> “It is all a matter of time scale. An event that would be unthinkable in a hundred years may be inevitable in a hundred million.” -Carl Sagan
There’s some speculation that NASA, later this week, might announce evidence for life on Saturn’s moon Titan.
I’m not going to comment on the speculation, but it’s worth asking the question, scientifically, “How would the Universe make life, from scratch?”
Let’s start by telling you what “scratch” means. If you’re familiar with the story of the Universe, one of the things you know is that things were very hot and dense in the past. So hot that you couldn’t have neutral atoms, or even protons and neutrons bound to one another.
But the Universe cooled quickly, and by time it was a mere 4 minutes old, it’s too cool to keep fusing elements together; all you’ve got at this point is a Universe that’s (by number) 92% Hydrogen, 8% Helium, and less than 0.0000001% anything else. Sure, your Universe will expand and cool, but it isn’t for millions of years (and more likely, tens of millions of years) that you start to change what the Universe is made out of.
Because it takes that long for gravity to pull this primitive gas into a dense enough region that we can — for the first time in the Universe — form stars!
And these stars, like all bright stars, get their energy by fusing these light elements into heavier ones. If we could look inside the most massive of these stars, know what we would find?
That a great deal of this hydrogen and helium has fused into heavier elements, including Carbon, Nitrogen, Oxygen, Phosphorous, Silicon, Sulfur, and Iron: many of the building blocks of life!
But these stars don’t live forever. If the star is up to about four times as massive as our star, when it runs out of fuel, it blows off the majority of its outer layers in a spectacular display, producing a planetary nebula, like the Helix Nebula (below).
But if your star is more massive than that — and some of them are hundreds of times as massive as our Sun — you get an explosion that rips the star apart in seconds (instead of thousands of years), known as a supernova!
Either way, what happens is that the whole region of space around the dead star gets “enriched” with these heavier elements. So it isn’t just hydrogen and helium anymore, there’s also carbon, nitrogen, oxygen, and a whole host of other elements floating around.
And the 13.7 billion years our Universe has been around is more than enough for this to have happened multiple times. And about 4.6 billion years ago, a highly enriched cloud of gas and dust — mostly hydrogen but with plenty of other elements — collapsed to form our Solar System.
But when you get a whole bunch of elements together, spinning around, they don’t simply collapse to form moons, planets and stars, although they do form those things, like Titan, shown below.
You also create the largest chemistry sets in the Universe. With carbon, nitrogen, oxygen, and hydrogen, plus a few trace amounts of other elements and some energy, you can create a brilliant laboratory setup to re-create what might have happened billions of years ago on Earth.
This setup is known as a Miller-Urey Experiment, and can, among other things, produce sugars and amino acids. In other words, organic molecules.
Variations on this experiment have gone as far as producing molecules such as adenine, one of the building blocks of DNA and RNA.
That’s a pretty story, of course, and you might ask what evidence we have that the Universe — on its own — actually does this. It’s one thing to do it in a lab, but it’s quite another to leap to the conclusion that the Universe does this on its own.
I mean, it’s not like the evidence just falls out of the sky, right? Right?
Take a look at a fragment of the Murchison Meteorite, a meteorite totaling over 100 kilograms that fell in Australia in 1969. Over 14,000 organic molecules were identified in this meteorite, including over 70 amino acids not found on Earth.
In other words, just the presence of these atoms in space, in a typical star system, will give you the building blocks of life! The Universe, through simple chemistry of the elements made in the nuclear furnaces of stars, gives you all the ingredients for life.
Which brings us back to Titan. With liquid ocean and towering cryovolcanoes, could Titan be harboring life? We may only need to look beneath its atmosphere to find out.
Right now, there’s no direct evidence, and I seriously doubt that’s going to change on Thursday, when NASA makes their announcement. But the building blocks of life are everywhere, and I’d be shocked if we didn’t discover life itself elsewhere in our galaxy in the near future. After all, the building blocks are everywhere…
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