My Science School

The ice caps on the Martian northern and southern Polar Regions, called Planum Boreum and Planum Australe respectively, are made up of - you guessed it - ice. But not just any ice. Only about 70 per cent of it is water in solid form. The rest is solidified carbon dioxide - called dry ice - and dust!

During the cold and dark winters on a Martian pole, nearly one-sixth of the atmosphere freezes and deposits on the permanent ice cap to form a metre-thick layer of dry ice. Months later when spring arrives bringing sunlight to the poles, the dry ice sublimes (or, directly turns from solid to gas). By summer, most of the carbon dioxide layer on the North Pole vanishes leaving behind a water-ice cap. But the South Pole has a permanent cover of dry ice and water-ice beneath this temporary layer.

Beneath the residual ice caps lies a formation called polar layered deposits, which are nothing but sheets of ice and dust stacked one on top of the other, like the pages of a book. Scientists say that since these deposits are the result of seasonal cycles and dust storms, they can give us clues about how Martian climate used to be in the past. Polar layered deposits rest on frozen ground made up of loose sand, dust and water-ice. In the north, this surface is called north polar basal unit, and in the south, Dorsa Argentea Formation.

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Planning a trip to Mars? Better carry all your blankets along! Because the Red Planet is a much colder place than the Earth.

Near the equator, summer afternoons can be a pleasant 20 degrees Celsius. But don’t let that fool you. At night you may get a freezing minus 73 degrees Celsius! For comparison, the freezers we have at home, even the very best ones, can only go up to minus 23 degrees Celsius. Winters are worse, with temperatures at the poles dropping down to minus 125 degrees Celsius. In fact, the average temperature on Mars is around minus 60 degrees Celsius compared to our planet’s 15!

There are more than a few reasons for this Martian ‘coldness.’ One, the average distance between the Sun and Mars is almost 50 per cent more than that between the Sun and the Earth. So the amount of sunlight reaching the Red Planet is lesser, only about 43 per cent of what we get here. Two, Mars has a more elliptical orbit when compared to the Earth, which periodically takes it closer to, and farther from the Sun. During this second phase, Mars’ axial tilt keeps its south pole further away from the Sun, making southern winters quite extreme. Three, the Martian atmosphere is very thin, only one-hundredth as dense as the Earth’s. So it cannot store heat and act like a “thermal blanket” for Mars.

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For Mars observers, 1877 was a special year. The Sun and Mars aligned on opposite sides of the Earth (a phenomenon called “opposition”), while Mars came closest to the Sun in its orbit. This “perihelic opposition,” where Mars appeared at its biggest and brightest phase, gave astronomers the perfect opportunity to study the planet. During this period, an Italian astronomer started mapping the surface of Mars. He was the director of the Brera observatory (in Milan, Italy), and his name was Giovanni Virginio Schiaparelli.

Schiaparelli called the light-and dark-coloured areas on the Martian surface “continents” and “seas,” respectively, and the inter-connected lines he saw through his telescope, “canali.” There were almost 40 such canali on his map, and he named them after well-known rivers on the Earth.

“Canali” was an Italian word that meant “channels” or “grooves,” features that could be natural to a planet’s topography. However, when “canali” was translated to English, it became “canals,” meaning artificial water-ways! This led many to imagine there were intelligent beings on Mars who had constructed these magnificent 40-odd “canals!”

Though most astronomers of those times could not spot Schiaparelli’s canali, it remained a hotly-debated topic in academic circles, until proof emerged that the lines Schiaparelli saw were optical illusions. Nevertheless, the concept of intelligent life on Mars was immensely popular, and continued to inspire countless works of science fiction.

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Fresh grass of spring, sun in summer, falling leaves of autumn and snow in winter - change of seasons make our planet beautiful, doesn’t it? Like the Earth, Mars too has all four seasons, thanks to its “axial tilt” (25.2 degrees, compared to the Earth’s 23.4 degrees). But Martian seasons are nothing like the ones we have on the Earth! To know why, we must understand two things about Mars’ orbit.

One, the planet takes 687 days to complete a full orbit, about twice the time the Earth does. Therefore Martian seasons are also nearly twice as long. Two, while the Earth has a near-circular orbit, Mars’ orbit is more elliptical, or elongated, in shape with the Sun located at one of its two foci. As a result, during a certain period of the Martian year, the red planet is close to the Sun, and in another, it is far away. It so happens that Mars’ southern hemisphere is always tilted towards the Sun during the first phase, and away from the Sun in the second. This makes summers in the southern hemisphere warmer, and winters, colder.

