Mars

Mars is the 4th planet from the sun. It is known as the "red planet" because it appears red from the outside. Mars only has about a third of Earth's gravity, 38 percent to be exact, and it has two small moons, Phobos and Deimos. **Mars** is the the second-smallest planet in the Solar System, being larger than only Mercury. In English, Mars carries the name of the Roman god of war and is often referred to as the "**Red Planet**". The latter refers to the effect of the iron oxide prevalent on Mars's surface, which gives it a reddish appearance distinctive among the astronomical bodies visible to the naked eye. Mars can easily be seen from Earth with the naked eye, as can its reddish coloring. Its apparent magnitude reaches −2.94, which is surpassed only by Venus, the Moon and the Sun. Optical ground-based telescopes are typically limited to resolving features about 300 kilometers (190 miles) across when Earth and Mars are closest because of Earth's atmosphere.

Mars is approximately half the diameter of Earth, with a surface area only slightly less than the total area of Earth's dry land. Mars is less dense than Earth, having about 15% of Earth's volume and 11% of Earth's mass, resulting in about 38% of Earth's surface gravity. The red-orange appearance of the Martian surface is caused by iron(III) oxide, or rust. It can look like butterscotch; other common surface colors include golden, brown, tan, and greenish, depending on the minerals present.

Water has been proven to exist on Mars, on the poles, under rocks, on the surface and on the sub-surface of the dusty red planet. Potential microbes can exist on Mars. NASA claimed that mars has fossils possible bacteria-like microbes. Similar findings have been found on the surface of Mercury and on the surface of the Moon.

## Surface

The surface on Mars is rocky, with a lot of canyons, volcanos and craters everywhere. The average surface temperature of Mars is -62 degrees celsius, but there is red dust that covers most of its surface, giving Mars the red look. This red dust sometimes causes dust storms because Mars has wind and clouds.

Although Mars has no evidence of a structured global magnetic field, observations show that parts of the planet's crust have been magnetized, suggesting that alternating polarity reversals of its dipole field have occurred in the past. This paleomagnetism of magnetically susceptible minerals is similar to the alternating bands found on Earth's ocean floors. One theory, published in 1999 and re-examined in October 2005 (with the help of the *Mars Global Surveyor*), is that these bands suggest plate tectonic activity on Mars four billion years ago, before the planetary dynamo ceased to function and the planet's magnetic field faded.

It is thought that, during the Solar System's formation, Mars was created as the result of a stochastic process of run-away accretion of material from the protoplanetary disk that orbited the Sun. Mars has many distinctive chemical features caused by its position in the Solar System. Elements with comparatively low boiling points, such as chlorine, phosphorus, and sulphur, are much more common on Mars than Earth; these elements were probably pushed outward by the young Sun's energetic solar wind.

After the formation of the planets, all were subjected to the so-called "Late Heavy Bombardment." About 60% of the surface of Mars shows a record of impacts from that era, whereas much of the remaining surface is probably underlain by immense impact basins caused by those events. There is evidence of an enormous impact basin in the Northern Hemisphere of Mars, spanning 10,600 by 8,500 kilometres (6,600 by 5,300 mi), or roughly four times the size of the Moon's South Pole – Aitken basin, the largest impact basin yet discovered. This theory suggests that Mars was struck by a Pluto-sized body about four billion years ago. The event, thought to be the cause of the Martian hemispheric dichotomy, created the smooth Borealis basin that covers 40% of the planet.

## Composition

Mars is composed of crust, mantle and a core.

Mars is fundamentally an igneous planet. Rocks on the surface and in the crust consist predominantly of minerals that crystallize from magma. Most of our current knowledge about the mineral composition of Mars comes from spectroscopic data from orbiting spacecraft, *in situ* analyses of rocks and soils from six landing sites, and study of the Martian meteorites. Spectrometers currently in orbit include THEMIS (Mars Odyssey), OMEGA (Mars Express), and CRISM (Mars Reconnaissance Orbiter). The two Mars exploration rovers each carry an Alpha Particle X-ray Spectrometer (APXS), a thermal emission spectrometer (Mini-TES), and Mössbauer spectrometer to identify minerals on the surface.

