Mars


Mass (Earth=1)0.107
Equatorial diameter (km)6,790
Period (years)1.88
Mean distance from Sun, 106 km228
Density (water=1)3.95
Surface gravity m/s23.72

The Red Planet features ice caps of carbon dioxide and water, a volcano 15 miles high (Olympus Mons), a canyon 3,000 miles long and 4 miles deep (the great rift valley, Valles Marinerus), and dry river channels. Many such features were explored in 1971-72 by the Mariner-9 craft. The later Viking landers performed surface tests, looking for evidence of life.

Perhaps Mars, now locked in an ice age, once had a denser atmosphere and liquid water on its surface. But NASA's two Viking landers (1976) found no life.

Mars' moons
Planetary data
Size comparison with Earth
Index

Mars Concepts

Solar System Illustration

Solar System Concepts
 
HyperPhysics********** Astrophysics R Nave
Go Back





Mars Size Comparison with Earth

Index

Solar System Illustration

Solar System Concepts

Mars Study Guide
 
HyperPhysics********** Astrophysics R Nave
Go Back





Moons of Mars


Phobos
Color image of Phobos, imaged by the Mars Reconnaissance Orbiter on 23 March 2008. It was taken from a distance of about 6,800 kilometers (about 4,200 miles). Image credit NASA / JPL-Caltech / University of Arizona
Phobos has a mean radius of 11 km and is seven times as massive as the outer moon, Deimos. "Phobos orbits 6,000 km (3,700 mi) from the Martian surface, closer to its primary body than any other known planetary moon. It is so close that it orbits Mars much faster than Mars rotates, and completes an orbit in just 7 hours and 39 minutes. As a result, from the surface of Mars it appears to rise in the west, move across the sky in 4 hours and 15 minutes or less, and set in the east, twice each Martian day."(from Wikipedia)

Deimos
Color-enhanced image of Deimos, a moon of Mars, captured by the HiRISE instrument on the Mars Reconnaissance Orbiter on 21 Feb 2009.

The small rocky moons of Mars, Deimos and Phobos, are irregular in shape and comparable in size to the asteroid Gaspra. The three objects are shown at the same scale and almost the same lighting conditions in the image linked below. All three bodies have irregular shapes, testament to their violent histories. Their surfaces are distinctly different, most likely because of very different impact histories.

Closeups of Deimos and Phobos
Size comparison with asteroid Gaspra
Index

Solar System Illustration

Solar System Concepts
 
HyperPhysics********** Astrophysics R Nave
Go Back