The temperature differences between the northern and southern halves are so extreme that they generate winds often strong enough to sweep up fine dust from the surface and become massive dust storms.

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Polar Regions, southern highlands, and northern plains. Do they sound like remote regions of the Earth? Or do they remind you of a fictional terrain made for books, like Tolkien’s Middle-earth? In reality, they are the names given to three distinct regions on the Martian surface!

Similar to the Earth’s Polar Regions, Martian poles also have ice caps. Surface temperatures are the lowest here compared to anywhere else on the planet. The ice cap on the south lies at a higher level than the north, and is also colder. In fact, a large portion of Mars’ southern side lies on higher ground compared to the north (by one to three kilometres), which gives it the name, southern highlands. Here, we can find a lot of craters created by the impact of meteors that are said to have bombarded the planet nearly 4 billion years ago.

The northern part of Mars, however, has far fewer craters even though it covers nearly one-third of the planet. The flat terrain of the low-lying northern plains is said to have been created by lava flows. The iron-rich dust and sand on the plains give it a pale appearance. Decades ago when telescopes were far less powerful than the ones we have today, astronomers mistook the northern plains for continents, and the dark-coloured southern highlands, for oceans!

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Our ancestors spent centuries observing the positions and movements of Mars. And yet, how the planet looked up-close remained a mystery. But an amazing invention in the hands of a talented Italian astronomer-cum-scientist changed that!

Galileo Galilei started observing Mars in 1610 using a low-power telescope he himself made. Though he could not make out any details of the Martian surface, this was the first time anyone was seeing Mars through a telescope. It also inspired many astronomers to follow in Galileo’s footsteps, and by 1659 we had our first sketch of the Martian surface! This drawing, made by Christiaan Huygens (a Dutch scientist), clearly shows Mars’ characteristic “dark spot” - a region called Syrtis Major Planum.

Huygens also determined the size of Mars, and the time it takes for it to complete a full rotation about its axis. In 1666, an Italian astronomer-cum-engineer, Giovanni Domenico Cassini, gave a better estimate; he said a day on Mars is 24-hours-and-40-minutes long, which is just three minutes more than the actual duration! He is also credited with the discovery of Mars’ polar ice caps.

By the 19th century, we had a better understanding of Mars’ topography. Detailed maps and more accurate estimates of Mars’ rotational period and size could be made, thanks to more powerful telescopes.

In fact, it was the U.S. Naval Observatory’s refracting telescope (the world’s largest one during that time) that helped the American astronomer, Asaph Hall, discover the two moons of Mars, Deimos and Phobos, in 1877.

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To someone who has read the book of fiction, The Martian, or seen its movie version, a Martian storm seems rather terrifying. As the astronaut’s equipment goes flying in the wind, it injures him badly. His camp gets damaged too. In reality, are the winds on Mars that powerful? There are two things you should know.

One, because of its low gravitational pull - amounting to just one-third that on the Earth - Mars has a much thinner atmosphere. It is hardly one-hundredth as dense as the Earth’s atmosphere! That means, to move anything around, Martian winds have to blow very fast.

Two, winds on Mars generally blow at a speed of 16 to 32 kilometres per hour. This is influenced by many factors, such as temperature variations, atmospheric circulation patterns (large-scale movement of air by which heat is redistributed across the planet), and landscape. Often winds gather enough speed to sweep up Mars’ fine red dust and become dust storms. Some are intense enough to be spotted through telescopes here on the Earth! Moderately big dust storms, covering continent-size areas, occur annually. But once every few years, they grow really massive and blow across the entire planet, blanketing it in dust for weeks. Even so, maximum wind speeds on Mars are only about 100 kilometres per hour!

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Did you know that ancient Egyptians were excellent star-gazers? It is said that they prepared the oldest map of the skies, known as the Senenmut star map, in 1534 BCE. And in this map, we can find one of the earliest records of “Her Desher,” or “the red one!” Mars is also depicted in the tomb of an Egyptian pharaoh, Seti I, and on the ceiling of Ramesseum, the memorial temple of Ramesses the Great. What is even more impressive is how the ancient astronomers of Egypt were aware of the forward-reverse-forward path tracked by Mars on the night sky (called apparent retrograde motion) as early as the 2nd millennium BCE!

