The Planet

Mars is no place for the faint-hearted. Arid, rocky, cold and apparently lifeless, the Red Planet offers few hospitalities. Fans of extreme sports can rejoice, however, for the Red Planet will challenge even the hardiest souls among us. Home to the largest volcano in the solar system, the deepest canyon and crazy weather and temperature patterns, Mars looms as the ultimate lonely planet destination.

Size

Volumetric Mean Radius

Volumetric Mean Radius


Distance from the planet's center to its surface, if the planet's volume were contained in a symmetric sphere

About half (53.2%) that of Earth

Mars:
3,389.5 kilometers
or
2,106.1 miles

Earth:
6,371 kilometers
or
3,958.8 miles

Polar Radius

Polar Radius


Half the diameter of the planet from pole to pole

About half (53.1%) that of Earth

Mars:
3,376.2 kilometers
or
2,098 miles

Earth:
6,356.8 kilometers
or
3,950 miles

Equatorial Radius

Equatorial Radius


Half the diameter of the planet at its equator

About half (53.2%) that of Earth

Mars:
3,396.2 kilometers
or
2,110 miles

Earth:
6,378.1 kilometers
or
3,963 miles

Equatorial Circumference

Equatorial Circumference


A measurement of the distance around the equator of Mars

About half (53.2%) that of Earth

Mars:
21,339 kilometers
or
13,259 miles

Earth:
40,075 kilometers
or
24,901 miles

Radius of the Core

Radius of the Core


The distance from the planet's center to the outer boundary of the core

About half (50%) that of Earth

Mars:
Total core:
1,700 kilometers
or
1,056 miles

Earth:
Total core:
~3,400 kilometers
or
2,113 miles

"Solid" inner core:
~1,220 kilometers
or
758 miles

Liquid outer core:
~2,266 kilometers
or
1,408 miles

Surface Area

Surface Area


The sum of the areas of all shapes that cover the surface of the planet

About 28% that of Earth

Mars:
144,371,391 square kilometers
(1.4437 x 108 km2)
or
55,742,106 square miles

Earth:
510,064,472 square kilometers
(5.1006 x 108 km2)
or
196,936,994 square miles

Bulk

Volume

Volume


The quantity of three-dimensional space that a planet contains

About 15.1% that of Earth

Mars:
163,115,609,799 cubic kilometers
(1.63116 x 1011 km3)

Earth:
1,083,206,916,846 cubic kilometers
(1.0832 x 1012 km3)

Mass

Mass


A measurement of the amount of matter Mars contains

About 11% that of Earth

Mars:
641,693,000,000,000,000,000,000 kilograms
(6.4169 x 1023 kg)

Earth:
5,972,190,000,000,000,000,000,000 kilograms
(5.9722 x 1024 kg)

Mean Density

Mean Density


The planet's total mass divided by its total volume, which gives some clues about the planet's makeup (e.g., how much metal it has) and whether it is solid or gaseous

About 71% as dense as Earth

Mars:
3,933 kilogram/meter3

Earth:
5,514 kilogram/meter3

Gravity and More

Surface Gravity

Surface Gravity


The gravitational acceleration experienced at a planet's surface

About 38% that of Earth

Mars:
3.71 meters per second squared
or
12.2 feet per second squared

Earth:
9.80665 meters per second squared
or
32.174 feet per second squared

Escape Velocity

Escape Velocity


The speed an object needs to break free from the gravitational attraction of a planet, moon, or other body without further propulsion

About 45% that of Earth

Mars:
18,108 kilometers per hour
(5.03 km/second)
or
11,252 miles per hour

Earth:
40,284 kilometers per hour
(11.19 km/second)
or
25,030 miles per hour

Temperature

Land Surface Temperature

Temperature of the Surface
(Typical Minimum/Maximum)


How hot or cold the surface varies between day and night and among seasons

Mars is colder than Earth because it is farther from the Sun.

