Across the Universe: Hidden inclusions

This column first ran in The Tablet in July 2013

I was in a state of high excitement (or what passes for such when you’re sixty years old): the Pope was coming to lunch with our Jesuit community at the Vatican Observatory! Meanwhile, I was also preparing a paper for the annual Meteoritical Society meeting, and I had just noticed a wonderful correlation in my data. These sorts of insights are as rare as Papal visits… if indeed I had really made one.

Cutting into an iron meteorite (this is Mt. Dooling) reveals dark sulfide inclusions, along with the famous crystal pattern of nickel-rich and nickel-poor metal

I’ve been studying iron meteorites; and it’s been hard work. For one thing, they are, quite literally, hard – lumps of nickel-iron, too hard to cut up easily to see what’s inside. I’ve seen iron meteorites being cut at the Smithsonian in Washington, DC; their saw sits in a room the size of gymnasium, makes an awful racket, and spews water everywhere. (The water cools the meteorite while a diamond-encrusted wire scrapes through it.)

When you do slice them open, you find iron crystals several millimeters wide, alternately nickel rich and nickel poor, along with similarly large lumps of sulfide. The meteorites in our collection have another ingredient as well: rust, the result of sitting in the ground for hundreds of years after their fall before being found by some collector. You might see sulfides or rust on the surface of a sample, but there’s no way to tell how much is present inside. Likewise, iron meteorites are classified by their nickel and other trace element content; but you can’t tell their class just by looking.

The meteorite Agustinovka is a rusty lump of iron, which could have lumps of sulfide hidden inside... somewhere.

But I can measure their densities. And if I drop them in liquid nitrogen, I can measure how much nitrogen boils away, which tells me how much heat they hold. Both density and heat capacity ought to vary with the nickel, sulfide, or rust that’s present.

I’d measured dozens of iron meteorite samples, and when I plotted density against heat capacity I saw a nice “vee-shaped” pattern. The sample that plotted at the point of the V looked to be free of sulfides or rust; the rustier meteorites plotted farther from this point. When I measured one sample that was almost completely sulfide, it plotted far from the others – as expected – but exactly on a line with one of the strokes of the “V”. Clearly, the more sulfide a sample has, the further along this line it should plot!

The next step would be to measure some very rusty meteorites, samples so degraded that I’d never thought I would have a use for them. I knew, in my heart, that these would certainly plot along the other stroke of the V; where one trend showed me the sulfide content, the other should show the rust content. The Pope’s wonderful visit came first; but once that was over I could get back into the lab and prove my thesis.

With only a handful of points it's always tempting, but risky, to jump to the conclusion that we're seeing real trends in the data

The result? Yes, they plot exactly on a line; but the wrong line. The rusty samples line up exactly on the same line as the sulfide sample. In other words, I have no idea what’s going.

An “insight” is to “see in”, to see what is hidden within; but my vision here is still cloudy. Maybe when I present this result at our convention, some colleague will have a helpful idea. That’s why we do science as a community; talking about it with other people helps us further our insights.

But the social aspect of science is also what motivates me to do the work in the first place. The excitement I felt was not only anticipating a new discovery, but anticipating the fun of telling my colleagues about it. That’s the joy of being with a friend, whether it’s a scientist or a Pope: sharing insights, stories, or a meal. That’s what the Mass is, after all.

Br. Guy Consolmagno

About Br. Guy Consolmagno

Brother Guy Consolmagno SJ is Director of the the Vatican Observatory and President of the Vatican Observatory Foundation. A native of Detroit, Michigan, he earned undergraduate and masters' degrees from MIT, and a Ph. D. in Planetary Science from the University of Arizona; he was a postdoctoral research fellow at Harvard and MIT, served in the US Peace Corps (Kenya), and taught university physics at Lafayette College before entering the Jesuits in 1989.

At the Vatican Observatory since 1993, his research explores connections between meteorites, asteroids, and the evolution of small solar system bodies, observing Kuiper Belt comets with the Vatican's 1.8 meter telescope in Arizona, and applying his measure of meteorite physical properties to understanding asteroid origins and structure. Along with more than 200 scientific publications, he is the author of a number of popular books including Turn Left at Orion (with Dan Davis), and most recently Would You Baptize an Extraterrestial? (with Father Paul Mueller, SJ). He also has hosted science programs for BBC Radio 4, been interviewed in numerous documentary films, appeared on The Colbert Report, and for more than ten years he has written a monthly science column for the British Catholic magazine, The Tablet.

Dr. Consolmagno's work has taken him to every continent on Earth; for example, in 1996 he spent six weeks collecting meteorites with a NASA team on the blue ice regions of East Antarctica. He has served on the governing boards of the Meteoritical Society; the American Astronomical Society Division for Planetary Sciences (of which he was chair in 2006-2007); and IAU Commission 16 (Planets and Satellites). In 2000, the small bodies nomenclature committee of the IAU named an asteroid, 4597 Consolmagno, in recognition of his work. In 2014 he received the Carl Sagan Medal from the American Astronomical Society Division for Planetary Sciences for excellence in public communication in planetary sciences.

This blog is made possible by contributions from visitors like yourself. PLEASE help by supporting this blog.

Get the VOF Blog via email - free!

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

Leave a Reply