My Science School

Of all the planets in the Solar System, Mars most resembles Earth. Its day is only slightly over 24 hours, and it is tilted at the same angle as our planet, meaning that seasons are very similar to ours. Early on in its history, Mars had water on its surface. Oceans formed, kept warm by volcanic activity, and primitive life may have started here. Today, freezing conditions on Mars, and the planet’s thin atmosphere, mean that life can no longer exist on the planet’s surface.

The search for life on Mars shouldn’t focus exclusively on the distant past, some researchers say. Four billion years ago, the Martian surface was apparently quite habitable, featuring rivers, lakes and even a deep ocean. Indeed, some astrobiologists view ancient Mars as an even better cradle for life than Earth was, and they suspect that life on our planet may have come here long ago aboard Mars rocks blasted into space by a powerful impact.

Things changed when Mars lost its global magnetic field. Charged particles streaming from the sun were then free to strip away the once-thick Martian atmosphere, and strip it they did. This process had transformed Mars into the cold, dry world we know today by about 3.7 billion years ago, observations by NASA's MAVEN orbiter suggest. (Earth still has its global magnetic field, explaining how our planet remains so livable.)

One of the most promising hiding places is the Martian underground. Though the Red Planet's surface has no liquid water these days — apart, possibly, from temporary flows on warm slopes now and again — there’s a likely lot of the wet stuff in buried aquifers. For example, observations by Europe’s Mars Express orbiter suggest that a big lake may lurk beneath the Red Planet’s South Pole.

Earth’s diverse residents advertise their presence in dramatic and obvious ways; an advanced alien civilization could probably figure out pretty quickly, just by scanning our atmosphere, that our planet is inhabited. 

We don’t see any such clear-cut evidence in the Martian air, but scientists have spotted some intriguing hints recently. For example, NASA's Curiosity rover has rolled through two plumes of methane inside the 96-mile-wide (154 kilometers) Gale Crater, which the six-wheeled robot has been exploring since its 2012 touchdown. The rover mission also determined that baseline methane concentrations in Gale's air go through cycles seasonally.

More than 90% of Earth's atmospheric methane is produced by microbes and other organisms, so it's possible the gas is a signature of modern Martian life.

But the jury is most definitely still out on that. Abiotic processes can generate methane, too; the reaction of hot water with certain types of rock is one example. And even if the Mars methane is biogenic, the creatures that created it could be long dead. Scientists think the Red Planet methane plumes leaked out from underground, and there's no telling how long the gas lay trapped down there before making its way to the surface.

In the 19th century, the astronomer Giovanni Schiaparelli claimed that Mars was covered by a network of channels. Many people believed that these were canals created by an intelligent civilization to help carry water from the Polar Regions to drier areas around the Equator. Recent photographs of Mars have shown that there are many channels on the planet, but scientists believe these were created naturally by running water billions of years ago.

The space-heads among you have undoubtedly heard about the Curiosity rover's first significant discovery: the remnants of an ancient streambed on Mars, which would seem to indicate the presence of water in the planet's history. This jagged pile of alluvial rock and dust my not took like much, but it brings to mind one of my favorite pieces of Martian historical arcana.

For a time in the late 19th century, it was believed that there were canals on Mars. The Italian astronomer Giovanni Schiaparelli, who observed Mars in 1877, was the first to describe, name, and lovingly illustrate mysterious straight lines along its equatorial regions, which he called canal. Viewed with the telescopes of the day, in brief instances of still air amidst the optical strangeness of atmosphere, Mars was tough to figure. There are areas which appear darker or lighter (these are called Albedo features); to an enthusiastic observer, it was easy to speculate of continents, oceans, or even straight-line canals.

Beset by the same optical illusions, many astronomers seconded Schiaparelli's observations. The maps of the day show a Mars riven with peculiar webs and lines–lines which successive high-resolution mapping of the planet have definitively shown do not exist. The mechanism that caused this illusion appears to be internal: faced with a shifting landscape of foggy forms, glimpsed at through simple lenses of glass through the refractive index of Earth’s atmosphere, the human brain tends to impose order.

The persistence of belief in Martian canals is often attributed to a linguistic fluke, that the Italian canal, meaning "channel" (or watercourse, and not necessarily of unnatural origin), was mistranslated to the English "canal." I really love this narrative of language shaping reality, but unfortunately it's the astronomical equivalent of an urban legend. "Canal," in fact, was used in the earliest English accounts, and Schiaparelli made no move to correct the misunderstanding, if he was aware of it.

When the planets were forming, they were in a molten state. In any object, gravity pulls from the centre, and parts of the object at the same distance from the centre are pulled inward with equal force, creating a sphere. This will only happen to objects with sufficient mass, such as planets and stars. Smaller objects, such as asteroids, have a weaker gravitational force, so they cannot pull themselves into a spherical shape. Gravity is also responsible for denser materials being pulled to the centre of a star or planet.