On October 17, 2012, the Curiosity rover on the planet Mars at "Rocknest" performed the first X-ray diffraction analysis of Martian soil. The results from the rover's CheMin analyzer revealed the presence of several minerals, including feldspar, pyroxenes and olivine, and suggested that the Martian soil in the sample was similar to the "weathered basaltic soils" of Hawaiian volcanoes.

Mars has a composition that is extremely similar to that of Earth and at the same time incredibly different from that of Earth. Mars is pretty much always characterized as a planet that is very similar to Earth, and also at the same time, characterized as a planet that is very different from Earth. Bellow, talking about the crust, mantle and core, we will see major similarities and differences between Earth and Mars. We have already seen some differences and similarities above as well. Let's see more bellow in the crust, mantle and core:

### Crust

The crust is around 10 - 50 (6-30 km) km thick, composed of a volcanic basalt rock and covered in a fine talcum powder and is made of iron, nickel, and sulfur. Landslides in the crust speed up the crust to hundreds of kilometers an hour (up to 725 km/h). The crust right above the mantle is made of iron, nickel, sulfur, magnesium, aluminum, calcium, and potassium. The crust of Mars, like the Moon and Mercury has impact craters, because of asteroids. Impact craters were first identified on Mars by the Mariner 4 spacecraft in 1965. Early observations showed that Martian craters were generally shallower and smoother than lunar craters, indicating that Mars has a more active history of erosion and deposition than the Moon.

### Mantle

The mantle has been dormant, seeing no volcanic activity for millions of years. It is made primarily out of silicon, oxygen, iron and magnesium, and is theorized to have the consistency of a rocky-paste. It goes from the crust to a depth of around 1,240 to 1,880 km.(770 to 1170 miles thick). **Martian** meteorite analysis suggests that the planet's **mantle** is about twice as rich in iron than Earth's **mantle** actually is. The planet's distinctive red color is due to iron oxides on its surface and iron oxides like come from it's core and are driven towards the surface by the mantle.

### Core

Like Earth, the core of Mars is solid, comprised of iron, nickel and sulfur. Sadly, the core of Mars isn't moving and Mars doesn't have a magnetosphere, lacking habitability. However, water found on the surface of Mars suggests that small organisms may have thrived on Mars in the past anyway and are probably still thriving. **Mars** is differentiated, which—for a terrestrial planet—implies that it has a central **core** made up of metallic iron and nickel surrounded by a less dense, silicate mantle and **crust**. Like Earth, **Mars** appears to have a molten iron core, or at least a molten outer core. It's core is much richer in sulfur in comparison to Earth's.

## Atmosphere

The **atmosphere of Mars** is the layer of gases surrounding Mars. It is primarily composed of carbon dioxide (95%), molecular nitrogen (2.8%) and argon (2%). It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen and other noble gases. The atmosphere of Mars is much thinner than Earth's. The average surface pressure is only about 610 pascals (0.088 psi) which is less than 1% of the Earth's value, 100 times thinner than Earth's atmosphere. The currently thin Martian atmosphere prohibits the existence of liquid water at the surface of Mars, but many studies suggest that the Martian atmosphere was much thicker in the past. The highest atmospheric density on Mars is equal to the density found 35 km (22 mi) above the Earth's surface. The atmosphere of Mars has been losing mass to space throughout history, and the leakage of gases still continues today. Mars has an atmosphere 100 times thinner than Earth's, but 3.9 billion years ago, the planet used to have a thick enough atmosphere for water to run its surface. Mars probably had life a few billion years ago and the atmosphere was lost, likely because of powerful stellar winds emitted from the Sun, that blew away a major part of Mars's atmosphere, and allowed radiation to reach the surface of the red planet, leaving now an atmosphere that is 100 times thinner than Earth's.

The leading theory is that Mars' light gravity, coupled with its lack of global magnetic field, left the atmosphere vulnerable to pressure from the solar wind, the constant stream of particles coming from the sun. Over millions of years, the sun's pressure stripped the lighter molecules from the atmosphere, thinning it out. This process is being investigated by NASA's MAVEN (Mars Atmosphere and Volatile Evolution) mission. Other researchers hypothesize that perhaps a giant impact by a small body would have stripped the atmosphere away. Mars' thin atmosphere and its greater distance from the sun mean that Mars is much colder than Earth. The average temperature is about minus 80 degrees Fahrenheit (minus 60 degrees Celsius), although it can vary from minus 195 F (minus 125 C) near the poles during the winter to as much as a comfortable 70 F (20 C) at midday near the equator. The atmosphere of Mars is also roughly 100 times thinner than Earth's, but it is still thick enough to support weather, clouds and winds. There is also radiation at its surface, but it shouldn't be enough to stop Mars exploration; analysis by the Curiosity rover found that a single mission to Mars is comparable to the radiation guidelines for astronauts for the European Space Agency, although it does exceed those of NASA.

