
Still, the environment is harsh.
The atmosphere is, for example, 50 times drier than the driest places on Earth.
Cloud droplets are not made of liquid water, but of concentrated sulfuric acid.
The acidic environment is billions of times more acidic than the most acidic environments on Earth.
The components of life on Earth, including DNA, proteins, and amino acids, would be instantly destroyed in sulfuric acid.
Any life in Venusian clouds would have to be made up of different building blocks than life on Earth, or be protected within a layer made of sulfuric acid resistant material like wax, graphite, sulfur, or something else.
People have been speculating about the presence of life in the clouds of Venus for more than 50 years, beginning with Carl Sagan.
Scientists are sometimes reluctant to openly admit their interest in such a marginal topic.
However, our team leader, Jane Greaves of Cardiff University in the UK, purposely decided to search for signs of life on Venus using phosphine gas.
She proposed using the James Clerk Maxwell Radio Telescope (JCMT) on Mauna Kea in Hawaii to observe phosphine at radio wavelengths.
By coincidence, my team at MIT had also been working on phosphine gas as part of a larger project trying to understand what gases present on exoplanets (planets that orbit stars other than the sun) could indicate the presence of life.
A mutual contact connected us.
When I first heard about Jane's find, I just didn't believe it.
However, my team at MIT worked with Jane's team on a proposal to use the Atacama Large Millimeter Array (ALMA), which is more powerful.
When the data came back and analyzed, the phosphine signal was even stronger than before.
I was still so shocked, so in awe, but now we had to accept that the find was real.
We diligently lobbied to support our detection, we continued to work and rule out chemical processes as a source of phosphine, and we double-checked that no other gas could mimic the presence of phosphine gas.
Our solar system has a growing number of bodies of interest in the search for life.
NASA's Mars Perseverance rover is on its way to Mars to search for signs of ancient life.
Jupiter's moon Europa, the moons of Saturn, Enceladus, and Titan are fascinating potential targets.
Our finding of phosphine gas now raises Venus as one more place to get serious in the search for life beyond Earth - maybe not so crazy after all.
Venus