Closer home, the earliest records of Mars observations can be traced back to the period before the Zhou Dynasty rule in China, sometime around 1045 BCE. By around 6th century BCE, the astronomers of Babylonia also started observing the movement of planets across the night sky, and developing calculations to predict planetary positions more accurately. They even knew how long it takes Mars to complete a full orbit. Up until this period, the Greeks, who had associated Mars with Ares, their god of war, had given no further attention to planetary observations. This was to remain so until the times of Plato and Aristotle.

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Martian soil is a farmer’s nightmare! The reason? It has no organic content. It is not aerated either. Instead, all it contains is mineral matter, largely in the form of sand, the product of weathering of volcanic rocks. Mars is also extremely dry. Scientists say the trace amount of water in the soil, about 2 per cent, may have been absorbed from the atmosphere.

The Martian surface layer is made up of fine dust. Rich in iron oxides, or rust, this dusty layer gives the planet its unique red colour! Though similar iron-rich soils can also be found on the Earth, it is limited to certain places. Not so, on Mars. Dust storms sweep across it occasionally, transporting fine dust all over the planet. So the Martian surface layer is largely homogenous, like a huge desert.

Photographs of steep slopes, such as those of hills, craters and troughs, often reveal thin dark lines on the Martian surface. Sometimes, these “streaks” start small and gradually grow until they are hundreds of meters in length! They may grow lighter in colour with time, and even follow the edges of rocks and boulders blocking their path to get to the other side. What are these strange lines? Are they flow paths of water, or growth of organisms? No one knows for sure. Scientists think they may just be hidden darker layers of soil that are revealed by dust avalanches or spinning columns of dust, called dust devils.

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Mars was not always the dry planet we know today. Evidence suggests that four million years ago, liquid water used to flow across the Martian surface and form pools and lakes! Jezero crater is one such long-dried-out lake found by the U.S. National Aeronautics and Space Administration (NASA). Many other stream and lake beds have also been discovered.

Scientists say that if Mars had been able to hold liquid water in the past, its atmosphere and climate too, would have been vastly different back then. Maybe, once upon a time, it was like Venus, or the Earth! After all, all the three planets are made up of similar materials. So in their early stages, their surface conditions may have been similar too! But over the years, these planets became quite different - the Earth and Venus still have most of their thick protective atmosphere, whereas Mars was able to retain only a thin layer.

Water on Mars today exists majorly as polar ice caps, 3.7 kilometres thick in the south, and 1.5 to 2 kilometres thick in the north. Water is also present in the Martian atmosphere as ice and vapour. But in comparison, the Earth’s atmosphere is richer in water content by nearly a hundred times! As a result, Mars’ precipitation is also considerably lesser than the Earth’s - even cold seasons produce only a thin film of frost, less than a millimetre thick!

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The story of Mars started ages ago, when the planets that we see today were super-hot, dense radioactive masses that often crashed into one another. These masses melted, and the heavier elements in them sank to the core while the lighter ones floated. This process is called planetary differentiation. All planets, including Mars, and a few other dwarf planets and moons have undergone differentiation.

As a result, if we cut open Mars, we will find a dense core, a mantle and a thin crust, like that in the Earth. Latest research estimates that the core is molten and has a radius of around 1,810 to 1,860 kilometres. It is made up mainly of iron and nickel, and a considerable amount of sulphur, around 16 to 17 per cent. The concentration of lighter elements present in its core is said to be twice that of the Earth’s!

The next layer, called mantle, is lighter than the core and made up of silicate rock. On the Earth, the mantle sometimes melts at certain locations, and this is what causes earthquakes and eruption of volcanoes. But on Mars, it seems that such activity has not been happening for a long time. The outermost layer, or crust, of Mars is composed largely of silicon, oxygen, iron, magnesium, aluminium, calcium, and potassium.

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Bigger than Mercury, but smaller than Venus, Mars is the second-smallest planet in our solar system. With a radius of 3,396 kilometres when measured along the equator, and a radius of 3,379 kilometres when measured along the poles, Mars is small. It is only a little more than half the size of the Earth! Mars is also less dense. This gives Mars a mass that comes around to just 11 per cent that of the Earth. As a result, its gravitational pull is also lesser - only 3.72 metres per second square, approximately one-third that of the Earth.