Giant dust devils routinely kick up the oxidized iron dust that covers Mars' surface. Dust is also a permanent part of the atmosphere, with higher amounts of it in the northern fall and winter, and lower amounts in the northern spring and summer. The dust storms of Mars are the largest in the solar system, capable of blanketing the entire planet and lasting for months. These usually take place in the spring or summer. One theory as to why dust storms can grow so big on Mars starts with airborne dust particles absorbing sunlight, warming the Martian atmosphere in their vicinity. Warm pockets of air flow toward colder regions, generating winds. Strong winds lift more dust off the ground, which in turn heats the atmosphere, raising more wind and kicking up more dust. A 2015 study further suggested that the momentum of Mars – which is affected by other planets – generates planet-circling dust storms when that momentum is at its greatest during the early part of the dust storm season.

At times, it even snows on Mars. The Martian snowflakes, made of carbon dioxide rather than water, are thought to be very small particles that create a fog effect rather than appearing as falling snow. The north and south polar regions of Mars are capped by ice, much of it made from carbon dioxide, not water. Today, NASA says seasonal changes are due to the waxing and waning of the carbon dioxide ice caps, dust moving around in the atmosphere, and water vapor moving between the surface and the atmosphere. (Most of the water comes from the north water ice cap, which is exposed and sublimates during the Martian summer when carbon dioxide evaporates off the cap.)"During winter, the temperatures in the polar regions are cold enough for the CO2 [carbon dioxide] in the atmosphere to condense into ice on the surface. The CO2 then sublimates off the ice cap in the spring and summer, returning to the atmosphere," NASA stated."In the northern hemisphere, the CO2 ice cap completely vanishes in the summer, uncovering a large perennial H2O ice cap. During the southern hemisphere summer, a small CO2 covered ice cap survives; this perennial ice cap is offset from the south pole. This cycling of CO2 into and out of ice on the surface changes the atmospheric mass by tens of percent over the course of a Martian year."

## Methane on Mars

Methane has been detected in the Martian atmosphere; it occurs in extended plumes, and the profiles imply that the methane is released from discrete regions. The concentration of methane fluctuates from about 0.24 ppb during the northern winter to about 0.65 ppb during the summer.

Estimates of its lifetime range from 0.6 to 4 years, so its presence indicates that an active source of the gas must be present. Methane could be produced by non-biological process such as serpentinization involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars. Methanogenic microbial life forms in the subsurface are among possible sources. But even if rover missions determine that microscopic Martian life is the source of the methane, the life forms likely reside far below the surface, outside of the rover's reach.

The principal candidates for the origin of Mars' methane include non-biological processes such as water-rock reactions, radiolysis of water, and pyrite formation, all of which produce H2 that could then generate methane and other hydrocarbons via Fischer–Tropsch synthesis with CO and CO2. It has also been shown that methane could be produced by a process involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars. The required conditions for this reaction (i.e. high temperature and pressure) do not exist on the surface but may exist within the crust. Detection of the mineral by-product serpentinite would suggest that this process is occurring. An analog on Earth suggests that low-temperature production and exhalation of methane from serpentinized rocks may be possible on Mars. Another possible geophysical source could be ancient methane trapped in clathrate hydrates that may be released occasionally. Under the assumption of a cold early Mars environment, a cryosphere could trap such methane as clathrates in a stable form at depth, that might exhibit sporadic release.

On modern Earth, volcanism is a minor source of methane emission, and it is usually accompanied by sulfur dioxide gases. However, several studies of trace gases in the Martian atmosphere have found no evidence for sulfur dioxide in the Martian atmosphere, which makes volcanism on Mars unlikely to be the source of methane. Although geologic sources of methane such as serpentinization are possible, the lack of current volcanism, hydrothermal activity or hotspots are not favorable for geologic methane.

