Mars |
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Mars was among the first bodies in the Solar System to be viewed through a telescope. Early astronomers saw faint surface features along with evidence of changing seasons and speculated about an advanced Martian civilisation. Though these ideas are comical today, the search for more primitive life continues.
NASA's Mariner and Viking probes in the 1960s and 1970s found a cold, apparently lifeless planet with huge volcanoes and canyons and evidence of past surface floods.
More recently, six-wheeled rovers have confirmed that water ice exists below the surface. |
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Photo: Mars taken by Mars Global Surveyor (NASA/JPL/MSSS) |
About Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts, and polar ice caps of Earth. The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, as is the tilt that produces the seasons. Mars is the site of Olympus Mons, the highest known mountain within the Solar System, and of Valles Marineris, the largest canyon. The smooth Borealis basin in the northern hemisphere covers 40% of the planet and may be a giant impact feature.
Until the first successful flyby of Mars occurred in 1965, by Mariner 4, many speculated about the presence of liquid water on the planet's surface. This was based on observed periodic variations in light and dark patches, particularly in the polar latitudes, which appeared to be seas and continents; long, dark striations were interpreted by some as irrigation channels for liquid water. These straight line features were later explained as optical illusions, though geological evidence gathered by unmanned missions suggest that Mars once had large-scale water coverage on its surface. In 2005, radar data revealed the presence of large quantities of water ice at the poles, and at mid-latitudes. The Mars rover Spirit sampled chemical compounds containing water molecules in March 2007. The Phoenix lander directly sampled water ice in shallow Martian soil on July 31, 2008.
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 is currently host to three functional orbiting spacecraft: Mars Odyssey, Mars Express, and the Mars Reconnaissance Orbiter. On the surface are the Mars Exploration Rover Opportunity and its recently decommissioned twin, Spirit, along with several other inert landers and rovers, both successful and unsuccessful. The Phoenix lander completed its mission on the surface in 2008. Observations by NASA's now-defunct Mars Global Surveyor show evidence that parts of the southern polar ice cap have been receding. Observations by NASA's Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest months on Mars.
Mars can easily be seen from Earth with the naked eye. Its apparent magnitude reaches −3.0 a brightness surpassed only by Jupiter, Venus, the Moon, and the Sun. Optical ground based telescopes are typically limited to resolving features about 300 km (186 miles) across when Earth and Mars are closest, because of Earth's atmosphere. |
Mars Reconnaissance Orbiter (MRO)
The Mars Reconnaissance Orbiter, launched in 2005, is currently making a detailed survey of the Red Planet. The spacecraft's instruments include a spectrometer, radar and a high resolution camera powerful enough to pick out the six-wheeled rovers Spirit and Opportunity from orbit.
The probe is looking for evidence that liquid water persisted for a long time on the Martian surface and is studying the planet's mineral make-up and weather patterns. |
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Photo: The Mars Reconnaissance Orbiter's view of the rover Opportunity (circled) at the rim of Victoria Crater (NASA/JPL-Caltech) |
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Mars Exploration Rover
Starting in 2004, NASA's Mars Exploration Rover mission sent two unmanned robotic probes, Spirit and Opportunity, crawling across the Red Planet's surface. The six-wheeled vehicles found strong evidence of past flowing water, including apparent ancient lakeshore deposits.
Their mission was designed to last 90 days. However, both probes vastly exceeded their predicted lifetimes and in 2009, though showing signs of age, they were still responding to mission control's commands. |
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Photo: Artist's impression of Spirit on the surface of Mars (NASA)
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Mars Pathfinder
The Mars Pathfinder mission demonstrated a new landing technique and showed that it was possible to send a robotic wheeled rover to explore another planet.
Before it hit the Martian surface in 1997, a cluster of airbags inflated and enveloped the probe. Already slowed by its heat shield, parachutes and rockets, the craft bounced across Mars until it came to rest. The lander opened and sent a robotic vehicle, Sojourner, down a ramp to photograph and sample the surface. |
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Photo: Sojourner leaves tracks on Mars (NASA/JPL) |
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Deimos
One of a pair of irregular, small moons orbiting Mars, Deimos was discovered by the American astronomer Asaph Hall in 1877 along with its fellow satellite, Phobos.
Both moons are grey in colour, cratered and generally similar in appearance to asteroids that orbit between Mars and Jupiter. One theory is that both moons were once asteroids that were captured by Mars's gravitational force, but this has not been confirmed. |
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Photo: Deimos taken by the Mars Reconnaissance Orbiter (NASA/JPL-Caltech/University of Arizona) |
Phobos
One of a pair of irregular, small moons orbiting Mars, Phobos was discovered by the American astronomer Asaph Hall in 1877 along with its fellow satellite, Deimos.
Both moons are grey in colour, cratered and generally similar in appearance to asteroids that orbit between Mars and Jupiter. One theory is that both moons were once asteroids that were captured by Mars's gravitational force, but this has not been confirmed. |
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Photo: Phobos taken by the Mars Global Surveyor probe (NASA/JPL/Malin Space Science Systems) |
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