Planets are round because of its gravitational field. As a planet gets massive enough, internal heating takes over and the planet behaves like a fluid. Gravity then pulls all of the material towards the center of mass (or core). Because all points on the surface of a sphere are an equal distance from the center of mass, planets eventually settle on a spherical shape. For major planets, one of the requirements is that it’s large enough for its gravity to pull it into a sphere. Though, even for small asteroids and such, it’s not uncommon for these bodies to be “roundish” (though, they are often oval shaped).

It is interesting to note though that, because planets rotate, they aren’t perfect spheres and actually bulge out at the equator.

In the case of a cube, the corners are further away from the center of mass than the rest of the cube. Especially for objects as massive as a planet or a star, the corners would collapse under their own weight and the object would take on a spherical shape. As cool as a cubical planet would be, they simply can’t exist. Well, correction, a cubic planet could probably be engineered by a civilization bent on assimilating all life in the galaxy, but the point is a square planet won’t form without outside help.

All of the planets in the Solar System formed from the same cloud of debris. The inner planets have solid cores of iron, surrounded by rocky mantles, topped with a very thin silicate crust. The Gas Giants have solid cores of rock and ice, but these are much smaller in proportion to those of the inner planets. Jupiter and Saturn are made of hydrogen and helium, which becomes denser towards their centres. Uranus and Neptune both have mantles of icy water, methane and ammonia.

Astronomers think the giants first formed as rocky and icy planets similar to terrestrial planets. However, the size of the cores allowed these planets (particularly Jupiter and Saturn) to grab hydrogen and helium out of the gas cloud from which the sun was condensing, before the sun formed and blew most of the gas away. 

Since Uranus and Neptune are smaller and have bigger orbits, it was harder for them to collect hydrogen and helium as efficiently as Jupiter and Saturn. This likely explains why they are smaller than those two planets. On a percentage basis, their atmospheres are more "polluted" with heavier elements such as methane and ammonia because they are so much smaller.

Scientists have discovered thousands of exoplanets. Many of these happen to be "hot Jupiters," or massive gas giants that are extremely close to their parent stars. (Rocky worlds are more abundant in the universe, according to estimates from Kepler.) Scientists speculate that large planets may have moved back and forth in their orbits before settling into their current configuration. But how much they moved is still a subject of debate.

There are dozens of moons around the giant planets. Many formed at the same time as their parent planets, which is implied if the planets rotate in the same direction as the planet close to the equator (such as the huge Jovian moons Io, Europa, Ganymede and Callisto.) But there are exceptions. 

One moon of Neptune, Triton, orbits the planet opposite to the direction Neptune spins — implying that Triton was captured, perhaps by Neptune's once larger atmosphere, as it passed by. And there are many tiny moons in the solar system that rotate far from the equator of their planets, implying that they were also snagged by the immense gravitational pull.

Our solar system formed from the force of an exploding star. When some stars reach the end of their lives, they can explode into a supernova, sending shockwaves of energy deep into space. Roughly 4.5 billion years ago, a shock-wave from a supernova, travelling at 30 million kilometres (19 million miles) per hour, hit a cloud of ice, dust and gas. The force of the impact caused the cloud to flatten and rotate. From this spinning disc, our Solar System began to form.

The most widely accepted scientific explanation for the formation of the Solar System is called the Solar Nebular Model. According to this model, the entire Solar System formed around 4.5 billion years ago from the gravitational collapse of a small fraction of a giant molecular cloud, also known as a nebula. 

A disturbance, most likely a nearby supernova, caused a giant cloud of gas and dust floating in space to contract and begin to collapse on itself. Most of the gas collected in the center to form a gaseous sphere that would eventually become the Sun. As more gas was drawn inward by the force of gravity, friction and pressure caused this sphere, called a protostar, to become hot and start to glow. 

As the nebula continued to contract, conservation of angular momentum caused it to spin faster. It flattened out into a protoplanetary disk, with the hot, dense protostar in the center. Over millions of years, all eight planets formed by accretion from this disk. In other words, gravity pulled the disk into many clumps of gas and dust. These clumps stuck together and grew larger and larger, turning into planetesimals. The planetesimals further coalesced to eventually form planets, with comets and asteroids being the leftovers. Gravitational interaction with the planets caused them to be grouped into distinct regions such as the asteroid belt and Kuiper belt. 

Due to their higher boiling points only metals and silicates could exist in the warm inner solar system, and these would form the rocky planets of Mercury, Venus, Earth, and Mars. Since metallic elements only comprised a very small fraction of the solar nebula, the terrestrial planets could not grow very large. It is thought that as many as 100 small protoplanets used to exist in the inner solar system, but they eventually collided and merged to create the four inner planets we know today. 

The gas giants (Jupiter, Saturn, Uranus, and Neptune) formed further out, beyond the frost line where icy compounds can remain solid. The gas and ice that formed the Jovian planets was more abundant within the protoplanetary disk, allowing them to become massive enough to gain large atmospheres of hydrogen and helium and grow to mammoth proportions. Uranus and Neptune are thought to have formed closer to the Sun, and then migrated out to their current orbits. 

