Mass Spectrometry: How to Weigh an Atom
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Journey Back in Time
Comets are so fascinating to scientists because they contain the stuff with which the solar system was created. While other celestial bodies have evolved over time, chemically and physically, due to radioactive heat and collisions with each other, comets are considered comparatively pristine. Scientists estimate that trillions of them populate our solar system. Though a tiny minority of them venture closer to us, they mostly keep to themselves on the frigid periphery called the Oort Cloud (well beyond Pluto) and have been preserved there in roughly the same way pork chops keep in your freezer.
Each grain is a tiny time capsule bursting with data. If these comets contain the building blocks of our solar system, they must then contain the building blocks of the Earth and, it would follow, of all life on the planet. These comets are, in other words, our atomic ancestors.
PHYSICS FACTOID: The highly elliptical orbits of comets sometimes bring them near large planets. These close encounters can alter their orbits, sometimes drawing comets closer to the Earth and sun (as happened to Wild 2 in 1974 after passing near Jupiter), sometimes ejecting them farther out.
Some 4.6 billion years ago our solar system – at that time an immense cloud of gas and dust – began to form. Catalyzed by some outside galactic event – perhaps a shockwave from a supernova – this nebula began to collapse under its own gravity, heating up and compressing in the process. At the center formed what would become our sun; the gas and dust that orbited it eventually coalesced into planets. Much of the matter entering the inner solar nebula may have been vaporized by the heat, erasing all knowledge of its past.
Well, not all of it. After the sun and planets formed, some material was left over on the fringe of the new solar system, sort of like the dusting of unused flour bordering your countertop after you roll out your pastry dough and pop it in the pie plate. This material was scraped together and the solar system’s fleet of comets was born. So scientists believe.
Wild 2 and other comets contain this ur-matter, these unadulterated ingredients that went into our star and planets before they got baked. That’s why scientists salivate at the thought of what comet dust could tell us.
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