NASA’s Psyche spacecraft completed a highly successful flyby of Mars, giving the mission a carefully planned gravitational boost while also producing valuable scientific data. Researchers are now examining those observations as they prepare for the spacecraft’s arrival at the asteroid Psyche in 2029.
On May 15, the spacecraft passed Mars and used the planet’s gravity to increase its speed and make a slight adjustment to its path. The maneuver placed Psyche on the trajectory needed to reach its metal-rich target in the main asteroid belt.
The encounter also offered mission scientists a rare chance to test the spacecraft’s instruments around a well-studied planet. Mars served as a practice target for the tools that will eventually investigate Psyche. Data returned after the flyby showed that the instruments performed as expected and matched established knowledge about Mars, while also adding several useful observations from the spacecraft’s unusual viewing position.
“The mission’s imager, magnetometer, and gamma-ray and neutron spectrometer teams worked overtime to make full use of this planetary encounter, and all instruments delivered great results,” said Lindy Elkins-Tanton, principal investigator for Psyche at the University of California, Berkeley. “We didn’t anticipate big discoveries, given how extensively the planet has been studied, but we did complement Mars science with the data we collected through Psyche’s unique perspective.”
Psyche Detects Neutrons From Mars
The gamma-ray and neutron spectrometer received an important test during the flyby. At asteroid Psyche, the instrument will help scientists identify the chemical elements present in the object’s surface material.
When high-energy cosmic rays strike a planetary body, they transfer energy to elements at the surface. Those elements can then release neutrons and gamma rays at different energy levels. By measuring those signals and comparing them with known elemental signatures, researchers can determine what a world is made of.
Psyche passed Mars at an altitude of 2,864 miles (4,609 kilometers). That distance was too great for the instrument to detect gamma rays coming from the planet, but scientists believed it might still register neutrons escaping from the Martian surface and atmosphere.
“Around the time of Mars closest approach, the neutron spectrometer detected a count-rate enhancement close to what we anticipated. It was very gratifying to see,” said David Lawrence, the science lead for Psyche’s spectrometer at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland. “As expected, we didn’t detect gamma rays from Mars, but we put the instrument through its paces, and it performed excellently.”
Measuring Mars’ Magnetic Environment
Psyche’s magnetometer has been operating since the spacecraft launched in 2023. Its main purpose is to study the magnetic field of asteroid Psyche and help researchers investigate whether the object could be the exposed metallic core of a planetesimal, an early building block of a rocky planet.
During the cruise, the magnetometer has continuously monitored the magnetic field carried by the solar wind. It has also recorded disturbances caused by occasional coronal mass ejections passing over the spacecraft. The Mars flyby, however, marked the first time the instrument measured the magnetic signature of a celestial body.
“As the spacecraft passed close to Mars, the magnetometer saw an intense uptick in magnetic field corresponding to the bow shock region, where the solar wind slams into the planet’s magnetic field,” said Ben Weiss, Psyche’s deputy principal investigator and the magnetometry investigation lead at Massachusetts Institute of Technology in Cambridge. “This flyby calibration effort validated the instrument’s performance under dynamic conditions while also revealing the fascinating physics of planetary magnetism.”
Rare Images of the Red Planet
Psyche’s multispectral imager began returning views of Mars in early May and continued observing the planet throughout the flyby. The instrument consists of two identical cameras designed to photograph asteroid Psyche in multiple wavelengths of light.
Because the spacecraft approached Mars at a high-phase angle, the planet first appeared as a narrow, bright crescent. Sunlight scattering through the Martian atmosphere helped create the striking view.
As Psyche moved closer, the cameras recorded detailed features on the surface, including wind-shaped craters, the south polar ice cap, and the large double-ringed Huygens crater. The full monthlong sequence was assembled into a time-lapse video showing the spacecraft’s approach and departure. [See link to video after the end of the article.]
“The imager performed brilliantly, delivering some rarely seen views of the Red Planet,” said Jim Bell, the Psyche imager instrument lead at Arizona State University in Tempe. “Besides the obvious beauty of the photos, we were also able to fully test its calibration and sensitivity to scattered light, including picking out the Martian moons Phobos and Deimos from very far away as a part of a practice for the satellite search that we’ll use at the asteroid Psyche to look for any moonlets there.”
The distant detections of Phobos and Deimos served as a rehearsal for the mission’s future search for small moons around asteroid Psyche.
Comparing Psyche’s Mars Images With Other Missions
To evaluate and calibrate the imager, researchers are comparing Psyche’s flyby observations with data collected by other spacecraft and rovers at Mars.
Those sources include NASA’s Mars Reconnaissance Orbiter, 2001 Mars Odyssey orbiter, and Curiosity and Perseverance rovers, along with ESA’s (European Space Agency’s) Mars Express and ExoMars Trace Gas Orbiter, and the United Arab Emirates Mars Mission’s Hope Orbiter.
These comparisons will help the team better understand the cameras’ performance before Psyche begins studying its much less familiar asteroid target.
On Course for Asteroid Psyche in 2029
Following the successful gravity assist, the spacecraft is now traveling directly toward asteroid Psyche, which orbits in the main asteroid belt between Mars and Jupiter.
“This gravity assist was years in the making, and the navigation team nailed it — Psyche flew by Mars on exactly the trajectory we needed to set us on a path to rendezvous with the asteroid in the summer of 2029,” said Bob Mase, Psyche’s project manager at NASA’s Jet Propulsion Laboratory in Southern California. “The spacecraft is in great shape, and we’re on schedule to resume sustained thrusting with the solar-electric propulsion system later this fall.”