Mars:
-190 to 86° Fahrenheit
-120 to 30° Celsius
150 to 303 Kelvin

Earth:
-126 to 136° Fahrenheit
-88 to 58° Celsius
185 to 331 Kelvin

Average Temperature of the Atmosphere

Average Temperature of the Atmosphere


Measurement of how hot or cool the atmosphere is at different altitudes (heights relative to the surface)

Mars:
-81° Fahrenheit
-63° Celsius
210 Kelvin

Earth:
59° Fahrenheit
15° Celsius
288 Kelvin

Composition

The Planet

Composition of the Planet


The chemical materials that make up a planet

Mars' composition is similar to Earth's

Mars:
Crust and Surface : mostly iron-rich basaltic rock similar to Earth's thin crust

Mantle: Silicate rock

Core: probably an iron, nickel, and sulfur core, but whether it is hot liquid or cooled metal is not known

Earth:
Crust and Surface: iron magnesium silicate igneous rocks, like basalt

Mantle: Silicate rock rich in magnesium and iron

Core: Iron-nickel alloy

Atmosphere

Composition of the Atmosphere


The chemical materials that make up the layers of gases surrounding a planet or moon, which are held in place by the object's gravity

Mars' atmosphere is 100 times less dense than Earth's

Mars:
Main Gases:
96% Carbon Dioxide (CO2)*
1.93% Argon (Ar)**
1.89% Nitrogen (N2)
0.145% Oxygen (O2)
<0.01% Carbon Monoxide (CO)

Earth:
Main Gases:
78.09% Nitrogen (N2)
20.95% Oxygen (O2)
0.93% Argon (Ar)
0.039% Carbon Dioxide (CO2)


Both planets also have other gases in very small amounts (trace gases).

Did you know...?
*Carbon dioxide is used for carbonation in beverages. Frozen carbon dioxide is "dry ice."

**Argon is used to make blue "neon lights."


In Space

Distance

Perihelion

Perihelion


The closest distance between the Sun and Mars as the Red Planet travels in its orbit around the Sun

1.405 times that of Earth

Mars:
206,655,215 kilometers
2.06655 x 108 km
or
128,409,598 miles
or
1.381 AU

Earth:
147,098,291 kilometers
1.47098 x 108 km
or
91,402,640 miles
or
0.9833 AU*



An AU is an astronomical unit. In simple terms, 1 AU is the average distance between the Sun and Earth.

Did you know...?
*The reason that the perihelion of Earth is less than 1 AU is that this is a measure of its closest distance from the Sun (its minimum distance). 1 AU is the average between the minimum and maximum distances.
Aphelion

Aphelion


The farthest distance between the Sun and Mars as the Red Planet travels in its orbit around the Sun

1.639 times that of Earth

Mars:
249,232,432 kilometers
2.49232 x 108 km
or
154,865,853 miles
or
1.666 AU

Earth:
152,098,233 kilometers
1.52098 x 108 km
or
94,509,460 miles
or
1.017 AU


An AU is an astronomical unit. In simple terms, 1 AU is the average distance between the Sun and Earth.

Orbit

Orbit Size Around Sun

Orbit Size Around Sun
(semi-major axis)


One half of the longest diameter of an orbital ellipse (radius of the orbit at the orbit's two most distant points)

About 1.5 times that of Earth

Mars:
227,943,824 kilometers
2.2794382 x 108 km
or
141,637,725 miles
or
1.523662 AU

Earth:
149,598,262 kilometers
1.4959826 x 108 km
or
92,956,050 miles
or
1.000 AU


An AU is an astronomical unit. In simple terms, 1 AU is the average distance between the Sun and Earth.

Circumference of Orbit

Circumference of Orbit


The distance Mars travels in its orbit around the Sun.