So if you ever get a chance to go to Mars, don’t forget to pack your weighing scales, because once there, you will see that you weigh only about one-third of what you did on the Earth! You can even jump three times higher than you normally do! Cool, isn’t it?

If all this fun makes you want to settle down on Mars and never come back, you can be sure of one thing - you will never have to worry about finding living space. Though Mars has only 28 per cent of the Earth’s total surface area, it is equivalent to the land mass available here. (Remember, two-thirds of our planet is covered by water!) So there is, theoretically speaking, enough space to accommodate all of us on Mars. We just have to find ways to make food, water, air and shelter to survive!

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Did you know that the distance between the Sun and its planets is not constant? This is because the paths of planets around the Sun, called orbits, are not exactly circular! They are elliptical, which are nothing but slightly flattened circles with two foci instead of one. Our Sun is located in one of these two foci.

This means that the distance between the Sun and Mars can be anywhere between 206.6 million and 249.2 million kilometres. Quite a huge range, isn’t it? For the sake of convenience, we say that the mean distance between the two is 228 million kilometres. This is approximately 1.5 times the distance between the Earth and the Sun. It takes Mars nearly twice as much time as the Earth to complete one full orbit, 686.97 Earth days to be exact.

We have to specify ‘Earth’ days here because a ‘Mars’ day or sol is slightly longer than an Earth day. It is approximately 24 hours, 39 minutes, 35 seconds long. A Martian year is approximately 668 sols, equivalent to approximately 687 Earth days or 1.88 Earth years.

In this manner, as Mars moves around the Sun, there comes a period when the two come on either side of the Earth. This “opposition” phase is the best time to view Mars from the Earth as its full face gets illuminated by the Sun’s rays.

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Once every so often while gazing up on a clear night, you may be able to spot a small reddish disc shining in the sky. Meet Mars, a planet that has been inspiring our imagination since time immemorial!

Bigger than Mercury, but smaller than Venus, Mars is the second-smallest planet in our solar system. Distance-wise, it is the fourth planet from the Sun, and our closest neighbour right after Venus. This is a reason why, when Mars comes closest to the Earth, it is one of the brightest natural objects in the night sky, next only to Venus and the Moon. Even with the naked eye, it can be easily distinguished from other astronomical bodies thanks to its unique reddish appearance. This colour is the result of the abundance of rusty-red iron oxides on its surface.

It is not just the colour that has fascinated us over the centuries, but also the idea of life on this “Red Planet” Scientists have long debated whether Mars was once a living planet, and puzzled over its ability to support life in the present or the near future. This is because, in many ways, Mars is similar to the Earth. It is a terrestrial planet with seasons and weather patterns, and a thin atmosphere. Even though it carries impact craters like those on our Moon, it also has geographical features seen on the Earth, like valleys, volcanoes, canyons, deserts and polar ice caps. Scientists have found on Mars what seem to be evidences of ancient floods. Some Martian hillsides even carry traces of salt water flows.

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Centuries ago, the Romans identified seven celestial objects that were brighter than the rest in the sky - the Sun, the Moon and five planets - and gave four of them the names of Roman gods - Mercury, Venus, Jupiter and Saturn. But one among them was exceptionally red. It might have reminded those ancient astronomers of blood because they called it “Mars,” after their god of war!

The Greeks too, saw their god of war in the planet, and called it Ares. In fact, in 1877 when an American astronomer, Asaph Hall, discovered the two natural satellites of Mars, he decided to name them Deimos and Phobos, thereby carrying forward the analogy! According to Greek mythology, Deimos and Phobos were the sons of Ares. The literal meanings of their names are “dread” and “fear”!

Other ancient cultures had their own names for Mars. To the Chinese it was the “Fire Star” and to the Egyptians, it was “Her Desher,” or “the red one,” showing us yet again how Mars’ distinctive colour made a powerful impression on the minds of our ancestors!

Mars has also been linked to masculinity and strength. Have you seen the symbol used to represent the male gender? It is a circle with an arrow attached to its upper-right part, the arrowhead pointing outwards. This sign owes its origin to the symbol of Mars!

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