What’s it like Inside Mars?

We humans have made it to Mars, well, vicariously with machines. One day humans will set foot on Mars and witness Martian existence, feel its wind, the regolith beneath their boots.

But until then we depend on the machines in place on, roving around, and in orbit around Mars to send us data about its atmosphere, rocks, and soil. One machine in particular, NASA’s lander InSight, is delving deeper, looking into Mars below its surface. InSight was made to study Mars’ interior, as its full mission name implies; INterior exploration using Seismic Investigations, Geodesy and Heat Transport. InSight is a lot simpler to say! So, while other machines are sniffing and scraping, drilling, and digging, InSight is measuring Mars’ body temperature, reflexes, and pulse.

Mars’ pulse comes from marsquakes, detected by a seismometer appropriately named SEIS. The InSight lander placed it on Mars’ surface just alongside itself after a soft-landing using rockets. It’s the marsquakes that help InSight look deeply into Mars interior, not unlike how geologists use seismic information to picture Earth’s crust, mantle, and core. Like earthquakes marsquakes produce seismic energy waves that travel through the planet via solid rock.

While that all sounds straight forward, and the technology is, Mars needs to cooperate. Due to Mars’ low level of tectonic activity, most marsquakes are too mild to give a good picture of interior formations, so it took many months before any of sufficient power occurred. When some finally happened, investigators started getting a good image of Mars’ interior. So, what’s the interior like?

First, the crust seems thinner than expected, based on early analyses, and needs to be verified via additional data. Deeper down, it’s a clearer picture. Mars’ mantle extends between 400 and 600 km below the crust and is a single layer, vs Earth’s two layers. The result of a simple, single layer mantle is quicker heat loss due to more efficient heat transfer outward from the core.

At approximately 3700 km across, Mars’ core is larger with respect to the planet’s diameter than Earth’s. It blocks seismic waves coming from marsquakes near Tharsis Rise on the other side of Mars, indicating it’s a completely liquid core. Not having a solid inner core explains why Mars has a weak magnetic field. In contrast, Earth’s core has a solid inner core and liquid outer core that forms a spinning dynamo, producing our strong magnetic field. Our magnetic field is crucial for protecting us from the intense stream of charged particles coming from our Sun. With its weak magnetic field, Mars is continuously bombarded by solar radiation, and this is one of the many things planners need to consider when sending humans to Mars.

What’s in the Sky?

December 1; dusk; south-southwest:  Jupiter, Saturn, and Venus form a line above the horizon that will be visible during December as it changes formation.