Struck by Asteroids
Francesca DeMeo has a passion for asteroids. This former undergraduate in the Department of Earth, Atmospheric and Planetary Sciences (EAPS), back at MIT after a stint at graduate school in Paris, is currently a postdoc in Professor Rick Binzel’s group. In this article, she shares her fascination with abundant and varied asteroids.

I was born and raised here in Cambridge, Massachusetts, so I haven’t gone very far even though my research has taken me all over the world. I can’t remember a time when I wasn’t interested in space and astronomy. Growing up, my science projects were always on stars, astronauts, and galaxies. So when I started as an undergraduate at MIT, I knew immediately that I would study physics and planetary science in EAPS.

It was as a junior that my love for asteroids struck. I was doing an undergraduate research project with planetary astronomer and asteroid aficionado Professor Rick Binzel. As I was collecting observations and reducing data, I started to get really excited about asteroids and understanding their context within the larger solar system.

Why Are Asteroids Important?

Asteroids are small bodies, typically meters to hundreds of kilometers in size, that exist all over the solar system, whether as icy bodies in the outer solar system or as rocky ones closer to the sun than Jupiter. Most asteroids that we know of reside in the main asteroid belt between Mars and Jupiter. There are about a million asteroids larger than one kilometer across in that region. A second source of asteroids is in the Kuiper Belt, where many objects have orbits similar to Pluto’s. Asteroids in the main belt are more rock rich while asteroids further out in the Kuiper Belt are more ice rich.

Each asteroid is a tiny marker of the conditions of the early solar system. By gathering information from thousands of asteroids, we learn how the solar system formed and how it has changed over time. Asteroids were the initial building blocks for planets, so we can learn more about Earth, what it was originally composed of, and where its water came from. From a more practical point of view, there are 10,000 currently known near-Earth asteroids. While most pose no threat to Earth, a few pose a risk of collision, such as the infamous asteroid Apophis. It’s currently a priority to discover all of these potentially hazardous asteroids and to understand their composition so that we can keep them away from Earth.

A Different Kind of Differentiation

In my research, I seek to understand the distribution of differentiated material in the main asteroid belt. What do I mean by differentiated? Take the Earth as an example: Our planet is one large body that was heated so much in the interior (through decay of radioactive particles that release heat) that all of the heaviest materials (iron, for example) separated and sank into the interior, while the lighter materials remained on top. The result is the Earth’s system of layers (core, mantle, crust) familiar from any geology textbook. The same thing happens in some smaller bodies within the asteroid belt. While some haven’t changed since they were first formed around 4.5 billion years ago, others were large enough and hot enough that, like Earth, they could differentiate by forming a metal core with a lighter composition surface.

"There really is just so much untapped potential in terms of discovery so close to our Earth. That’s why I love studying space."
Part of my research is to search for pieces of these differentiated asteroids. Over time, some of these large bodies are hit by other asteroids, scattering fragments all over the asteroid belt. My job is to find out where they have journeyed and how they were originally formed: Were they formed close to the sun or farther out? How many were heated early on to melt and differentiate?

A Day in the Life of a Scientist

To collect my data on specific asteroids, I use the NASA infrared telescope facility (IRTF) in Hawaii on Maunea Kea and the Magellan telescope in Chile at Las Campanas Observatory. Typically I might use the IRTF once or twice a month, to accumulate the data I need to answer the questions I’m interested in. The remainder of my time is spent analyzing data and using it to recreate the story of what we’re seeing. That’s one of the compelling things about astronomy: The experiment has already been done so we have to try and recreate the story of what happened all the way back to a set of unknown initial conditions. If I find anything frustrating about research, it is that it takes such a long time. It might take 2 years to take all the telescope observations that I need and then to reduce and analyze the data. Of course, it can be extremely rewarding when there’s something really new and exciting, but sometimes you just have to admit that we still don’t yet have the answer.

What’s Next in Asteroid Research?

One of NASA’s main goals is to find all asteroids in near-Earth space. Once we’ve found them, we need to determine their composition as that helps us understand the risk they pose to Earth. I foresee more development in this area in the future. In fact, a private company, Planetary Resources, was recently created to mine asteroids for their important resources. I wasn’t expecting the type of research I’m doing to be useful so soon, but understanding the composition of asteroids will pave the way for selecting the best to mine.

Spacecraft data may represent the next big step in asteroid science. We’ll send spacecraft to asteroids, take samples, and bring them back to Earth for further study. In fact, we already have an approved NASA mission OSIRIS-REx launching in 2016 just for this purpose. There really is just so much untapped potential in terms of discovery so close to our Earth. That’s why I love studying space.

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