In 1973, NASA launched the Mariner 10 spacecraft in what would become the first ever mission to approach the planet Mercury. Fortunately, NASA scientists figured out a way to do this by having a spacecraft use the gravity of the planet Venus to adjust the spacecraft’s velocity and eventually enter into orbit around Mercury. At this speed, it is tremendously difficult to launch a spacecraft that can adjust its velocity to enter orbit around Mercury. The result is that Mercury is the fastest planet in the solar system, moving around the Sun at a speed of 29.5 miles per second (47.4 km/s). Since Mercury is the closest planet to the Sun, it experiences the most extreme gravitational effects of the Sun. In 1965, American scientists attempted to replicate the observations done in the Soviet Union and confirmed that Mercury’s rotational period was 59 Earth days. The data suggested that Mercury had a rotational period of 59 Earth days, a discovery that astronomers were reluctant to accept. Soviet scientists bounced radar signals off Mercury’s surface to not only map the planet, but to also measure how fast the planet was rotating. The belief that Mercury had synchronous rotation persisted in the astronomical community until the 1960s, when the Soviet Union began the first ever radar observations of Mercury. When a planet has a rotational and orbital period that are identical, it is called synchronous rotation. Decades later in the 1880s, another astronomer by the name of Giovanni Schiaparelli made the most detailed observations of Mercury’s surface and estimated that Mercury had a rotational and orbital period of 88 Earth days. In 1800, the astronomer Johann Schroter observed surface features on Mercury, claiming to have seen large mountains on the planet’s surface. It wasn’t until the 1800s that telescopes became advanced enough that astronomers could actually start observing Mercury in detail and make out surface features. Since Mercury orbits so close to the Sun, it is one of the most difficult planets to observe with a telescope. Unfortunately, Galileo’s telescope was not strong enough to make out any specific details of Mercury, and so Galileo discovered very little about Mercury. In the 1600s, the astronomer Galileo Galilei became the first human being to observe Mercury through a telescope. This was the general belief until the invention of the telescope. Historical Observations Of Mercury Images of Mercury's Surface Taken by the Messenger Spacecraft, NASAĪncient civilizations often viewed the planets as deities or related to a god in some form. In fact, the Greek equivalent to Mercury was Hermes, the messenger of the gods who often travelled between the realm of the gods and mortals at high speeds. Due to the planet Mercury being located so close to the Sun, it appeared as though it was chasing the Sun at high speeds, and so the Greeks and Romans viewed Mercury as a messenger that moved swiftly. In Roman mythology, Mercury was the messenger of the gods.

In the case of Mercury, it is named after the Roman god of commerce and messages. Like every other planet in the solar system, Mercury gets its name from Roman mythology. In fact, Mercury is never visible at night, but rather, is visible in the very early evening just as the Sun is setting. Since Mercury is the closest planet to the Sun, it is one of the most difficult planets to see with the naked eye. Since Mercury is visible without needing any kind of equipment, its existence has been known since ancient times, with the earliest recorded observations of Mercury dating back to the Sumerian civilization of ancient Mesopotamia. Mercury is a rocky world with an iron core and a rocky crust. Mercury is the smallest planet in the solar system with a diameter of 3,032 miles, only 435 miles larger than Earth’s moon. Mercury is the closest planet to the Sun in our solar system.

Mercury temperature