Mercury Unveiled: The Smallest Planet In Our Solar System

wesknows
Jun 10, 2024
4 min read

Updated: Mar 1

Cartoon moon with big eyes, arms, and legs, wearing boots and smiling. It appears to be dancing in a starry black space background.

What makes the littlest guy in our solar system so special? Get your read on, scroll through the post and find out why Mercury is tiny but mighty!

A colorful, enhanced image of the planet Mercury, showing craters and diverse surface features in vivid blue, yellow, and brown hues. — Credit: Sickmoose via Canva

Mercury is the smallest of the eight planets in our solar system and has been known since ancient times. This is because it can be seen without the aid of binoculars or a telescope. Despite being the closest planet to the Sun, Mercury isn't the hottest—that title goes to Venus, which we’ll cover next.

Four planets, labeled Venus, Mars, Mercury, and Earth, are arranged against a gray background. Earth is blue and white; others vary in colour. This is a size comparison illustration

Characteristics of Mercury

Terrestrial Planet

Like Venus, Earth, and Mars, Mercury is a terrestrial planet. This means it's a rocky planet, also known as an inner planet. Although Mercury is solid, you wouldn't want to stand on it because it's too hot and lacks an atmosphere. It is composed of 70 percent metal which is understood to be mostly Iron, and 30 percent other materials like silicate, nickel, and possibly carbon and sulphur.

Cross-section illustration of planet Mercury showing layers: gray crust, orange mantle, yellow liquid outer core, red solid inner core. Labels detail each layer.

No Moons

Mercury doesn’t have any moons because of its small size and proximity to the Sun. Being the smallest planet in the Solar System, its weak gravity makes it difficult to capture or hold onto a moon. Additionally, its close orbit around the Sun means that any potential moon would likely be pulled away by the Sun’s powerful gravity before it could remain in orbit.

Cratered Surface

It's surface is covered in craters, which are the result of meteoroids and comets colliding with it over time. These impact scars are named after famous artists, musicians, and authors like Michelangelo, Shakespeare, and Dr Seuss.

Day and Night Cycle

From sunrise to sunrise, a full day on Mercury (including both day and night) lasts 176 Earth days! thats pretty crazy. The temperature during the night can drop to a chilly minus 180°C, making the temperature swing from extremely hot to extremely cold.

Mercury Data Dump

Colour: Mercury is grey in colour, which is because of the graphite in it's composition.

Diameter: Mercury has the smallest diameter of all the planets in the solar system, measuring about 4,879 kilometres (3,032 miles).

Temperature: The average temperature on Mercury is around 167 degrees Celsius (333 degrees Fahrenheit). Whoa, thats hot!

Proximity to the Sun: Mercury is about 58 million kilometres (36 million miles) away from the Sun.

Planet Mercury with cratered surface in space, glowing orange sunlight on left, dark starry background. Atmospheric and cosmic mood. — Credit : Buradaki Getty Images via Canva

Rotation Period: Mercury takes 58.6 Earth days to complete one rotation on its axis, meaning a single day on Mercury lasts 58.6 Earth days.

Orbital Period: Mercury's year, or the time it takes to orbit the Sun, is just 88 Earth days. So, Mercury has very long days and short years.

Axial Tilt: Mercury's axial tilt is almost non-existent at 0.01 degrees, meaning it doesn't experience seasons like Earth does.

Elliptical Orbit: Mercury's orbit is elliptical, meaning it has a closest and a furthest distance from the Sun. At its closest, Mercury is about 46 million kilometres (29 million miles) from the Sun, and at its farthest, it's 70 million kilometres (44 million miles) away.

Diagram of Mercury's perihelion precession around the Sun, showing orbital paths in green against a black background, with labeled text. — Credit: Wiki Media

Space Missions to Mercury

One significant mission to Mercury was NASA's MESSENGER spacecraft.

(MErcury Surface, Space ENvironment, GEochemistry, and Ranging)

Launched from Cape Canaveral Air Force Station in Florida, USA in August 2004, it took almost seven years to reach Mercury, finally entering its orbit in March 2011.

Messenger gathered extensive data about Mercury's environment and geology, and it discovered that Mercury’s north pole has regions of water ice in permanently shadowed craters.

After four years orbiting Mercury and uncovering its secrets, MESSENGER went out with a bang—literally! On April 30, 2015, the spacecraft crash-landed onto Mercury’s surface at over 14,000 km/h, creating a brand-new crater. Yes thats right- a new 16 meter wide crater. With no fuel left, it had no way to stay in orbit, so NASA gave it a grand finale, squeezing out every last bit of science before its dramatic impact.

Fun Facts About Mercury

Transit Events: A transit occurs when Mercury passes directly between the Earth and the Sun. The last transit of Mercury was on 11 November 2019, and the next one will be on 12-13 November 2033. Mark your calendars for this exciting event!

the planet mercury transits across the sun. Fiery sun against a black background with black dots crossing its surface, depicting a planetary transit. Bright orange and yellow flames. 3D modeling. — Credit: Thomas Faull Getty Images via Canva

Mercury has a what? Did you know that Mercury, has a tail like a comet? This fascinating phenomenon occurs because the solar wind—a stream of charged particles from the Sun—strips away particles from Mercury's surface. These particles form a thin, glowing tail that can stretch for millions of kilometres in space, just like a comet's tail.

Mercury phenomonon of a glowing tail like a comet. charged solar stream of charged particles from the sun. Bright pink light glowing against a muted teal background, creating a mysterious, ethereal atmosphere with blurred surroundings.

Mercury may be small, scorched, and moonless, but it’s still one of the most fascinating planets in our Solar System. From its extreme temperatures to its mysterious shrinking surface, this little planet is packed with surprises. While it’s not exactly a vacation hotspot (a sizzling 430°C during the day and a freezing -180°C at night), Mercury proves that even the tiniest planets can hold some big secrets.