Category Man and the Moon

How long do footprints last on the Moon?

Astronauts Neil Armstrong and Edwin (Buzz) Aldrin were the first humans to step foot on the Moon on July 20, 1969, and naturally, they left behind their footprints.

But do these still exist? Yes, they do!

How long will they last?

The first footprints, rather, all the footprints left on the Moon between 1969 and 1972, when the last human mission to the Moon happened, will still be there.

They might actually be there for years and years together, and if we are lucky, probably as long as the Moon lasts.

Why?

This is because unlike Earth, there is no erosion by water or wind on the Moon as it has no atmosphere and all the water on its surface is frozen. Also, there is no volcanic activity on the Moon which can change the lunar features. So, nothing really gets washed away from the Moon’s surface.

It may or may not last forever

The reason there is no guarantee that the footprints will remain permanently on the Moon is because of meteorites and solar wind.

Like the planets and other objects in the solar system, the Moon too is prone to bombardment by meteorites. Even one little space rock that lands anywhere near any of the footprints can wipe them off.

Due to the lack of atmosphere on the Moon, it is exposed to solar wind, which is a stream of charged particles coming from the Sun. Over time, this solar wind can act like the weather on Earth and scour the surface of the Moon, wiping away all footprints.

The good news though is that this process is very, very slow. So, footprints on the Moon are likely to remain there for a really long time.

 

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WHAT HAPPENS DURING A LUNAR ECLIPSE?

          A lunar eclipse occurs when the Earth comes directly between the Sun and the Moon. As the Moon moves through Earth’s shadow, the planet prevents direct sunlight from reaching the surface of the Moon. The Moon does not disappear but turns red because Earth’s atmosphere bends the Sun’s rays. A lunar eclipse can occur only on the night of a full moon. The type and length of a lunar eclipse depend on the Moon’s proximity to either node of its orbit.

          During a total lunar eclipse, Earth completely blocks direct sunlight from reaching the Moon. The only light reflected from the lunar surface has been refracted by Earth’s atmosphere. This light appears reddish for the same reason that a sunset or sunrise does: the Rayleigh scattering of bluer light. Due to this reddish color, a totally eclipsed Moon is sometimes called a blood moon.

          Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth. A total lunar eclipse can last up to nearly 2 hours, while a total solar eclipse lasts only up to a few minutes at any given place, due to the smaller size of the Moon’s shadow. Also unlike solar eclipses, lunar eclipses are safe to view without any eye protection or special precautions, as they are dimmer than the full Moon.

          Earth’s shadow can be divided into two distinctive parts: the umbra and penumbra. Earth totally occludes direct solar radiation within the umbra, the central region of the shadow. However, since the Sun’s diameter appears about one-quarter of Earth’s in the lunar sky, the planet only partially blocks direct sunlight within the penumbra, the outer portion of the shadow.

          A penumbral lunar eclipse occurs when the Moon passes through Earth’s penumbra. The penumbra causes a subtle dimming of the lunar surface. A special type of penumbral eclipse is a total penumbral lunar eclipse, during which the Moon lies exclusively within Earth’s penumbra. Total penumbral eclipses are rare, and when these occur, the portion of the Moon closest to the umbra may appear slightly darker than the rest of the lunar disk.

          A partial lunar eclipse occurs when only a portion of the Moon enters Earth’s umbra, while a total lunar eclipse occurs when the entire Moon enters the planet’s umbra. The Moon’s average orbital speed is about 1.03 km/s (2,300 mph), or a little more than its diameter per hour, so totality may last up to nearly 107 minutes. Nevertheless, the total time between the first and the last contacts of the Moon’s limb with Earth’s shadow is much longer and could last up to four hours.

          The relative distance of the Moon from Earth at the time of an eclipse can affect the eclipse’s duration. In particular, when the Moon is near apogee, the farthest point from Earth in its orbit, its orbital speed is the slowest. The diameter of Earth’s umbra does not decrease appreciably within the changes in the Moon’s orbital distance. Thus, the concurrence of a totally eclipsed Moon near apogee will lengthen the duration of totality.

          A central lunar eclipse is a total lunar eclipse during which the Moon passes through the centre of Earth’s shadow, contacting the anti-solar point. This type of lunar eclipse is relatively rare.

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WHY IS THE SKY ALWAYS BLACK ON THE MOON?

          If you are standing on the moon, the sky would always appear black, whether it was night or day. This is because there is no atmosphere to scatter sunlight. On Earth, atoms of oxygen and nitrogen in the atmosphere have an effect on sunlight passing through them. Light scatters when it passes through particles that are one tenth as large as the light’s wavelength. The atoms of oxygen and nitrogen are one tenth the size of the blue wavelength, so blue light is scattered more effectively than other colours.

          We see the sky as colored because our atmosphere interacts with the sunlight passing through it. This phenomenon is called “scattering.” The type of scattering responsible for blue sky is known as Rayleigh scattering. Because this effect becomes sharply more pronounced as the energy of light increases, wavelengths at the blue end of the spectrum, where energy is the highest, are scattered preferentially. The sunlight reaching our eyes has a high ratio of short, bluish wavelengths compared to medium and long wavelengths, so we perceive the sky as being blue.

          Without an atmosphere the sky appears black, as evidenced by the lunar sky in pictures taken from the moon. But even a black sky has some lightness. At night, the sky always has a faint color, called “skyglow” by astronomers. Much of this skyglow is light pollution – sources of light prevalent in urban areas that reduce our ability to see stars, planets, and other celestial phenomena.

          In the absence of light from human sources, skyglow is present due to a faint airglow in the upper atmosphere (a permanent, low-grade aurora) and starlight scattered in the atmosphere. Even beyond our atmosphere, faint skyglow is caused by sunlight reflected off interplanetary dust (zodiacal light), and background light from faint, unresolved stars and nebulosity.

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WHY DOES THE MOON HAVE PHASES?

          Like the earth, half of the Moon is always lit by the Sun, while half remains in darkness. Its orbit around the Earth, and Earth’s orbit around the Sun, means that we see the Moon with different amounts of sunlight on its surface. Although it appears to be altering its shape, only the position of the Sun’s light on the Moon’s surface is changing. These phases follow a cycle from a new Moon, where the dark side is facing us and the Moon appears invisible, to a full Moon, where the entire sunlit part is visible.

          For millennia, humans have kept track of time by observing the changing face of the moon. In fact, you may have noticed that the word “moon” shares its first few letters with the word “month” — and that’s no coincidence. 

          The phases of the moon — new moon, first quarter, full moon and last quarter — repeat themselves about once every month. But why does the moon have phases at all? To answer this question, it’s necessary to understand two important facts. First of all, the moon revolves around the Earth once every 29.5 days. And secondly, as the moon carries out its voyage around the planet, it’s lit from varying angles by the sun. 

          One half of the moon is always illuminated by the sun. But here on Earth, we can’t always see the half of the moon that’s lit up. What we call the phases of the moon represent the different fractions of the moon’s lighted half that we can see as the moon circles the Earth.

          When the moon and the sun are on opposite sides of the Earth, we perceive the moon as full. However, when the sun and the moon are on the same side of the Earth, we say the moon is “new.” During a new moon, the side of the moon that we can see from Earth is not illuminated by direct sunlight at all.

          Between the new moon and the full moon, the moon is a crescent (less than half illuminated). It then waxes — grows bigger — into a half-moon (half-illuminated). The first half moon after the new moon is called the first quarter because at that point, the moon is one-quarter of the way through its monthly cycle of phases. After the first quarter come the gibbous moon (more than half illuminated) and finally a full moon.  This cycle of phases then repeats itself in reverse. After a full moon, the moon wanes — becomes smaller — into a gibbous moon, a half-moon (also called last quarter), a crescent and finally a new moon. 

