How Big Is Mars?

What is Mars's actual size?

According to NASA, Mars has an equatorial diameter of about 4,212 miles (6,779 km). Earth's diameter is roughly 7,918 miles, so Mars is about 53 percent of Earth's size. Mars's mass is about 11 percent of Earth's, and its surface area is around 55.9 million square miles, compared to Earth's 196.9 million square miles. Mars is the second-smallest planet in our solar system, larger only than Mercury.

How does Mars compare to Earth's land area?

Mars's total surface area is roughly equivalent to Earth's land area. Earth is about 71 percent water and 29 percent land, with around 57 million square miles of dry land. Mars, with around 55.9 million square miles of surface, has nearly that much usable real estate. For anyone thinking about future colonization or exploration, Mars effectively has a continent's worth of territory waiting, just very cold and very dry.

Where does Mars rank among the planets?

Seventh by size, ahead of only Mercury. The order from largest to smallest is Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury. Mars is significantly smaller than the gas giants (Jupiter is about 27 times Mars's diameter) and meaningfully smaller than Earth and Venus. Among rocky planets, Mars is the runt other than Mercury. Its small size is part of why it lost most of its atmosphere and most of its surface water over billions of years.

Why is Mars smaller than Earth?

Because Mars formed in a region of the early solar system with less material to draw from. The young Sun's heat and the gravitational pull of Jupiter likely cleared away much of the material that would have otherwise gone into building Mars. Some models suggest Mars stopped growing earlier than Earth did, which is why Mars never developed the same kind of long-lasting geological activity or atmosphere. Mars is essentially a planet that was never quite finished.