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 currently studying these observations in preparation for the spacecraft’s arrival at the asteroid Psyche in 2029.
On May 15, the spacecraft passed Mars, using Mars’ gravity to increase its speed and slightly adjust its orbit. This maneuver placed Psyche in the orbit needed to reach metal-rich targets in the main asteroid belt.
The encounter also provided mission scientists with a rare opportunity to test the spacecraft’s instruments around a well-studied planet. Mars ultimately served as a training object for the tools to investigate Psyche. Data returned after the flyby showed that the instruments performed as expected and were consistent with established knowledge about Mars, while also adding some useful observations from the spacecraft’s unusual observing position.
“The mission’s imager, magnetometer, and gamma-ray and neutron spectrometer teams worked overtime to make the most of this planetary encounter, and all instruments delivered impressive results,” said Lindy Elkins Tanton, principal investigator for Psych Research at the University of California, Berkeley. “We didn’t expect any major discoveries given Mars has been extensively studied, but we were able to complement Mars science with the data we collected through Psyche’s unique perspective.”
Psyche detects neutrons from Mars
Gamma-ray and neutron spectrometers underwent important tests during the flyby. On the asteroid Psyche, this instrument will help scientists identify the chemical elements present in the object’s surface material.
When high-energy cosmic rays hit a planetary body, energy is transferred to the elements on the surface. These elements can emit neutrons and gamma rays at different energy levels. By measuring those signals and comparing them to known elemental signatures, researchers can determine what the world is made of.
Psyche passed Mars at an altitude of 2,864 miles (4,609 kilometers). That distance was too far for the instrument to detect gamma rays coming from the planet, but scientists believed it might still be recording neutrons leaking from Mars’ surface and atmosphere.
“Around Mars’ closest approach, the neutron spectrometer detected an increase in count rate that was close to what we expected, and we were very happy to see that,” said David Lawrence, scientific director of the Psyche spectrometer at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland. “As expected, we did not detect any gamma rays from Mars, but when we put the device through its paces, it performed admirably.”
Measuring Mars’ magnetic environment
Psyche’s magnetometer has been operational since the spacecraft’s launch in 2023. Its main purpose is to study the asteroid Psyche’s magnetic field and help researchers investigate whether the object could be the exposed metallic core of a planetesimal, an early building block of rocky planets.
During the cruise, magnetometers continuously monitored the magnetic field carried by the solar wind. Disturbances caused by occasional coronal mass ejections passing over the spacecraft have also been recorded. But the Mars flyby marked the first time the instrument had measured the magnetic signature of a celestial body.
“As the spacecraft passed close to Mars, the magnetometer observed a strong rise in the magnetic field, corresponding to the bow shock region, where the solar wind collides with Mars’ magnetic field,” said Ben Weiss, Psyche’s deputy principal investigator and magnetometer investigator at the Massachusetts Institute of Technology in Cambridge. “This flyby calibration effort validates the instrument’s performance under dynamic conditions while also revealing the interesting physics of planetary magnetism.”
Unusual images of the red planet
Psyche’s multispectral imager began returning views of Mars in early May and continued to observe Mars throughout the flyby. The instrument consists of two identical cameras designed to image the asteroid Psyche in multiple wavelengths of light.
The spacecraft approached Mars at a high phase angle, so Mars initially looked like a thin, bright crescent moon. Sunlight scattering through Mars’ atmosphere helped create the impressive scenery.
As Psyche approached, the cameras recorded detailed features on the surface, including wind-shaped craters, the Antarctic ice sheet, and the large double-ring Huygens crater. The entire month-long sequence was compiled into a time-lapse video showing the spacecraft’s approach and departure. (See link to video at the end of the article.)
“The imager worked beautifully and delivered a rarely seen view of the Red Planet,” said Jim Bell, head of the Psyche Imager instrument at Arizona State University in Tempe. “In addition to the obvious beauty of the photo, we were also able to thoroughly test its calibration and sensitivity to scattered light, including spotting the Martian moons Phobos and Deimos from great distances as part of the satellite search exercise we use to search for asteroids with asteroid Psyche.”
The long-range detections of Phobos and Deimos served as a rehearsal for future missions to search for small moons around the asteroid Psyche.
Compare 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 Mars rovers and rovers.
These sources include NASA’s Mars Reconnaissance Orbiter, 2001 Mars Odyssey Orbiter, Curiosity and Perseverance spacecraft, as well as ESA’s Mars Express and ExoMars Trace Gas Orbiters, and the United Arab Emirates Mars Mission’s Hope Orbiter.
These comparisons will help the team better understand the camera’s performance before Psyche begins studying less familiar asteroid targets.
Orbiting the asteroid Psyche in 2029
After a successful gravity assist, the spacecraft is now flying directly toward the asteroid Psyche, which orbits the main asteroid belt between Mars and Jupiter.
“This gravitational assist feature was developed over many years, and our navigation team pulled it off with flying colors. Psyche flew by Mars in exactly the orbit we needed to set it on a path to rendezvous with the asteroid in summer 2029,” said Bob Mace, Psyche’s project manager at NASA’s Jet Propulsion Laboratory in Southern California. “The spacecraft is in very good condition and we plan to resume sustained propulsion with our solar-powered propulsion system later this fall.”
