This video is sponsored by Magellan TV.
Welcome back to Launch Pad, I'm Christian Ready your friendly neighborhood astronomer.
And by now I'm sure you've heard the news that astronomers announced the detection
of a gas called phosphine that may be a sign of life in the atmosphere of Venus.
To be absolutely clear, this is NOT an announcement of a detection of life,
but rather the detection of what may be a possible biomarker in Venus' atmosphere.
Now, Venus is often referred to as Earth's "twin" planet. And sure,
it has almost the same mass and radius as Earth. If you stood on its surface, you'd weigh almost as
much as you do here on Earth. But that's about the extent of Venus' status as Earth's twin.
It's blanketed with a thick and poisonous atmosphere of carbon dioxide,
sulfuric acid, and other toxic gasses. Temperatures on the surface reach nearly 500 °C.
That's 900 °F. That's hot enough to melt lead. The atmosphere insulates the planet so well,
there's no respite from the heat at night or even at the poles. The massive atmosphere bears down
hard on the surface, raising the pressure to 90 times sea level on Earth. That's the equivalent of
being nearly a kilometer underwater. Just trying to walk upon the surface of Venus would require
great effort as you shove your way through the thick and toxic air.
Venus really isn't so much Earth's twin as it is Earth's hellish doppelgänger.
It's the last place most of us would consider hospitable for life. At least, on the surface.
Conditions further up in Venus' atmosphere are actually much better by comparison. The
atmospheric pressure falls to 1 bar, and the temperature drops to a hot,
but survivable 50-60 °C. Survivable that is, for airborne microbial life.
But before we get into speculation about life, we need to take a step back.
Actually, a couple of steps back. We're going to talk about exactly what was detected,
why this may be an indicator of life, how hypothetical life might survive on Venus,
and what would need to happen next to investigate further.
But first, I would like to thank MagellanTV who are very kindly sponsoring today's video.
Magellan is a documentary streaming service featuring content on History, Art,
Nature, and of course, Space and Science.
Their Exploring Venus series delves into why astronomers
believe Venus may in fact be a home for life beyond Earth.
Other episodes show how Venus turned from an Earthlike oasis into the hellish planet it is
today. There are even episodes that discuss how we might explore and even colonize Venus someday.
New programs are added weekly and can be watched on Roku,
AmazonFireTV, AppleTV, Google Play, and iOS. You can even cast directly from your phone to your TV.
If you enjoy the content here on Launch Pad Astronomy, then I think you’ll enjoy MagellanTV.
That’s why I’m delighted to tell you about a special offer just for my viewers.
By signing up at the link below, you’ll get an extra month of MagellanTV absolutely FREE.
Please make sure to use the link in the description.
In 2017, a team of astronomers led by Dr. Jane Greaves used the James Clerk Maxwell
telescope at Maunakea, Hawaii to determine the amount of phosphine gas in Venus' atmosphere.
They were looking for phosphine because while there's actually a great deal of
oxygen in Venus' atmosphere, it's bound up in gasses like carbon dioxide, carbon monoxide,
ozone, and sulfur dioxide. Nothing that aerobic life can make use of.
So phosphine was proposed as possible indicator of anaerobic biology.
Phosphine is a molecule made of 1 phosphorous atom and 3 hydrogen atoms. On Earth, it's produced
artificially, but also produced naturally as a byproduct of anaerobic life such as microbes
living underneath lakes, in penguin dung, and possibly by decaying E.coli bacteria.
If phosphine is preset in Venus' atmosphere, it should also absorb microwave light radiating from
the planet at a wavelength of about 1 millimeter. After spending five mornings looking at Venus,
the James Clerk Maxwell Telescope revealed a strong absorption line at the expected wavelength.
Fascinating, but detections like these need confirmation. So in 2019, Greaves and her team
made follow-up observations with the Atacama Large Millimeter Array,
which has much higher resolution than JCMT.
ALMA's observations confirm that there was in fact strong absorption at this wavelength. And,
because of ALMA's high resolution, the team were able to take spectra of Venus at
individual locations across the planet's disk.
They found that the phosphine absorption was strongest at mid-latitudes and
likely originating from somewhere in the middle altitudes of Venus' cloud layers.
The team calculated that Venus' phosphine concentrations would have to be around
20 parts-per billion to create the absorption lines that were detected.
