Mars — The Red Planet Reading Comprehension Lesson

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Mars — The Red Planet

Mars is the fourth planet from the Sun and the second-smallest planet in our solar system, after Mercury. It is sometimes called the ‘Red Planet’ because iron oxide (rust) on its surface gives it a reddish appearance that is visible from Earth with the naked eye. Mars has a diameter of about 4,212 miles (6,779 km) — about half the diameter of Earth — and a mass about one-tenth of Earth’s. A Martian year (one orbit around the Sun) takes about 687 Earth days, but a Martian day is close to Earth’s: 24 hours and 37 minutes. Mars has two small moons — Phobos and Deimos — which are thought to be captured asteroids and are much smaller and irregularly shaped compared to Earth’s Moon.

Mars has the most dramatic topography of any planet in the solar system. Olympus Mons is the largest volcano in the solar system: about 374 miles (600 km) across at the base and 16 miles (25 km) high — three times higher than Mount Everest. It is a shield volcano, similar in shape to Hawaii’s volcanoes but vastly larger. Nearby are three other large shield volcanoes in the Tharsis region. Valles Marineris is a vast canyon system stretching about 2,500 miles (4,000 km) across Mars — roughly the width of the continental United States — and reaching depths of up to 7 miles (11 km), making it about four times deeper than the Grand Canyon. Both of these features were formed by volcanic and tectonic processes billions of years ago.

Mars has a thin atmosphere composed mainly of carbon dioxide (95%), with small amounts of nitrogen and argon. The atmospheric pressure at Mars’s surface is less than 1% of Earth’s — not enough to support liquid water on the surface today. Temperatures on Mars average about -80 degrees Fahrenheit (-62°C), ranging from about -220°F (-140°C) near the poles in winter to as warm as 70°F (20°C) at the equator during summer days. Mars has polar ice caps made of water ice and dry ice (frozen carbon dioxide) that expand and contract with the seasons. Dust storms on Mars can be enormous — sometimes covering the entire planet for months.

One of the most compelling questions about Mars is whether it ever supported life. Scientists have found strong evidence that Mars had liquid water on its surface billions of years ago, when it had a thicker atmosphere and warmer temperatures. Dry riverbeds, ancient lake basins, and minerals that form in the presence of water all suggest a wetter past. The Mars rovers — including Spirit and Opportunity (2004–2018), Curiosity (2012–present), and Perseverance (2021–present) — have found sedimentary rocks, organic molecules, and other evidence that conditions on early Mars may once have been suitable for life. Perseverance is actively searching for signs of ancient microbial life and collecting rock samples for eventual return to Earth.

Mars has been explored by more spacecraft than any other planet. The first successful flyby was Mariner 4 in 1965. Since then, dozens of missions have been sent to Mars, including orbiters, landers, and rovers. The Viking landers (1976) were the first spacecraft to successfully land on Mars; they conducted biological experiments looking for signs of life but produced inconclusive results. NASA’s Insight lander (2018–2022) studied Mars’s interior using seismometers. Looking ahead, NASA and other space agencies have plans for human missions to Mars, possibly in the 2030s or 2040s. Mars remains one of the most studied and most fascinating objects in the solar system.

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