Is There Life In The Clouds?

Dispatches from the edge of our atmosphere.

Hello! This is Everything Is Amazing, an enthusiastic romp through the sciences in search of a good “wow!”.

Today in the United States was the first of the Stand Up For Science rallies, protesting the “wrecking ball to science” recently unleashed by the Trump administration.

If I wasn’t so late in getting this newsletter out, I would have given details on how you could attend. (Ghagh. Apologies.)

Here instead is

Ryan McCormick, M.D.

showing the scene at the protest in Philadelphia:

And here is astronomer Phil Plait in D.C.:

Here are the goals of the movement. (I really hope they help move the needle, which is currently pointing towards “utterly devastating”.)

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Okay! To today’s story, which takes us back to this season’s main theme:

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In January I told you the blood-curdling story of early aeronauts Coxwell and Glaisher, trapped in a balloon that wouldn’t stop rising until they’d reached a height of around 32,000-37,000 feet (9.7-11.3km), all without supplementary oxygen.

Without meaning to, these unfortunate explorers had risen to the top of our atmosphere’s lowest layer, the troposphere.

As much as we like to think our ‘home’ is the planet we call Earth, in truth we’re entirely tropospheric, spending all our lives within this relatively narrow band of high-pressure air wrapped around the world - and without it, or some mechanical replacement for it, we wouldn’t last more than a handful of seconds.

That would have been Coxwell & Glaisher’s fate, had their balloon continued to drag them upwards. They were rocketing into the tropopause, the upper atmospheric boundary between the survivable and instantly lethal parts of our sky. (It varies greatly according to latitude, and even in one location it’s a little different every day, like the weather - here’s today’s forecast.)

A fun fact about the troposphere: because the gases and airborne particles within it filter out different wavelengths of light compared to other layers of the atmosphere, from a distance it has a different colour, usually a ruddy orange - as seen in this famous 2010 photo of the Space Shuttle Endeavour taken from the International Space Station:

But what if the English aeronauts had kept going upwards, and somehow survived the experience? What would they have found?

Well, we know because on November 11th 1935, Captains Albert W. Stevens and Orvil A. Anderson clambered inside a sealed spherical capsule, dumped 34kg of its lead-shot ballast, and were immediately catapulted into the air above South Dakota by the enormous helium balloon above their heads. (You can see the balloon here.)

Over the next four and a half hours, their ship would soar far above the giddy heights attained by Coxwell & Glaisher - eventually settling at a maximum altitude of 22.66 kilometres (72,395 feet).

On the way they discovered, unsurprisingly enough, that it’s heart-stoppingly cold within the tropopause: around minus 60°F / -51°C. But it doesn’t stay that way. As you rise into the lower stratosphere (the white layer in the above photo), the temperature starts to rise again - and the reason is the behaviour of a particularly wonderful inorganic molecule that we probably don’t appreciate nearly enough for what it does for us every day:

If you’ve ever gone for a walk as a thunderstorm approaches, you might have noticed a coppery, vaguely bleach-like smell in the air. That’ll be ozone (O_3),the same stuff that forms a layer in the stratosphere that protects us from cancer-triggering ultraviolet light, and now should continue to do so after one of the most successful environmental campaigns in human history.

Ozone forms when lightning rips the air apart to form oxygen and nitrogen, leading to the formation of nitric oxide, which is important to biological health (Molecule of the Year in 1992!), and conventional oxygen (O₂) - and, every now and again, ozone.

You’re smelling it because of an enormous downdraft of air that comes before a storm, which drags ozone down from higher altitudes. What’s filling your nostrils is the aroma of the atmosphere 20 miles above your head - if it wasn’t so cold up there that your nose would immediate freeze solid, of course.

- From “Why the sky smells great”.

It’s this ozone heating up as it absorbs ultraviolet energy from the Sun that makes things so relatively toasty up there - and later experiments would find that the stratopause, the upper boundary of the stratosphere, is a surprisingly balmy -2.5 Celsius / 27.5 °F.