          Just before and just after the new moon, when a slim crescent of the moon is lit, you can also see the rest of the moon lit dimly. This owes to sunlight that bounces off the Earth and illuminates the otherwise dark portion of the moon that’s facing us, an effect known as “earthshine.”

          The major phases of the moon — new moon, first quarter, full moon, last quarter and next new moon — occur, on average, about 7.4 days apart. If you need some help tracking these phases yourself (or if you want to see where the moon was on an important day in history), NASA provides an online calendar of the dates and times of all phases of the moon for the six thousand year period between 2000 BCE to 4000 CE. 

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HOW DID THE MOON FORM?

          Nobody knows exactly how the Moon formed. The most common theory is that shortly after Earth formed; it was hit by an object the size of Mars. The impact was so powerful that it sent billions of tonnes of molten material into space. This debris was held in orbit around Earth, and eventually solidified to form the Moon.

          Analysis of samples brought back from the NASA Apollo missions suggest that the Earth and Moon are a result of a giant impact between an early proto-planet and an astronomical body called Theia.

          ‘There used to be a number of theories about how the Moon was made and it was one of the aims of the Apollo program to figure out how we got to have our Moon,’ says Sara. Prior to the Apollo mission research there were three theories about how the Moon formed. Capture theory suggests that the Moon was a wandering body (like an asteroid) that formed elsewhere in the solar system and was captured by Earth’s gravity as it passed nearby. In contrast, accretion theory suggested that the Moon was created along with Earth at its formation. Finally, according to the fission scenario, Earth had been spinning so fast that some material broke away and began to orbit the planet.

          What is most widely accepted today is the giant-impact theory. It proposes that the Moon formed during a collision between the Earth and another small planet, about the size of Mars. The debris from this impact collected in an orbit around Earth to form the Moon.

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IS THE MOON HOT OR COLD?

          The moon experiences temperatures both hotter and colder than those on Earth. When the Sun is directly over-head, the temperature on the Moon’s surface is higher than the boiling point of water — 100°C (212°F). However, at night, the Moon becomes very cold, with temperatures dropping to —173°C (-280°F). Earth and the Moon are approximately the same distance from the Sun, and therefore receive the same amount of heat. But the lack of an atmosphere on the Moon means that its temperature range is much more extreme. The Sun’s radiation is not filtered out by gases in the atmosphere, and there are no clouds to stop heat escaping at night.

          The moon rotates on its axis in about 27 days. Daytime on one side of the moon lasts about 13 and half days, followed by 13 and a half nights of darkness. When sunlight hits the moon’s surface, the temperature can reach 260 degrees Fahrenheit (127 degrees Celsius). When the sun goes down, temperatures can dip to minus 280 f (minus 173 c). Temperatures change all across the moon, as both the near and far side experience sunlight every lunar year, or terrestrial month, due to lunar rotation.

          The moon tilts on its axis about 1.54 degrees — much less than Earth’s 23.44 degrees. This means the moon does not have seasons like Earth does. However, because of the tilt, there are places at the lunar poles that never see daylight.

          The Diviner instrument on NASA’s Lunar Reconnaissance Orbiter measured temperatures of minus 396 F (minus 238 C) in craters at the southern pole and minus 413 F (minus 247 C) in a crater at the northern pole. 

          “These super-cold brightness temperatures are, to our knowledge, among the lowest that have been measured anywhere in the solar system, including the surface of Pluto,” David Paige, Diviner’s principal investigator and a UCLA professor of planetary science, said in a 2009 statement. Since then, NASA’s New Horizons mission set Pluto’s temperature range at a comparable minus 400 to minus 360 F (minus 240 to minus 217 C).

          Scientists suspected that water ice could exist in the moon’s dark craters that are in permanent shadow. In 2010, a NASA radar aboard India’s Chandrayaan-1 spacecraft detected water ice in more than 40 small craters at the moon’s North Pole. They hypothesized that over 1.3 trillion lbs. of water ice hid among the permanently darkened craters.

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HOW FAR AWAY IS THE MOON?

          The Moon is Earth’s closest neighbour in space. Its orbit around Earth is elliptical, rather than circular, which means that its distance from us varies. At its closest point to Earth (its perigee), the Moon is 384,400km (240,000 miles) away. Incredibly, the Moon’s orbit is slowly carrying it away from Earth at a rate of around 5cm (2in) a year.

          The distance between London, where I live, and Oxford, where I used to live, is about 100 km (or 60 miles). It takes about 90 minutes by car and about 120 minutes by bus. I can easily make sense of that distance.

          Harder to consider: the distance between the Earth and the moon, which is 384,400 km (240,000  miles). It’s a fact we’ve likely all learned in high school. Unlike the distance between London and Oxford, however, it’s not easy to comprehend what 384,400 km means in real terms.

          Luckily, you don’t have to think too hard. A NASA spacecraft has solved that problem for us. In October, OSIRIS-REX, a spacecraft that’s bound to intersect an asteroid in August this year, took the photo above from about 5 million km (3 million miles) away from the Earth. NASA posted the picture on Jan. 2, providing the public with a unique view of our planet and its moon. The angle is great to get a grasp of what the distance between the two celestial bodies really looks like, but it’s not perfect.

          Here’s a back-of-the-envelope calculation to explain why. For ease, we’re going to use round figures. The Earth’s diameter is about 13,000 km (8,000 miles). That means, in the 390,000 km distance between the Earth and the moon.

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WHAT IS THE MOON MADE OF?

          Although the moon’s interior structure is difficult to study, scientists believe that it has a small iron core. Surrounding this is a partially molten zone called the lower mantle. Above this lies the mantle, which is made up of dense rock, and the crust, which is also made of rock. Together, the mantle and the crust form the lithosphere, which can be up to 800km (500 miles) thick. There are only two basic regions on the Moon’s surface — dark plains called mania and lighter highlands. These heavily cratered highlands are the oldest parts of the Moon’s crust, dating back over four billion years. The darker plains are craters that were filled with lava.

          The composition of the Moon is a bit of a mystery. Although we know a lot about what the surface of the Moon is made of, scientists can only guess at what the internal composition of the Moon is. Here’s what we think the Moon is made of.

          Like the Earth, the Moon has layers. The innermost layer is the lunar core. It only accounts for about 20% of the diameter of the Moon. Scientists think that the lunar core is made of metallic iron, with small amounts of sulfur and nickel. Astronomers know that the core of the Moon is probably at least partly molten.

          Outside the core is the largest region of the Moon, called the mantle. The lunar mantle extends up to a distance of only 50 km below the surface of the Moon. Scientists believe that the mantle of the Moon is largely composed of the minerals olivine, orthopyroxene and clinopyroxene. It’s also believed to be more iron-rich than the Earth’s mantle.

          The outermost layer of the Moon is called the crust, which extends down to a depth of 50 km. This is the layer of the Moon that scientists have gathered the most information about. The crust of the Moon is composed mostly of oxygen, silicon, magnesium, iron, calcium, and aluminum. There are also trace elements like titanium, uranium, thorium, potassium and hydrogen.

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Is India planning on sending humans into space?

           After Chandrayaan 2, sending Man into space is India’s next biggest dream. The ISRO has already made plans for the Indian Human Spaceflight Programme and is working on a crewed orbital spacecraft- Gaganyaan.

          Gaganyaan is expected to be launched in 2020 and its manufacturing is carried out in co-operation with Hindustan Aeronautics Ltd. Gaganyaan is designed to carry three people into space and is supposed to orbit the Earth at an altitude of 400 kilometres for seven days. It is planned to be launched by GSLV Mk III, the same launch vehicle that put Chandrayaan 2 in its course to the Moon.

