Mars

Definition

Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, being larger than only Mercury. It is often referred to as the 'Red Planet' due to its reddish appearance caused by the iron oxide prevalent on its surface. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth.

5 Must Know Facts For Your Next Test

1. Mars has two small and irregularly shaped moons, Phobos and Deimos, which are believed to be captured asteroids.
2. The Martian day is slightly longer than an Earth day, lasting approximately 24 hours and 37 minutes.
3. Mars has a thin atmosphere composed primarily of carbon dioxide, nitrogen, and argon, with a surface pressure less than 1% of Earth's.
4. The polar ice caps on Mars are composed of frozen carbon dioxide (dry ice) and water ice.
5. Mars has a lower density than Earth, indicating that it is composed of lighter materials, such as iron, magnesium, aluminum, and silicon.

Review Questions

• Explain how the elliptical orbit of Mars around the Sun relates to Kepler's Laws of Planetary Motion.
  • According to Kepler's First Law, also known as the Law of Ellipses, the orbit of every planet is an ellipse with the Sun at one of the two foci. This means that Mars, like all other planets in the Solar System, orbits the Sun in an elliptical path, rather than a perfect circle. Kepler's Second Law, the Law of Equal Areas, states that a line joining a planet and the Sun sweeps out equal areas during equal intervals of time as the planet orbits the Sun. This law describes how the speed of a planet's motion varies as it travels along its elliptical path, with the planet moving faster when it is closer to the Sun and slower when it is farther away. Kepler's Third Law, the Law of Harmonies, establishes a relationship between a planet's orbital period and the semi-major axis of its elliptical orbit, which can be used to determine the distance of Mars from the Sun.
• Analyze how the eccentricity of Mars' elliptical orbit affects the planet's distance from the Sun and the seasonal variations on its surface.
  • The eccentricity of Mars' elliptical orbit, which is approximately 0.0934, means that the planet's distance from the Sun varies significantly throughout its orbit. When Mars is at its closest point to the Sun, known as perihelion, it is about 206 million km away. At its farthest point, or aphelion, Mars is approximately 249 million km from the Sun. This variation in distance affects the amount of solar radiation the planet receives, leading to significant seasonal changes on its surface. During the Martian summer, when the planet is closer to the Sun, the polar ice caps partially melt, and the planet's atmosphere experiences greater heating and expansion. Conversely, during the Martian winter, when Mars is farther from the Sun, the polar ice caps grow, and the atmosphere cools and contracts. These seasonal variations, driven by the eccentricity of Mars' orbit, have a profound impact on the planet's climate and weather patterns.
• Evaluate the role of Mars' two moons, Phobos and Deimos, in the context of Kepler's Laws of Planetary Motion and their potential implications for future space exploration.
  • Kepler's Laws of Planetary Motion, which describe the motion of planets around the Sun, can also be applied to the moons of Mars, Phobos and Deimos. These small, irregularly shaped moons orbit Mars in elliptical paths, with Phobos completing an orbit in just 7 hours and 39 minutes, and Deimos taking 30 hours and 18 minutes. The short orbital periods of these moons, particularly Phobos, are a result of their proximity to Mars, as described by Kepler's Third Law. The close orbits of Phobos and Deimos, combined with their small sizes and irregular shapes, present unique challenges and opportunities for future space exploration. Understanding the dynamics of these moons, including their potential to be used as way stations or refueling points for interplanetary missions, is an area of active research and planning for future Mars exploration efforts.

Related terms

Kepler's Laws of Planetary Motion:

A set of three scientific laws describing the motion of planets around the Sun, formulated by the German astronomer Johannes Kepler in the early 17th century.

Elliptical Orbit:

The path of a planet or other celestial body as it revolves around another body in an ellipse, or oval-shaped curve.

Eccentricity:

A measure of how much an elliptical orbit deviates from a perfect circle, with a value between 0 and 1.