Throughout all this, the infant Sun continued to grow hotter. Once the temperature and pressure at the core was high enough, thermonuclear fusion of hydrogen began, and the Sun became a fully-fledged main-sequence star. Solar wind swept away the remaining gas and dust leftover from the protoplanetary disk into interstellar space, ending the growth of the planets. This entire process of solar system formation happened within several hundred million years and was finished by around 4.5 billion years ago. 

Planets and moons are just a few of the objects orbiting the Sun. Astronomers already know of thousands of large rocky bodies called asteroids (shown right), and icy objects called comets. Millions of smaller rocks, called meteoroids, also orbit the Sun.

More than 150 moons orbit worlds in our solar system. Known as natural satellites, they orbit planets, dwarf planets, asteroids, and other debris. Among the planets, moons are more common in the outer reaches of the solar system. Mercury and Venus are moon-free, Mars has two small moons, and Earth has just one. Meanwhile, Jupiter and Saturn have dozens, and Uranus and Neptune each have more than 10. Even though it’s relatively small, Pluto has five moons, one of which is so close to Pluto in size that some astronomers argue Pluto and this moon, Charon, are a binary system.

Too small to be called planets, asteroids are rocky chunks that also orbit our sun along with the space rocks known as meteoroids. Tens of thousands of asteroids are gathered in the belt that lies between the orbits of Mars and Jupiter. Comets, on the other hand, live inside the Kuiper Belt and even farther out in our solar system in a distant region called the Oort cloud.

The solar system is enveloped by a huge bubble called the heliosphere. Made of charged particles generated by the sun, the heliosphere shields planets and other objects from high-speed interstellar particles known as cosmic rays. Within the heliosphere, some of the planets are wrapped in their own bubbles—called magnetospheres—that protect them from the most harmful forms of solar radiation. Earth has a very strong magnetosphere, while Mars and Venus have none at all.

Most of the major planets also have atmospheres. Earth’s is composed mainly of nitrogen and oxygen—key for sustaining life. The atmospheres on terrestrial Venus and Mars are mostly carbon dioxide, while the thick atmospheres of Jupiter, Saturn, Uranus, and Neptune are made primarily of hydrogen and helium. Mercury doesn’t have an atmosphere at all. Instead scientists refer to its extremely thin covering of oxygen, hydrogen, sodium, helium, and potassium as an exosphere.

Moons can have atmospheres, too, but Saturn’s largest moon, Titan, is the only one known to have a thick atmosphere, which is made mostly of nitrogen.

The planets in the Solar System form two very different groups — inner and outer. The inner planets, often called terrestrial planets, are composed mainly of rock and metal, with solid surfaces, no rings and few satellites. The outer planets, called Jovian or Gas Giants, are much larger than their inner neighbours. They are composed primarily of hydrogen and helium, have very deep atmospheres, rings and lots of satellites.

Our solar system consists of many planets, one of which is Earth. The total number of planets is eight although there have been disagreements to this statement with some saying there are more than eight (the opponents of the theory that Pluto is not a planet). Whatever the case, when we talk about planets we divide them into two groups; inner planets and outer planets. This classification is relative to the planets’ position with respect to the Sun. The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. We shall now make clear which of these are inner planets and which are outer planets and what actually differentiates them.

Inner planets are those planets which are closest to the sun and include the first four planets (Mercury, Venus, Earth and Mars) in order of increasing distance from the Sun. Mercury is the closest, followed by Venus, Earth and then Mars. Outer planets are those which are further away from the Sun and include the next four planets in order of increasing distance from the Sun (Jupiter, Saturn, Uranus and Neptune), with Neptune being the furthest.

The inner planets are made up of rock and metal and are therefore solid. These planets move slowly as they are considered to be heavy. They have an average diameter of about 13000 km as they are small planets. On the other hand, the outer planets are said to be made of gases and they are not really solid. The gases which make them up are Hydrogen and Helium; huge balloons floating in the space are considered as giant gas planets by people and they have an average diameter of about 48000 km.

Furthermore, the inner planets are warmer than outer planets simply due to the fact that they are closer to the Sun. Outer planets are composed of lighter elements such as gases and inner planets are composed of heavy elements such as iron. Inner planets have fewer moons, small, silicate surface, nickel-iron core, higher density and rotate more slowly compared to outer planets. Outer planets have a greater number of moons, no solid part; rotate faster, have a lower density as well as rings in some cases (Jupiter and Saturn). Outer planets are significantly bigger than the inner planets as Jupiter is measured to be 88846 miles in diameter and Mercury is measured to be 3031 miles in diameter.

There is significant difference between the rotation and the orbit of the two types of planets. For example, for Jupiter it would take 9 hours and 55 minutes for a day to complete (or to complete one rotation) and on Venus it would take 234 hours for a day to complete. (The time period of a day is that compared to the standard 24 hour day on Earth.) The inner planets take lesser time to orbit the Sun whereas the planets which are far away need more time as they have to cover more ground. For example, Jupiter takes 164 Earth years to complete one orbit!