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What is the status of Chandrayaan 2?

          After the Vikram lander had a crash landing, the ground control lost contact with it. For two weeks, both ISRO and NASA tried to locate it. Though it was later located by the orbiter of Chandrayaan 2, the communication hasn’t been restored. Efforts are made to establish communication with the lander.

          K Sivan, the chairman of ISRO had set up a Failure Analysis Committee to look into the causes of failure. This committee is headed by P S Goel, senior scientist at ISRO.

          The orbiter remains intact and is expected to remain functional for seven years. All the payloads in the orbiter remain operational and their initial trials were completed successfully. The orbiter continues to perform the scheduled scientific experiments.

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Who is known as the ‘Rocket Woman of India’?

 

          Since the conception of Mangalyaan, ISRO had made significant efforts to involve more women in their project. Thirty per cent of the Chandrayaan 2 crew is constituted by women. Ritu Karidhal is one among them and is known as the ‘Rocket Woman of India’.

          Ritu Karidhal is an aerospace engineer and she now works as the Mission Director of Chandrayaan 2. She had played a crucial role in the development of the Mangalyaan project, holding the position of the Operations Director. Recognizing her work and potential, Ritu Karidhal was awarded the ISRO Young Scientist Award in 2007.

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Why was the launch of Chandrayaan 2 delayed?

          ‘Better late than never.’ This saying is true in the case of Chandrayaan 2. Though India was ready with all the payloads for the mission as per the schedule, it had to be first postponed to January 2013 and then to 2016. This happened because Russia was unable to develop the lander on time.

          Later, Russia withdrew from the project following the failure of Fobos-Grunt, a Russian mission to one of the moons of Mars. The technology used in Fobos-Grunt was also used in the lunar project and needed reviewing. Finally, Russia backed out, failing to deliver the lander by 2015. Following this, ISRO decided to go ahead with the project independently.

          After the development of the lander, Chandrayaan 2 was scheduled to be launched in March 2018. But, it was further delayed to conduct relevant tests and was planned for the first half of 2019.

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Does Chandrayaan 2 have a Russian connection?

          Chandrayaan 2 does have a Russian connection. ISRO had made an agreement to work with Roscosmos, the Russian Federal Space Agency for the development of Chandrayaan 2. By an agreement made on 12 November, 2007, the two agencies signed to share the responsibilities of the lunar mission.

          ISRO was to take the major responsibility of building the orbiter and rover while Roscosmos was supposed to develop the lander. The government of India chaired by Manmohan Singh approved this pact in September, 2008. Within a year, the design of the spacecraft was completed and was approved by the scientists from both the countries after a joint review.

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Which launch vehicle was used for launching Chandrayaan 2?

          Chandrayaan 2 was launched with the help of Geosynchronous Satellite Launch Vehicle Mark III. It is popularly known as GSLV Mk III.

          GSLV Mk III is a three-stage medium-lift launch vehicle developed by the ISRO. It is a multi-purpose launch vehicle, initially designed to launch communication satellites into a geostationary orbit. It is now identified as the launch vehicle for manned missions under the Indian Human Spaceflight Programme. It has a higher payload capacity than GSLV Mk 2. It can carry a payload up to 10,000 kilograms to the Low Earth Orbit and 4,000 kilograms to the Geostationary Transfer Orbit.

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How many payloads did Chandrayaan 2 carry?

          Chandrayaan 2 carried a total of fourteen payloads- eight for the orbiter, four for the lander, and two for the rover. Though NASA and the European Space Agency initially planned to provide scientific instruments, ISRO had to reject them due to weight restrictions.

          In fact, ISRO in 2010 made it clear that it won’t be carrying foreign payloads. However, a month before its launch, NASA made an agreement with ISRO in which it was decided to carry a small retro-reflector developed by the NASA. This was added to the lander’s payload, which contained other instruments designed for measuring seismic activity, determining the elemental composition of the lunar surface, mapping the lunar surface, studying electron density and so on.

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What is special about the Pragyan rover?

          The third module of Chandrayaan 2, the Pragyan rover is a robotic vehicle with six wheels. It weighs 27 kilograms and is designed to operate on solar power.

          Pragyan rover was built to perform a detailed on-site analysis of the lunar surface and transmit the data to the lander. It was expected to work for one lunar day, moving at a speed of 1 centimetre per second. Two of its wheels have the ISRO logo and India’s emblem that would leave a patterned track on the Moon. It contains two payloads and was designed to travel a distance of 500 metres.

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What was Chandrayaan 2’s lander known as?

          Chandrayaan 2 paid tribute to Vikram Sarabhai, the founder of the Indian space programme by naming the lander Vikram. 2019 marks Vikram Sarabhai’s 100th birth anniversary. It was designed to function for one lunar day that is 14 Earth days. It weighed 1,471 kilograms.

          Vikram lander contained a total of five engines and a set of scientific instruments. It was supposed to detach from the orbiter and get into a low lunar orbit in order to deploy the rover. After detaching the rover, the lander was supposed to stay on the lunar surface for further scientific explorations for fifteen days. Unfortunately, Vikram could not attain soft-landing, it crash landed instead. The connection with the lander was lost initially. Though the lander was later spotted through thermal imaging, its condition is not known.

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What do we know about the design of Chandrayaan 2?

          Chandrayaan 2 had three components- an orbiter, a lander and a rover.

          The orbiter carried eight scientific instruments. Out of these, two are improvised versions of the instruments on Chandrayaan 1. The orbiter’s structure was manufactured by the Hindustan Aeronautics Limited. It weighed 2,379 kilograms and was designed to work for the span of a year.

          The orbiter was designed to make scientific observations of the Moon. The Orbiter High Resolution Camera made high resolution observation of the landing sites before the separation of the rover and the lander.

          The orbiter transmits the information collected by the lander and rover back to Earth; it is capable of communicating with the Indian Deep Space Network. It orbits around 100 kilometres above the lunar surface. The orbiter works on solar energy and was expected to last for 7.5 years.

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When was Chandrayaan 2 launched?

          The launch of Chandrayaan 2 was initially scheduled for 14 July, 2019. But, it was postponed due to a technical error. After the long wait, Chandrayaan 2 was launched on its course to the Moon on 22 July, 2019, a decade after the launch of Chandrayaan 1. Planned for duration of seven years, the mission was launched at 2:43 PM by GSLVMk III from the second launch pad at the Satish Dhawan Space Centre, Sriharikota.

          On 20 August, 2019, Chandrayaan 2 reached the orbit of the Moon and began its efforts to land the Vikram lander. Both Vikram and the rover were scheduled to land in the South Polar Region. But things did not quite go as planned. The Vikram lander slightly deviated from its intended path and the communication with it was lost for a while. K Sivan, 1SRO chairman later confirmed the location of the lander.

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What makes Chandrayaan 2 unique?

          Chandrayaan 2 was a highly complex mission. It aimed to explore the lunar exosphere, lunar surface and the sub-surface in a single mission with special focus on the lunar South Pole. Also, it was the first mission that aimed at soft landing on the lunar South Pole.

          The lunar South Pole remains in shadows for much longer time than the lunar North Pole. Therefore, there is a possibility of presence of water in these permanently shadowed areas. Chandrayaan 2 contained India’s first lunar rover made out of home-grown technology. Though Chandrayaan 2 was faced with many challenges, it succeeded in proving India’s technological advancement.

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What were the primary objectives of Chandrayaan 2?

          Chandrayaan 1 was definitely an encouragement for future endeavours in space studies. Chandrayaan 2 is it’s more technologically and scientifically advanced follow up.

