January 17, 2020
Journey of a Lifetime
I started working on meteorites more than three decades ago and quickly fell in love with iron meteorites. These were samples of the great inaccessible layer of any planet or asteroid that ever melted. All of the rocky planets of our Solar System — from Mercury to Mars — melted to form a layer-cake world with a metallic core. Yet the idea that we would ever see one of these cores was little more than a fantasy. Our own Earth’s core sits nearly 3000 km below our feet, far outside the reach of humans. Yet, iron meteorites had been liberated from the depths of ancient asteroids and fell to Earth, holding all the secrets of this inner world.
My work on iron meteorites quickly landed me as one of the world’s experts in the field, something not all that hard to do when fewer than 10 people devoted much effort to these unusual objects. After moving around a good chunk of the United States, I wound up at the Smithsonian in charge of unquestionably the best collection of iron meteorites in the world. These objects would occupy much of my time for two decades.
In those two decades, I heard discussions about a mission to a metallic asteroid and even saw a few proposals, but the serious drive to visit a metal world never seemed to materialize. Imagine my surprise when a team led by Lindy Elkins-Tanton got serious about putting together a proposal to finally visit Psyche. As always, it would be an uphill struggle to even put together a strong proposal, yet alone get selected. Really, it was too good a chance to pass up. I was even more surprised — really, shocked — when it was selected the first time it was proposed.
Psyche will be my sixth robotic spacecraft mission, having already worked on three asteroid missions, a mission to the planet Mercury, and having helped operate rovers on Mars for five years. The trick, if you want to call it that, is to figure out how what we measure in the laboratory on scales as small as 1/1000th of a millimeter can be related to measurements made often at the scale of an entire asteroid. The key is to focus not on the exact element or mineral measured, but the process we want to understand. While we might use the abundance of tungsten in an iron meteorite to look at how reactions give and take oxygen (redox reactions), we can use the ratio of iron to nickel to do the same thing on an asteroid.
Psyche will likely be the last mission I work on for my career. It’s a fitting end to a journey that began with a fascination looking in detail at iron meteorites those many years ago. I don’t know exactly what we’ll find, but it’s already been the journey of a lifetime and I can’t wait to see how it ends.