An object’s ORBIT is the path it takes around another, more massive object in space. Each of the nine planets in the Solar System is held in orbit by the Sun’s gravitational pull. However, the planets do not orbit the Sun in circular paths but in elliptical (oval) ones. Orbit lengths, and the orbital period (the time it takes a planet to complete one orbit) increase with successively distant planets.

Orbit is the path of a body as it moves under the influence of a second body. An example is the path of a planet or comet as it moves around the Sun. Planets and satellites that orbit other bodies trace out a path called an ellipse. An ellipse is a closed curve of oval shape wherein the sum of the distances from any point on the curve to two internal focal points is constant. In everyday life you probably just call this an oval. As shown in the picture below, an ellipse has a major axis and a minor axis.

The major axis is always at least as long as or longer than the minor axis. When both the major and minor axes are the same length, this is a special case of an ellipse we commonly call a circle. Therefore, orbiting bodies can also trace out a circular path. Although a circle is a special type of ellipse, people commonly refer to satellite and planetary orbits as either circular or elliptical. The orbital period is the time to complete one full orbit.

After ten years of work, Kepler discovered the relationship between the time it takes a planet to orbit the Sun and its distance from the Sun. Kepler's third law says that the square of the orbital period of a planet is directly proportional to the cube of the average distance of the planet from the Sun. Mathematically, this is given by the ratio T^2/r^3 and applies to all planets. The practical application of Kepler’s third law is to calculate the radius of a planet's orbit by observation of that planet's orbital period.

Jupiter is the fifth planet from the Sun and the largest planet in the Solar System. It is a gas giant with thick bands of brown, yellow, and white clouds. Its atmosphere is made up of hydrogen and helium gas, just like our Sun, and if it was much more massive, it could become a star! Jupiter took shape when the rest of the solar system formed about 4.5 billion years ago, when gravity pulled swirling gas and dust in to become this gas giant. Jupiter took most of the mass left over after the formation of the Sun, ending up with more than twice the combined material of the other bodies in the solar system. In fact, Jupiter has the same ingredients as a star, but it did not grow massive enough to ignite. As a gas giant, Jupiter doesn’t have a true surface. The planet is mostly swirling gases and liquids. While a spacecraft would have nowhere to land on Jupiter, it wouldn’t be able to fly through unscathed either. The extreme pressures and temperatures deep inside the planet crush, melt and vaporize spacecraft trying to fly into the planet.

Giant planet

Jupiter is the king of solar system. It is an amazing 143,000 km (89,000 miles) wide. Jupiter is so large that all of the other planets could fit inside it! The planet is mostly made of hydrogen and helium surrounding a dense core of rocks and ice, with most of its bulk likely made up of liquid metallic hydrogen, which creates a huge magnetic field. Jupiter is visible with the naked eye and was known by the ancients. Its atmosphere consists mostly of hydrogen, helium, ammonia and methane.

Juno Mission

NASA’s Juno spacecraft is helping scientists to understand how Jupiter formed. It is orbiting closer to the gas giant than any spacecraft has before.

Juno's mission is to measure Jupiter's composition, gravity field, magnetic field, and polar magnetosphere. It will also search for clues about how the planet formed, including whether it has a rocky core, the amount of water present within the deep atmosphere, mass distribution, and its deep winds, which can reach speeds up to 618 kilometers per hour (384 mph).

Juno is the second spacecraft to orbit Jupiter, after the nuclear powered Galileoorbiter, which orbited from 1995 to 2003. Unlike all earlier spacecraft sent to the outer planets, Juno is powered by solar arrays, commonly used by satellites orbiting Earth and working in the inner Solar System, whereas radioisotope thermoelectric generators are commonly used for missions to the outer Solar System and beyond. For Juno, however, the three largest solar array wings ever deployed on a planetary probe play an integral role in stabilizing the spacecraft as well as generating power.

Beneath the clouds

Any spacecrafts that passed through Jupiter’s clouds would be crushed and melted by the huge pressure. Scientists believe that beneath the clouds there is a giant ocean made of liquid metal.

Jupiter’s rings

Jupiter has three thin rings, called the Jovian Rings. They are mostly made of dust and can only be seen when viewed from behind Jupiter, when they are lit up by the Sun. The main ring is flattened. It is about 20 miles (30 km) thick and more than 4,000 miles (6,400 km) wide.

The inner cloud-like ring, called the halo, is about 12,000 miles (20,000 km) thick. The halo is caused by electromagnetic forces that push grains away from the plane of the main ring. This structure extends halfway from the main ring down to the planet's cloud tops and expands. Both the main ring and halo are composed of small, dark particles of dust.

The third ring, known as the gossamer ring because of its transparency, is actually three rings of microscopic debris from three of Jupiter's moons, Amalthea, Thebe and Adrastea. It is probably made up of dust particles less than 10 microns in diameter, about the same size of the particles found in cigarette smoke, and extends to an outer edge of about 80,000 miles (129,000 km) from the center of the planet and inward to about 18,600 miles (30,000 km).

Great Red Spot

One of the Jupiter’s most famous features is the Great Red Spot. It is a huge storm, more than three times the size of Earth, that has been raging for hundreds of years!

