Next week I am off to St. Petersburg (Russia, not Florida) to give an invited lecture at the 4th International Conference on the Periodic Table — a celebration of the 150th anniversary of Dmitri Mendeleev’s proposal that the chemical elements could be laid out in a table where elements in each row (now columns) shared many properties. This periodicity of properties led this method of organization to be called a “periodic table.”
|Pope Paul VI in one of the Vatican Observatory’s domes
reading a message to the Apollo 11 astronauts.
The lecture I’ve been asked to give is based on an essay I wrote for Nature Chemistry earlier this year, “Isotopic Enrichment” (Isotopes are variants on elements. For example, carbon-14 dating tracks the radioactive decay of a heavier than normal variant of a carbon atom. Most carbon is carbon-12, where the number indicates the mass of a single atom,) The title of this blog post comes from an article ten years ago in Science by Frank Poitrasson on what the distribution of the isotopes of iron can tell us about the history of the earth and the moon. (He describes events so cataclysmic as to be unimaginable. Think two planets colliding and some of the iron on earth vaporizing off into space.) History has a literal weight. The weights of atoms in minerals can tell us not only their age, but also what has happened to them. Were they heated so hot that the lighter versions were blown away?
|Bob Macke SJ (left) and Guy Consolmagno SJ (attired for
the occasion) in front of a display of ephemera from Apollo
missions at the Vatican Observatory outside Rome.
When I was 11 or 12, a touring moon rock (I presume from Apollo 11 or 12) was on display at the Museum of Science and Industry in Chicago. I was long space obsessed and having devoured Heinlein’s Have Space Suit Will Travel, anxious to go traipsing across the surface of the moon myself. (That’s also the book where I first learned about isotopes, half-lives and their use as clocks to measure huge stretches of time. The same potassium you find in a banana contains an isotopic “clock” — potassium-40 — that ticks off time on the billion year time scale, back to the birth of the universe.) So I was anxious to see this off-world connection.
|A lunar sample collected by Apollo 17 astronauts Gene Cernan
and Harrison Schmitt, sealed in acrylic.
There was a field trip to the museum. I rode the yellow school bus in from the tiny Illinois town I lived in. I stashed my lunch in its wrinkled brown bag along with the rest of my groups’ lunches to be picked up at our set time. Then I made a mad dash to the moon rock display. There was already a long line, which inched forward. Finally I was close enough to see the case — a Star Trek-esque dias, from which a light glowed in the dim room. People passed the case, oohing and aahing. At last I was there. To discover there was nothing I could see. Even standing on my tiptoes, all I could see was the very top of the glass dome over the sample. The moon was as inaccessible to me as ever.
When I came to Bryn Mawr, I was excited to discover that one of my new colleagues, Weecha Crawford, had been one of the first geologists to study the lunar specimens, which had to be handled as if they were precious jewels (which they are). But still, I had yet to see a moon rock.
Fast forward to yesterday, where Bob Macke, the Jesuit brother who is the curator of meteorites for the Vatican Observatory, assembled the observatory’s collection of Apollo ephemera for us to enjoy at the morning coffee. One piece of which is a moon rock from Apollo 17, along with a small Vatican City State flag that went to the moon and returned! (Samples and country flags from that mission were given to each sovereign state at the time, including the Holy See.)
At last, I have been as close to (a piece of) the moon as I will get. Like St. Thomas, I didn’t need to touch it, to know it was real. Unlike Thomas, I didn’t even need to have seen to have believed. Happy anniversary to Apollo 11!