          When Indian scientists conceived the idea of a second lunar mission, they wanted to demonstrate its ability to soft-land on the surface of the Moon and operate a lunar rover. They were also looking for an extensive mapping of the lunar surface to prepare detailed 3D maps. It also aimed at a broad study of the lunar South Pole with focus on the thickness of the lunar regolith, and evidences of water ice. The mission also planned to study the variations in the lunar surface composition.

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When was Chandrayaan envisioned?

          We now know a lot about Chandrayaan 1. But when did the Indian scientists conceive the idea of a lunar mission? Let’s now dig up a little history.

          It all began in 1999 in a meeting at the Indian Academy of Sciences-that’s where they discussed the first Indian scientific mission to the Moon. This discussion was taken forward by the Astronautical Society of India (ASI). It was followed by the setting up of the National Lunar Mission Task Force by the ISRO in 2000. By 2003, over hundred eminent Indian scientists from different fields including Earth sciences, planetary sciences, physics, chemistry, astronomy, astrophysics, engineering, and communication sciences confirmed that our country was capable of conducting such a mission.

          Following this, Atal Bihari Vajpayee, the then prime minister of India announced the Chandrayaan 1 project during his Independence Day speech the same year. Government approval for the same was gained three months later in November. From then on, hundreds of Indian scientists devoted their time and brains to make this dream a reality.

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Did Chandrayaan 1 gain global recognition?

          Chandrayaan 1 lifted Indian space research to a global platform. India exhibited its self-sufficiency in space technology through the Chandrayaan 1 project. India’s efforts certainly gained global recognition.

          The American Institute of Aeronautics and Astronautics (AIAA) recognized ISRO’s contribution to space science and technology with the AIAA SPACE 2009 award.

          Chandrayaan 1 was bestowed with the International Co-operation Award in 2008 by the International Lunar Exploration Working Group. It was the recognition for accommodating the most number of international tests and lunar payloads. In 2009,    Chandrayaan 1 was also awarded the Space Pioneer Award by the US based National Space Society.

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What was the revolutionary discovery that Chandrayaan 1 made?

          For decades, scientists have been searching for the evidences of the presence of water on the lunar surface. On its landing on the Moon, Chandrayaan 1 confirmed the presence of water on the Moon.

          The Moon Impact Probe on Chandrayaan 1 had discovered traces of water ice on the lunar surface. The Moon Mineralogy Mapper, another instrument in Chandrayaan 1’s payload detected absorption features on the lunar surface. This feature was more prominent in cooler high latitudes. The lunar scientists confirmed that the water on the Moon was scattered throughout its surface in sheets of ice and some water was locked up in minerals.

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What is special about Chandrayaan 1’s Moon Impact Probe?

         The Moon Impact Probe (MIP) is the first ever Indian made object to reach the surface of the Moon. It is famous for discovering the presence of water on the Moon. This probe is the result of the vision of our former president Dr. APJ Abdul Kalam. He believed that India should not be left behind in the exploration of the Moon.

          The MIP was launched on 22 October, 2008 and weighed 34 kilograms at the time of its launch. It is box shaped and contained three instruments within- a C-band radar altimeter to measure the altitude of the probe, a mass spectrometer for measuring the constituents of the lunar atmosphere, and a video imaging system to take photographs of the lunar surface.

          The MIP separated from the orbiter on 14 November, 2008 and had a controlled landing on the lunar South Pole. The main objective of the MIP was to demonstrate the qualifying technology for any future soft landing.

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How were Chandrayaan 1’s payloads developed?

          Chandrayaan 1 serves as one of the best examples of the successful collaboration between various space research centres around the world. Six out of the eleven payloads were developed in association with the European Space Agency, NASA, and the space agencies of Bulgaria, Sweden and Germany. The other instruments were the result of the fruitful labour and technological expertise of Indian space scientists.

          All the payloads were used to learn more about the composition of the Moon. They performed activities like monitoring the radiations on the lunar surface, searching for water ice, and different types of mappings including chemical mapping, surface mapping and magnetic field mapping.

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What do we know about the scientific payload of Chandrayaan 1?

          Payloads are the scientific instruments carried aboard in a spacecraft. Chandrayaan 1 went to the Moon carrying a total of eleven instruments- five Indian instruments and six foreign instruments that altogether weighed 90 kilograms.

          The Indian instruments included a Terrain Mapping Camera that captures black and white images to map the topography of the Moon, a Hyper Spectral Imager that would perform mineralogical mapping, and a Lunar Ranging Instrument that would help in determining the height of the surface topography. India also sent a High Energy aj/gamma x-ray spectrometer (HEX), and the Moon Impact Probe developed by the ISRO.

          The instruments from other countries included a Radiation Dose Monitor Experiment (RADOM 7), Moon Mineralogy Mapper, a near infrared spectrometer, X-ray fluorescence spectrometer, a Mini SAR, and the Sub-keV Atom Reflecting Analyzer.

          Though these names sound complicated, all of them were deployed to understand the Moon.

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When was Chandrayaan 1 launched?

          On 22, October, 2008, Indians woke up to news that made each one of them proud. India had successfully launched its first mission to the Moon, Chandrayaan 1. This lunar probe was launched by the ISRO from the Satish Dhawan Space Centre at Sriharikota with the help of a PSLV C-11 rocket.

          Chandrayaan 1 was an unmanned lunar exploration that included a lunar orbiter and a Moon Impact Probe. It entered the lunar orbit on 8 November 2008. On 14 November, 2008, the Moon Impact Probe separated successfully from the Chandrayaan orbiter and landed on the lunar South Pole. The location of its impact is known as Jawahar Point.

          Though Chandrayaan 1 was intended to survey the surface of the Moon for two years, the ground control lost contact with the probe ten months after its launch. It also had some technical issues like poor thermal shielding and the failure of the star tracker.

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Why is Chandrayaan 1 a great achievement for India?

          Like many other countries, India too wanted to send people to the Moon. When Indian scientists worked out the plan for a mission to the Moon, they wanted to design, develop and launch a spacecraft to the Moon using a launch vehicle made in India. This would upgrade India’s technological expertise, provide ample experience of space technology and prepare India for future planetary explorations.

          Chandrayaan 1 aimed at mapping the Moon in terms of minerals, elements and topography that would help in the preparation of a three dimensional atlas of the Moon. It also includes the search for the presence of water and ice on the Moon. Though the contact with the lunar probe was lost after ten months of its launch, Chandrayaan 1 was a grand success; it completed almost all of the major objectives of the mission.

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What are India’s remarkable achievements in the field of space research?

          India is a major force in space research. In 1975, India launched its first satellite named Aryabhatta. A few years later, our country sent two remote sensing satellites into orbit- Bhaskara I and II in 1979 and 1981 respectively. These satellites were launched to observe the Earth.

          In 1979, India launched a series of satellites named Rohini. Rohini helped our scientists to understand the technology behind the functioning of larger rockets better. Later, India developed its first satellite launch vehicle- SLV 3. On July 18, 1980, SLV 3 made its first launch- the launch of satellite Rohini that weighed 40 kilograms. After SLV 3, India successfully developed PSLV and GSLV.

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Which organisation carries out India’s space research?

 

          The Indian Space Research Organisation, popularly known as the ISRO heads India’s space research. ISRO is headquartered at Bangalore. K. Sivan currently serves as the chairman of ISRO.

