Category Archives: cosmic chemistry

cosmic chemistry, life

The Cosmic Garden of Eden

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Complex Molecules in Space

A few months ago I attended a day-long workshop about the chemical origins of life. The talks were aimed at tracing the chemicals that make up our very basic units (RNA, DNA) from first principles to the garden of biologic diversity we inhabit today. One of the talks focused on the finding the chemical precursors of life in interstellar dust clouds, which is really kind of a mind-blowing concept. But, when you think about it, since everything is chemical in origin, it makes sense that some of the chemicals that existed in the cloud our solar system formed in would also play a part in the origin of life.

There are organic molecules everywhere in space (and obviously here on Earth, but also at Jupiter, Saturn, and Titan. Researchers at Imperial College in London (England) have identified xantine and uracil — two very complex molecules needed to form RNA and DNA — in fragments of a meteorite that landed in Australia. The molecules didn’t come from Earth; they were present in whatever place the meteorite first formed. Which means that those molecules existed when the solar system formed, some 4.5 billion years ago. Eventually, rocks containing those molecules landed on Earth. It’s not much of a leap of the imagination to see that the ingredients for life could well have been delivered from space, and that we are really and truly “space stuff.”

What this should tell you is that the search for life in the universe isn’t really a search for little green men or cosmic omnisciences. It’s a journey that organic chemistry will lead, and all we have to do is study what it gives us.

chemistry, cosmic chemistry, spectroscopy

Hidden in the Light

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A spectrum showing lithium in a metal-poor star
A spectrum showing lithium in a metal-poor star

Not all the great stuff astronomers get the from sky is in the form of pretty pictures. Granted, gorgeous astrophotos are addictive, but they don’t tell the whole story of the universe. Astronomers also study data in the form of spectra. The figure above is a good example of a spectrum. Basically it tells astronomers that a star called G271-162 has a certain amount of an element called “lithium” — which is relatively rare in the cosmos compared to other elements. This star is what is known as a “metal-poor” star — one that formed in the earliest times of the universe. “Metal-rich” stars are those formed from interstellar gas and dust that has probably been “recycled” through at least one star and enriched with metals. So, if we study older stars like G271-162 and figure out how much they have of certain elements, that will tell us a lot about what elements were most plentiful in the early, early universe. Astronomers want to understand how much lithium was produced in the birth of the universe — the Big Bang — some 12 to 14 billion years ago. The amount of lithium older star will help them understand it.

You can’t take a picture of lithium, but you can study the light coming from a star — and break it up into a spectrum. If lithium is present in the star, it will show as a “dip” in the spectral line — which is exactly what you see in this graph.