| | This images shows the current relative positions of the Earth and Mars in their orbits (as of today). The "stick" through each planet represents its axis of rotation. Image courtesy of the Center for Mars Exploration (CMEX).
Two other perspectives of the orbits of Earth and Mars. This "near-sideways" angle makes it easier to the see axis tilt of each planet.
As of midnight GMT today, this is the part of Mars that was facing the Earth (simulated telescope view).
The CMEX creates an online "poster" daily with these images and others. Click on the thumbnail to the right for a larger version of the poster.
Visit Mars Today or CMEX for more information. |
| This app computes the current distance from the Earth to Mars (the length of the white line between Earth and Mars shown in the images on the above left). An "astronomical unit" (AU) is the average distance from the Earth to the Sun (a measure commonly used in astronomy). The "light time" shown here is the time it takes light (or a radio signal) to traverse the current Earth-Mars distance. |
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Mars has two natural satellites (or moons) called Phobos and Deimos. Phobos (in the lower orbit) is an irregularly-shaped rock measuring 26 km by 22 km by 18 km. It orbits at a distance of roughly 9,380 km, making a complete orbit in less than eight hours.
Deimos is roughly half as large (15 km by 12 km by 10 km) and orbits roughly 23,460 km from Mars, with an orbital period of 30.4 hours.
Top left: This GIF animation shows the relative orbital speeds of Martian moons Phobos and Deimos (sped up by a factor of more than 10,000).
Bottom left: Another GIF animation (made from photographs) showing Phobos transiting across the sun (taken from the surface by Mars Rover Opportunity).
Top right: A color-enhanced image of Phobos taken by the Mars Reconaissance Orbiter.
Bottom right: An image of Deimos taken by Viking 1. | 
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 | This excellent poster offers information on every Mars mission, past and future. This is a must-see. |
Help us build this section into the world's finest collection of Mars related information! If you have any facts you want us to add or you would like to become a member of MarsDrive please contact us at info@marsdrive.com
Martian Day (or Sol): 24.6 Earth Hours
Martian Year: 1.88 Earth years = 687 Earth days = 669 Mars days
Distance from the Sun: Minimum 206,000,000 km to Maximum 249,000,000 km
Distance from Earth: Minimum 56,000,000 km to Maximum 399,000,000 km
Size: Diameter: 6792 km vs. 12,756 km for Earth
Surface Gravity: 0.38 (about 1/3) times Earth's gravity
Temperature: -125°C (-193°F) to 25°C (77°F)
The Mart ian atmosphere contains 95% carbon dioxide, 3% nitrogen, 1.5% argon, trace amounts of water, and no oxygen.
Earth has 78% nitrogen, 21% oxygen, 1% argon, and 0.03% carbon dioxide.
Mars (Greek: Ares) When the recent Mars Exploration Rovers landed it was reported the JPL website monitoring their progress had more visits than any website in internet history. What is it about Mars that seems to create such constant interest these days? Isn't it just a dry dusty red planet millions of miles away in space?
Many of the robotic explorers that have landed on the surface of Mars have been set down in what is know as "Runway Zones" because they resemble the wide open and flat areas similar to modern airport runways. These are usually the featureless and boring areas we see beamed back to us and mostly robotic probes are landed in such areas for safety reasons. These sorts of dry and featureless pictures have not proven to be very interesting to the casual viewer and as a result images of a dead and barren desert have been seared into our minds as what is typical of Mars.
Yet Mars is more far interesting than you may realize. Only 100 years ago, we knew virtually nothing about the surface of Mars; but now in recent years a new series of robotic missions to the red planet has uncovered an increasing number of strange new details we have never seen before. 130 meter wide cave entrances have been spotted on the slopes of one of Mars highest mountains, Arsia Mons, and carbon dioxide jets were imaged over the south pole of Mars. Water ice has been observed gushing out of the side of gullies and craters on Mars; we have found lakes of ice and buried oceans also.
Mars is home to the highest mountain in the solar system, the towering Olymous Mons (or Mount Olympus), which rises 26 kilometers above the surrounding plains, over three times the height of our own Mt. Everest.
