Mars & Moons
Mars is the fourth planet from the Sun and last of the terrestrial planets and is around 227,940,000 km from the Sun. The planet is named after Mars, the Roman god of war. It was known to the ancient Greeks as Ares, their god of war. This is thought to be because of the blood-red color of the planet which was also used by other ancient cultures. Chinese astronomers call Mars the “fire star” while ancient Egyptian priests called it “Her Desher” meaning “the red one”. The landmass of Mars and Earth is very similar. Despite Mars being just 15% the volume and 10% the mass of Earth, it actually has a similar landmass because water covers about 70% of Earth’s surface. The surface gravity of Mars is about 37% the gravity found on Earth. This means that on Mars you could in theory jump 3x higher than you could on Earth. Only 16 of the 39 Mars missions have been successful. Beginning with the USSR’s Marsnik 1 which was launched in 1960, 39 orbiters, landers and rovers have been to Mars but only 16 of those missions were a success. In 2016, Europe’s Exobiology on Mars program will search the planet for signs of Martian life as well as study the surface and terrain of the planet and map potential environmental hazards to future manned missions to Mars. Pieces of Mars have been found on Earth. It is believed that trace amounts of the Martian atmosphere were within meteorites that the planet ejected. These meteorites then orbited the solar system for millions of years amongst the other objects and solar debris before eventually entering the Earth’s atmosphere and crashing to the ground. The study of this material has allowed scientists to discover more about Mars before launching space missions. Mars was once believed to be home to intelligent life. This came from the discovery of lines or grooves in the surface called canali by Italian astronomer Giovanni Schiaparelli. He believed that these were not naturally occurring and were proof of intelligent life. However, these were later shown to be an optical illusion. The tallest mountain known in the solar system is on Mars. Olympus Mons is a 21 km high and 600 km diameter shield volcano that was formed billions of years ago. Scientists have found a lot of recent evidence of volcanic lava which suggests Olympus Mons may still be active. It is the second highest mountain in the entire solar system, topped only by the Rheasilvia central peak on the asteroid Vesta, which is 22 km high. Mars experiences huge dust storms – the largest in our solar system. This is due to the elliptical shape of the planet’s orbit path around the Sun. The orbit path is more elongated than many of the other planets and this oval shaped orbit results in fierce dust storms that cover the entire planet and can last for many months. The Sun looks about half its size half it does from Earth when seen from Mars. When Mars is closest to the Sun in its orbit the southern hemisphere points toward the Sun and this causes a very short but fiercely hot summer. In the north it experiences a brief but cold winter. When the planet is farthest from the Sun, Mars experiences a long and mild summer because the northern hemisphere points toward the Sun. This is compared with a cold and lengthy winter in the south. With the exception of Earth, Mars is the most hospitable to life – a number of space missions are planning for the next decade the further increase our understanding of Mars and when it has the potential for extraterrestrial life, as well as whether it may be a viable planet for a colony. Martians, also known as extraterrestrials from Mars, are a common character in science fiction books and movies. This makes Mars one of the most popular and talked about planets in the solar system. It takes Mars 687 Earth days to orbit the Sun with its orbit radius of 227,840,000 km. Mars is the only other planet besides Earth that has polar ice caps. The northern cap is called the Planum Boreum, with Planum Australe in the south. Water ice has also been found under the Martian ice caps. Mars has seasons like Earth, but they last twice as long. This is because Mars is tilted on its axis by about 25.19 degrees, which is similar to the axial tilt of the Earth (22.5 degrees). The orbit of Mars is the most eccentric of the eight planets. This means it is the least circular orbit path of the planets. The two moons of Mars, Phobos and Deimos, were written about in the book ‘Gulliver’s Travels’ by author Jonathan Swift – 151 years before they were discovered. Mars does not have a magnetic field – although there are some scientists that believe it did have a magnetic field somewhere around 4 billion years ago. It was believed life existed on Mars for much of the nineteenth century. The reason behind this belief was part mistake and part imagination. In 1877, the astronomer Giovanni Schiaparelli observed what he believed to be straight lines on Mars’ surface. As others noticed these lines, some suggested that they were too straight and could only be the work of intelligent life. The popular conclusion as to the nature of these lines was that they were canals constructed for irrigation purposes. However, with the development of more powerful telescopes in the early twentieth century, astronomers were able to view the Martian surface more clearly and determine that these straight lines were merely an optical illusion. As a result, the earlier claims of life on Mars were without evidence and, therefore, discarded. The large amount of science fiction written during the twentieth century was a direct outgrowth of the belief that Mars possessed life. From little green men to death rays, Martians were the focus of many television and radio programs, comic books, movies, and novels. Although the discovery of Martian life in the eighteenth century eventually proved to be false, Mars is nonetheless the planet most hospitable for life other than the Earth. As such, recent planetary missions have tried to determine if even the most basic of life exists on the planet’s surface. The Viking mission in the 1970s conducted experiments on the Martian soil in hopes of detecting microorganisms. While it was initially believed that the formation of compounds during the experiments were a result of biological agents, it has since been determined that these compounds can be created without biological mechanisms. Even though the results lean toward the absence of life on Mars, scientists have speculated that conditions are right for life to exist beneath the planet’s surface. Future planetary missions scheduled to test the possibility of past and present life include the Mars Science Laboratory and ExoMars missions.