The red colour of the Great Red Spot is thought to be caused by organic molecules, red phosphorous or other elements that come from inside Jupiter. Some theories propose that the colour is caused by reactions between these chemicals in Jupiter’s atmosphere, or by lightning striking the molecules. The colour is not always the same, either: sometimes it is dark red, while at other times it is a pale pink colour, or even white! Perhaps Jupiter’s Great Red Spot is not so red after all!

 

Picture Credit : Google

 

Between the planets Mars and Jupiter lies the asteroid belt. It is home to tens of thousands of asteroids. These rocky objects are leftovers from the early Solar System, and are too small to be considered planets. They come in different shapes and sizes with the smallest being less than 1 km (0.6 miles) wide. Some asteroids have moons and one even has rings!

Most of the asteroids in the Main Belt are made of rock and stone, but a small portion of them contain iron and nickel metals. The remaining asteroids are made up of a mix of these, along with carbon-rich materials. Some of the more distant asteroids tend to contain more ices. Although they aren't large enough to maintain an atmosphere, but there is evidence that some asteroids contain water.

Some asteroids are large, solid bodies — there are more than 16 in the belt with a diameter greater than 150 miles (240 km). The largest asteroids, Vesta, Pallas and Hygiea, are 250 miles (400 km) long and bigger. The region also contains the dwarf planet Ceres. At 590 miles (950 km) in diameter, or about a quarter of the size of our moon, Ceres is round yet is considered too small to be a full-fledged planet. However, it makes up approximately a third of the mass of the asteroid belt.

Other asteroids are piles of rubble held together by gravity. Most asteroids aren't quite massive enough to have achieved a spherical shape and instead are irregular, often resembling a lumpy potato. The asteroid 216 Kleopatra resembles a dog bone.

Asteroid orbits

Not all of the asteroids in our Solar System are found in the asteroid belt. Some asteroids pass near other planets, including Earth. Asteroids that come close to Earth are called Near Earth Objects. The planet Jupiter even shares its orbit around the Sun with two groups of asteroids, which are called Trojans.  If something slows an asteroid, it may "fall" towards the Sun, towards Mars, or towards Jupiter. As both Jupiter and Mars move past the asteroids in their orbits, they may be pulled slightly towards those huge bodies in their orbits. In fact, Phobos and Diemos, the two tiny moons of Mars, may be captured asteroids. Some scientists believe that the asteroid belt was made when a planet that was there exploded or collided with something else and broke up. Other scientists believe that the material making the asteroids never came together into a planet at all.

Craters

Craters are nicknamed “Snowman” because they look just like a snowman! They are on Vesta, one of the largest asteroids in the asteroid belt.

Many impact craters are found on the Earth’s surface, although they can be harder to detect. One of the best-known craters on Earth is Meteor Crater, near Winslow, Arizona. The crater was created instantly when a 50-meter (164-foot), 150,000-ton meteorite slammed into the desert about 50,000 years ago. Meteor Crater is 1.2 kilometers (0.75 miles) in diameter and 175 meters (575 feet) deep.

Impact craters are found on most of the solar system’s rocky planets and moons. The so-called “gas giants” of the solar system—Jupiter, Saturn, Uranus, and Neptune—don’t have craters. These planets are made up almost entirely of gases, so there is no hard surface for a meteor to impact. Meteors entering the atmosphere of a gas giant simply break up.



Cratering is a rare occurrence in the solar system today. Planets, moons, comets, and other celestial bodies have fairly stable orbits that do not interact with each other. Meteors do collide with planets—including Earth—every day. However, most of these meteors are the size of a speck of dust and do not cause any cratering. Most meteors burn up in the atmosphere as “shooting stars” before ever colliding with the surface of the Earth.

Ceres 

By far the largest object in the asteroid belt is Ceres. Made mostly of rock is Ceres. Made mostly of rock and ice, it was the first asteroid ever discovered. It has since been classed as a Dwarf Planet, because it is more like a planet than its neighbours in the main asteroid belt.

Ceres takes 1,682 Earth days, or 4.6 Earth years, to make one trip around the sun. As Ceres orbits the sun, it completes one rotation every 9 hours, making its day length one of the shortest in the solar system.

Ceres' axis of rotation is tilted just 4 degrees with respect to the plane of its orbit around the sun. That means it spins nearly perfectly upright and doesn't experience seasons like other more tilted planets do.

Ceres formed along with the rest of the solar system about 4.5 billion years ago when gravity pulled swirling gas and dust in to become a small dwarf planet. Scientists describe Ceres as an "embryonic planet," which means it started to form but didn't quite finish. Nearby Jupiter's strong gravity prevented it from becoming a fully formed planet. About 4 billion years ago, Ceres settled into its current location among the leftover pieces of planetary formation in the asteroid belt between Mars and Jupiter.

 

Picture Credit : Google

Scientists have always longed to explore Mars. They believe that in the past the Red Planet could have been far warmer and wetter than it is now. There may once have even been life on Mars, and tiny life forms, such as bacteria, could live on the planet today. Many spacecraft have already visited Mars and in the future humans will too.