By contrast, phosphine concentrations in Earth's atmosphere are measured in the parts per trillion!
So naturally, the next question is what's causing all of this phosphine? Well,
there are many ways to make phosphine without the need for biology.
For example, Jupiter and Saturn both have very high concentrations of phosphine. But they're
gas giants with large amounts of hydrogen. Deep in their interiors, the temperatures and
pressures are high enough to produce phosphine through the chemical equivalent of brute force.
The temperature and pressure on Venus are much higher than any other terrestrial planet, but
they don't come anywhere close to those of Jupiter and Saturn. So the team considered other ways to
make phosphine, such as photochemical reactions - that is, chemical reactions triggered by sunlight.
But they found that photochemistry produced phosphine at a rate that
was about four to six orders of magnitude too low.
In other words, 1/10,000th to 1/1 millionth the amount of phosphine detected.
Lightning was considered as another way to make phosphine,
but was found to be 7 orders of magnitude, or 10 million times too low. Phosphine delivered
by meteorite was 100 million times too low. And, geochemical production inside rocks
would only yield phosphine levels measured in the parts per quadrillion!
But what if, just what if, what we're seeing really isn't phosphine at all? What if we're
being fooled by a different molecule absorbing light at the same wavelength as phosphine?
Well, the team got looked into this as well. It turns out that sulfur dioxide will produce
an absorption line at the detected wavelength, but only under two conditions. First, it would have
to be about twice as hot as the surrounding gas. That would produce an absorption line at a shorter
wavelength than phosphine. Then, if the hot sulfur dioxide were sinking at a rate of 1.3 km/s
then its absorption line would be doppler-shifted to the observed wavelength.
The problem though, is that hot gases rise instead of sink, so this scenario didn't seem very likely.
With no other imposter candidates identified, and with independent confirmation from ALMA,
and consistent results under independent processing methods,
the team's confidence in their phosphine detection was calculated at the 15-sigma confidence level.
To put that into context, the Higgs Boson was confirmed at a 5-sigma confidence level.
So yeah, it's more than likely phosphine that's either being created by some new,
exotic form of chemistry or it's being created by life.
Well, Occam's Razor says that when deciding between two hypotheses,
the less complex explanation is usually the right one.
But even simple life is very complex chemistry. So we're presented with a choice
between an unknown form of complex chemistry or the extremely complex chemistry of life.
Given how little we know about Venus, it's understandable why the researchers themselves
are making it very clear they are NOT announcing the detection of life.
Quoting from their paper, "Even if confirmed, we emphasize that the detection of PH3
is not robust evidence for life, only for anomalous and unexplained chemistry."
However, that didn't some of the researchers from also published a paper in August where
they considered what it would actually take for life to survive somewhere in Venus' atmosphere.
On Earth, some microorganisms are swept up by convection
and reside in tiny micro droplets of water. Some microbes may get swept up
high into the stratosphere where they dry out. If they don't find water,
they may die from prolonged desiccation or from exposure to ultraviolet sunlight.
But luckier mircobes manage to find water droplets that eventually merge with other
droplets and grow heavier. Eventually the drops rain down to the surface,
carrying the microbes with them. The microbes reproduce, and the cycle repeats.
Clouds on Earth are transient phenomena, so the airborne life cycle only lasts for a few days to
maybe a week or so. But on Venus, the clouds are permanent,
so in principle they could accommodate far more microbes living a similar life cycle
in the temperate zone of Venus' atmosphere. But even there, the challenges to life are daunting.
The clouds are made of sulfuric acid. Granted, extremophile microbes called acidophiles
live in acid baths on Earth. In fact,
there's some evidence that suggests ultra tiny organisms called nanohaloarchaea may
exist in the Dallol geothermal fields of Ethiopia; the most acidic region on Earth.
But Venus's clouds are estimated to be as much as 10^11 times as acidic as Dallol. That's
100 billion times as acidic. Whereas Dallol's water is "only" a 5% solution of sulfuric acid,
Venus' clouds are sulfuric acid with maybe a small solution of water droplets dissolved inside.
One way life could avoid getting dissolved in the acid is if it's covered in a shell of sulfur.
There's plenty of sulfur in Venus' clouds. A microorganism protected by a sulfur shield would
adhere to acid droplets but not get enveloped by them. But the problem with sulfur is that it would
also shield the organism from water as well. So a sulfur-coated microbe doesn't have
much chance of getting anything there. Even so, water concentrations on Venus are
estimated at 40-200 parts per million. That's works out to a relative humidity of 0.07%.