          ISRO aims at harnessing space technology for national development. It was set up 50 years ago in 1969; the same year Neil Armstrong set foot on the Moon. ISRO is credited with the milestones in Indian space research like the first satellite, the first rocket, and the first satellite launch vehicle. The notable achievements of ISRO include the launch of lunar orbiter Chandrayaan 1 launched in 2008, and the Mars Orbiter Mission, also known as Mangalyaan launched in 2013. ISRO recently launched Chandrayaan 2, its second lunar mission. The future endeavours of ISRO include the development of a reusable launch vehicle, human spaceflight, a space station, and a solar spacecraft mission.

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What were the objectives of the Lunar Prospector?

          The Lunar Prospector was a part of NASA’s Discovery Programme, a series of low cost space missions to explore the solar system. It was designed over 19 months in order to carry out a low polar orbit investigation of the Moon. Its objectives were to map the surface composition of the Moon including polar ice deposits, to measure magnetic and gravitational fields, and to study other lunar phenomena.

          A detailed map of the surface composition of the Moon was made from the data obtained from the Lunar Prospector. After gathering necessary information about the presence of water ice in the poles, the Lunar Prospector was deliberately crashed into a crater near the lunar South Pole.

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What were NASA’s other Moon endeavours?

          After the 1970s, the Moon was largely left unexplored till the 1990s. Moon exploration began again in the 1990s with the US sending three probes that took new pictures and explored the lunar surface with more scientifically advanced instruments.

          The orbiter Galileo passed by the Moon twice in 1990 and 1992, while taking a roundabout path to Jupiter. In 1994, Clementine orbited the Moon. Four years later, Lunar Prospector was placed in the orbit around the Moon. Both Clementine and Lunar Prospector returned with evidences of the presence of water on the lunar surface, something that scientists had long believed existed. However, when the Lunar Prospector crashed onto the surface of the Moon in 1999, it failed to detect the presence of water in the debris.

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What is special about Apollo 17?

          Apollo 17 was the last spacecraft of NASA’s Apollo mission. It was launched in December, 1972. Commanded by Eugene Cernan, the crew consisted of Ronald Evans and Harrison Schmitt.

          Apollo 17 also carried out biological experiments on five mice- Fe, Fi, Fo, Fum and Phooey. These five mice travelled from the Earth along with the astronauts and circled the Moon 75 times! Radiation monitors were implanted under their scalp to see whether they would suffer any damage from cosmic rays. One of the mice died while the other four were either killed or dissected for further studies upon their return.

          Cernan and Schmitt landed on the Moon, completed three moonwalks, and collected lunar samples that would give evidences of volcanic activity in lunar highlands.

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What happened to Apollo 13?

          Apollo 13 was the third mission aimed at landing on the Moon and was launched on April 11, 1970. Unfortunately, one of the oxygen tanks in the service module exploded. This happened because of the explosion of the fuel cell tank that resulted in the loss of power and oxygen. An insulation wire inside the tank was damaged which led to the explosion. Therefore, the crew had to cancel the plan to land on the Moon. However, they orbited around the Moon and returned safe on April 17, 1970.

          Apollo 13 was commanded by Jim Lovell and the crew included Jack Swigert and Fred Haise.

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Who first drove on the Moon?

 

          We know about the humans who landed on the Moon for the first time. But who was the first one to drive a lunar rover? David Scott and James Irwin, the crew of Apollo 15 are credited with this remarkable achievement.

          Apollo 15 was the fourth spacecraft to land on the Moon. It stayed on the Moon for a longer time than the other spacecraft and had a sharper scientific objective. David Scott and James Irwin landed near Hadley Rill. They travelled further from the lunar module with the help of a lunar rover and surveyed the local area. They spent eighteen and a half hours on the surface of the Moon, collecting almost 77 kilograms of surface material. While David and James explored the lunar surface, Alfred Worden, the Command Module Pilot orbited the Moon to collect data.

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Why is Eagle famous?

          Neil Armstrong and Buzz Aldrin had to take the help of a lunar module, a special landing vehicle to descend to the Moon. This was because the mother ship, the main spacecraft travelled too fast. Once the mother ship entered the lunar orbit, the astronauts got into the lunar module and separated from the main craft. Their lunar module was named Eagle.

          Eagle had spidery legs; they cushioned the landing and could be folded while in flight. They also had footpads that prevented them from sinking into the lunar soil. The body of the Eagle was covered in golden foil. This was done in order to protect it from the Sun’s heat.

         Eagle comprised of two parts; the top, known as the ascent stage carried the astronauts while the descent stage at the bottom carried the scientific equipment. The ascent stage also had navigation control, communications, life support, environmental control, electric power and propulsion system. The additional electric power, water and oxygen for the ascent stage was stored in the descent stage.

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Why did Apollo 11 create history?

           Even after half a century, Apollo 11 is remembered with great pride not only by the Americans but the whole of humanity. Apollo 11 made it possible for America, to fulfil a dream that it had cherished for years, and a mission that no one had attempted before – to leave human footprints on the Moon.

          It was July 20, 1969. Apollo 11 travelled 3,84,400 kilometres in space carrying three astronauts and landed on the Moon. Neil Armstrong was the first to step on the Moon. He was followed by Buzz Aldrin while Michael Collins controlled the system. “That’s one small step for a man, one giant leap for mankind.” This was what Neil Armstrong said immediately after setting foot on the Moon.

          With Apollo 11, America succeeded in taking man to the Moon and back safely, thus accomplishing the national goal set by President John F Kennedy. It also conducted the scientific exploration of the lunar surface and deployed a camera to transmit signals to the Earth.

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What do we know about the design of the Apollo spacecraft?

          Apollo was a three-part spacecraft that consisted of a command module, service module and a lunar module. The command module or the CM contained the crew’s quarters and the flight control section.

          It contained all the necessary commands and instruments to operate the spacecraft and to return to the Earth. The CM was in fact the only part that returned to the Earth and the astronauts were provided with reclining couches, specially fitted for them.

          The Apollo spacecraft’s service module or the SM carried the rocket engine that could be started or stopped whenever needed. The SM held the spacecraft’s electrical power system. It also contained the fuel. The third part known as the lunar module, or the LM, took the crew to the surface of the Moon. This module also provided the astronauts with the necessary support on the Moon and returned them to the command module.

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Which was the first manned-flight of the Apollo mission?

          Launched in October 1968, Apollo 7 is credited with the first manned flight; it is the first mission in the Apollo programme to carry a crew into space.

          In fact, Apollo 1 was intended to take the first astronauts into space. Unfortunately, its cabin caught fire in one of the test flights, killing the crew. This happened in January 1967. NASA then banned all manned flights until the reason for the fire was found out. Safety measures were improved after the investigations and Apollo 7 was launched after that.

          Commanded by Walter M Schirra, Apollo 7 was a complete success which gave NASA enough confidence to launch Apollo 8.

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How did Saturn V play an important role in Moon explorations?

 

 

 

          The Apollo programme would not have been the same if not for Saturn V. It is the most powerful rocket ever built; Saturn V is a three-stage rocket that uses high performance liquid hydrogen fuel for propulsion. This launch vehicle was specially developed to support the Apollo programme.

          Saturn V is taller than a 36 storeyed building and holds a cluster of five engines in its first two stages. It was flight tested twice without a crew. In December 1968, the first manned Saturn V sent the Apollo 8 astronauts into the orbit around the Moon. A year later, Saturn V launched the first manned landing on the Moon. This legendary rocket was launched 13 times from the Kennedy Space Centre. It was also used to launch Skylab, America’s first space station.

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What are the challenges a lunar probe faces on its journey to the Moon?

          We now know that reaching the Moon is not impossible. But it is not as easy as you may think. For a lunar probe to reach the Moon, it has to first escape Earth’s gravity. For this, the probe has to move at a great speed that can be achieved only by rockets.