Understanding whether life existed elsewhere in the Universe beyond Earth is a fundamental question of humankind. Mars is an excellent place to investigate this question because it is the most similar planet to Earth in the Solar System. Evidence suggests that Mars was once full of water, warmer and had a thicker atmosphere, offering a potentially habitable environment.

While life arose and evolved on Earth, Mars experienced serious climate change. Planetary geologists can study rocks, sediments and soils for clues to uncover the history of the surface. Scientists are interested in the history of water on Mars to understand how life could have survived. Volcanoes, craters from meteoroid impacts, signs of atmospheric or photochemical effects and geophysical processes all carry aspects of Mars’ history.

Samples of the atmosphere could reveal crucial details on its formation and evolution, and also why Mars has less atmosphere than Earth.

Water on Mars

In 2015, NASA found the strongest evidence yet that liquid water exists on Mars. This was a hugely exciting discovery because scientists looking for life in our Solar System think that where there is liquid water, there could be life.

Many lines of evidence indicate that water ice is abundant on Mars and it has played a significant role in the planet's geologic history. The present-day inventory of water on Mars can be estimated from spacecraft imagery, remote sensing techniques and surface investigations from landers and rovers. Geologic evidence of past water includes enormous outflow channels carved by floods, ancient river valley networks, deltas, and lakebeds; and the detection of rocks and minerals on the surface that could only have formed in liquid water. Numerous geomorphic features suggest the presence of ground ice (permafrost) and the movement of ice in glaciers, both in the recent past and present. Gullies and slope linear along cliffs and crater walls suggest that flowing water continues to shape the surface of Mars, although to a far lesser degree than in the ancient past.

Curiosity Rover

The photo of the Curiosity rover was taken on the surface of mars. The six-wheeled, car-sized robot lives and works on the planet, operated by a team of scientists back on earth. Their instructions take about 15 minutes to reach Mars! Curiosity has other instruments on board that are designed to learn more about the environment surrounding it. Among those goals is to have a continuous record of weather and radiation observations to determine how suitable the site would be for an eventual human mission.

Curiosity's Radiation Assessment Detector runs for 15 minutes every hour to measure a swath of radiation on the ground and in the atmosphere. Scientists in particular are interested in measuring "secondary rays" or radiation that can generate lower-energy particles after it hits the gas molecules in the atmosphere. Gamma-rays or neutrons generated by this process can cause a risk to humans. Additionally, an ultraviolet sensor stuck on Curiosity's deck tracks radiation continuously.

Human exploration

To reduce the cost and risk for human exploration of Mars, robotic missions can scout ahead and help us to find potential resources and the risks of working on the planet.

Before sending astronauts, we need to understand the hazards. Inevitably, astronauts would bring uncontained martian material when they return to Earth, either on their equipment or on themselves. Understanding any biohazards in the soil and dust will help the planning and preparation of these future missions.

Going to Mars is hard and it is even harder for humans because we would need to pack everything to survive the trip to our neighbouring planet and back. Designing a Mars mission would be easier if we could use resources that are already available locally. Water is a valuable resource for human expeditions, both to consume by astronauts and for fuel. Samples gathered by robots could help to evaluate where potential resources are available for future human explorers and how to exploit them.

 

Picture Credit : Google

Like Earth, Mars has seasons. This is because the planets are tilted at similar angles. Different parts of the planet learn towards the Sun at different times during the year, making it warmer or cooler. Mars is an extremely cold planet with an average temperature around minus-80 degrees. Temperatures can dip to minus-225 degrees around the poles. Periods of warmth are brief — highs can reach 70 degrees for a brief time around Noon at the equator in the summer.

There’s no need to worry about rain on Mars — it hasn’t occurred for millions of years. With only trace amounts of water vapor, the planet is a dry and desolate place. Clouds do form, but they are very high in the sky and at the surface, where haze and fog forms as a result of the very steep lapse rates near the ground. Snow, on the other hand, is possible in the very high latitudes, though it’s nothing like the snow here on Earth.

With a very hot equator area and extremely cold poles, there are huge variations in temperature across the planet, which end up driving high wind speeds. Low pressure systems can form and polar fronts develop at the southern end of the polar ice cap, especially at times of seasonal changes.

Sometimes, these winds can lift very fine dust particles to create massive dust storms that envelop much of the planet. Heated dust particles can rise to over 20 miles above the surface. Wind velocities can reach 60 miles per hour or more in these storms.

 

Picture Credit : Google

Mars is nicknamed the Red Planet because of its rusty soil. Like Earth, it has a rocky surface, polar ice caps, mountains, valleys, and clouds in the sky. However, the fourth planet from the Sun has a far more extreme environment than ours. It is very cold and dry with a thin unbreathable atmosphere. Like Earth, Mars has seasons, polar ice caps, volcanoes, canyons, and weather. It has a very thin atmosphere made of carbon dioxide, nitrogen, and argon.

