Mars Facts
Mars – the fourth planet from the Sun – is a dustycolddesert world with a very thin atmosphere. This dynamic planet has seasonspolar ice capsextinct volcanoescanyons and weather.
Introduction
Mars is one of the most explored bodies in our solar systemand it's the only planet where we've sent rovers to roam the alien landscape. NASA missions have found lots of evidence that Mars was much wetter and warmerwith a thicker atmospherebillions of years ago.
Namesake
Mars was named by the ancient Romans for their god of war because its reddish color was reminiscent of blood. Other civilizations also named the planet for this attribute – for examplethe Egyptians called it "Her Desher," meaning "the red one." Even todayit is frequently called the "Red Planet" because iron minerals in the Martian dirt oxidizeor rustcausing the surface to look red.
Potential for Life
Scientists don't expect to find living things currently thriving on Mars. Insteadthey're looking for signs of life that existed long agowhen Mars was warmer and covered with water.
Size and Distance
With a radius of 2,106 miles (3,390 kilometers)Mars is about half the size of Earth. If Earth were the size of a nickelMars would be about as big as a raspberry.
From an average distance of 142 million miles (228 million kilometers)Mars is 1.5 astronomical units away from the Sun. One astronomical unit (abbreviated as AU)is the distance from the Sun to Earth. From this distanceit takes sunlight 13 minutes to travel from the Sun to Mars.
Orbit and Rotation
As Mars orbits the Sunit completes one rotation every 24.6 hourswhich is very similar to one day on Earth (23.9 hours). Martian days are called sols – short for "solar day." A year on Mars lasts 669.6 solswhich is the same as 687 Earth days.
Mars' axis of rotation is tilted 25 degrees with respect to the plane of its orbit around the Sun. This is another similarity with Earthwhich has an axial tilt of 23.4 degrees. Like EarthMars has distinct seasonsbut they last longer than seasons here on Earth since Mars takes longer to orbit the Sun (because it's farther away). And while here on Earth the seasons are evenly spread over the yearlasting 3 months (or one quarter of a year)on Mars the seasons vary in length because of Mars' ellipticalegg-shaped orbit around the Sun.
Spring in the northern hemisphere (autumn in the southern) is the longest season at 194 sols. Autumn in the northern hemisphere (spring in the southern) is the shortest at 142 days. Northern winter/southern summer is 154 solsand northern summer/southern winter is 178 sols.
Moons
Mars has two small moonsPhobos and Deimosthat may be captured asteroids. They're potato-shaped because they have too little mass for gravity to make them spherical.
The moons get their names from the horses that pulled the chariot of the Greek god of warAres (whose Roman counterpart is Mars).
Phobosthe innermost and larger moonis heavily crateredwith deep grooves on its surface. It is slowly moving towards Mars and will crash into the planet or break apart in about 50 million years.
Deimos is about half as big as Phobos and orbits two and a half times farther away from Mars. Oddly-shaped Deimos is covered in loose dirt that often fills the craters on its surfacemaking it appear smoother than pockmarked Phobos.
Rings
Mars has no rings. Howeverin 50 million years when Phobos crashes into Mars or breaks apartit could create a dusty ring around the Red Planet.
Formation
When the solar system settled into its current layout about 4.5 billion years agoMars formed when gravity pulled swirling gas and dust in to become the fourth planet from the Sun. Mars is about half the size of Earthand like its fellow terrestrial planetsit has a central corea rocky mantleand a solid crust.
Structure
Mars has a dense core at its center between 930 and 1,300 miles (1,500 to 2,100 kilometers) in radius. It's made of ironnickeland sulfur. Surrounding the core is a rocky mantle between 770 and 1,170 miles (1,240 to 1,880 kilometers) thickand above thata crust made of ironmagnesiumaluminumcalciumand potassium. This crust is between 6 and 30 miles (10 to 50 kilometers) deep.
Surface
The Red Planet is actually many colors. At the surfacewe see colors such as browngoldand tan. The reason Mars looks reddish is due to oxidization – or rusting – of iron in the rocksregolith (Martian “soil”)and dust of Mars. This dust gets kicked up into the atmosphere and from a distance makes the planet appear mostly red.
Interestinglywhile Mars is about half the diameter of Earthits surface has nearly the same area as Earth’s dry land. Its volcanoesimpact craterscrustal movementand atmospheric conditions such as dust storms have altered the landscape of Mars over many yearscreating some of the solar system's most interesting topographical features.
A Very Large Canyon
A large canyon system called Valles Marineris is long enough to stretch from California to New York – more than 3,000 miles (4,800 kilometers). This Martian canyon is 200 miles (320 kilometers) at its widest and 4.3 miles (7 kilometers) at its deepest. That's about 10 times the size of Earth's Grand Canyon.
The Largest Volcano
Mars is home to the largest volcano in the solar systemOlympus Mons. It dwarfs Earth's highest peakMount Everest — which rises 29,029 feetor 8,848 metersabove the Earth's surface. Olympus Mons stands more than 25 miles (that's more than 132,000 feetor 40 kilometers) tall from base to summitwith the base covering an area as large as the state of Arizona.
Water on Mars
Mars appears to have had a watery pastwith ancient river valley networksdeltasand lakebedsas well as rocks and minerals on the surface that could only have formed in liquid water. Some features suggest that Mars experienced huge floods about 3.5 billion years ago.
There is water on Mars todaybut the Martian atmosphere is too thin for liquid water to exist for long on the surface. Todaywater on Mars is found in the form of water-ice just under the surface in the polar regions as well as in briny (salty) waterwhich seasonally flows down some hillsides and crater walls.
Atmosphere
Mars has a thin atmosphere made up mostly of carbon dioxidenitrogenand argon gases. To our eyesthe sky would be hazy and red because of suspended dust instead of the familiar blue tint we see on Earth. Mars' sparse atmosphere doesn't offer much protection from impacts by such objects as meteoritesasteroidsand comets.
The temperature on Mars can be as high as 70 degrees Fahrenheit (20 degrees Celsius) or as low as about -225 degrees Fahrenheit (-153 degrees Celsius). And because the atmosphere is so thinheat from the Sun easily escapes this planet. If you were to stand on the surface of Mars on the equator at noonit would feel like spring at your feet (75 degrees Fahrenheit or 24 degrees Celsius) and winter at your head (32 degrees Fahrenheit or 0 degrees Celsius).
Occasionallywinds on Mars are strong enough to create dust storms that cover much of the planet. After such stormsit can be months before all of the dust settles.
Magnetosphere
Mars has no global magnetic field todaybut areas of the Martian crust in the southern hemisphere are highly magnetizedindicating traces of a magnetic field from 4 billion years ago.
NASA Launches Twin Satellites to Investigate Mars' Space Weather
NASA's Escape and Plasma Acceleration and Dynamics Explorers (ESCAPADE) missionwhich launched Nov. 13will study Mars' real-time response to the solar windhelping us better understand Mars' climate history — from a planet that hosted riverslakesand floods billions of years agoto the colddry desert we see on the surface today. The twinrefrigerator-sized orbiters are scheduled to arrive at Mars in September 2027and begin their science mission the following spring.
Learn More About the ESCAPADE Mission