(That’s almost shirt-sleeves weather - if you were willing to put up with all the moisture in your body instantly boiling away, amongst other indignities!)

During their 80 minute stay at 22km high, Stevens and Anderson became the first human beings to observe and photograph the curve of the Earth. This is a thing anyone can infer at ground level by watching a ship disappear over the horizon, but actually eyeballing the curvature of our planet in person must be a whole other level of “wow”.

They also collected data on cosmic rays and their effects on mold samples brought along specifically for that purpose. They monitored how much ozone there was, and what the air seemed to be made of, and how luminous the Sun, Moon and the ground so far below appeared to be…

And after they returned to ground level, touching down in a field near White Lake at 4:13 pm, they confirmed what their onboard instruments were saying.

There was life up there.

Side note:

When I’m writing up a story like this one, I usually bump against the limits I’m working within. For example, the fact I’m an amateur enthusiast, not a scientist or professionally trained science writer. Or how I don’t have access to all the published science hidden behind expensive paywalls (although if you have the time, it’s always worth contacting the authors of those studies directly, because they would much rather share their research for free than see it locked up by monopolist publishers). And so on.

Back in October, when I stumbled over a throwaway line in a Scientific American story about the existence of living microbes in the stratosphere, I felt like that was well worth including in this season. I knew they existed in the lower atmosphere - as I’ll explain below - but, seriously, all the way up there, where there’s just one-thousandth of the oxygen and where they’d be cooked every day by solar radiation strong enough to leave us riddled with every variety of cancer?

I pieced together what I could from reports and studies. But there really didn’t seem to be much in the way of science writing about it, which I found both curious and exciting. Oh hooray, thought my ego - I have something very distantly approaching a scoop!

I felt that way until last week, when I discovered that legendary science journalist Carl Zimmer had just published a piece in Smithsonian specifically about microbial life in the upper & lower atmosphere. Worse still, it was an excerpt from his new book, Air-borne: The Hidden History Of The Life We Breathe, which he apparently started assembling during the pandemic, according to this interview:

“The more I went back, the more I realized that these issues about the air go back much longer than just COVID. They’ve been quite neglected, and there have been all of these remarkable people who I’d never heard of before, who’d had no biographies written about them, who were just lost.”

To my mind, there’s no mystery here. Carl Zimmer is clearly a secret reader of my newsletter, and he also must have found a way to send a message back in time to the 2020 version of himself, so he could get all the glory and make me look bad.

It’s deeply disappointing behaviour to encounter in someone so high-profile and universally well-regarded - but to choose a metaphor appropriate for this whole topic, I’ve decided to rise above it, and allow him to take all the credit, for the good of science in general.

(See? That’s how it’s done, Carl.)

End of side-note.

In Carl Zimmer’s infuriatingly brilliant article “A Brief and Amazing History of Our Search for Life in the Clouds” he notes the absolutely staggering number of bacteria and fungal spores entering the air every year : a trillion trillion in both cases.

(That’s a number that’s impossible to even begin to get your head around. And then you have to do that twice.)

What’s so surprising here is how long these microbes stay in the air - creating a distinct new biological region (biome) for our planet that’s capable of sustaining life, even if that life is temporary and passing through, an “ecosystem of visitors”. That includes us humans and the way we usually treat the sky, not as a place to linger, but a medium connecting two places we actually want to spend most of our time in.

The success of a biome usually depends on the availability of food, and its seems the lower atmosphere is no different. By breaking down around a million tons of airborne organic carbon every year, airborne bacteria sustain themselves by eating the clouds they live in - and they even seem to have a role to play in making those clouds produce rain.

(This also makes every rainstorm an absolute deluge of single-celled life - maybe an unsettling thought when you’re caught in a storm, but that’s because most of us associate the word “bacteria” with “disease” when the reality is that over 50% of the cells in our healthy bodies are bacterial. This makes each of us a united collective effort, comprised of bacteria working alongside human cells, that would put any attempt at human social collaboration to absolute shame. We could be the ultimate immigration feel-good story.)