There are signs of ancient floods on Mars, but now water mostly exists in icy dirt and thin clouds. On some Martian hillsides, there is evidence of liquid salty water in the ground.

Scientists want to know if Mars may have had living things in the past. They also want to know if Mars could support life now or in the future

Mars’ moons

Mars has two moons, called Phobos and Deimos, which are much smaller than Earth’s Moon. Their names mean “panic” and “fear”. They were probably asteroids pulled towards Mars by its gravity.

 Phobos is a bit larger than Deimos, and orbits only 3,700 miles (6,000 kilometers) above the Martian surface. No known moon orbits closer to its planet. It whips around Mars three times a day, while the more distant Deimos takes 30 hours for each orbit. Phobos is gradually spiraling inward, drawing about six feet (1.8 meters) closer to the planet each century. Within 50 million years, it will either crash into Mars or break up and form a ring around the planet.

To someone standing on the Mars-facing side of Phobos, Mars would take up a large part of the sky. And people may one day do just that. Scientists have discussed the possibility of using one of the Martian moons as a base from which astronauts could observe the Red Planet and launch robots to its surface, while shielded by miles of rock from cosmic rays and solar radiation for nearly two-thirds of every orbit.

Like Earth's Moon, Phobos and Deimos always present the same face to their planet. Both are lumpy, heavily-cratered and covered in dust and loose rocks. They are among the darker objects in the solar system. The moons appear to be made of carbon-rich rock mixed with ice and may be captured asteroids.

Olympus Mons

Towering high above the Martian landscape is Olympus Mons. It is the largest volcano in our Solar System and nearly three times as high as Mount Everest!

Olympus Mons holds the title for tallest mountain in the solar system, and it is the second tallest mountain in the Universe. It likely became so large because Mars does not have tectonic plates. Therefore, the lava was likely able to flow outwards from a hotspot in the same place for quite a long time with no crust shifts to impede it.

The volcano is located in Mars's western hemisphere near the uplifted Tharsis bulge region. Since Mars is a small planet, and the slopes of Olympus Mons are so gradual, the edge of the volcano cannot be seen as it extends further than the horizon. Olympus Mons is so tall that it is often the only thing visibly protruding through Mars's massive dust storms.

Valles Marineris

 Valles Marineris is a 4,000 km (2500 mile) crack across the surface of Mars, at parts 7 km (4 miles) deep. It is a system of canyons, including the vast Coprates Chasma. Measuring the length of the entire United States, Mars’ Valles Marineris—Mariner Valley—is an enormous canyon that makes our Grand Canyon appear minuscule. Located along Mars’ equator, Valles Marineris spans one-fifth of the entire circumference of the planet. With depths of up to 4 miles and widths reaching up to 120 miles, the 2,500-mile-long canyon system is one of the largest in the entire Solar System. To put things into perspective, the Grand Canyon is a fraction of the size, running 277 miles long, up to 18 miles wide, and with a depth of only up to a little over a mile.

 

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In outer space there is no air to breathe and the temperature can quickly change from being very hot to very cold. To survive astronauts must wear spacesuits. They are like an astronaut’s personal spacecraft, allowing them to do important jobs – such as repairing the space station.

Lots of layers

Spacesuits have 14 layers of material to help keep astronauts safe. The liquid cooling and ventilation garment makes up the first three layers. On top of this garment is the bladder layer. It creates the proper pressure for the body. It also holds in the oxygen for breathing. The next layer holds the bladder layer to the correct shape around the astronaut's body and is made of the same material as camping tents. The rip stop liner is the tear-resistant layer. The next seven layers are Mylar insulation and make the suit act like a thermos. The layers keep the temperature from changing inside. They also protect the spacewalker from being harmed by small, high-speed objects flying through space. The outer layer is made of a blend of three fabrics. One fabric is waterproof. Another is the material used to make bullet-proof vests. The third fabric is fire-resistant.

Life support system

The PLSS is worn like a backpack. It provides astronauts many of the things they need to survive on a spacewalk. Its tanks supply oxygen for the astronauts to breathe. It removes exhaled carbon dioxide. It contains a battery for electrical power.



The PLSS also holds water-cooling equipment, a fan to circulate oxygen and a two-way radio. A caution and warning system in this backpack lets spacewalkers know if something is wrong with the suit. The unit is covered with protective cloth layers. 

Spacesuit gloves have heaters in the fingertips to stop an astronaut’s fingers from getting cold! EVA gloves are made to protect astronauts from the space environment. They are also made so spacewalkers can move their fingers as easily as possible. The fingers are the part of the body that gets coldest in space. These gloves have heaters in the fingertips. A piece called a bearing connects the glove to the sleeve. The bearing allows the wrist to turn.

Astronauts see out of a clear plastic bubble, and also have a visor to protect them from the Sun’s harmful rays. The helmet keeps the oxygen at the right pressure around the head. The main part of the helmet is the clear plastic bubble.



The bubble is covered by the Extravehicular Visor Assembly. The visor is coated with a thin layer of gold that filters out the sun's harmful rays. The visor also protects the spacewalker from extreme temperatures and small objects that may hit the spacewalker.