Mars also has the largest, longest, and deepest canyon in the solar system -- Valles Marineris. A feature so massive it can be spotted from Earth based telescopes and one which helped give rise to the tales of "Martian canals" of the 19th century. This canyon ranges from 2 to 8 Km deep, 4500 km long and up to 200 km wide. If you were standing in the middle of it you could not see the canyon walls, because they are so far away. Mars truly is a world of mystery, and with every new mission we discover new facts which tell us more about the history and differences between Mars and our own planet.
Mars has been known since prehistoric times. Of course, it has been extensively studied with ground-based observatories. But even very large telescopes find Mars a difficult target -- it's just too far away. It is still a favorite of science fiction writers as the most favorable place in the Solar System (other than Earth!) for human habitation. But the famous "canals" that were "seen" by Lowell and others were unfortunately just as imaginary as the Barsoomian princesses in the fiction of the 1930s.
The first spacecraft to visit Mars was Mariner 4 in 1965. Several others followed including Mars 2, the first spacecraft to land on Mars and the two Viking landers in 1976. Ending a long 20 year hiatus, Mars Pathfinder landed successfully on Mars on 1997 July 4. In 2004 the Mars Expedition Rovers "Spirit" and "Opportunity" landed on Mars, sending back geologic data and many pictures; they are still operating after several years on Mars.
Four Mars orbiters (Mars Reconnaissance Orbiter, Mars Global Surveyor, Mars
Odyssey, and Mars Express) are also currently in operation. The orbit of Mars is significantly elliptical. One result of this is a temperature variation of about 30 C at the subsolar point between aphelion and perihelion. This has a major influence on the Martian climate.
While the average temperature on Mars is about 218 K (-55 C, -67 F), Martian surface temperatures range widely from as little as 140 K (-133 C, -207 F) at the winter pole to almost 300 K (27 C, 80 F) on the day side during summer. Though Mars is much smaller than Earth, its surface area is about the same as the land surface area of Earth. Mars is named for the Roman god of War. The planet probably got this name due to its red color; Mars is sometimes referred to as the Red Planet. (An interesting side note: the Roman god Mars was a god of agriculture before becoming associated with the Greek Ares; those in favor of settling and terraforming Mars may prefer this symbolism.) The name of the month March derives from Mars.
courtesy of Nine Planets.org
A terrestrial planet, Mars has a thin atmosphere and surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts, and polar ice caps of Earth. In addition to its geographical features, Mars’ rotational period and seasonal cycles are likewise similar to those of the Earth.
Until the first flyby of Mars by Mariner 4 in 1965, it was speculated that there 
might be liquid water on the planet. This was based on observations of periodic variations in light and dark patches, particularly in the polar latitudes, which looked like seas and continents, while long, dark striations were interpreted by some observers as irrigation channels for liquid water. These straight line features were later proven not to exist and were instead explained as optical illusions. Still, of all the planets in our solar system, Mars is the most likely, other than Earth, to harbor liquid water and perhaps life.
Mars is currently host to four functional orbiting spacecraft, more than any planet except Earth. The surface is also home to the two Mars Exploration Rovers (Spirit and Opportunity). Geological evidence gathered by these and preceding missions suggests that Mars previously had large-scale water coverage, while observations also indicate that small geyser-like water flows have occurred in recent years. Observations by NASA's Mars Global Surveyor show evidence that parts of the southern polar ice cap have been receding.
Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Martian Trojan asteroid. Mars can be seen from Earth with the naked eye. Its apparent magnitude reaches −2.9, a brightness surpassed only by Venus, the Moon, and the Sun, though for much of the year Jupiter may appear brighter to the naked eye than Mars. From Wikipedia.
Planetary Data
Mars Orbiters
Mars Express
Mars Recon Orbiter
"Live" images from the Odyssey Orbiter
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Mars Exploration Missions -to date
Future Mars Exploration Missions
Russian Mission Plans
Phobos-Grunt 2009
Mars, A History and Future
Mars Science Lab
ESA Mission Plans
The article in the link above contains a good amount of information of the history of humans mission designs, including our own recent efforts.
