Front Image: InSight’s first full selfie taken on Mars’ surface in December, 2018. cr. NASA
After Two Mission Extensions, NASA Retires Mars InSight Lander
By: Linda Grimm
On December 21, 2022, NASA announced the official retirement of its Mars InSight lander and the conclusion of four years of unprecedented data collection on the Red Planet. The agency decided after two consecutive attempts to contact the lander via the Mars Relay Network failed. The lander’s last communication had been received on December 15. The loss of contact was predicted by mission engineers, who had been tracking the steady decline of InSight’s power levels as dust accumulated on its two, seven-foot-long solar panels.
“While saying goodbye to a spacecraft is always sad, the fascinating science InSight conducted is cause for celebration,” said Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate. “The seismic data alone from this Discovery Program mission offers tremendous insights not just into Mars but other rocky bodies, including Earth.”
Launched on May 5, 2018, from Vandenberg Air Force Base in California, InSight (Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport) was designed to study the Red Planet’s deep interior to help scientists understand how the rocky planets of the inner solar system—Earth, Mercury, Venus, and Mars—formed and evolved over time. This made it unique among NASA’s missions to Mars, which had previously focused on exploring the planet’s surface. InSight’s science goals included determining the size, thickness, density, and structure of Mars’ core, mantle, and crust. It was also tasked with studying Mars’ present-day tectonic activity and meteorite impacts, as well as the rate at which heat continued to escape from the planet’s interior. Scientists consider Mars to be an ideal target for this type of planetary research because it is large enough to have undergone the same internal heating and differentiation processes experienced by other terrestrial planets, but, unlike Earth, it is also small enough to have retained a geologic record of those processes for more than four billion years.
To conduct its investigations, InSight was equipped with a science payload comprised of two main instruments: the Seismic Experiment for Interior Structure (SEIS), provided by the French Space Agency (CNES), and the Heat Flow and Physical Properties Package (HP3), provided by the German Space Agency (DLR). InSight also carried the Auxiliary Payload Sensor Suite (APSS), which enabled it to collect continuous weather data—and even, during its prime mission, to provide daily “weather reports” from Mars.
InSight’s extensive data collection began shortly after it landed at Mars’ Elysium Planitia on November 26, 2018. In its roughly four years of operation, the lander detected 1,319 marsquakes, the largest of which occurred in May 2022 and measured a magnitude of 5. Some of these marsquakes were caused by meteoroid impacts, including one event with a magnitude of 4 that was detected in 2021. This impact was particularly notable because it churned up boulder-sized pieces of water ice in an unexpected location that may now become a future landing site for crewed missions to Mars.
Observing how seismic waves from these quakes traveled through the planet provided scientists with information about the composition and thickness of Mars’ interior layers. Data gathered by InSight enabled scientists to confirm that Mars’ core is both molten and, with a radius of about 1,120 miles, surprisingly large. Measuring the core’s size was a significant achievement in and of itself. “It took scientists hundreds of years to measure Earth’s core; after the Apollo missions, it took them 40 years to measure the Moon’s core,” noted Simon Stähler, a professor at the Swiss research university ETH Zurich and lead author of a paper on the topic. “InSight took just two years to measure Mars’ core.” Scientists have also learned that Mars’ crust is thinner than initially projected, measuring somewhere between 15 and 25 miles deep, and it is comprised of three sub-layers. These discoveries have prompted scientists to revise their models of planetary formation. “We’ve already been able to eliminate probably two-thirds of the models for planetary formation that are out there, just by looking at the size and density of the core and the thickness of the crust,” said Bruce Banerdt, InSight principal investigator for NASA’s Jet Propulsion Laboratory, which controlled the lander.
One major challenge encountered early in the mission prevented InSight from measuring the thermal state of Mars’ interior. The lander was equipped with a self-hammering spike known as “the mole” that was supposed to dig a 16-foot-deep hole, into which a 16-inch heat-sensing probe would be dropped. The spike was designed to penetrate the sandy, loose type of soil found on prior missions to Mars, however, the dirt surrounding the lander was clumpier and prevented the mole from gaining sufficient traction. Despite their persistent troubleshooting attempts, mission engineers could not resolve the issue and ultimately settled on burying the probe just below the planet’s surface. This enabled the lander to gather new data on the physical and thermal properties of Martian soil.
Additionally, InSight collected extensive weather data from the planet’s surface. Its sensors detected thousands of dust devils, observed various weather fronts, and measured everything from turbulence to bore waves.
Creative use of the lander’s robotic arm to remove some of the dust from its solar panels, combined with a near-total shutdown in the summer of 2022, helped to stretch InSight’s battery life well beyond its two-year prime mission, which concluded in November 2020. NASA twice extended the mission’s duration, acknowledging that InSight had “produced exceptional science.” Although the lander is no longer operational, the unique and voluminous data it collected has been archived and made available to the global scientific community. Banerdt said he expects scientists to continue analyzing mission data for decades to come.
“Before InSight, the interior of Mars was a giant question mark,” he said. “We just had this really fuzzy picture of what was going on inside Mars. Now we can actually draw a quantitatively precise picture.”
About the author: Linda Grimm is a professional writer-editor from the Washington D.C. metro area. She writes for publishing companies, trade and professional associations, and academic institutions, among others.