A billion miles from Earth and counting, NASA's Psyche spacecraft just passed one of its biggest tests — and aced it.
On July 28, the spacecraft completed a successful Mars gravity-assist flyby, swinging around the Red Planet to gain the speed and orbital trajectory needed to reach its ultimate destination: the metal-rich asteroid 16 Psyche. The maneuver was a critical milestone for the mission, and by all accounts, it went flawlessly.
A slingshot through the solar system
Gravity-assist maneuvers are one of the great elegant tricks in spaceflight. Rather than burning extra fuel to accelerate, a spacecraft flies close to a massive planet, stealing a small amount of its orbital momentum to boost its own speed. It is the same physics that allowed Voyager 1 and 2 to reach the outer solar system decades ago.
For Psyche, the Mars flyby was essential. The spacecraft, which launched in October 2023, does not carry enough propellant to travel directly to asteroid 16 Psyche under its own power. The Mars slingshot provides the extra velocity needed for the journey.
"The team is just thrilled," said Lindy Elkins-Tanton, the mission's principal investigator at Arizona State University. "We have been working toward this moment for years. Seeing everything perform as expected is deeply satisfying."
Eyes wide open
As Psyche swept past Mars at roughly 2,600 miles above the Martian surface, the spacecraft was more than a passive traveler. The flyby was a prime opportunity to put all of its scientific instruments through a real-world test.
The magnetometer — designed to measure the magnetic field of asteroid 16 Psyche — took readings near Mars. The mass spectrometer sampled charged particles in the Martian environment. The multispectral imager captured photographs of the Martian surface and even caught a remarkable glimpse of Phobos, one of Mars's two moons. All instruments performed as designed.
"This was our shakedown cruise," said David Oh, the mission's chief engineer at NASA's Jet Propulsion Laboratory. "We wanted to make sure everything works before we get to Psyche. And it does."
What waits at the end of the journey
Asteroid 16 Psyche is unlike anything humanity has visited before. Most asteroids are rocky or icy — remnants of the early solar system. Psyche appears to be made largely of metal: iron, nickel, and other heavy elements that are typically found deep inside planets, not exposed at the surface.
Scientists believe 16 Psyche may be the exposed core of an ancient protoplanet — a world that formed early in solar system history and was stripped of its rocky outer layers through catastrophic collisions. If true, visiting Psyche would give us our first direct look at the kind of material that forms the hidden hearts of rocky worlds, including Earth.
The spacecraft is now on course for its 2029 arrival, where it will spend approximately two years in orbit mapping the surface, measuring composition, and studying the asteroid's magnetic field. The data could fundamentally reshape our understanding of how planets form and what lies beneath their surfaces.
A mission that endured
Psyche had a bumpy road to launch. A software delivery delay in 2022 forced the mission to miss its original launch window, pushing it back a full year and adding considerable cost. NASA conducted a thorough review of the mission before giving it the green light to proceed.
Now, with the Mars flyby in the books and every instrument working perfectly, the team is focused on what lies ahead. In 2029, Psyche will become the first spacecraft to orbit a metallic asteroid — opening a window onto the deep interior architecture of planets.
