Skeptophilia (skep-to-fil-i-a) (n.) - the love of logical thought, skepticism, and thinking critically. Being an exploration of the applications of skeptical thinking to the world at large, with periodic excursions into linguistics, music, politics, cryptozoology, and why people keep seeing the face of Jesus on grilled cheese sandwiches.

Friday, November 18, 2022

A projectile from deep space

Sometimes the most interesting questions to ask in science are the ones about facts so commonplace that we don't usually even think about them.  For example: how did the Earth end up with the composition it has?

The crust of the Earth -- the part that (obviously) we're most familiar with -- is largely made of silicate rocks (especially feldspars), with a good bit of magnesium, aluminum, potassium, and sodium thrown in.  The mantle, the liquid-to-semisolid bit beneath the crust, is also rich in silicates, but as you go deeper the iron and magnesium content increases (minerals with those elements are generally denser than silicates, so the silicates float to the top).  The core is mainly iron and nickel.

The oceans and atmosphere are a thin layer that is insignificant in terms of contribution to the mass of the Earth as a whole.  (Pretty damn significant to life on Earth, of course.)  And the impressive mountains and valleys, not to mention things like the oceanic trenches, aren't as impressive as they seem from our vantage point.  I remember being blown away when one of my geology professors said that the highest mountain ranges and deepest trenches have less topographic relief than you find on a typical billiard ball.

The Earth formed during the early days of the Solar System from accretion of asteroids, dust, and debris that pulled together from what was probably a set of rings around the Sun similar to what still exists around the planet Saturn.  During that phase, the energy of the constant collisions and bombardment heated the nascent Earth to beyond the melting point of the rock that it was made of, rendering the whole mass molten, glowing orange-hot.  (Some of that heat is what still makes the interior of the Earth hot today; the rest comes from the breakdown of radioactive elements in the core and mantle.  It's what keeps the Earth tectonically active, and the liquid metallic outer core is very likely why our planet has a magnetic field.)

But the specific makeup of the particular rocks that came together early in Earth's history determined what we have here today.  That includes the water in our lakes, rivers, and oceans.  The vast majority of our water arrived during the coalescence of our world -- but we just found out a little more about that particular feature from a much more recent arrival.

On the 28th of February, 2021, a football-sized meteorite streaked across the skies of Winchcombe, a town in Gloucestershire, in the southwest of England.  The intense heating from friction in the atmosphere made the rock explode, and a large chunk of it landed in the driveway of Rob and Cathryn Wilcock, who donated it to the Natural History Museum of London.

Rob Wilcock's photograph of what was left of the Winchcombe meteorite after it smashed into his driveway in February of 2021

The meteorite turned out to be a carbonaceous chondrite, a rare sort of meteorite that is carbon and water-rich.  And the first cool thing was that when the scientists measured the hydrogen-to-deuterium ratio of the the water in the meteorite, they found that it was identical to that in the Earth's oceans.

But you want the kicker?  Also present in the Winchcombe meteorite were various amino acids and a slew of other organic compounds -- the biochemical building blocks of life.

It's discoveries like this that that make me even more certain there's life out there in the cosmos.  Intelligent life is another matter; we still have yet to explain the Fermi paradox (Enrico Fermi's comment that if extraterrestrial life is common, then "where is everybody?" -- a topic about which I wrote in some detail a while back).  But non-technological life?  I'd bet a significant amount of money that it'll turn out to be abundant.  Think of what we could learn from a biology that was entirely separate from us, that had no ancestral connection to anything on Earth.

The mind boggles.

Studies like the one just done on the Winchcombe meteorite give us a perspective not only on how our planet formed, but what else might be out there waiting for us to find.  To quote Carl Sagan: "The universe is a pretty big place.  If it's just us, it seems like an awful waste of space."


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