Physical Characteristics
Mars has half the radius of Earth and only one-tenth the mass, being less dense, but its surface area is only slightly less than the total area of Earth's dry land. While Mars is larger and more massive than Mercury, Mercury has a higher density. This results in a slightly stronger gravitational force at Mercury's surface. The red-orange appearance of the Martian surface is caused by iron(III) oxide, more commonly known as hematite, or rust.
Geology
Based on orbital observations and the examination of the Martian meteorite collection, the surface of Mars appears to be composed primarily of basalt. Some evidence suggests that a portion of the Martian surface is more silica-rich than typical basalt, and may be similar to andesitic stones on Earth; however, these observations may also be explained by silica glass. Much of the surface is deeply covered by a fine iron(III) oxide dust that has the consistency of talcum powder.
Although Mars has no intrinsic magnetic field, observations show that parts of the planet's crust have been magnetized. This paleomagnetism of magnetically-susceptible minerals has properties that are very similar to the alternating bands found on the ocean floors of Earth. One theory, published in 1999 and re-examined in October 2005 (with the help of the Mars Global Surveyor), is that these bands demonstrate plate tectonics on Mars 4 billion years ago, before the planetary dynamo ceased to function (and, thus, the magnetic field).
Current models of the planet's interior imply a core region approximately 1,480 kilometres (920 mi) in radius, consisting primarily of iron with about 15–17% sulfur. This iron sulfide core is partially fluid, and has twice the concentration of the lighter elements than exist at the Earth's core. The core is surrounded by a silicate mantle that formed many of the tectonic and volcanic features on the planet, but now appears to be inactive. The average thickness of the planet's crust is about 50 km (31 mi), with a maximum thickness of 125 km (78 mi). Earth's crust, averaging 40 km (25 mi), is only a third as thick as Mars’ crust relative to the sizes of the two planets.
The geological history of Mars can be split into many epochs, but the following are the three main ones:
- Noachian epoch (named after Noachis Terra): Formation of the oldest extant surfaces of Mars, 3.8 billion years ago to 3.5 billion years ago. Noachian age surfaces are scarred by many large impact craters. The Tharsis bulge volcanic upland is thought to have formed during this period, with extensive flooding by liquid water late in the epoch.
- Hesperian epoch (named after Hesperia Planum): 3.5 billion years ago to 1.8 billion years ago. The Hesperian epoch is marked by the formation of extensive lava plains.
- Amazonian epoch (named after Amazonis Planitia): 1.8 billion years ago to present. Amazonian regions have few meteorite impact craters but are otherwise quite varied. Olympus Mons formed during this period along with lava flows elsewhere on Mars.
Liquid water cannot exist on the surface of Mars with its present low atmospheric pressure, but water ice is in no short supply, with two polar ice caps made largely of ice. In March 2007, NASA announced that the volume of water ice in the south polar ice cap, if melted, would be sufficient to cover the entire planetary surface to a depth of 11 metres (36 ft). Additionally, an ice permafrost mantle stretches down from the pole to latitudes of about 60°. Much larger quantities of water are thought to be trapped underneath Mars' thick cryosphere, only to be released when the crust is cracked through volcanic action. The largest such release of liquid water is thought to have occurred when the Valles Marineris formed early in Mars' history, enough water being released to form river valleys across the planet. A smaller but more recent event of the same kind occurred when the Cerberus Fossae chasm opened about 5 million years ago, leaving a sea of frozen ice still visible today on the Elysium Planitia.
More recently the high resolution Mars Orbiter Camera on the Mars Global Surveyor has taken pictures which give much more detail about the history of liquid water on the surface Mars. Despite the many giant flood channels and associated tree-like network of tributaries found on Mars there are no smaller scale structures that would indicate the origin of the flood waters. It has been suggested that weathering processes have denuded these, indicating the river valleys are old features. Higher resolution observations from spacecraft like Mars Global Surveyor also revealed at least a few hundred features along crater and canyon walls that appear similar to terrestrial seepage gullies. The gullies tend to be located in the highlands of the southern hemisphere and to face the Equator; all are poleward of 30° latitude. The researchers found no partially degraded (i.e. weathered) gullies and no superimposed impact craters, indicating that these are very young features.
More information on Mars can be found here.