It had also been proposed that the methane might be replenished by meteorites entering the atmosphere of Mars, but researchers from the Imperial College London found that the volumes of methane released this way are too low to sustain the measured levels of the gas. It has been suggested that the methane was produced by chemical reactions in meteorites, driven by the intense heat during entry through the atmosphere. Although research published in December 2009 ruled out this possibility, research published in 2012 suggest that a source may be organic compounds on meteorites that are converted to methane by ultraviolet radiation. Lab tests demonstrated that bursts of methane can be produced when an electrical discharge interacts with water ice and CO2. The discharges from the electrification of dust particles from sand storms and dust devils in contact with permafrost ice may produce about 1.41×1016 molecules of methane per joule of applied energy.

Current photo-chemical models cannot explain the apparent rapid variability of the methane levels in Mars. Research suggests that the implied methane destruction lifetime is as long as ≈ 4 Earth years and as short as ≈ 0.6 Earth years. This unexplained fast destruction rate also suggests a very active replenishing source. A team from the Italian National Institute for Astrophysics suspects that the methane detected by the *Curiosity* rover may have been released from a nearby area called Medusae Fossae Formation located about 500 km east of Gale crater. The region is fractured and is likely volcanic in origin.

## Phobos

The innermost and largest moon of the two. Discovered in 1877, it is a pile of rocks which have coalesced, held together by a thin layer of crust. Phobos, since it is the closest, and maybe a little bit too close, has its crust getting torn apart by tidal forces. In roughly the same amount of time it'll tale Earth's moon to stray away far enough for total solar eclipses to become impossible, Phobos will get near enough to get torn completely apart by Mars' tidal forces. This will either make it collide with Mar, or turn it into a planetary ring.

Phobos is a small, irregularly shaped object with a mean radius of 11 km (7 mi). 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.

Phobos is one of the least reflective bodies in the Solar System, with an albedo of just 0.071. Surface temperatures range from about −4 °C (25 °F) on the sunlit side to −112 °C (−170 °F) on the shadowed side. The defining surface feature is the large impact crater, Stickney, which takes up a substantial proportion of the moon's surface. In November 2018, astronomers concluded that the many grooves on Phobos were caused by boulders ejected from the asteroid impact that created Stickney, and rolled around on the surface of the moon. An alternative theory is that the grooves are stretch marks caused by tidal forces. Images and models indicate that Phobos may be a rubble pile held together by a thin crust that it is being torn apart by tidal interactions. Phobos gets closer to Mars by about 2 centimeters per year, and it is predicted that within 30 to 50 million years it will either collide with the planet or break up into a planetary ring.

## Deimos

Deimos is the smallest and furthermost moon of Mars. Discovered in 1877, by the same guy named Asaph Hall, it is a very asteroid-like moon, having many characteristics of an asteroids, which is quite possibly what it used to be, eventually get somehow caught by Mars. Whilst having many craters, big ones and small ones, only two completely random craters have been named, for some reason. Deimos is composed of rock and carbonaceous material, much like an asteroid. But unlike one, it is very smooth, considerably smoother than Phobos. Deimos has a mean radius of 6.2 km (3.9 mi) and takes 30.3 hours to orbit Mars. Deimos is 23,460 km (14,580 mi) from Mars, much further than Mars's other moon, Phobos. It is named after Deimos, the Ancient Greek god and personification of dread and terror, and who is also a son of Ares and Aphrodite and the twin brother of Phobos.

Deimos was discovered by Asaph Hall, III at the United States Naval Observatory in Washington, D.C. on 12 August 1877, at about 07:48 UTC (given in contemporary sources as "11 August 14:40" Washington Mean Time, using a pre-1925 astronomical convention of beginning a day at noon, so 12 hours must be added to get the actual local mean time). Hall also discovered Phobos on 18 August 1877, at about 09:14 GMT, after deliberately searching for Martian moons.

It is named after Deimos, a figure representing dread in Greek mythology. The names, at first spelled *Phobus* and *Deimus*, were suggested by Henry Madan (1838–1901), Science Master of Eton, from Book XV of the *Iliad*, where Ares (the Roman god Mars) summons Dread (Deimos) and Fear (Phobos).