(0:00) We love nothing more than bringing you news about the most exciting discoveries being made in space.

But we have to remember, sometimes discoveries involve finding out what we don't know. And in the past week there is some important stuff about life, the universe and everything that we're beginning to think we might have gotten totally wrong.

(0:16) For the first time, astronomers have definitively found, and measured, the abundance of life's favorite compound — water — on a planet outside of our Solar System. Exciting, no?

(Intro)

(0:29) But, the results were not at all what scientists were expecting, so much so that we may have to rethink how planets form in the first place. As far as we can tell, water is the most essential ingredient for a planet's habitability. And we do think we've detected traces of it on exoplanets in the past. But in order to get better at finding water and being sure of it, a team of Cambridge astronomers wanted to look in some easy — though not very habitable — places. So they chose three nearby Gas Giants between 60 and 900 light years away and used the Hubble Space Telescope to measure the spectra of infra-red light being reflected by their atmospheres.

The analysis revealed, for the first time, definitive water vapor — but way less than they expected. Between 1/10th and 1/1000th of what's predicted by the models we use to study planet formation.

(1:10) You see, gas giants like these are supposed to form when matter accretes, or gets drawn together by gravity, on the particles of rock and ice. So frozen water should be there in the first place to get the ball, as it were, rolling. And also according to this model, all the matter that accretes to form a gas giant should pretty much reflect the composition of the matter floating around in its star system.

(1:27) Oxygen is actually pretty abundant where planets form and since water is one of the more common molecules that contains oxygen, that's another reason astronomers expected to find a decent amount of water on these worlds.

But they didn't.

(1:39) So this could mean that we have to revise all our theories about how planets form. And if alien water is really as scarce as these findings suggest, we might need to get a little more choosy in where we search for habitable planets.

Luckily, there are lots of smart people out there brainstorming new ways to improve our search for life outside the solar system.

(1:54) Last week, a team of Harvard astronomers proposed a new method for detecting intelligent, alien life using the James Webb Space Telescope. When measuring chemical spectra on far away planets, we already look for certain chemical signals — like specific combinations of oxygen and methane, or an abundance of CO₂ — as indicators of respiration, and therefore, life.

But the Harvard team suggests looking further for chemical signals that could be associated with intelligent (or not so intelligent) life — depending on how you look at it. 

(2:18) Pollution.

We could look for concentrations of molecules with high global warming potential, like methane and ammonia. But these can also be naturally emitted. The trick the astronomers argue, is to look for a chemical that's clearly synthesized.

So they propose that we start looking for things like Chlorofluorocarbons or CFCs, human-made molecules containing carbon, chlorine, and fluorine, whose properties make them good refrigerants, propellants, and solvents.

The synthesis of these compounds is closely regulated today, because after we released loads and loads of them in our atmosphere during the 20th century, we realized that they break apart and release chlorine atoms, which steal oxygen atoms from ozone molecules. 

(2:53) In other words, CFCs trap heat and contribute to the greenhouse gas effect, while also destroying our atmosphere's protective layer of ozone, which shields us from the sun's UV radiation. 

The team theorizes that alien civilizations like ours might release similar chemicals as a result of industrial development. They went so far as to focus on two common CFC molecules that we should target — carbon tetrafluoride and tricholoro-fluoromethane — and worked out which patterns the spectrographs on the James Webb telescope would need to look for to detect these molecules.

(3:20) Problem is, the James Webb telescope probably isn't powerful enough to find dirty alien worlds this way. As it stands now, it would only be able to spot the chemicals if they were 10 times as abundant as they are on Earth, which is saying something. So hey, at least we have another option!

Since it sounds like we might have to go back to the drawing boards to figure out how to find water on other worlds, at least we can also start looking for signs of aliens poisoning their planets.

(3:42) Thank you, as always, for watching SciShow Space News. If you want to keep exploring the universe with us, check out subbable.com/scishow to learn how you can help support us. And don't forget to go to youtube.com/scishowspace and subscribe.