Atmosphere The composition of Mars’ atmosphere is extremely similar to Venus’, one of the least hospitable atmospheres in all of the Solar System. The main component in both atmospheres is carbon dioxide (95% for Mars, 97% for Venus), yet a runaway greenhouse effect has taken hold of Venus, producing temperatures in excess of 480° C, while temperatures on Mars never exceed 20° C. Thus, something other than the composition is at work. The huge difference lies in the density of the two atmospheres. Whereas Venus’ atmosphere is exceedingly thick, Mars’ is quite thin. Simply put, Mars would resemble Venus if it possessed a thicker atmosphere. Additionally, with such a thin atmosphere, the resulting atmospheric pressure is only about 1% of that found at sea level on Earth. That is the equivalent pressure found at 35 km above the Earth’s surface. One of the long standing areas of research regarding the Martian atmosphere is its impact on the presence of liquid water. What the research has shown is that even though the polar caps possess frozen water and the air contains water vapor—as a result of the freezing temperatures and low pressure caused by the weak atmosphere—it is not possible for liquid water to exist on the planet’s surface. However, evidence provided by planetary missions suggests liquid water does exist one meter below the planet’s surface. Surprisingly, despite the thin atmosphere, Mars experiences weather patterns. The primary form of this weather consists of winds, with other manifestations that include dust storms, frost, and fog. As a result of this weather, some erosion has been seen to take place at particular locations on the planet’s surface. As a final note on the Martian atmosphere, leading theories claim that it may have once been dense enough to support large oceans of water. However, through some means in the planet’s past the atmosphere was drastically altered. One popular explanation for this change is that Mars was struck by a large body and in the process a large portion of its atmosphere was ejected into space.
Surface The surface of Mars can be separated into two broad features, which, coincidentally, are divided by the planet’s hemisphere. The northern hemisphere is seen to be relatively smooth with few craters, whereas the southern hemisphere is an area of highlands that are more heavily cratered than the northern plains. Other than topographical differences, the distinguishing feature of the two regions appears to be geological activity, with the northern plains being much more active. The Martian surface is home to both the largest known volcano, Olympus Mons, and largest known canyon, Valles Marineris, in the Solar System. With a height of 25 km and a base diameter of 600 km, Olympus Mons is three times the height of Mt. Everest, the tallest mountain on the Earth. Valles Marineris is 4,000 km long, 200 km wide, and almost 7 km deep. To put the shear magnitude of its size into perspective, Valles Marineris would stretch from the East to West coast of the United States. Perhaps the most significant discovery regarding the Martian surface was the presence of channels. What is so meaningful about these channels is that they appear to have been created by running water, and thus providing evidence to support the theory that Mars could have been much more similar to the Earth at one time. A surface feature that has remained in popular culture since its image surfaced is the “Face on Mars.” When this photograph was captured by the Viking I spacecraft in 1976, many took it to be proof that alien life existed on Mars. However, subsequent images showed that lighting (and a little imagination) are what brought life to the formation.
Interior Similar to the other terrestrial planets, Mars’ interior is divided into three layers: a crust, mantle, and core. Although precise measurements cannot be made, scientists can make predictions as to the thickness of the planet’s crust based on the depth of Valles Marineris. Such a deep, extensive valley system, located in the southern hemisphere, could not be present unless the crust there is significantly thicker than the Earth’s. Estimates put its thickness in the northern hemisphere at 35 km, and 80 km in the southern hemisphere. There is a significant amount of research being conducted to determine whether or not Mars’ core is solid. Some scientists point to the lack of a significant magnetic field as an indication that the core is solid. However, within the past decade much data has been gathered to indicate that the core is at least partially liquid. With the discovery of magnetized rocks on the planet’s surface, it appears, at the very least, that Mars did possess a liquid core at some point in its history.
Orbit & Rotation The orbit of Mars is noteworthy for three reasons. First, its eccentricity is second largest among all the planets, smaller only than Mercury’s. As a result of this more elliptical orbit, Mars’ perihelion of 2.07 x 108 km is much larger than its aphelion of 2.49 x 108 km. Second, evidence suggests that this high degree of eccentricity has not always been present, and it may have been less than the Earth’s at some point in Mars’ history. The cause for this change is attributed to the gravitational forces exerted upon Mars by neighboring planets. Third, of all the terrestrial planets, Mars is the only one having a year that lasts longer than the Earth’s. This, of course, is due to its orbital distance. One Martian year is equal to almost 686 Earth days. It takes Mars about 24 hours 40 minutes to complete one full rotation, easily making the Martian day the closest in length to an Earth day. At roughly 25°, Mars’ axial tilt is yet another similarity the planet shares with Earth. What this means is Mars actually experiences seasons like those on Earth, though each is substantially longer because of the orbital distance of Mars. Unlike the Earth, however, Mars’ two hemispheres experience quite different temperatures for each season. This is due to the much larger eccentricity of the planet’s orbit. © The Planets.org
Underground Water on Mars
2. Mars Has Frozen Water Today: We’re very interested in the question of water because it implies habitability; simply put, life as we know it is more likely to exist with water there. In fact, the Curiosity rover’s mandate on Mars right now is to search for habitable environments (in the past or present). Mars has a thin atmosphere that does not allow water to flow or remain in large quantities on the surface, but we know for sure that there is ice at the poles — and possibly frosty locations elsewhere on the planet. The question is if the ice is capable of melting enough water in the summer long enough to support any microbes.
