Christopher Hamilton explores the architecture of other worlds

Extreme geology on Earth holds clues to what we could find throughout the solar system

Christopher Hamilton

ALIEN TERRAIN  Christopher Hamilton is studying lava on Earth to learn how other worlds were built. “We have to know what’s there, and how we can work with it.”

Christopher Hamilton

Christopher Hamilton, 39
Planetary science
University of Arizona

Christopher Hamilton wanted to be an architect.

Yet the planetary scientist at the University of Arizona in Tucson is exploring a very different kind of built environment: the strange structures created by volcanoes on worlds across the solar system, from Earth to Mars to the moon.

And he’s using an unusually diverse toolbox of techniques, including neural networks used in artificial intelligence and good old-fashioned geologic field mapping.

“He is constantly moving between worlds,” says Laura Kerber, a planetary geologist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “It’s one of the extraordinary things about him.”

Hamilton’s first crossover — switching from architecture to geology as an undergraduate student at Dalhousie University in Halifax, Nova Scotia — has a certain logic. “A blueprint and a geologic map are extraordinarily similar,” says Hamilton, 39. Each can tell you what was there before, how something was built and how it could be dismantled.

That’s where lava, a fundamental part of shaping any terrestrial planet, comes in. To understand how otherworldly volcanic landscapes formed, scientists first look closer to home, seeing how lava shapes features on Earth that act as stand-ins for alien terrain.

Iceland, for example, “is truly an otherworldly place,” Hamilton says. During college, he spent a year there studying and mapping volcanic structures buried beneath a thick blanket of emerald-green moss. The structures are remnants of one of the largest volcanic eruptions in recorded history.

About 240 years ago, the volcano Laki awoke in fury, sending molten basalt lava pouring across the landscape. When the lava encountered water bodies, such as swamps or lakes, boom! Powerful steam explosions left deep dents in the ground. Scientists call these craterlike structures volcanic rootless constructs, or cones, because they are unconnected to any underground magma supply.

Mars has similar terrain. Early images of the Red Planet suggested that the ground was littered with rootless constructs, offering tantalizing clues to the planet’s watery past. Hamilton made the study of these features the focus of his Ph.D. research at the University of Hawaii at Manoa.

CRATER COUSINS Iceland is dotted with rootless cones (one shown, left, at Lake Myvatn), which form when lava flows across a watery landscape. Mars, too, has these false craters, remnants of the Red Planet’s watery past. This one (right) is in Amazonis Plantitia, a region covered in ancient lava. Hansueli Krapf/Wikimedia Commons (CC BY-SA 3.0), Univ. of Arizona, JPL-CALTECH/NASA

Working with adviser Sarah Fagents, Hamilton mapped 167 groups of rootless cones on Mars. The researchers estimated that the constructs formed when lava flowed across the region sometime between 250 million and 75 million years ago. The lava interacted with abundant water ice that simulations suggest was buried at least 42 meters beneath the surface. Those interactions may also have created short-lived hydrothermal systems that could have been a habitable environment for microbes, the researchers hypothesized in 2010 in the Journal of Geophysical Research: Planets.

“He’s a very inquisitive, thirst-for-knowledge kind of person,” Fagents says. “He has an ability to really delve deep into a problem — and he’s not afraid to jump into new areas.”

In fact, by the time he finished his Ph.D., Hamilton was thinking about unfamiliar environs. “I didn’t want to just focus on a single place,” he says. “I wanted to understand how different geologic processes work throughout the solar system.” At NASA’s Goddard Space Flight Center in Greenbelt, Md., from 2011 to 2014, Hamilton turned his attention to other extraterrestrial volcanic processes.

One project focused on Jupiter’s innermost moon, fiery Io, the most active volcanic body in the solar system. Researchers have long thought that Io’s intense volcanism results from what’s known as “tidal heating” of the presumably solid moon. Competing gravitational tugs from two nearby moons and Jupiter itself squeeze and stretch Io, heating its insides. But that hypothesis doesn’t fully explain Io’s heat production. Hamilton demonstrated in 2015 that observations better match simulations if Io is considered to be partly fluid.

Today, Hamilton leads a research group that’s studying volcanic processes on Earth to understand how these processes can shape the surfaces of other worlds. The team is devising a proposal to NASA to study Io’s tidal heating more thoroughly with the aid of a computer algorithm that can identify patterns of tidal heating captured in hundreds of thousands of satellite images.   

He’s also working with Kerber on a proposal to NASA for a low-cost mission to send a rover to Earth’s moon to rappel into ancient lava tubes known as skylights. The desire to understand how these tubes formed and what they’re made of is reminiscent of one of Hamilton’s earliest studies, in which he reconstructed how lava channels formed from a 1970s lava flow at Hawaii’s Kilauea volcano.

A theme runs through Hamilton’s work: To truly explore — and, possibly, someday inhabit — other worlds, scientists must first understand what materials and resources are available on those worlds. It is, in a way, another kind of architecture.

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