Exploring the Mysteries of the Interior of the Earth with the Psyche Mission

Friday - September 1 2023, 13:11 UTC - 1 year ago

French novelist Jules Verne tantalised 19th-century readers with the idea of a journey to the center of the Earth. Now, scientists are planning to do the impossible with NASA's Psyche mission, a robotic mission to explore a metallic world in the asteroid belt. The mission aims to understand the nature of metal worlds, planet formation, and the catalog of planets in the Milky Way.

French novelist Jules Verne delighted 19th-century readers with the tantalizing notion that a journey to the center of the Earth was actually plausible. Since then, scientists have long acknowledged that Verne’s literary journey was only science fiction. The extreme temperatures of the Earth’s interior—around 10,000 degrees Fahrenheit (5,537 Celsius) at the core—and the accompanying crushing pressure, which is millions of times more than at the surface, prevent people from venturing down very far.

Still, there are a few things known about the Earth’s interior. For example, geophysicists discovered that the core consists of a solid sphere of iron and nickel that comprises 20 percent of the Earth’s radius, surrounded by a shell of molten iron and nickel that spans an additional 15 percent of Earth’s radius. That, and the rest of our knowledge about our world’s interior, was learned indirectly—either by studying Earth’s magnetic field or the way earthquake waves bounce off different layers below the Earth’s surface.

But indirect discovery has its limitations. How can scientists find out more about our planet’s deep interior? Planetary scientists like me think the best way to learn about inner Earth is in outer space. NASA’s robotic mission to a metal world is scheduled for liftoff on Oct. 5, 2023. That mission, the spacecraft traveling there, and the world it will explore all have the same name—Psyche. And for six years now, I’ve been part of NASA’s Psyche team.

About the Asteroid Psyche .

Asteroids are small worlds, with some the size of small cities and others as large as small countries. They are the leftover building blocks from our solar system’s early and violent period, a time of planetary formation. Although most are rocky, icy, or a combination of both, perhaps 20 percent of asteroids are worlds made of metal similar in composition to the Earth’s core. So it’s tempting to imagine that these metallic asteroids are pieces of the cores of once-existing planets, ripped apart by ancient cosmic collisions with each other. Maybe, by studying these pieces, scientists could find out directly what a planetary core is like. Psyche is the largest-known of the metallic asteroids. Discovered in 1852, Psyche has the width of Massachusetts, a squashed spherical shape reminiscent of a pincushion, and an orbit between Mars and Jupiter in the main asteroid belt. An amateur astronomer can see Psyche with a backyard telescope, but it appears only as a pinpoint of light.

About the Psyche Mission .

In early 2017, NASA approved the $1 billion mission to Psyche. To do its work, there’s no need for the uncrewed spacecraft to land—instead, it will orbit the asteroid repeatedly and methodically, starting from 435 miles (700 kilometers) out and then going down to 46 miles (75 km) from the surface, and perhaps even lower. Once it arrives in August 2029, the probe will spend 26 months mapping the asteroid’s geology, topography, and gravity; it will search for evidence of a magnetic field; and it will compare the asteroid’s composition with what scientists know, or think we know, about Earth’s core. The central questions are these: What are metal worlds like? What can they tell us about planet formation and the catalog of planets in the Milky Way? .