About 1.5 times that of Earth

Mars:
1,429,085,052 kilometers
(1.429 x 109) km
or
887,992,283 miles

Earth:
939,887,974 kilometers
(9.399 x 108) km
or
584,019,311 miles


Orbital Eccentricity

Orbital Eccentricity


A measurement of how much Mars' orbit around the Sun differs from a perfect circle; 0 = a perfect circle, and values between 0 and 1 represent an elliptical (oval) orbit

Mars' orbit is about 5.6 times more eliptical than that of Earth, which is nearly a perfect circle

Mars:
0.0933941

Earth:
0.01671123

Orbit Inclination

Orbit Inclination


The angle an orbit is "tilted" relative to a reference plane

Earth's orbital plane is almost flat, but Mars' has a slight tilt

Mars:
1.85 degrees

Earth:
0.00005 degrees


0 degrees (reference plane for describing the position of bodies in the solar system)

The ecliptic is the plane of Earth's orbit around the Sun

Speed

Average Orbital Velocity

Average Orbital Velocity


The rate of change in Mars' position: how fast it is moving in its orbit around the Sun (its speed)

About 81% (0.808) that of Earth

Mars:
86,677 kilometers per hour
(2.4077 x 104 meters per second)
or
53,858 miles per hour

Earth:
107,218 kilometers per hour
(2.9783 x 104 meters per second)
or
66,622 miles per hour

Year

Length of Year

Length of Year
(Sidereal Period or Revolution)


The time it takes for a planet or other body to make a full orbit of the Sun (or outside of our solar system, its primary star)

About twice as long as an Earth year

Mars:
about 687 Earth days

Earth:
365.25 Days

Tilt / Seasons

Axial Tilt

Axial Tilt
(Obliquity)


The angle between Mars' orbital plane and its spin axis

Very similar to Earth's - only a 2-degree difference

Mars:
25.2°

Earth:
23.5°

Change in Axial Tilt

Change in Axial Tilt


Variations in the angle of tilt

The tilt of Mars changes more dramatically over time

Unlike Earth, substantial changes in the obliquity (or tilt) of Mars occur on timescales of hundreds of thousands to millions of years and result in long-term climate change

Change in Axial Tilt Seasons

Seasons


Changes in the amount of sunlight reaching different latitudes due to the varying orientation of the axial tilt as the planet orbits the Sun

Mars' year is almost twice as long as Earth's so its seasons are longer too

4 seasons, roughly twice as long as those on Earth, but with more variation given Mars' eccentric orbit and the fact its orbital speed varies more as result (fastest when at perihelion; slowest at aphelion)

Season (Northern Hemisphere) Length of Season on Earth Length of Season on Mars
Spring 93 194
Summer 93 178
Autumn 90 142
Winter 89 154


Day

Average Length of Day

Average Length of Day
(Sidereal Rotation Period)


The time it takes for a planet or other body to make one rotation (one spin on its axis)

About 37 minutes longer than an Earth day

Mars:
24 hours, 37 minutes
(24.623 hours)
1.029 Earth days

Earth:
23 hours, 56 minutes
(23.934 hours)

In Our Night Sky

Mars Opposition

Mars Opposition

The distance to Mars varies from about 56 million kilometers (about 35 million miles) to 400 million kilometers (about 249 million miles). Why the difference? And why so close now?

Solar Conjunction

Solar Conjunction

When the Sun comes between Earth and Mars, communications with Mars spacecraft diminish drastically. Find out how the mission teams cope!

Mars Retrograde

Mars Retrograde

When Mars is close, it appears to move backwards from night to night! Find out why.

Find out where and when Mars will be in your neighborhood.

Mars Close Approaches

Mars Close Approaches

Close is a relative term. At its closest, Mars is still tens of millions of miles away from Earth. Still, the decreased distance during "closest approach" allows for fuel-conserving flights to Mars every 26 months and a good view of Mars once or twice every 15 to 17 years for Earth-bound sky watchers. For help viewing Mars, please contact your local Night Sky Network astronomy club.

Human Time

Human Time

Humans from all cultures around the world have been curious about the "Red Planet" Mars since before recorded history.