Mars, often called the Red Planet, is Earth’s celestial neighbor and a subject of immense fascination. Its distinctive reddish hue comes from iron minerals in its soil, which rust, or oxidize, over time. As the fourth planet from the Sun, Mars shares some similarities with Earth, possessing polar ice caps and a tilted axis that results in seasons. Understanding the planet’s journey around the Sun provides insight into its environment and our observations of it.
The Martian Year
A Martian year is significantly longer than an Earth year, lasting approximately 687 Earth days. This means one full orbit of Mars around the Sun takes nearly twice as long as Earth’s orbital period. Within this longer year, Mars experiences about 668.6 Martian solar days, known as “sols,” where each sol is slightly longer than an Earth day, at roughly 24 hours, 39 minutes, and 35 seconds.
Mars’s path around the Sun is an ellipse, meaning its distance from the Sun changes throughout its year. At its closest point to the Sun, called perihelion, Mars is about 207 million kilometers away, while at its farthest, aphelion, it is approximately 249 million kilometers. This varying distance influences the amount of sunlight Mars receives, affecting the intensity and duration of its seasons.
Factors Governing Planetary Orbits
The duration of a planet’s year is directly related to its distance from the Sun. Planets farther from the Sun must travel a greater distance to complete one orbit, extending their years.
Beyond the longer path, planets more distant from the Sun also move at a slower average speed. The Sun’s gravitational pull weakens with increasing distance, causing more distant planets to orbit at a slower pace. Consequently, the combination of a longer journey and a slower speed contributes to the significantly longer orbital periods observed for outer planets.
Comparing Planetary Journeys
Earth completes one orbit around the Sun in approximately 365.25 days. Mars’s 687-day year is significantly longer than Earth’s 365.25-day year. This substantial difference in orbital periods influences how often Earth and Mars align in their celestial dance.
Due to their differing speeds and orbital paths, Earth and Mars are favorably positioned for observation, a phenomenon known as opposition, roughly every 26 months. During these times, Earth passes between Mars and the Sun, bringing the two planets relatively close together. Particularly close oppositions occur approximately every 15 to 17 years, when Mars is near its perihelion during this alignment.