Mars is smaller than Earth. It has a diameter of roughly 4,222 miles (6,794 km) — about half Earth's diameter, according to the European Space Agency (ESA). The Red Planet is rocky, much like Earth.

Mars is probably smaller than you think. It's just half the size of Earth, with barely a third of its mass. Even the Martian ...

The surface of Mars is extremely cold, irradiated, and desiccated. But at one time, the planet was much warmer and wetter, ...

Mars is about 140 million miles from our cozy planet. A human mission to that cold, rocky neighbor would mean being away from Earth for about 3 years. But the things those explorers would see and ...

A new study has revealed that lichens can withstand the intense ionizing radiation that hits Mars' surface. (The lichen in this photo is Cetraria aculeata.). | Credit: Pensoft Earth-based ...

These are rocky worlds that are more massive than Earth but smaller than ice giants like Neptune and Uranus. Super-Earths generally have masses between two and 10 times that of our planet.