Finding this microbial life in the stratosphere is truly astonishing. As Carl Zimmer writes:

“However microbes get to the stratosphere, they end up in what may be the most ruthless environment on Earth. Gases become wispy, water practically nonexistent. In the stratosphere, microbes can be ravaged by ultraviolet light, fast‑moving subatomic particles blasted out from the sun and cosmic rays streaming in from other parts of the galaxy. The collisions can destroy genes and proteins alike. It’s possible that the microbes that manage to reach the stratosphere are equipped with proteins that repair radiation damage. They may also survive by hiding on the shady side of dust grains. And they may then return to Earth, to the land or the sea, to continue to multiply and create more life that may have a chance to rise back up into the air. Whatever their secret, those stratospheric voyages mark the outer limits of the aerobiome—and thus of life as we know it.”

But he also notes that in 1974, Soviet scientists in Kazakhstan fired rockets into the upper atmosphere which were designed to break apart, take a “gulp” of whatever air was up there, and come back down to earth for analysis. Some of these samples suggested the presence of bacteria and fungal spores at a height of 77 kilometres (48 miles) - that’s well above the warmed stratopause and into the much colder, radiation-flooded mesosphere, where meteors tend to burn up.

One recurring theme in modern science is the discovery that life can thrive in the most unexpected places - like around the hydrothermal vents at the bottom of the Atlantic, as I previously wrote about here. So could the confirmed presence of living organisms in the stratosphere suggest it could live in the clouds of other planets in the Solar System?

“Venus, for example, has a surface temperature hot enough to melt lead. But the clouds that blanket Venus are much cooler, and at an altitude of 30 miles, they have the same temperature and pressure as clouds on Earth. Sara Seager, an astrobiologist at the Massachusetts Institute of Technology, has speculated that life might have arisen on the surface of Venus early in its history, when it was cooler and wetter. As the planet heated up, some microbes found refuge in the clouds. Instead of sinking back to the surface, they might have bobbed up and down in the atmosphere, riding currents for millions of years.”

There’s also the tantalizing - if highly speculative - idea that since it’s not yet understood how life is created, there could be living creatures out there that defy all current predictions of what life looks like and how it’s biologically comprised.

This may seem like it belongs in the realm of science fiction, and tall tales encountered at the pub on a Friday night (which is when I’m writing this, so, erm, judge accordingly).

But there’s one example I can’t get out of my head - and it washes up on the beach of the town I live in every year.

This is a Lion’s Mane jellyfish (Cyanea capillata), with tentacles that pack a painful sting. Every year, countless thousands of them are stranded on Scottish beaches, alongside vast numbers of the completely harmless Moon jellyfish, the most common in the UK.

To describe a jellyfish as “biologically weird” is a profound understatement. It has no heart. No blood courses through its veins - partly because doesn’t have veins either, meaning it doesn’t have circulation in the way we do.

If you want to understand how your own circulatory system keeps you healthy and upright, my other half

Dr. Mariana Calleja Ross

just wrote a great newsletter about that:

This Is Your Circulatory System | Part 3

Jellyfish, on the other hand, absorb and expel everything they need through their cell membranes (hence no need for blood), they don’t have a skeleton, they seem to “think” with their nerve-endings - and their bodies are 95% water.

95%!

(I guess that means any jellyfish you see on the beach almost entirely isn’t one?)

I’ve talked about it before, but once again I’d like to point you to this incredible painting by Adolf Schaller, for the book version of Carl Sagan’s Cosmos. The illustration is purely a work of fiction, but it’s one that’s asking what seems to be an increasingly interesting question…

If a living creature can be 95% water, why can’t there exist one that is 95% made of air?

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Further Reading:

- Air-borne: The Hidden History Of The Life We Breathe: Carl Zimmer (2025)

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Images: NASA; Wolf Zimmermann; frame harirak; Joakim Honkasalo.