         If the lunar probe is to land on the Moon safely, it has to slow down very much. Or else the probe will end up crash landing. In addition to that, returning to the Earth safely is another challenge. Rockets have to be used again to leave the Moon and the original spacecraft has to return to the atmosphere in such a way that it does not catch fire.

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What were the other major studies about the Moon before the invention of the telescope?

          Aristotle brought out a philosophical description of the universe. In it, the Moon was described as a border element, a boundary between the Earth and other imperishable stars. This philosophical view dominated the thoughts about the Moon for centuries.

          Some important studies about the Moon and its movement came out in the second century BC. Seleucus of Seleucia studied and theorized tides and tidal movements. He found out that tides were formed due to the attraction of the Moon, and that their height depended on the Moon’s position relative to the Sun.

          Aristarchus is credited with another important finding. He computed the size and distance of the Moon from the Earth. According to his findings, the distance from the Earth to the Moon is almost twenty times the radius of the Earth. Ptolemy studied and improved these values further.

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Why did the Babylonians show a special interest in studying about the Moon?

          The temple astronomers of Babylon had observed the skies for centuries and had recorded their observations in astronomical diaries, and other catalogues. Their predictions are almost accurate to this day.

          In fact, the Assyrians and Babylonians regarded lunar eclipses as evil omens. They believed that eclipses were directed against their kings. This was one reason why they studied more about the Moon. They studied the length of the synodic month, the period between two full moons. Their observations were almost error free. Using these data on the synodic month, the Babylonian astronomers were able to predict lunar eclipses and solar eclipses later.

          They also recorded the 18-year Saros cycle of lunar eclipses. A Saros cycle is the period of 223 synodic months-18 years and 11.3 days- after which lunar and solar eclipses repeat themselves. The predictability of the lunar eclipse made it possible for the Babylonians to appoint substitute kings who would bear the burden of the wrath of the gods.

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What were the initial studies about moonlight?

 

          Ancient scientists and astronomers were fascinated by moonlight. The ancient Greek philosopher Anaxagoras was one of the first scholars to understand the nature of moonlight. His investigations suggested that the Sun and the Moon were both giant spherical rocks, and that the Moon reflected the light of the Sun.

          The Chinese of the Han dynasty believed in the ‘radiating influence’ of the Moon. They recognized that the light of the Moon was merely a reflection of the Sun. Jing Fang of the Han dynasty studied further about the spherical nature of the Moon.

          Indian astronomer Aryabhatta studied about the physical characteristics of the Moon. In Aryabhatiya, he notes that reflected sunlight is the cause of the shining of the Moon. The Arab astronomer Alhazen threw more light on the way the Moon reflected sunlight. He found that sunlight was not merely reflected from the Moon like a mirror, rather it was emitted from every part of the Moon’s sunlit surface in all directions.

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What do we know of the ancient studies about the Moon?

           The journey to the Moon had to be somehow made possible. This thought was the driving force behind all the studies about the Moon.

           The early developments were crucial in moulding the later growth. It all began thousands of years ago with sketching the Moon; humans began drawing pictures to track the changes of the Moon. Later, their observations of the Moon led to creating calendars.

           Understanding the Moon’s cycles was the earliest development in astronomy. Astronomers from India studied the monthly elongation of the Moon while the Babylonian astronomers worked towards finding formulas to predict the lunar eclipse. The Chinese astronomer Shi Shen is noted for his instructions for predicting solar and lunar eclipses. The Chinese also studied the physical form of the Moon, including moonlight and gravitational pull. There were also efforts to calculate the distance between the Earth and the Moon. However, the Moon was believed to be a sphere with a smooth surface before the invention of the telescope.

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Does the Moon influence animal behaviour?

 

          We are familiar with the word lunacy, which means madness. Did you know that this word comes from Luna, the Latin word for the Moon?

          There are many stories about mysterious events that happen during the full moon. This includes strange and violent behaviour of animals including wolves and dogs. It is believed that the full moon brings out the worst in humans and animals. However, there are no satisfactory scientific explanations for any of this, though there are some evidences about the lunar phases affecting the behaviour of birds, fish, insects and even mammals. It’s a growing research area now.

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Can the Moon slow down the speed of the Earth?

          About 350 million years ago, a day on the Earth was around three hours shorter than today. The Earth slowed down because of the Moon. Aren’t you surprised?

          The Moon can slow down the Earth, even with its weak gravitational and magnetic field. This happens when there’s a force of friction between the surface of the Earth and the tidal bulges.

          During its rotation, the Earth drags the tidal bulge directly under the Moon. This causes friction between the Earth’s surface and the tidal bulge. The friction generated during this action slows down the rotation of the Earth on its axis. This results in a longer day and even a longer month.

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How are tides formed?

          The oceans and seas rise and fall at definite intervals. This rise and fall happens because of the gravitational force between the Earth and the Moon.

          We know that the Moon has a weak gravitational force. But it is strong enough to cause these periodic rises and falls known as tides.

          As our planet rotates, the Moon’s pull is exerted on different parts of the Earth. The Moon’s gravitational force exerts a pull on the oceans that generates tidal energy. It causes both the Earth and the oceans to bulge out in the direction of the Moon and away from it, and is known as tides. Because of the rotation of the Earth around the Sun, two tides occur each day- high tide and low tide.

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Why is a blue moon called so?

          Will a month have two full moons? Sounds almost impossible. Let’s take a look. The Moon takes almost twenty nine and a half days to change from one full moon to another. But, an average month has a span of thirty days. This makes it very unlikely for a month to have two full moons.

          However, some months do have two full moons and it happens very rarely. If there are two full moons in a month, the second full moon is called ‘blue moon.’ This name is not linked to the colour. In a century, there will be forty-one blue moons.

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How does a lunar eclipse occur?

          For a while, we have been talking about sunlight illuminating the Moon. What would happen if something blocks the sunlight that it receives? Will the Moon vanish from the night sky?

          In some instances, the Earth blocks the sunlight that is supposed to fall on the surface of the Moon. This happens when the Earth’s shadow falls on the Moon as it comes between the Sun and the Moon. This phenomenon is known as lunar eclipse.

          Lunar eclipse happens only during the full moon when the Earth either blocks sunlight completely or partially. Depending on this, lunar eclipse can be total or partial. However, the Moon will not disappear completely during the eclipse. This is because of a small amount of indirect sunlight that falls on it.

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Why does the Moon take more time to change from a new moon to the next new moon than the time taken for one trip round the Earth?

          It takes almost 27 days for the Moon to complete one trip around the Earth. This is known as the sidereal month. But it takes almost 29 days to change from a new moon to the next new moon. This is known as the synodic month. There is a difference of roughly two days. Wonder why?

          We already know that the Moon’s phases change according to the sunlight that falls on it and new moon occurs when the Moon is placed between the Earth and the Sun.

          While the Moon moves around it, the Earth moves around the Sun. The Earth moves farther in space during the time the Moon completes one orbit. So, for the Moon to come between the Earth and the Sun again, it has to move a little farther. It takes two days for the Moon to travel this extra distance.

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How is waxing different from waning?

          The shape of the Moon changes throughout the lunar month. The period in which the new moon grows to a full moon and back to another new moon is known as a lunar month.

          A lunar month is characterized by waxing and waning. Waxing occurs between the new moon and full moon, when the moon grows in size. The side of the Moon illuminated by the sunlight becomes bigger; it grows from a waxing crescent to waxing gibbous and then to full moon. During the gibbous phase, 51-99 per cent of the moon’s surface is illuminated.

          On the other hand, waning occurs between the full moon and new moon. When the Moon is waning, its surface illuminated by the sunlight decreases day-by-day. The Moon changes from full moon to the waning gibbous phase. It then changes to the waning crescent and finally the new moon.

