Well, did you hear the big news today?
Life on Venus.
Life… on...
Venus.
Now, where have we heard this before?
Oh right, life on Mars.
If you’ve been watching any of my videos or listening to Astronomy Cast, you’re cautiously
optimistic.
Skeptical, but hopeful.
That’s the right position to take, because buckle up, the internet’s about to run with
this news.
It’s going to be difficult to figure out what was really discovered, and what this
means for the search for life in the Universe.
All right, let’s get into it.
On Monday, September 14, 2020, an international team of astronomers announced the discovery
of a very rare molecule called phosphine in the atmosphere of Venus.
This chemical exists here on Earth, but it’s only produced by industrial processes, or
as a waste gas by bacteria that live in oxygen-free environments.
Since there probably aren’t factories on Venus, belching out phosphine gas, that leaves
bacteria as a possible source.
That said, the conditions on the surface are terrible for life.
Temperatures reach 471 degrees Celsius day or night, equator, or at the poles.
That’s hot enough to melt Tellurium.
The atmospheric pressure is 90 times what we experience here on Earth.
Not to mention, it’s a horribly acidic environment with steamy rains of corrosive sulphuric acid.
But there are a few places where Venus could be mildly habitable.
Once you get high up into the cloudtops, above 50 km or so, the temperature and pressure
drop down to the point that they’re much more Earthlike.
It’s possible that there could be bacterial life, held aloft in droplets that shift up
and down in the atmosphere of Venus, staying alive long enough to produce these waste gasses.
At this point, I’m hoping you’re intrigued.
First, let’s talk about how phosphine was discovered.
How are astronomers sure this was what they found?
Phosphine is a chemical that’s made up of one atom of phosphorus and three atoms of
hydrogen.
Here on Earth, it’s a gas that smells absolutely horrible, often an indication of rotting corpses.
It’s highly unstable, quickly combining with any oxygen it can get its atomic bonds
on, which is why it’s surprising to see in the Venusian atmosphere with enormous amounts
of oxygen in it.
Phosphine has been seen on other planets in the Solar System, like Jupiter and Saturn,
but these are rich in hydrogen and have very little oxygen.
Because it should be consumed so quickly on terrestrial planets, it has been suggested
as the perfect biosignature to search for life on exoplanets.
Find phosphine, and you could very well be looking at a planet containing life.
But astronomers were never expecting to see this chemical on a world as awful as Venus.
The initial discovery was made using the 15-meter James Clerk Maxwell Telescope in 2017 over
the course of five mornings of observations.
Phosphine absorbs radiation in the 1-mm region of the electromagnetic spectrum, where the
JCMT operates.
After studying the data, astronomers saw a hint there was phosphine in the atmosphere
of Venus, so they requested time on an even more sensitive telescope: the 45 antennae
of the Atacama Large Millimeter/submillimeter Array or ALMA, in Chile.
This more powerful observatory confirmed the discovery.
Very impressive when you know that there are probably only 20 phosphine atoms for every
billion atoms in the atmosphere.
The researchers considered every natural way that phosphine could be produced, from sunlight,
minerals blown up from the surface, lightning strikes, and even meteorites entering into
the atmosphere.
But none could account for the amount of phosphine.
Volcanoes could produce this much phosphine if they were 200 times more active than the
amount of volcanism we have on Earth.
And from what we can tell, Venus has very little volcanism these days.
But Earth bacteria would only need to working at about 10% of their maximum productivity
to be able to generate this quantity of phosphine.
In other words, bacteria could be struggling, just barely able to survive on that hellscape
Venus, and still, be able to easily account for the signal.
But how could life actually survive high up in the atmosphere, without any solid ground?
I’ll get to that in a second, but first I’d like to thank:
Richard Leis Kuri the Vegan
Tanner Mckenney Eric Mowery
Dima Chumakov William Fisk
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Phosphine-producing bacteria is a great idea and all.
And sure, maybe the temperature and pressure high up in the clouds could be survivable
by airborne bacteria.
