- The innermost planet in Earth’s solar system
- Because of its small size – a diameter of just 3,030 miles, it’s not the easiest of planets to observe.
- Averaging an orbital velocity of 47.87 km per second, Mercury is the fastest-moving planet in our solar system.
- Due to the small difference between Mercury’s orbital and rotational periods, the interval between night and day on the planet is 88 Earth days
- If you were sitting on the planet’s hot pole during a sunrise, the Sun would approach the zenith (getting larger as it does so), but since the orbital angular velocity is greater than the constant-spin angular velocity for a time, the Sun appears to stop, retreat backward for 8 Earth days, stop again, and then resume its original course.
- In 1991, very powerful radio telescopes noticed large sheets of ice contained on the poles, areas unseen by Mariner 10.
- Due to its 3,600 km iron core, Mercury has the greatest density in the Solar System (after Earth). Composed of 70% iron and 30% rock, Mercury has a molten core, a 600-km thick mantle, and a crust of silicates.
- Its largest known surface feature is the Caloris Basin with a 1350 km diameter.
- Mercury’s magnetic field is inclined at 11% to its rotational axis and has the same polarity as Earth’s – just enough to protect it from the full force of the solar wind.
- Because of its low escape velocity, Mercury hasn’t much of an atmosphere
- German scientist Johannes Hevelius (1611 – 1687) was among the first to observe a Mercurial transit and discovered the Mercurial phases.
- Most information has been collected by the Mariner 10 space probe that made three successful passes of the planet (March 29 1974, September 21 1974, and March 16 1975) before losing contact with Earth.