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How is a full moon different from a new moon?

          When the Moon and Sun are placed at opposite directions from the Earth, the sunlight falls on the side facing the Earth. Therefore, the Moon appears as a round shining disc and is known as full moon.

          On the other hand, when the Moon comes between the Earth and the Sun, sunlight falls on the side that faces away from the Earth. During this time, the side facing the Earth appears dark and is known as new moon. The sky looks bright during the full moon while the Moon will not be visible during the new moon, making it dull.

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Why does the Moon have different phases?

 

          The Moon does not appear in the same shape every day, it is ever changing. On some days, it looks like a shining disk, on some days it looks like an elongated C. These different shapes of the Moon are called the phases of the Moon.

          The orbiting of the Moon around the Earth is the secret behind the different phases of the Moon. We already know that the Moon has no light of its own. As the Moon moves around the Earth, different parts of it are lit by the Sun, thus causing different phases. In a fortnight’s time, the Moon goes from full moon to new moon.

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What is the interior of the Moon composed of?

          The Apollo astronauts placed instruments known as seismographs on the Moon to study about its interior. What we know about it now comes primarily from their studies.

          The Moon is made up of different layers like any other celestial body. It has an outer crust, an inner mantle and an innermost core. The outer crust is hard, dry and dusty. It is almost 60 kilometres thick in the near side while it is almost twice as thick in the far side.

          The mantle has a thick layer of rock at the exterior and is semi-rigid in the interior. The mantle runs down almost 800 kilometres. The Moon’s core is constituted of rocks rich in iron.

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What is lunar soil known as among scientists?

 

          Scientists have special terms to indicate each scientifically relevant object around us. At times, these words may confuse an ordinary person as scientists often use big words that are difficult for a common man to understand. For instance, the scientific term for dry skin is xerosis. Similarly, lunar soil is known as lunar regolith among scientists.

          Lunar regolith is formed as a result of comets or meteorites that fall on the surface of the Moon. It is rich in oxygen and various metals. The thickness of the regolith varies from one place to another; it is three to five metres thick in the Maria, while the thickness in the highlands is ten to twenty metres.

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Why does the Moon have extreme temperatures?

          The temperature on the Moon is not constant; it varies from boiling hot to freezing cold, depending on the position of the Sun. The Moon has no atmosphere to either trap the heat or to insulate its surface.

          A day on Earth is 24 hours. Daytime on the Moon is thirteen and a half Earth days long. A long night of thirteen and a half days follows a Moon’s day. When sunlight hits the surface of the Moon during the day, the temperature can go up to 127 degree celsius. In contrast, the temperature on the Moon can drop to minus 173 degree celsius during the night.

          The temperature at the Moon’s core is much higher than its surface temperature. However, there are regions on the Moon that never receive sunlight. This is because of the slight tilt of its axis. Unlike Earth, the Moon doesn’t have different seasons either.

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Would the compass point towards the north on the Moon?

          If you take a compass to the Moon, it would not point northwards. It is not because your compass is faulty. A compass shows directions in alignment with the Earth’s magnetic field. We already know that the Moon has a very weak gravitational field. It does not have a strong magnetic field either. To understand this better, let us take a look at how the Earth’s magnetic field is formed.

          The core of the Earth is filled with hot liquid iron. This molten iron swirls as our planet rotates, thus producing the Earth’s magnetic field. The Moon’s core is less dense than the Earth. Therefore, the Moon’s core may contain only a little amount of metal; this might not even be heavy iron. On the Moon, the fluid motion of the conducting material is either very less or not present at all. As a result, the Moon has a weak magnetic field compared to that of Earth. It is around one hundredth of the Earth’s magnetic field.

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What is libration?

 

          The Moon has a dark side. Don’t worry; we are not talking about anything evil here. The side that faces away from the Earth is known as the Moon’s dark side. This is because of the shape of the lunar orbit.

          We know that the lunar orbit is elliptical. As a result, the Moon travels at different speeds at different points. Because of this, we can see more than half of the Moon’s surface. This phenomenon is known as libration. About 59 per cent of the Moon’s surface is visible from the Earth because of this phenomenon. Johannes Hevelius studied librations in detail and published his findings in 1647. His work was titled Selenographia.’

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Why are the Earth and the Moon referred to as the double planet?

          Many planets in the solar system have natural satellites. But Earth and its natural satellite share a special relationship.

          The Moon is Earth’s only natural satellite. Though our Moon is small when compared to the moons of Jupiter or Saturn, its size in relation to that of Earth is quite large.

          Along with revolving around the Earth, the Moon also revolves around the Sun in sync with the Earth. They look more like two sister planets than a planet and its satellite.

          Therefore, together, the Earth and the Moon are considered as a double planetary system.

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How is the near side of the Moon different from its far side?

          The Moon has a near side and a far side. The side that permanently faces the Earth is known as the near side while the side that faces away is known as the far side. Though these sides are so, the amount of sunlight they receive is almost the same.

          The surface of the near side differs from the far side; the near side is covered by large patches of dark areas. Early scientists proposed that these dark areas were seas with water. The dark patches are still known as seas. The far side does not have such seas. The crust here is thicker than the side facing the Earth.

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How long does the Moon take to complete one rotation?

 

 

          The Earth takes 24 hours to complete one rotation. But the Moon’s rotation is not that short; it takes 27 days, 7 hours and 43 minutes for the Moon to complete one rotation.

          The Moon’s axis is similar to that of the Earth; it is tilted towards one side. The Moon completes one round in its orbit around the Earth in almost the same time taken for one spin.

          Since the time taken for both movements are the same, the Moon always keeps the same side facing the Earth. This means that we get to see only one side of the Moon.

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What are perigee and apogee?

          The Moon’s orbit is elliptical; it is shaped like a flattened circle. Because of this shape, the distance between the Moon and the Earth is different at different positions and it varies as it moves around the Earth.

          When the Moon is closest to the Earth on its orbit, it is said to be at perigee. The word perigee is of Greek origin and means ‘near Earth’. At perigee, the Moon is 356,400 kilometres away from the Earth.

          The word apogee comes from a Greek word that means ‘far from Earth’. When the Moon is at the farthest point from Earth in its orbit, it is said to be at apogee. At apogee, the Moon is 406,700 kilometres away from the Earth.

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How big is the Moon?

          The Moon is the biggest and brightest object that one can spot on the night sky. It appears quite large because it is the closest celestial body to Earth.

          The equatorial radius of the Moon is around 1737 kilometres and the equatorial diameter is about 3472 kilometres. It is almost one-fourth the size of Earth. You can roughly fit in four moons inside the Earth. The Moon’s surface is as big as North and South America put together. According to NASA, “if Earth was the size of a nickel, the Moon would be about as big as a coffee bean.”

          The Moon is not a perfect sphere, just like the Earth. It is slightly flattened towards the poles. The diameter of the Moon from pole to pole is lesser than its equatorial diameter.

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Why does the Moon appear in different colours?

          Poets often describe the silvery moon. But, the Moon doesn’t always appear silvery; it is sometimes white, sometimes yellow, grey or even red at times.

          When the Moon is low in the sky, it is closer to the horizon. The light that travels through the air scatters near the horizon as it passes through a thick layer of atmosphere. As a result, the Moon looks yellowish or orange at times. When the Moon is high in the sky, the scattering effect is much lesser and it appears whitish. During a total lunar eclipse, the Moon appears to be red; this too is caused by the scattering of light. The colours of the Moon give us clues about the minerals present on its surface.

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How does the Moon shine?

