The number attached to asteroid 16 Psyche is so large that it almost stops being a number. Around $10,000 quadrillion. Ten quintillion dollars. More than the annual output of the entire world economy by orders of magnitude.

That figure has followed Psyche for years because the asteroid is not an ordinary carbon-rich or stony body. It is a large, metal-rich object in the main asteroid belt between Mars and Jupiter, and scientists have long suspected that it contains enormous amounts of iron and nickel. If someone takes a rough estimate of that metal and multiplies it by terrestrial commodity prices, the result is the kind of figure that sounds less like economics than astronomy wearing a dollar sign.

But the useful way to read the number is not as a mining forecast. It is not an asset valuation. It is not evidence that a future company could retrieve the asteroid, sell its contents and become richer than Earth. It is a scale marker: a way of saying that Psyche may contain more metal than human markets are built to imagine.

A metal-rich world, not a gold bar

NASA describes Psyche as one of the most intriguing objects in the main asteroid belt: a giant metal-rich asteroid roughly 140 miles, or 226 kilometres, wide in one common shorthand description. Its actual shape is irregular and potato-like. NASA’s asteroid page says that if Psyche were sliced through the equator, it would measure about 173 miles by 144 miles, or 280 by 232 kilometres, across that section.

The asteroid orbits the Sun roughly three times farther out than Earth, between Mars and Jupiter. It was discovered in 1852 by Italian astronomer Annibale de Gasparis and is called 16 Psyche because it was the 16th asteroid discovered. What makes it unusual is not its orbit, but its composition.

For a long time, Psyche was often described as a possible exposed core of an early planetesimal: a building block of a planet that may have been stripped of its outer layers by violent collisions. The appeal of that idea is obvious. Earth has an iron-rich core, but we cannot visit it. A remnant core in space would let scientists study something like planetary interior material directly, from orbit.

The newer picture is more complicated. NASA now says the best analysis indicates Psyche is probably a mixture of rock and metal, with metal making up about 30% to 60% of its volume. That is still extraordinary for an asteroid of this size, but it is not the same as a solid sphere of nickel-iron.

Where the valuation comes from

The $10,000 quadrillion figure is a back-of-the-envelope calculation. It asks a deliberately artificial question: if Psyche contains vast amounts of iron and nickel, and if those metals were valued at current Earth prices, what would the total theoretical number look like?

That calculation quickly runs into absurdity. A value of $10,000 quadrillion is $10 quintillion. Current global output is measured in the low hundreds of trillions of dollars, not quintillions. The comparison is therefore not close. Psyche’s theoretical metal value is not just bigger than the world economy; it belongs to a different scale of arithmetic.

Yet the word “value” needs careful handling. Markets are not simple multiplication machines. If an impossible quantity of nickel or iron suddenly appeared for sale, the price would not remain unchanged. Supply would alter the market. Delivery costs would matter. Extraction costs would matter. Legal and political questions would matter. Most of all, the asteroid is hundreds of millions of kilometres away in the main belt, and no human technology is close to mining and returning such material at economic scale.

So the valuation is best treated as a thought experiment. It tells us that Psyche is metal-rich enough to strain ordinary comparisons. It does not tell us that Psyche is a trillionaire’s quarry waiting to be claimed.

Why NASA is going there

NASA’s Psyche mission is not a mining mission. It is a planetary science mission. The Psyche spacecraft launched on October 13, 2023, and is on its way to the asteroid after a Mars gravity assist on May 15, 2026. NASA says asteroid Psyche’s gravity should capture the spacecraft in late July 2029, with the prime mission beginning in August and lasting about two years.

Once there, the spacecraft will orbit the asteroid and map it using a multispectral imager, a gamma-ray and neutron spectrometer, a magnetometer and a radio science investigation for gravity measurements. Those instruments are meant to answer basic questions that telescopes from Earth cannot settle: what Psyche is made of, whether it carries a magnetic record, how its surface varies and whether it really resembles the exposed core of a small early world.

That last question is the scientific centre of the mission. If Psyche is a remnant core, it could offer a rare indirect view into the formation of rocky planets. If it is instead a mixed body with metal-rich regions, silicates, impact debris and a complicated surface history, that answer is also valuable. It would show that some objects we once sorted into neat categories are actually products of repeated collisions and partial differentiation.

Recent research has leaned toward that more complicated story. A 2021 Planetary Science Journal paper led by Michael Shepard reported a shape model and radar analysis suggesting that Psyche’s upper regolith has significant iron-nickel content, but the authors could not reduce the asteroid to a simple pure-core model. Their preferred interpretation was a differentiated world whose surface is peppered with localized regions of high metal concentration.

The metal may be uneven

That unevenness matters. If Psyche’s metal were concentrated in patches, mixed with silicate material or present in surface layers rather than throughout the whole asteroid, then any simple market-value calculation becomes even more fragile. The asteroid could still contain immense metal resources in a physical sense while being far less straightforward than the popular number implies.

Other studies have pointed in the same direction. Laboratory spectral work has explored mixtures of metal, pyroxene and carbonaceous material as possible analogues for Psyche’s surface. Thermal and polarization studies have also suggested that the surface may be heterogeneous, with metal-rich and silicate-rich regions distributed unevenly across the asteroid.

NASA’s own summary reflects that uncertainty. It says the asteroid’s composition has been inferred from radar observations and thermal inertia, but adds that until the Psyche spacecraft sees the asteroid up close, we will not know what it actually looks like. That sentence is the brake on all the stronger claims. Psyche may be one of the most metal-rich worlds we have ever studied, but it has not yet been visited.

The economy is the wrong measuring stick

The temptation with Psyche is to tell the story as a buried treasure tale. A metal world bigger than many countries. A price tag too large for ordinary speech. A spacecraft on the way. The ingredients almost write the wrong article by themselves.

But Psyche is more interesting when the dollar sign is put back in proportion. The asteroid is not valuable because it could be sold tomorrow. It is valuable because it may preserve information about the violent period when the solar system was assembling planets from smaller bodies. It may show us what happens when metal, rock, heat and collisions interact inside a world that never became a planet.

The mining thought experiment still has a purpose. It reminds us that the asteroid belt contains material on scales Earth industries rarely consider. Iron and nickel are ordinary metals on Earth, but in the context of planet formation they are also the stuff of cores, magnetic fields and differentiated worlds. Psyche turns that familiar material into a planetary question.

By the time NASA’s spacecraft arrives in 2029, the headline number may matter less than the measurements. Is Psyche truly a remnant planetary core? Is it a mixed rock-metal body shaped by impacts? Are its metallic regions global, local, deep or superficial? Does it carry magnetization from an ancient dynamo?

Those answers will not make the asteroid spendable. They may do something better: explain what kind of world Psyche actually is, and why a body rich in iron and nickel ended up orbiting quietly between Mars and Jupiter, carrying a theoretical price tag no real economy could absorb.

Sources

NASA Science: Asteroid Psyche overview
NASA Science: Psyche mission page
NASA: Psyche mission aces Mars flyby, targets metal-rich asteroid
Shepard et al., 2021: Asteroid 16 Psyche shape, features and global map
Cantillo et al., 2021: Constraining the regolith composition of asteroid 16 Psyche
Live Science report on Psyche valuation and ferrovolcanism research