If you rank the most habitable places in our
solar system Venus lands pretty low, with surface temperatures hot enough to melt lead
and sulphuric acid rain. And yet it may have just jumped to the front
of the pack. In fact we may have detected the signature
of alien life - Venusian life -for the first time. Our searches for life-beyond Earth have tended
to focus on the Martian subsurface and the ocean moons Enceladus and Europa and even
the methane lakes of Titan. And yet the horrible hellhole that is the
atmosphere of Venus has just yielded perhaps the most exciting lead for extraterrestrial
life. Arguably, it’s our only lead - the faint
signature of the chemical phosphine in Venus’s atmosphere, which may have been produced by
living organisms. I joked more that the weirdest end
to this very weird year would be the discovery of alien life. Let’s see if 2020 can make up for itself. Now, before we get to the evidence, let’s talk about Venus. It’s the brightest thing in the sky besides
the sun and moon, hanging just above sunrise and sunset. It’s bright because it’s close and it’s
big, at 90% Earth’s diameter, and its our closest planetary neighbor. In many ways it’s Earth’s twin - it’s
even inside that band around the Sun where liquid water is possible - the so-called habitable
zone. But for the longest time Venus was thought
to be among the LEAST habitable places in the solar system. See, Venus has what we call a runaway greenhouse
effect. Its atmosphere is 100 times the mass of Earth’s
and mostly carbon dioxide. This traps so much heat that the surface of
Venus reaches a temperature hot enough to melt lead, and with a pressure that would
crush most submarines. That atmosphere also sports a permanent thick
layer of sulfuric acid clouds, So yeah, when we realized just out just how
awful Venus was, our telescopes and hopes for finding ET swiveled outwards. To the outer solar system - Mars, Enceladus
and Europa in particular, and ultimately to planets around other stars. But Venus wasn’t ready to give up our attention
so easily. Our landers and orbiters - Venera, Pioneer, and Magellan - caught hints of unusual atmospheric chemistry. Various sulphur-bearing molecules were out
of the expected equilibrium quantities. But non-living, or abiotic processes like
volcanism could still explain these. The other weird thing is that the clouds of
Venus appear to absorb the Sun’s light in a weird way - more short wavelength visible
and UV light is sucked up than expected, leading to the yellow colour of the clouds and dark
patches that change over time. This could be due to dust churned up from
the surface - or it could be gigantic colonites of microbial life. Although the surface is completely hellish,
at around 50km altitude both the temperature and pressure are close to those at Earth’s
surface, with the only problem being that pesky sulphuric acid rain. But compared to the death-zone of Venus’s
surface, it’s a paradise, and we talked about the possibility of human cloud-city
settlements in a previous episode. In 1967, Carl Sagan and Harold Morowitz were
among the first to suggest that life might exist permanently aloft in Venus’s relatively
habitable upper atmosphere. These guys speculated about both microbes
and larger creatures, alien gas bags perhaps supported by in-built hydrogen balloons. But all these ideas were still pretty fringe. The attention of ET-hunters remained focused
outwards. One of the most promising avenues in the search
for life is to detect so-called atmospheric biosignatures - chemicals in a planet’s
atmosphere that are very hard to explain without the presence of life. There are lots of ways to do this - for example
seeing the effect on a star’s light as it passes through its own planets atmospheres. Another possibility is to look for the absorption
of the planet’s own light as it emerges from deep within its atmosphere. This can be done at far infrared and submillimeter
radio wavelengths where the star’s own glare doesn’t kill the signal. One possible biosignature in this range is
phosphine, which absorbs photons of around 1.1mm wavelength. Phosphine is produced in abundance by some
microbes, but not so easily produced by non-biological processes. A team of researchers led by Professor Jane
Greaves, mostly out of the United Kingdom, decided to explore phosphine as a possible
biosignature. They thought they’d take a look at Venus
using the James Clerk Maxwell telescope - more as a control to help guide their studies of
planets beyond our solar system, but not really expecting to see anything so close to home. But to their extreme surprise, they found
phosphine. The team followed up with ALMA - the Atacama
Large Millimeter/submillimeter Array - and confirmed that there had to be phosphine in
the upper atmosphere of Venus. Vastly more than expected. So there are two big questions here. Is the detection of phosphine real? And if so, how likely is it that the phosphine
came from life? Well, the fact that both JMCT and ALMA detected
the feature makes it pretty convincing that it’s real, although there’s still a chance
