Mercury Mystery Uncovered: Planet Has Solid Inner Core

According to newly emerged studies, Mercury, the smallest planet in our own solar system, has a core that is not only massive but solid, solving a mystery that has long baffled the scientific community.

Before crash-landing almost four years ago, NASA’s MESSENGER mission, in its final trip, pointed its cameras on the planet’s surface and zoomed in, enabling scientists to make detailed measurements of its overall internal structure, gravity and even spin cycles.

From this, they were able to come up with new data, which was then published in a researcher’s report in Geophysical Research Letters on April 10. According to the report, the planet has a solid inner core measuring about 2,000 kilometers in diameter. And since Mercury is a small planet, this easily makes up around half of its entire core.

Even way before this, however, scientists were already aware that the planet’s core is huge, taking up around 85 percent of the entire planet. That’s because back in 2007, radar observations detected small oscillations in Mercury’s spin rate. This suggested that the planet’s core was partially liquid, which is then confirmed by the data from MESSENGER, revealing that due to the molten metal in its liquid core, the planet was able to generate a weak magnetic field.

To study the planet’s internal core without actually going inside it, MESSENGER found another way by measuring its distribution of mass by tracking subtle variations in the planet’s gravitational pull. With the collected data, scientists were then able to estimate the type of interior composition that makes the most sense for Mercury and its spin cycle.

Out of all the rocky planets known, only Earth and Mercury have magnetic fields that are generated due to their cores. Such fields — like the magnetic one we have in our planet — can shield planets from being constantly battered by particles from outer space, as well those streaming from the Sun.

However, Mercury’s core is cooling at a much faster rate than Earth’s. Because of this, Mercury’s core might give us a peek of the future of our own magnetic field, according to researchers.