          Even if there are a thousand stars in the sky, it will look a bit dull if we can’t spot the Moon. It is the brightest object in the night sky. But, the Moon does not have a light of its own. How ironic!

          Moonlight is produced when sunlight is reflected by the white dust on the Moon’s surface. The Moon will reflect only 3-12 per cent of the sunlight that hits its surface.

          The other factors that influence the brightness of the Moon include the movement of the Moon around the Earth and the simultaneous movement of the Earth around the Sun.

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Why is it easy for astronauts to walk on the Moon?

          Some of you might have dressed up as astronauts for your school fancy dress competition. Was it easy for you to walk around in the costume? Surely not.

          An astronaut has to carry equipment with necessary supplies like oxygen. Their space suits are usually very heavy, weighing more than 90 kilograms. But, they walk around quite easily. This is because of the Moon’s lower gravitational pull.

          The Moon’s mass is 81 times smaller than the mass of the Earth. As a result, the force of gravity on the Moon is six times weaker than that on the surface of the Earth. A bag that would weigh six kilograms on Earth would weigh just one kilogram on the Moon. Astronauts feel lighter because of this reason and walk easily on the surface of the Moon.

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What is special about the footprints on the Moon?

          Neil Armstrong set foot on the Moon in 1969. If one were to visit the Moon now, one could still find the footprints that he left behind in 1969.

          If you leave a footprint on sand or mud on Earth, either wind or rain would wash it away and it would soon disappear. On the other hand, the footprints left on the Moon last almost forever. Wonder why? Unlike on Earth, there is no wind or water on the Moon to wash it off.

          Therefore, the footprints won’t be eroded and will last for a really long time. So don’t expect to do something mischievous on the Moon and get away with it as your footprints will give you away!

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How are craters formed on the surface of the Moon?

          We know that meteors fall like missiles on the surface of the Moon as there is no atmosphere to protect it. Instead of water, comets and chunks of asteroids rain on the surface of the Moon and their impact creates craters. These are known as impact craters.

          Craters are formed due to powerful volcanic explosions as well. When the Moon’s surface is pushed upwards by melted rock, hot lava and gases gush out of it, giving rise to craters. Some craters are more than two billion years old. Generally, the age of a large crater is determined by counting the number of smaller craters it contains.

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What are craters?

 

          The Moon’s surface is covered with flat, circular sunken areas known as craters. Some craters like Clavius are so big that they can be seen even without the help of a telescope. Clavius is 235 kilometres wide and is surrounded by huge mountains. Some craters however, are very small in diameter.

          The arrangement of mountains around a large crater is peculiar; they form a circular wall. These mountains slope down gently towards the outer surface while they form a steep slope inside. When Galileo first observed craters, they looked like cups. He named craters so from the Latin word for cup.

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Why do astronauts carry radios to the Moon?

 

          We know that the Moon does not have a protective layer of atmosphere around it. Likewise, there is no wind, rain or clouds on the Moon. There is only vacuum, and sound cannot travel through vacuum. Therefore, unaided communication is not possible on the Moon. This problem can be solved with the help of a radio.

          The helmets that astronauts wear are equipped with a device that would convert the sound waves to radio waves. Radio waves are electromagnetic in nature and can travel through vacuum. These radio waves are in turn transmitted to the ground or to their fellow astronauts.

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Why do meteors crash on the surface of the Moon?

          You might have observed the sudden flash of a bright moving object in the night sky. These bright trails are left by pieces of rocks in outer space, known as meteors. Millions of meteors speed towards our Earth every day, but they burn up due to the friction caused by Earth’s atmosphere.

          The Moon does not have an atmosphere to blanket itself. Therefore, there is no friction that would burn the pieces of rock approaching the Moon at great speeds. As a result, they crash on the surface of the Moon, forming lunar soil.

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Are there moon rocks?

          The Moon’s surface not only has mountains, it also has rocks. Scientists found out that these moon rocks are similar to the igneous rocks on the Earth. They too are formed when molten lava solidifies after cooling down. But, their chemical make-up is different from that of the rocks found on Earth.

          Moon rocks do not contain any traces of water. Much of the Moon’s surface is covered by tiny pieces of rocks, and dust. This is known as lunar soil.

          It takes billions of years to form lunar soil. It is formed when large and small pieces of rocks rain on the surface of the Moon. Unlike the Earth, there is less iron on lunar soil.

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What does the surface of the Moon look like?

          When seen with the naked eye from the Earth, the Moon looks like a smooth sphere, just like the globe, with dark and light patches here and there.

          A telescopic view of the Moon suggests otherwise. It would not be wrong if someone says that the Moon looks like cheese! Its surface has lots of holes and sometimes, it appears yellowish as well.

          The dark patches on the surface of the Moon are lowlands of rock. These areas were once thought to be water bodies by Galileo. It’s covered by a thin layer of rocky soil. On the other hand, the lighter areas are known as highlands. The highlands are mountainous and rough.

          Huge craters are found in the mountainous areas. Craters are found in the lowlands as well, but in much fewer numbers. The surface is barren and the sky always appears dark.

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What are the other popular theories about the formation of the Moon?

          Since a lot many people wondered about the Moon, we have several theories about its formation. Though we still don’t know exactly how the Moon came into existence, these theories are based on scientific explanations.

          The Capture Theory suggests that the Moon was a planet that once moved in its orbit around the Sun. The Earth, with its greater gravitational force pulled the Moon towards our planet. The Co-formation Theory suggests that the Earth and Moon were formed at the same time from a cloud of dust and gas.

          It was George Howard Darwin, Charles Darwin’s son who proposed the Fission Theory. According to G H Darwin, the Earth spun so fast in the early years that a bulge formed on one of its sides. After a while, the Sun’s gravitational pull tore off this bulge. It fell off in space and later formed the Moon.

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Is the Moon younger than the Earth?

          There are many theories that try to explain how the Moon was formed. ‘The Impact Theory’ is a popular one among them. This theory suggests that the Moon is younger than the Earth though it is billions of years old.

          The Impact Theory talks about something that happened about 4.5 billion years ago. Back then, the Earth did not have any satellites. A huge body about the size of Mars hit our planet. This shook off the Earth from its orbit as a result of which, portions of the Earth broke.

          Gradually, these broken pieces came together along with gas and dust, and solidified to form the Moon. This unification had other effects however; molten lava oozed out from the interior of the Moon for the next two billion years.

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Who was the first person to closely observe the Moon?

          Ever since Man started looking at the Moon with his naked eyes, he was curious to learn about this brightly shining heavenly body. It was an Italian scientist who closely observed the Moon for the first time. His name was Galileo Galilei.

          It happened in 1609. Galileo built an equipment called telescope that made objects in space look larger and closer.

          For centuries, scientists had believed that the Moon had a smooth surface. Galileo shattered this belief; he observed that the Moon’s surface was not so smooth; instead it had mountains, pits, valleys, shadows and other features, just like the surface of the Earth. He thought the vast dark shadowy areas to be seas of water and called them ‘maria’, the Latin word for sea. Galileo’s work laid the foundation for modern studies in astronomy.

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Why is the Moon called so?

          Tracing the origins of the Moon’s name is a bit difficult as the Moon existed from the prehistoric times.

          The Moon has been known by different names since times immemorial. For instance, the Greeks call it Selene, while Moon is known as Luna in Latin. However, the English ‘Moon’ comes from ‘mona’, an Old English word. This word is derived from a Latin word ‘mensis’ meaning month.

          In the olden days, people used the Moon to measure time. The satellites of other planets like Jupiter and Saturn are also commonly known as moons.

          You might have also heard words like lunar orbit and lunar rover. Anything related to the Moon is usually known as lunar.

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