that both observatories just happened to see a dip in the exact spot where phosphene produces
an absorption line. Followup observations will confirm or refute
this pretty quickly, but the detection is looking pretty solid at this point. Okay assuming it is real, does this mean we’ve
found life? Well, let’s first discuss why the presence of
a simple molecule might get people excited about the possibility of life. So phosphine is a tetrahedtron - pyramid or
d-4 - shaped molecule with one phosphorus and 3 hydrogen atoms. It's a common byproduct of living metabolisms,
although its also highly toxic. Now you don’t need biological processes
to make the stuff. It can form anywhere that you might have free
phosphorus and hydrogen atoms. That means anywhere that the more stable phosphorus
and hydrogen-containing molecules might be broken apart. For example, it’s formed deep beneath the
surfaces of Jupiter and Saturn and carried to the surface. We’ve spotted the characteristic absorption
features of phosphine in the two gas giants - but no one screamed life, because there’s
a clear mechanism for producing that phosphine by abiotic processes. So why the excitement with Venus? Well, although phosphine can be produced in
a number of different ways, it rarely lasts long no matter how it’s made. The stuff is very quickly oxidized - particularly
in the highly acidic atmosphere of Venus. That means something on Venus is making phosphine
faster than it can be destroyed. On Venus there are a few ways to make this
stuff - you’d definitely get some in the extreme heat and density near the surface. You might get some produced by lightning strikes
in the cloud layers, or by cosmic rays hitting the upper atmosphere. Most of the non-biological production is likely
to happen at the surface, and would take years to diffuse to the upper atmosphere. However the scientists calculate that almost
all of the phosphene would be destroyed in that time. The abiotic production rate of phosphine is
expected to be 10,000 to a million times too low to produce the amount of phosphine that
was observed. So we’re left with two possibilities - either
there’s some unknown non-biological process that produced this phosphine, or Venus has
life. Honestly, the former still seems the more
likely because, well, it’s never aliens until every other possibility is ruled out. But this may be the most promising lead to
extraterrestrial life we’ve ever had, so let’s talk about what that life might look
like. Almost certainly it would be floating microbes
like Sagan and co. talked about half a century ago. But the requirements for life in the clouds
of Venus are pretty strict. The entire lifecycle would have to remain
in the regions with survivable temperature and pressure, and the critters need to somehow
survive the crazy acidity. Sara Seager from MIT and collaborators proposed
a lifecycle that might just do the trick. Firstly, they assert that these critters are
microbes living in tiny droplets. Liquid environments are universally thought
to be essential to life, and in the extreme dryness of the Venusian atmosphere free-floating
microbes would quickly dry out. But those droplets would be mostly hydrochloric
acid - maybe 85% concentration, with the rest water. By comparison, the most extreme extremophiles
on Earth can survive in pools with something like 5% concentration of sulphuric acid - in
the Dallol pools in Ethiopia. So these Venutian microbes would have to be
very different to anything found on Earth. These droplets can only exist in a narrow
range in the atmosphere. Droplets are expected to form at a particular
height, but as they find each other and grow they begin to fall back down into the crushing
oven of the lower atmosphere, where they quickly evaporate again. So how does a droplet-dwelling organism survive
this? Seager and co. have an idea. What if the microbes enter a resilient spore
state as their droplets descend and dry out? Earth bacteria can transform into dormant
states in adverse conditions - bacterial spores. We previously talked about how these spores
can survive crazy conditions - including the vacuum of space and the extreme temperatures
and pressures of meteor impact or atmospheric reentry. So what if Venusian microbes passed through
such a spore state in the lower atmosphere? The life cycle would look like this: microbes
are in a metabolic state in sulphuric acid droplets in the upper atmosphere. Those droplets find each other and grow. Perhaps microbes multiply in this phase. As they fall and their droplets evaporate
they enter a spore state. These spores are extremely tiny and light,
and so they float in the haze below Venus’s cloud banks. Updrafts then carry spores into the temperature
range once again where they act as nucleation centers for new droplets to form, at which
point they become metabolically active again. And, like, churn out a bunch of phosphene
I guess. OK, nice story. The main stretch here is the whole sulphuric
acid thing. We just don’t know if life can exist in
those conditions. An important point here is that Venus’s
