Why is planet Mercury shrinking?

Artist depiction of the MESSENGER spacecraft in orbit around Mercury.

Mercury, the closest planet to the sun as well as the smallest planet in our solar system is getting even smaller…

A video version of this article.

How did we figure it out?

In August 2004, NASA launched the MESSENGER probe into space. MESSENGER, being the backronymn MErcury Surface, Space ENvironment, GEochemistry, and Ranging was named so after the deity Mercury in Roman mythology, who, not too coincidentally, was messenger to the other gods.

The MESSENGER probe travelled 7.9 billion kilometres over the next 6 years, 7 months and 16 days before it finally orbited Mercury.

Within the first year of orbit this probe collected close to a 100,000 images and completely mapped the surface of the planet by March 2013.

It’s from the images of the mountain ridges and grooves taken by the probe that scientists at the Carnegie Institute for Science in Washington discovered that the planet has contracted radially by around 7km (4.4 miles). — That’s around the length of 2, maybe 3 airport runways!

The reason was most likely due to the planet’s large, hot core slowly starting to cool down.

Unlike Earth which has a relatively small core, making up approximately 17% of the planet’s volume, nearly 42% of Mercury consists of its core.

And, because it hardly has any atmosphere, day and night temperatures vary greatly from a freezing-your-ass-off -173 degrees (-280F) to +427 degrees (800F), which is basically hell on earth.

It’s like Pluto with mood swings really… if Pluto was still a planet, which it isn’t because it’s too mainstream…

Data retrieved from the MESSENGER probe is still being processed, but we can be quite sure that the planet only has a diameter of around 4,879km left, which makes it is only slightly larger than the Earth’s moon.

What do you think? Are they right? Is Mercury shrinking? And what will happen when it can’t shrink anymore?

Like what you read? Give Ruan van Heerden a round of applause.

From a quick cheer to a standing ovation, clap to show how much you enjoyed this story.