New research claims NASA’s InSight lander’s enormous marsquake implies the Red Planet crust is “like heavy armor” in some places.

The NASA InSight lander’s seismometer measured seismic waves on Mars for three years until December 2022. In May 2022, it detected the greatest marsquake yet, 4.6.

NASA scientists claimed the Mars tremor was at the upper range of what Red Planet specialists predicted. The marsquake was the strongest ever measured.

“This marsquake sent out strong seismic waves that traveled along the surface of Mars,” research lead author and ETH Zurich Institute of Geophysics seismologist Doyeon Kim stated in a May 6 statement(opens in new tab). “From this quake, the largest recorded during the entire InSight mission, we observed surface waves that circled Mars up to three times.”

ESS Open Archive(opens in new tab) released the team’s study in March without peer review.

Thick skin

Kim and the crew discovered geological features by measuring seismic wave speed and frequency across the Red Planet. Data on Martian crust inner structures at various levels was released.

InSight detected seismic signals from two Mars meteorites before the massive quake. The space rock occurrence only offered regional details. The magnitude 5 quake expanded Red Planet investigations, revealing major ramifications.

InSight data was merged with Mars gravity and topography data from other missions. Scientists found that the Red Planet’s crust is 26 to 35 miles (42 to 56 kilometers) thick, with its thickest point at 56 miles (90 kilometers).

“The Martian crust (on average) is much thicker than that of the Earth or the moon,” Kim said, adding that smaller solar system worlds have thicker crusts than bigger ones.

The Apollo moon missions’ seismometers measured the lunar crust’s thickness at 21 to 27 miles (34 to 43 kilometers), compared to Earth’s 13 to 17 miles (13 to 17 kilometers).

The Isidis impact basin, a 746-mile (1200-kilometer)-wide ancient crater, has the thinnest Martian crust, according to InSight. The Martian crust is just 6 miles (10 kilometers) thick in the basin, located between the extensively cratered southern highlands and the northern lowlands.

However, in the huge Tharsis area, the crust is 56 miles (90 kilometers) thick and spans roughly the breadth of the United States, around 5,000 miles (8,000 kilometers). Tharsis is the center of a massive radial fracture system that covers one-third of Mars. It has huge volcanic plains and three of Mars’ biggest volcanoes.

We witnessed this tremor. “Using the same magnitude of quake as on Mars, we would have trouble determining Earth’s crust thickness,” Kim said. “Mars transports seismic energy better than Earth.”

Mars dichotomy

The team’s findings validated Mars’ northern and southern hemispheres’ differences. The planet’s north has flat lowlands and the south has lofty plateaus.

A 2007 peer-reviewed paper argues that astronomers and planetary scientists have seen the “Martian dichotomy” between north and south since Mariner 9’s pioneering NASA orbital mission in 1971-72.

Kim hypothesized that rock composition caused this variance. “One rock would be denser than the other.”

However, these recent data disprove composition. The Martian dichotomy is caused by crust thickness, not rock type.

InSight seismic measurements and gravity data showed that the crust in the northern lowlands and southern highlands had equal density.

The density finding matches InSight seismic data of the meteor hits, suggesting that the north and south crusts are the same material. (Seismic waves in rocky crust reveal composition.)

The team’s discovery of a thick Martian crust in certain locations illuminates the planet’s heat generation and evolution. The interior of Mars is heated by radioactive decay of thorium, uranium, and potassium.

The team believes 50% to 70% of these heat-producing components reside in the Martian crust. Thus, the variability in crust thickness across Mars may explain why melting processes may still be occurring in hotspots that contain higher heat-generating radioactive elements.

“This finding is very exciting, and allows an end to a long-standing scientific discussion on the origin and structure of the Martian crust,” Kim added.