But that doesn’t sound, exactly sustainable.
Eventually, the bacteria should fall into the oven-like conditions closer to the surface,
right?
Actually, some of the researchers who helped make this discovery recently published a paper
back in August describing a mechanism of how bacterial life could survive in the cloudtops
of Venus.
Their paper is called “The Venusian Lower Atmosphere Haze as a Depot for Desiccated
Microbial Life”.
This paper was actually on my to-do list of future video topics.
Little did I realize the researchers knew more than they were letting on when they published
this a month ago.
No problem, this actually makes for a way better video this way.
In the paper, the researchers describe a mechanism that could keep life aloft in the Venusian
clouds for hundreds of millions and even billions of years: liquid droplets.
Similar to clouds here on Earth, there are droplets of liquid in the atmosphere of Venus.
On Venus, however, these droplets are made of intensely acidic sulphuric acid with water
dissolved in them.
These droplets could be safe havens for microbes to carry out their photosynthesis life cycle,
using organic chemicals carried in the Venusian atmosphere.
Metallic elements needed by their lifecycle could be supplied by meteorites impacting
the atmosphere and burning up.
Over time, these droplets gain more liquid and grow more massive, eventually sinking
down into the atmosphere and raining down to the surface, where they evaporate and are
carried back up into the atmosphere.
Having their home rain down into the ovenlike conditions down below isn’t a sustainable
way to life, but microbes on Earth are capable of doing some amazing things, and one of those
is drying out, or becoming desiccated, and waiting for conditions to improve.
In fact, scientists recently revived 100 million-year-old microbes dug up from beneath the seafloor,
and it went back to living life, no problem.
Their theory is that the microbes release spores that hover in the hazy region at an
altitude of around 33 km, waiting for a droplet to carry them higher up in the atmosphere.
Lucky bacteria catch a trip up in a droplet of water, surviving long enough to release
more spores, and the cycle goes around and around.
Potentially for billions of years.
Evolution could have even adapted the organisms to help take advantage of the situation, even
having macroscopic life that could transport itself around in the atmospheric layers.
Humanity has been so focused on Mars that Venus is chronically underexplored.
Right now, the only spacecraft at Venus is the Japanese Akatsuki mission.
This spacecraft has been studying the atmosphere and larger weather patterns on Venus, but
it’s not the right mission to actually find evidence of life in the cloudtops.
Fortunately, there at least 14 missions on the drawing board to go to Venus, including
an atmospheric probe called DAVINCI+ that could fly to Venus as soon as 2026.
DAVINCI+ would drop a spherical probe of sensitive instruments right into the atmosphere of Venus,
measuring it at different altitudes as it descends down to the surface.
This could help confirm that the different layers are conducive to life.
And other missions like NASA’s Venus In-Situ Explorer and India’s Shukrayaan-1 could
study the atmosphere from the cloudtops for long periods of time.
Perhaps this is an exciting enough discovery that a more purpose-built spacecraft will
soon be in development.
We actually did a whole video about various missions that could visit the cloudtops of
Venus, which I’ll link at the end of this video.
So there you have it.
There’s firm evidence of a key chemical for life in the cloudtops of Venus.
In the immortal words of Carl Sagan, extraordinary claims require extraordinary evidence.
And this evidence is still circumstantial.
The researchers sat on this evidence for three years, trying to figure out every single reason
why they were wrong.
And you can expect the rest of the scientific community is going to go through the same
process, trying to think of every single rational explanation that doesn’t indicate life.
It’s not a slam dunk, case closed proof of life on Venus, but it’s definitely worth
more exploration.
It’s time to send missions back to Venus, to sample the atmosphere and help figure out
if there is even more evidence that there’s life in the cloudtops of Venus.
And if they do find it, is it related to Earth’s life somehow?
Very exciting.
What do you think?
Let me know your thoughts in the comments.
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We’ve actually done a whole video about prospective missions that could sample the
cloudtops of Venus directly with much higher precision than can be done from Earth, and
you can watch that video now.