When NASA announced in May that the InSight Mars lander was shutting down after a 4-year mission studying the planet’s crust, mantle, and core, headlines focused on the robot’s landmark discoveries about seismic activity and marsquakes.
“We’ve been waiting forever to get a magnetometer on the surface of Mars. So these results have been really impactful.”
But although they’ve received less attention, a secondary set of observations is also leading to important discoveries about the Red Planet’s weather and environment, including the first measurements of magnetism taken from Mars’s surface.
“We’ve been waiting forever to get a magnetometer on the surface of Mars,” said Rob Lillis, associate director of planetary science at the University of California, Berkeley. “So these results have been really impactful.”
First Look at Magnetism from the Surface
The magnetometer is part of InSight’s Auxiliary Payload Sensor Suite. This group of instruments, which also includes sensors measuring wind, temperature, and pressure, was originally intended to monitor and measure conditions that could affect the lander’s seismic readings.
“Their primary purpose was basically to be a support suite for the seismometer,” said Catherine Johnson, coinvestigator on the InSight science team and a professor in the Department of Earth, Ocean and Atmospheric Sciences at the University of British Columbia, who has been working with the lander’s magnetism data.
But even though the instruments were more limited than they would have been on a mission entirely dedicated to those observations, they still offered an unprecedented opportunity to gather data from the planet’s surface, she said. Scientists could create a more complete picture of the overall weather patterns around InSight and the nearby Curiosity rover and add on-the-ground magnetism measurements that complement orbital observations from satellites like MAVEN (Mars Atmosphere and Volatile Evolution) and the Mars Global Surveyor.
“We knew quite a bit about the magnetic field environment of the planet, but all of those observations came from above the atmosphere,” Johnson said. “This was our first chance to get a look at it on the surface of the planet.”
Magnetism researchers focused on two key groups of scientific questions. One group focused on crustal magnetism. Although Mars now lacks a planetary magnetic field, these rocks indicate that such a field once existed.
“Learning about these rocks is actually very important because it can help us better constrain the timing and strength of this ancient magnetic field on Mars,” Johnson said. “All this is tied to the overarching goal of InSight, which is to understand the interior structure and evolution of the planet.”
Previously, Mars orbiters had observed that the planet’s crustal magnetic fields were much stronger than Earth’s, Lillis noted. Scientists wanted to know if this was entirely due to the magnetization in the rocks themselves or if other factors contributed.
“Magnetic fields are cool because they connect the deep interior of the planet not just to the atmosphere but to the space around it.”
In fact, InSight found that the rocks were even more strongly magnetized than previously thought. “We thought maybe the fields…might be 100 nanotesla,” he said. “Turns out they were about 2,000 nanotesla—20 times stronger than any model had predicted.”
The second group of magnetism questions focused on how the magnetic field at the landing site would change over time, Johnson said. A number of factors contribute to fluctuations in magnetic fields, including space weather, the planet’s day-night cycle, and electrical currents generated in Mars’s weak atmosphere.
Understanding these fluctuations can provide insights to help explain the planet’s climate and atmospheric patterns. It can also lead to better understanding of space weather.
“These are also system-wide questions that are about understanding the planet as a whole,” Johnson said. “Magnetic fields are cool because they connect the deep interior of the planet not just to the atmosphere but to the space around it.”
It was especially helpful to have simultaneous observations from InSight on the surface and MAVEN in orbit, Lillis said.
A Bittersweet Ending
Johnson said she had mixed feelings on seeing the mission coming to an end.
“We’ve met and exceeded our primary mission goals and learned more than we had planned,” she said. “But the sad part is that all of the instruments have been working really well. It’s not like the instruments are deteriorating or we’re not getting good data anymore.” The mission will end because its dust-crusted solar panels will no longer be able to power the lander.
The timing is especially unfortunate because the Sun is now heading into solar maximum, a multiyear period of increased solar activity that would have led to interesting magnetism observations, she added.
Although InSight may be shutting down, it’s not the end of studying magnetism from the surface of Mars. Johnson and Lillis noted that the Chinese rover Zhurong is equipped with a magnetometer, and they said they hoped its observations would be made public soon. They also said InSight had laid the groundwork and served as a proof of concept for future NASA missions to study Mars’s magnetic fields in greater detail.
“This just gave us a little taste,” Lillis said, “but it’s a very tantalizing taste.”
—Ilima Loomis (@iloomis), Science Writer