hellish conditions are relatively young only perhaps only around 700 million years old. And before that they likely had oceans of liquid
water. Any lifeforms in its atmosphere today must
have evolved from presumably much more sensible critters that existed prior to the runaway
greenhouse effect. Could microbes really evolve to withstand
the transition from a watery to a sulphuric-acid-y environment? I guess we’re about to find out. And how exactly will we find that out? Well, the first thing is to confirm the presence
of phosphine with more observations. The previous observations were relatively
brief, but there’s now motivation to point our telescopes for much much longer at Venus. We'll need to look for other phosphine absorption
features also, and entirely different biosignatures. But ultimately we’re going to want to go
to Venus, to search for life signatures there or, even better, to bring samples back to
Earth. NASA is about to decide between two proposals
for the next mission to Venus. Neither mission has a direct life-detecting
instrument, but that might change given these developments. However it may be time to refocus our solar
system explorations. Ultimately we want to bring back samples of
the Venusian atmosphere - to actually get microbes under a microscope, if they exist. The discovery of alien life in our nearest
planetary neighbor would totally change our calculations about the frequency of life in
the universe. We may be forced to conclude that life is
cosmically abundant. 2020 is the year of weird microbes - but this
latest one, if it’s real, may prove extremely good news - granting us a grander perspective
on humanity’s place in a life-filled space time. Hey everyone. A few things before we get to comments. First up, if you're looking for some more great science content, you should check out Overview, on PBS Digital Studios' science
and nature channel Terra. Overview is hosted by Joe Hanson from It's
Okay to Be Smart and combines mesmerizing drone footage with deep science storytelling
to reveal all the things shaping our planet from the 10,000 foot view. So head over to Terra, and make sure to (politely)
tell them Space Time sent you! Next up, we just wanted to shout out again
to everyone who helps us out on Patreon. As always, your contributions make a huge
difference. But today an extra big shoutout goes to Scott
Gray who’s contributing at the Big Bang level - Scott, thank you so much. We’ve used your contributions so far to
bake a nice apple pie and send to welcome our Venusian neighbors to the solar system
- or at least into our awareness of their existence in the solar system. We look forward to neighborly relations with
the gentle Venusian gas-bag civilization. And, ultimately, to ally with them in war
against the cosmic string entities in the heart of the Sun that we discussed recently. So, Scott, I guess thanks for contributing
to the future ascendency of humanity. Okay, last week we talked about post-quantum
cryptography - possible solutions to the impending cryptography-cracking powers of quantum computers
that don’t themselves require quantum technology. We were delighted to find several crypto-geniuses
in our audience who called us out on a few errors. First up, Mina86 pointed out that our use
of mixing colors as an analogy for one-way functions in RSA protocol is more accurately
analogous to Diffie-Helman key exchange. I agree, and we should have been more careful
here. Our point was to illustrate one-way functions
themselves, but the way we said it could have been interpreted as illustrating RSA. So thank you for catching that. Several of you noticed that we skipped a power
of 2 in one of our graphics. We jumped form 256 to 1024. I think it comes from my habit of skipping
generations of processor in my computer upgrades. I go for every second Moore’s law doubling,
which leaves my machines basically paralyzed about half the time. And the last catch - a few of you noticed
I used the expression “factor a prime number” - which is dumb, because the factors of a
prime number are just itself and 1. Which I guess you don’t need a quantum computer
for. What I meant was factoring the product of
two primes INTO those primes. Anyway, thanks for keeping us straight. Finally, a few of you expressed your distaste
for lattice-based encryption protocols. Really, there were doubts that any salad-based
protocols would be meaty enough to resist quantum decryption.
I definitely agree with a point towards the end that this is probably the best candidate we've ever seen for possible extraterrestrial life. I didn't really get the significance at first until I learnt that the observed amounts of phosphine was like orders of magnitude greater than expected because its hard to make and is very short lived.
That means even if it turns out to be abiotic then the explanation is going to be very interesting.
Honestly, I feel like Matt undersold this.
He never mentioned that the phosphene is only found at the equator which is odd to say the least. Nor did he mention that the Venera probes detected particulate matter as they were descending into the clouds.
This is what I was waiting for! :D