Curiosity found organic (carbon-containing) molecules in rock on Mars. As of November 2026, scientists say more study is needed to learn where they came from.

Mars is the fourth planet from the Sun. It is about 1.5 times as far from the Sun as Earth is; Mars is about 6,780 kilometers (4,212 miles) across, which is about half the width of Earth. Mars looks red because there is rusty iron in its ground. Mars is a cold, dry, desert world.

Air pressure at the surface of Mars is only about one hundredth of Earth's, about 6 millibars; the air on Mars is about 95 percent carbon dioxide; people cannot breathe the air on Mars. Temperatures on Mars can drop to about minus 153 degrees Celsius and reach about 20 degrees Celsius on a warm day.

Olympus Mons on Mars is the biggest volcano in the Solar System. It rises about 25 kilometers (16 miles) above the plains around it, much taller than Mount Everest; the Tharsis Rise is a huge bulge in the surface of Mars, about 4,000 kilometers wide and 10 kilometers high, near the equator.

Valles Marineris on Mars is the biggest canyon in the Solar System; it is a canyon system about 4,000 kilometers (2,500 miles) long, long enough to stretch across the United States; Valles Marineris was made by the crust stretching and cracking, with walls collapsing in landslides, while the Grand Canyon on Earth was carved by a river. As of November 2026, Valles Marineris probably began as a crack in the crust as Mars cooled, but how it formed is not fully known.

Mars has ice caps at its north and south poles. On the Mars polar caps, carbon dioxide ice builds up in winter and turns straight into gas in summer, leaving water ice behind; radar on the Mars Reconnaissance Orbiter found large amounts of ice buried under the ground, often under rubble. The Phoenix lander landed in the far north of Mars in 2008 and confirmed that there is water ice under the soil.

InSight studied the inside of Mars; its seismometer listened to marsquakes, and the waves told scientists how big the core is; the core of Mars is large: InSight's marsquake data show it has a radius of about 1,840 kilometers. The rocky crust of Mars is about 10 to 50 kilometers thick; at the InSight landing site, the crust is 15 to 47 kilometers thick.

Scientists conclude that the solar wind and the Sun's radiation stripped away most of the air that Mars once had. Mars has no global magnetic field, so the solar wind hits its upper air directly; NASA's MAVEN orbiter studies how the solar wind and the Sun act on the upper air of Mars, to learn what happened to its once-thick atmosphere. Dust storms may have helped dry out Mars: dust-trapped water vapor may rise like an elevator to space.

In the 1890s Percival Lowell, who founded Lowell Observatory in Arizona, was sure the lines some astronomers drew on Mars were artificial canals; in 1965 Mariner 4 flew over where canals had been drawn and saw none.

In 1976 Viking 1 became the first American spacecraft to land safely on Mars. The Viking landers searched Mars soil for life in 1976; the results were mostly negative but not a clear answer.

Curiosity landed in Gale Crater in early August 2012 to assess whether Mars could ever have been a place for life; Curiosity showed that Gale Crater was once a lakebed with water and the chemical ingredients that could have supported life; the delta in Jezero Crater is a fan of ancient river mud and sand that holds evidence of a lake that once filled the crater.

In July 2024 Perseverance found a rock called Cheyava Falls with small 'leopard spots'. As of November 2026, NASA calls the spots a potential biosignature, a thing that might have a biological origin, and not proof of life.

As of November 2026, the Cheyava Falls rock that Perseverance found in 2024 sits in a region called Bright Angel, where an ancient river flowed billions of years ago.

Perseverance collected a sample from the Cheyava Falls rock, called Sapphire Canyon. As of November 2026, scientists say the key next step is to bring it back to Earth for lab tests.

Words to know

• organic: carbon-containing
• biosignature: possible life sign
• seismometer: quake listener
• canals: dug waterways
• lakebed: old lake floor