Mars is often called the world next door because it is one of Earth’s closest planetary neighbors and can be explored with spacecraft, rovers, and telescopes. Its rusty red color comes from iron oxide, the same kind of chemical compound found in rust on Earth. Mars has seasons, polar caps, volcanoes, canyons, dust storms, and evidence that liquid water once flowed across its surface.
Studying Mars helps scientists understand how planets change over time and whether life could have existed beyond Earth.
Key Facts
- Average distance from the Sun: Mars = 1.52 AU, Earth = 1.00 AU.
- Length of a Martian day: 1 sol = 24 hours 39 minutes.
- Surface gravity on Mars: g = 3.71 m/s^2, about 38% of Earth’s gravity.
- Mars has a thin atmosphere made mostly of carbon dioxide: about 95% CO2.
- Mars has two small moons: Phobos and Deimos.
- Weight on Mars can be estimated with W = mg, using g = 3.71 m/s^2.
Vocabulary
- Sol
- A sol is one full Martian day, lasting about 24 hours and 39 minutes.
- Regolith
- Regolith is the loose layer of dust, broken rock, and soil-like material covering a planet’s surface.
- Atmosphere
- An atmosphere is the layer of gases surrounding a planet or moon.
- Polar ice cap
- A polar ice cap is a frozen region near a planet’s pole made of water ice, carbon dioxide ice, or both.
- Tharsis
- Tharsis is a large volcanic region on Mars that includes Olympus Mons, the tallest known volcano in the solar system.
Common Mistakes to Avoid
- Thinking Mars is Earth-sized, which is wrong because Mars has only about half Earth’s diameter and much less mass.
- Assuming people could breathe on Mars, which is wrong because the atmosphere is extremely thin and mostly carbon dioxide.
- Treating Mars as warm because it is red, which is wrong because its average surface temperature is far below freezing.
- Confusing evidence of past water with proof of current oceans, which is wrong because most known surface water on Mars today is frozen or missing.
Practice Questions
- 1 A student has a mass of 60 kg. What is the student’s weight on Mars using W = mg and g = 3.71 m/s^2?
- 2 Mars has an average orbital distance of 1.52 AU from the Sun. If 1 AU is about 150 million km, how far is Mars from the Sun in millions of kilometers?
- 3 Mars has dry river valleys, minerals formed in water, and polar ice, but its atmosphere is thin today. Explain what this evidence suggests about how Mars has changed over time.