NASA’s Mars InSight has provided … well, insight, into the inner workings of the Red Planet. By monitoring “marsquakes” over the past two years the instrument has allowed scientists to measure the thickness and composition of Mars’ crust, mantle and core, revealing some surprises.
While InSight has so far detected 733 marsquakes in its two-year mission, the new studies focused on 35 of those quakes, all registering magnitudes between 3.0 and 4.0. That means they constitute some of the most powerful Mars has to offer – although they might sound pretty minor compared to what Earth is capable of.
The researchers used the data from these quakes to measure the depth, size, structure and composition of Mars’ crust, mantle and core. This can be done by measuring changes in the speed of the seismic waves as they transition between layers.
The team found that immediately below InSight, the Red Planet’s crust extends to a maximum depth of about 20 km (12 miles) if it has two sub-layers, or 39 km (24 miles) if it has three. Averaged across the planet, they calculate the crust is probably between 24 and 72 km (15 and 45 miles) thick. Either way, that’s much thinner than was expected, and suggests that the crust is rich in radioactive elements.
Underneath that lies the mantle, which may stretch as deep as 600 km (373 miles). That’s far deeper than Earth’s, but it fits with the model of Mars having one big continental plate. Interestingly, the Martian mantle seems to be made up of similar minerals to Earth’s upper mantle, but it doesn’t have a separate lower mantle.
Deeper down lies the core, which is now confirmed to be completely liquid, unlike Earth’s. The team estimates that the core of Mars has a radius of about 1,830 km (1,137 miles), which makes it about half the size of Earth’s, but still about 200 km (124 miles) larger than was expected. Because it’s so much bigger, it’s less dense, and is now thought to contain a larger proportion of lighter elements like sulfur, oxygen, carbon and hydrogen.
The scientists say that there’s still plenty more analysis to be done on the data InSight has gathered so far, as well as another 18 months of data collection to come. The team hopes that a larger quake might be detected in that time.
The research was published in three studies in the journal Science [1],[2],[3].
Sources: ETH Zurich, NASA