3. Mars Used To Have A Thicker Atmosphere: For water to flow in the past, the Red Planet needs more atmosphere. So something must have changed in the past few billion years. What? It is thought that the Sun’s energy striking the atmosphere must have “stripped” the lighter forms of hydrogen from the top, scattering the molecules into space. Over long periods of time, this would lessen the amount of atmosphere near Mars. This question is being investigated in more detail with NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft.
4. Mars Has Some Extreme Highs And Lows In Terrain: The surface gravity of Mars is only 37% of what you would find on Earth, which makes it possible for volcanoes to be taller without collapsing. This is why we have Olympus Mons, the tallest volcano known on a planet in the Solar System. It’s 16 miles (25 kilometers) high and its diameter is approximately the same as the state of Arizona, according to NASA. But Mars also has a deep and wide canyon known as Valles Marineris, after the spacecraft (Mariner 9) that discovered it. In some parts, the canyon is 4 miles (7 kilometers) deep. According to NASA, the valley is as wide as the United States and is about 20% of the Red Planet’s diameter.
5. Mars Has Two Moons – And One Of Them Is Doomed: The planet has two asteroid-like moons called Phobos and Deimos. Because they have compositions that are similar to asteroids found elsewhere in the Solar System, according to NASA, most scientists believe the Red Planet’s gravity snatched the moons long ago and forced them into orbit. But in the life of the Solar System, Phobos has a pretty short lifetime. In about 30 million to 50 million years, Phobos is going to crash into Mars'surface or rip apart because the tidal force of the planet will prove too much to resist.
6. We Have Pieces Of Mars On Earth: Remember the low gravity on Mars that we talked about? In the past, the planet has been hit by large asteroids — just like Earth. Most of the debris fell back on the planet, but some of it was ejected into space. That sparked an incredible journey where the debris moved around the Solar System and in some cases, landed on Earth. The technical name for these meteorites is called SNC (Shergottites, Nakhlites, Chassignites — types of geologic composition). Gases trapped in some of these meteorites has beenpractiacally identical to what NASA's Viking landers ampled on the Red Planet in the 1970s and 1980s.
7. Mars Would Kill An Unprotected Astronaut Quickly: There are a lot of unpleasant scenarios for somebody who took of their helmet. First, Mars is usually pretty cold; its average temperature is -50 degrees Fahrenheit (-45 degrees Celcius) at the mid-latitudes. Second, it has practically no atmosphere. The air pressure on Mars is only 1% of what we have (on average) on the Earth’s surface. And third, even if it did have atmosphere, the composition is not compatible with the nitrogen-oxygen mix humans require. Specifically, Mars has about 95% carbon dioxide, 3% nitrogen, 1.6% argon and a few other elements in its atmosphere.
8. In The Early Space Age, We Thought Mars Was Like The Moon: The early NASA probes that flew by the Red Planet all, coincidentally, happened to image spots on the planets that had craters. This led some scientists to (mistakenly) believe that Mars has an environment similar to the moon: cratered and practically unchanging. This all changed when Mariner 9 arrived at the planet for an orbital mission in November 1971 and discovered the planet engulfed in a global dust storm. What’s more, odd features were poking out above the dust — features that turned out to be dormant volcanoes. And as mentioned earlier, Mariner 9 found the vast Valles Marineris. It changed our view of the planet forever.
9. Mars Has Methane In Its Atmosphere: Methane can be interpreted as a sign of biological activity — microbes emit it — or even of geologic activity. And active planets, it is thought, are more likely to have life on them. So the question of methane on Mars is one that scientists are trying to figure out. The consensus? There is no consensus. Telescopic observations have had wildly different measurements over the years, and few spacecraft have been designed to probe for the element in detail. The Curiosity rover has detected tenfold spikes in methane in its area, but we don’t know where it came from and why the fluctuations are happening.
10. Mars Is A Popular Spacecraft Destination: There have been so many spacecraft that attempted a Martian mission that it’s hard to pick notable ones in a short article. NASA’s Vikings were the first landers in 1976; in fact, NASA is the only agency that has managed to land on the planet so far. Some of its other missions include Pathfinder-Sojourner (the first lander-rover combination) in 1997, the Mars Exploration Rovers Spirit and Opportunity in 2004, and the Curiosity rover of 2012. And this doesn’t even mention the fleet of orbiters that have mapped Mars over the years from the Soviet Union, NASA, the European Space Agency and India. And there are many more spacecraft to come in the next decade. © Universe Today.com