NASA's InSight lander revealed the heart of Mars — here's how

The InSight lander reached Mars' surface on Nov. 26, 2018. Though the mission has come to an end, the Insight mission has overseen a number of successes and one notable failure over a roughly four-year period — more than double the original intended mission time of two years.

Crucially, it has beamed a wealth of data back to Earth for scientists to analyze.

"The seismic dataset is amazing. From tiny local quakes to tectonic events on the far side of Mars and then confirmed impacts," Anna Harleston, a seismologist at the University of Bristol and co-lead of NASA InSight's Marsquake Service, told IE in an interview over email.

"We could not have asked for more from InSight."

Mars provides a window into the Earth's past

NASA's goal with the InSight lander mission was to better understand the evolution of Mars as a planet. This, in turn, would allow them to shed new light on planetary evolution as a whole. 

Unlike Earth, the red planet has no tectonic plates. During its early evolution, Mars did experience internal heating and separation into layers.

After a relatively short billion-year period, however, the planet cooled off, leaving behind an interior structure that has remained much the same in the intervening billions of years.

"Being half the size of the Earth," Harleston said, "the pressures and temperatures inside Mars are much lower than on Earth so we do not see all the geochemical transitions we see within the Earth."

"Mars has a crust — not unlike Earth's, but it is shattered at the surface from impact processes," Harleston continued.

"Below this, the mantle extends all the way to the core, with no clear boundary layers or discontinuities. That is unlike Earth, where we see a clear transition zone and mineralogical phase changes."

My power’s really low, so this may be the last image I can send. Don’t worry about me though: my time here has been both productive and serene. If I can keep talking to my mission team, I will – but I’ll be signing off here soon. Thanks for staying with me. pic.twitter.com/wkYKww15kQ

— NASA InSight (@NASAInSight) December 19, 2022

Essentially, Mars' composition means it provides a window into a period of planetary evolution that Earth left behind three billion years ago.

According to NASA's website, those conditions mean Mars may provide "the most in-depth and accurate record in the solar system of [geological] processes."

As with several other Mars missions, the InSight lander's solar panels were eventually obscured by Martian dust, preventing the spacecraft from drawing on its main energy source — solar power.

Before that happened, it was able to tap into the historic record of planetary evolution hiding beneath the Martian surface.

Revealing mysteries deep beneath the Martian surface

Alongside its several cameras, InSight features a seismometer, nicknamed "the mole", that was designed to hammer 5 m (16 ft) into the Martian soil to measure heat loss.

It also had a radio sensor that could detect planetary motion, meaning it could collect data on the red planet's mass and density. Finally, a magnetometer allowed it to analyze the planet's magnetic field history.

Unfortunately, the Insight lander's "mole" instrument was never able to reach its intended depth and was only able to burrow 0.35 m (1.1 ft.) under the surface.

This occurred due to soil clumping around the drill. Though it was undoubtedly a costly failure, NASA said it has gained new knowledge on the properties of Martian soil that it can carry over to other missions.

The spacecraft did, however, send seismic waves into the interior of Mars which it used to then measure the thickness of its layers by analyzing their reflection. The mission found that the planet's crust is thinner than previously believed, measuring roughly 25 to 40 kilometers (15 to 25 miles) in depth.

Mars' molten core, meanwhile, measures about 3,600 km (2,240 miles) in diameter, which is large for a planet that has a 6,779 km (4,212 miles) diameter.

Thanks to its instruments, NASA points out, InSight became the first spacecraft to detect seismic activity on Mars. During its mission, the lander detected over 1,300 active marsquakes. 50 of those were powerful enough that researchers were able to pinpoint their epicenter, or origin point.

"Mars has no plate tectonics so marsquakes are caused by stress release on pre-existing faults driven by planetary cooling," Harleston explained in her email exchange with IE.

"Most marsquakes we've observed are small in magnitude and, due to the fractured crust, the signals are highly scattered," she continued.

"However, we have seen some larger events which have much clearer signals, the majority of which originate in Cerberus Fossae, an area thought to have the most recent volcanism on Mars. These are likely caused by cooling around the dikes underlying the faults we see in this region."

NASA's InSight lander legacy lives on

The strongest quake InSight detected during its scientific operations was a magnitude 5 on May 4, 2022, which shook the planet for a total of six hours.

"We have also recorded the seismic shock waves from a handful of impacts — three close to InSight and two, large impacts at greater distances," Harleston said.

"The craters have been imaged using the cameras on the Mars Reconnaissance Orbiter and the time of formation fits with the source time for the marsquake signatures."

Though NASA's InSight lander has allowed scientists to peer beneath Mars' surface like never before, there is still a lot we don't yet know about the red planet.

The mission to uncover the red planet's mysteries continues, even as InSight — officially retired as of Dec. 21, 2022 — is lost beneath a layer of fine Martian dust.

"As far as we know so far, the core of Mars is large and liquid and we have not yet determined if there is an inner core," Harleston said.

"The temperatures and pressures are likely to be incompatible with the formation of a solid inner core in Mars but we will keep searching the seismic data to look for phases that may tell us more."