A TV camera and lights can be attached to the helmet.

Display unit

This module is the control panel for the mini-spacecraft. Switches, controls, gauges and an electronic display are on the module. The astronaut can operate the Primary Life Support Subsystem from this module.

Astronauts can attach their boots to special foot restraints on the space station to make working in space easier.

Flying free

This space jetpack is called a “Manned Maneuvering Unit”. It was used by astronauts in the 1980s to travel in space without being tied to their spacecraft. Today, astronauts have smaller versions in case of emergencies. The MMU is a self-contained astronaut backpack propulsion device that allows astronauts to venture untethered from an orbiting spacecraft.  The unit is powered by 24 nitrogen gas thrusters, and its main structure is aluminum.  Other elements include two 16.8-volt silver zinc batteries, a control electronics assembly, and two hand controllers.

To use the MMU, an astronaut exits the Space Shuttle crew compartment through an airlock into the cargo bay.  There the astronaut dons the MMU and releases himself from the flight support station.  To maneuver in space, the astronaut uses the hand controllers.  The control electronics assembly translates the hand controller movements and fires the thrusters.  The astronaut can activate an auto-pilot system which will hold his attitude.

When not in use, the MMU is stowed and recharged in the flight support stations located in the forward end of the orbiter's payload bay.

 

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The International Space Station (ISS) is the biggest object ever flown in space. It orbits at around 400 km (250 miles) above Earth and a team of astronauts have lived and worked here since the year 2000. It is our first step towards exploring deeper into the Solar System.

Astronauts do lots of scientific experiments on the space station to help us understand more about the effects of living in space. This will be useful knowledge for future deep-space exploration.

Keeping fit

There is no gravity in space, so astronauts exercise every day. It keeps them healthy and stops their muscles from getting weak. The heart and blood change in space. When we stand up on Earth, blood goes to our legs. The heart has to work extra hard against gravity to move the blood all around the body. In space, without the pull of gravity, the blood moves to the upper body and head. Water in the body also does the same thing. It makes the astronauts' faces look puffy. The blood and water are fluids in the body. These fluids move from the bottom of the body to the top. The brain thinks that there are too many fluids. It will tell the body to make less. When the astronauts come back to Earth, they do not have enough fluids in their systems. It takes their bodies a few days to make more blood and water. The astronauts have to rest so their bodies have time to make new blood and water. If they don't, they can feel very weak. They might even faint! 

Space walk

Sometimes astronauts have to go outside on spacewalks to repair the ISS. They wear special suits to protect them from the harsh environment of space. Inside spacesuits, astronauts have the oxygen they need to breathe. They have the water they need to drink.

Astronauts put on their spacesuits several hours before a spacewalk. The suits are pressurized. This means that the suits are filled with oxygen.

Once in their suits, astronauts breathe pure oxygen for a few hours. Breathing only oxygen gets rid of all the nitrogen in an astronaut's body. If they didn't get rid of the nitrogen, the astronauts might get gas bubbles in their body when they walked in space. These gas bubbles can cause astronauts to feel pain in their shoulders, elbows, wrists and knees. This pain is called getting "the bends" because it affects the places where the body bends. Scuba divers can also get "the bends."

Astronauts are now ready to get out of their spacecraft. They leave the spacecraft through a special door called an airlock. The airlock has two doors. When astronauts are inside the spacecraft, the airlock is airtight so no air can get out. When astronauts get ready to go on a spacewalk, they go through the first door and lock it tight behind them. They can then open the second door without any air getting out of the spacecraft. After a spacewalk, astronauts go back inside through the airlock.

Nice view

From the space station you can see entire countries, storms from above, and 16 sunsets and sunrises every day! Artificial structures visible from earth orbit without magnification include highways, dams, and cities. The Great Wall of China, often cited as the only human-made structure visible from space, is not visible from low Earth orbit without magnification, and even then can be seen only under perfect conditions. From US Space Shuttles, which typically orbited at around 135 mi (217 km), cities were easily distinguishable from surrounding countryside. Using binoculars, astronauts could even see roads, dams, harbours, even large vehicles such as ships and planes. At night, cities are also easily visible from the higher orbit of the ISS.

Metropolitan areas are clear at night, particularly in industrialized countries, due to a multitude of street lights and other light sources in urban areas

Robonaut

Robonaut 2 is a NASA (US space agency) robot astronaut that lives on the space station and helps the crew with sample tasks, such as changing air filters. Its head has cameras, which work like eyes, and its hands can operate simple tools.

One advantage of a humanoid design is that Robonaut can take over simple, repetitive, or especially dangerous tasks on places such as the International Space Station. Because R2 is approaching human dexterity, tasks such as changing out an air filter can be performed without modifications to the existing design.

Another way this might be beneficial is during a robotic precursor mission. R2 would bring one set of tools for the precursor mission, such as setup and geologic investigation. Not only does this improves efficiency in the types of tools, but also removes the need for specialized robotic connectors. Future missions could then supply a new set of tools and use the existing tools already on location.

 

Picture Credit : Google