Mars is the fourth planet from the Sun in our solar system, orbiting between Earth and Jupiter. Astronomers track its position using coordinates based on Earth's equator and prime meridian.
Mars follows an elliptical orbit around the Sun, taking about 687 Earth days to complete one revolution. Its average distance from the Sun is roughly 142 million miles (228 million kilometers), but this varies due to its oval-shaped path.
The planet's closest approach to Earth occurs roughly every 26 months, when both planets align on the same side of the Sun. During these close approaches, Mars appears brighter and larger in the night sky.
Mars' position in the sky changes throughout the year due to Earth's faster orbit. When Mars is near opposition (opposite the Sun from Earth's perspective), it rises in the east as the Sun sets and remains visible all night.
The planet's axial tilt of 25 degrees creates seasons similar to Earth's, though they last nearly twice as long due to Mars' longer year. Mars' two small moons, Phobos and Deimos, orbit close to the planet and complete revolutions in just a few hours.
Astronomers use a coordinate system called celestial longitude and latitude to pinpoint Mars' location. Celestial longitude measures eastward along the plane of Earth's equator projected onto the sky, while celestial latitude measures perpendicular to this plane.
These coordinates allow astronomers to predict Mars' position with high accuracy, essential for planning missions to the red planet. NASA's Jet Propulsion Laboratory maintains an online tool called the HORIZONS system that provides precise ephemerides (positional data) for Mars and other solar system bodies.
Many people believe Mars is always visible in the night sky, but it actually spends about 40% of each year too close to the Sun's glare to be seen. Others think Mars appears red because of its surface iron oxide, but the planet's reddish hue is primarily due to fine dust suspended in its thin atmosphere.
Another misconception is that Mars is always farther from Earth than any other planet. While Mars is often the farthest visible planet, more distant planets like Jupiter and Saturn can occasionally appear closer due to their different orbital paths.
When viewing Mars through a telescope, look for its polar ice caps, which grow and shrink with the seasons. The most prominent surface features include the dark region Syrtis Major and the massive volcano Olympus Mons, which is the tallest volcano in the solar system at 13.6 miles (22 kilometers) high and 370 miles (600 kilometers) wide.