NASA InSight lander spills the beans on Mars' core

The lander might be dead, but its scientific legacy lives on

NASA's Mars InSight lander may be dead, but the data it gathered is still filled with surprises – like the first direct observations of another planet's core, which scientists now believe is smaller and denser than previously thought.

In a paper published this week in the Proceedings of the National Academy of Sciences, a team of scientists poring over InSight's data found that two Marsquakes recorded in 2021 produced seismic waves that passed right through Mars' core, an event that had never before been captured. 

The pair of quakes were also the first that InSight detected from the far side of Mars, which made them harder to pick out from the background noise picked up by InSight's seismological instruments, but also ideal for observing the Martian depths. The further a quake is from InSight, NASA said, the deeper into the planet those waves have to go to be detected.

"Farside quakes are intrinsically harder to detect because a great deal of energy is lost or diverted away as seismic waves travel through the planet. We needed both luck and skill to find, and then use, these quakes," said lead paper author and University of Bristol Earth scientist Jessica Irving.

While scientists had previous InSight findings that provided some details about Mars' interior, previous seismic waves reflected off the planet's core and provided less data. These latest pair of seismic waves passed right through Mars' core, revealing it to be composed of liquid iron as well as around a fifth of it being made up of sulfur, oxygen, carbon and hydrogen.

"Determining the amount of these elements in a planetary core is important for understanding the conditions in our solar system when planets were forming and how these conditions affected the planets that formed," said co-author Doyeon Kim of ETH Zurich. 

InSight landed on Mars in 2018 with the goal of studying the interior surface of the Red Planet. While it exceeded its original mission duration, InSight met its fate because its solar panels, the lander's only source of energy, were covered by Martian dust, making it unable to draw enough power to carry on with its mission.

Speaking of solar power …

The Zhurong Mars rover, which has been just as mysteriously quiet as China's National Space Administration when asked about the rover's status, has finally been confirmed as unreachable by mission designer Zhang Rongquaio.

Zhurong, like InSight, is powered by solar panels, and the craft was designed to hibernate for several months of Mars' light-starved winter before waking in December for more experiments. Per Forbes, Zhang said dust on the rover's solar panels built up worse than expected, so the rover is unlikely to have the power reserves required to wake itself from hibernation. 

Still, China's space agency said it gathered 1,800 gigabytes of data from the combined instruments on the Zhurong and the Tianwen-1 orbiter that has led it to make several unspecified discoveries that Zhang said would be shared with the world beginning in May.

NASA took the opposite tack with the venerable Curiosity rover; instead of letting it rely on the Sun (energy from which is considerably weaker on Mars), NASA outfitted Curiosity with 10.6 pounds (4.8kg) of plutonium dioxide to generate power from heat generated by the plutonium's radioactive decay. Going on more than a decade of operation, that plutonium battery seems to be a much better choice for long-term exploration of Mars than solar panels, which have doomed more than one Mars mission. 

Future missions to Mars may even be able to offset the payload cost of less Sun-dependent power by opting to include pieces made from NASA's recently developed GRX-810 alloy, which has twice the strength to resist fracturing, three and a half times more flexibility, and 1,000x the durability under high temperatures as other state-of-the-art alloys, NASA said. 

GRX-810 can also be used in a 3D printer, which means it could be used to build new spacecraft more quickly. "This breakthrough is revolutionary for materials development. New types of stronger and more lightweight materials play a key role as NASA aims to change the future of flight," said Dale Hopkins, deputy product manager for NASA's Transformational Tools and Technologies project. ®