Mercury 101 | National Geographic

Key Concepts:

• Terrestrial planet, core, mantle, crust, tectonic plates, iron core, exosphere, solar winds, elliptical orbit, NASA's Mariner 10, Messenger.

Mercury: The Swift Planet

1. Introduction and Naming:

• Mercury is named after the Roman god Mercury, the messenger, due to its swift movement across the sky.

2. Size and Composition:

• Mercury is the smallest planet in our solar system, with a diameter of just over 3,000 miles, approximately the size of the continental United States.
• It is a terrestrial planet composed of three main layers: a core, a mantle, and a crust.
• Unlike Earth, Mercury's crust lacks tectonic plates.

3. Core Size and Planetary Shrinkage:

• Mercury's iron core is exceptionally large, making up 85% of its radius, compared to Earth's core which accounts for only 55%.
• The cooling and contraction of the hot iron core over 4.5 billion years has caused Mercury to shrink radially by more than four miles. This contraction pulled the planet's surface inward.

4. Orbit and Atmosphere:

• Mercury orbits the sun at an average distance of roughly 36 million miles, making it the closest planet to the sun.
• It possesses a very thin exosphere, the outermost layer of a planet's atmosphere, composed of oxygen, sodium, hydrogen, helium, and potassium.
• The exosphere's elements are whipped up from the planet's surface by solar winds.

5. Temperature Extremes:

• Due to the lack of a substantial atmosphere and its proximity to the sun, Mercury experiences extreme temperature variations.
• Surface temperatures can reach 800 degrees Fahrenheit during the daytime and plummet to 290 degrees below zero at night.

6. Orbital Speed and Period:

• The sun's gravity exerts a strong pull on Mercury, causing it to travel in an elliptical orbit.
• Mercury's speed varies, slowing down when farther from the sun and accelerating as it approaches.
• It orbits the sun at an average speed of over 100,000 miles per hour, completing one orbit in just 88 Earth days.

7. Observation and Exploration:

• Mercury is difficult to observe from Earth due to its proximity to the sun.
• It has been visited by two spacecraft: NASA's Mariner 10 and Messenger.
• These missions have provided significant data about Mercury, and future missions are planned to uncover more of its secrets.

8. Conclusion:

• Mercury, the smallest and innermost planet, presents numerous mysteries due to its unique characteristics, including its large iron core, extreme temperature variations, and swift orbit. Past and future space missions aim to further unravel these mysteries.