The driest location on Earth is the Atacama Desert. At midday in the summer,
the humidity falls to around 2%. That makes Venus 50 times more arid as the driest place on Earth!
When it comes to nutrients, well, there's plenty of carbon, nitrogen,
oxygen, phosphorous, and sulfur, but free hydrogen is only around 4 parts per billion
whereas on Earth its around 0.55 parts per million. Metals are also in very
short supply on Venus, but perhaps some kinds of life could make do without them.
The energy requirements for life would be fairly high because surviving in such
an environment would be energy-intensive. There's UV light from the Sun and indeed
there does appear to be huge swaths of UV-absorbing clouds in Venus' atmosphere.
Again, not evidence of life but life adapted to absorbing UV would certianly catch a break there.
So the proposed Venusian lifecycle would begin at a lower haze layer populated by dried out,
desiccated spores. The spores would be upswept to the temperate layer where
they would likely be encased in a liquid droplet of mostly sulfuric acid. But if
water is also dissolved in the droplet then the spores
might be able to hydrate and grow and divide in the liquid before getting dissolved. The droplets
merge with other droplets and rain down to lower atmosphere where they evaporate in the heat
and the "surviving" spores remain suspended in the haze layer and desiccate. The cycle repeats.
It's extremely unlikely such life could have initially evolved in Venus' clouds,
even in the temperate zone. But billions of years ago, Venus was a very different
place. The Sun was roughly 70% its present-day luminosity. Venus would have been much cooler,
and water could have remained liquid on the surface. Life would have a much better
chance of getting started or surviving if it was delivered via comets or asteroids.
Volcanoes pumped carbon dioxide, water, and sulfur dioxide into the atmosphere which
rained back down to the surface. But lacking any plate tectonics, Venus had no natural way of
sequestering those gasses back into the mantle, so the volcanoes continued to pump more heat-trapping
gasses into its atmosphere, which warmed the surface, which allowed more greenhouse gasses
to escape, which trapped yet more heat, and lead to a runaway greenhouse effect.
Meanwhile, the Sun brightened to its present-day luminosity,
further accelerating the runaway greenhouse, and sealed Venus' fate into the hellscape it is today.
But maybe, just maybe, those desiccated spores were swept up by the hot Venusian air convecting
off the surface and set into motion a new life cycle that produces the phosphine we see today?
It's a fascinating prospect, but it's also more than just a little
speculative. Again, nobody is saying that's what's happening,
only that there's at least one possible scenario where life may have a chance on Venus.
Now this work was done as a hypothetical exercise. Ideally, it will help to guide future
investigations into Venus. And I think that's fair because as a species, we've sent far more missions
to Mars in part because because we expected Mars to be much more likely to host life than Venus.
By comparison, Venus has remained largely unexplored and we know much less about it.
So hopefully, this detection will spur new interest in Venus, because the only way we're
going to know what's causing all of this phosphine is if we send spacecraft there. Orbiters will
allow us to better determine the composition and chemistry of Venus' atmosphere. But,
balloon-borne probes could sample the atmosphere and possibly put samples under a microscope.
We'll see. But for now, astronomers are going to look for evidence that either confirms
or contradicts these findings. And it's vey likely that we will see both kinds of results.
Science can be a messy, uncertain process that often produces contradictory findings. But if we
remain persistent and skeptical, we'll eventually learn what's causing the phosphine on Venus.
If that leads us to the discovery of life, then so much the better.
My gratitude as always goes to my Patreon supporters who are helping to keep Launch
Pad Astronomy going, and I'd like to welcome my newest patrons, Trung Doan,
Joe Hinton, Kevin Kolbe, Phillip Lakaschus,
and Leroy. I'm sorry if I mispronounced your names, I almost certainly have.
I'd also like to thank Anna for her Intergalactic Level Support and Michael Dowling, Steven J.
Morgan, and Morrison Waud for their Cosmological level support. If you'd like to support Launch
Pad for the price of a cup of coffee every month, please head on over to my Patreon page.
And if you’d like to join me on this journey through this incredible universe of ours,
well please make sure you subscribe and ring that notification bell so you don’t miss out
on any new videos. Until next time, stay home, stay healthy, and stay curious, my friends.