Mercury is the solar system’s smallest planet, and it’s also the one residing closest to the Sun. But while Mercury is commonly shrugged off as just a boring hot and rocky planet with seemingly no special features, it turns out that there’s a lot more going on there than meets the eye.
At just over 3,000 miles across, Mercury isn’t large, and it sports three main layers just like the Earth, including a core, a mantle, and the crust. One thing that helps Mercury stand out, however, is the sheer size of its molten icon core, which purportedly comprises of almost 85% of its radius. Comparatively, the Earth’s core only comprises of about 55% of our planet’s radius.
Mercury doesn’t sport any tectonic plates like Earth does, but another internal planetary process seems to result in bizarre surface features that compare to what we see here on Earth. Namely, the fact that the planet’s massive iron core is cooling and contracting, which is causing the planet overall to shrink. Consequently, this behavior leaves buckling marks all over Mercury’s surface.
At just 36 million miles away from the Sun, it’d be an understatement to say that the planet isn’t hot. By day, the surface climbs to 800º Fahrenheit, and by night, dips to -294º Fahrenheit. This tight-hugging orbit also contributes to a vastly lacking atmosphere so thin that planetary scientists merely call it an exosphere. It’s comprised of elements dragged from the planet’s surface into the skies by the Sun’s solar winds.
Only two spacecraft have ever visited Mercury before, but space agencies are working to bring new mission to life that will visit the planet once more with the latest technologies to learn more about what the planet might tell us about our solar system.
Related: Watch NASA's official footage from the 2019 Mercury transit