Dark Matter: A mystery of the Universe

Dark matter accounts for 27 percent of all matter and energy in the universe. What we see, the regular matter is just 5 percent of the universe. The dark matter can be failed stars or white dwarfs or black holes.

First, there was the Big Bang. For several million years after that, there was nothing - no stars, planets, moons or galaxies. This continued for 150 million years after the great Big Bang. Time went by. The first stars were created. Matter fused, stars clumped together, galaxies collected together. The formation of our planetary system began. To hold the solar system and clusters of galaxies together, we had gravity, our glue. Swiss astronomer Fritz  Zwicky who used the term 'dark matter first. He coined the term 'Dunkle Materie' to denote the invisible matter.

Dark Matter

But in some clusters, the space between the galaxies contains hot gases which cannot be seen using light telescopes. After measuring this gas, the scientists came to the opinion that there is more material involved in these clusters than meets the eye and that they cannot be detected. The undetected matter could amount to some five times the material in the cluster. This invisible matter that cannot be detected is called the 'dark matter. Dark matter accounts for 27 percent of all matter and energy in the universe. What we see, the regular matter is just 5 percent I of the universe.

It was the Swiss astronomer Fritz Zwicky who used the term 'dark matter first. He coined the term 'Dunkle Materie', which translates to dark matter, to denote the invisible matter. His subject was the Coma galaxy cluster. It should be noted that the speed of revolution of a particular cluster is dependent on the weight and position of the matter in the cluster. When he measured the speed, he found out that the cluster had more mass than it was supposed to meaning there was more matter involved. This was further confirmed by other scientists whose work on other galaxies suggested that they had more mass. The presence of dark matter was thus established.

What makes up Dark Matter

According to scientists, dark matter can be failed stars or white dwarfs or black holes. But these are just suggestions and the dark matter still continues to be a mystery. Scientists have however found ways to indirectly study dark matter. This is done by using gravitational lensing. Studies are still being carried out and we are just unraveling all the secrets of the universe.

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Freakish wonders of the universe

The universe is full of deep mysteries and even the fraction of what we know is too fascinating for words. This month let's take a look at some of the amazing yet scary inhabitants out there.

I'm coming to visit you

Black holes form when huge stars collapse and grow, taking up other objects around them. Think of them as giant invisible blenders that can tear apart planets even thousands of miles away. There aren't black holes anywhere close to our solar system, but did you know that they can actually travel through space? And scarier still, rapidly-moving black holes cannot be detected! Scientists have assured us that space is a big place and black holes are quite rare - so sit back and relax!

A big show off!

Ever heard of gamma ray bursts? Well, they are considered as the brightest electromagnetic events to occur in the universe, so much so, that they can be seen billions of miles away! Are you also wondering how powerful they are? Apparently they emit as much energy in a few seconds that our sun can in 10 billion years! We're glad that, like black holes, they are rare and far, far away from us.

Lone travellers

We imagine planets going around a star, endlessly orbiting it as long as they live. It turns out that not all planets exist this way. Astronomers have discovered a few Jupiter-sized planets drifting alone, without a place to call home or a star as a boss. They are thought to have been ejected out of their star system due to some massive explosion event. As long as they are not on a trajectory towards Earth, it's dreamy fun to think about these lonely nomadic travellers.

What a blast!

Earth is like a magnet but its magnetic field is quite weak; an MRI machine can produce a magnetic field thousand times stronger. Since we can put our head in through the MRI machine, we can obviously put up with that magnetic field. But imagine a magnetic field that is a trillion times stronger than that of Earth. That's the

kind of power that a magnetar possesses! Come within 1000 kilometres of a magnetar and the very molecules that make you up can dissolve! Here's a fun fact to freak you out in 2004, a magnetar located halfway across the Milky Way (500 quadrillion kilometres away) quaked and its effect was felt on the Earth's upper atmosphere!

Mission Impossible

What if you stepped too close to a black hole but not quite? That's exactly what hypervelocity stars did! They bolted away from the black hole at superfast speed. Hypervelocity stars were originally binary stars, of which one was captured and gobbled up by the black hole at the centre of our galaxy while the other lucky star was sent rocketing off at a very high speed, obviously very, very glad to escape.

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What happened after Mangalyaan entered Martian orbit?

It made history! On 24 September 2014, the Indian Space Research Organisation’s (ISRO) Mars mission, Mangalyaan, settled into its elliptical orbit around Mars as planned, with 40 kg of fuel to spare, 20 kg in excess of what was needed to complete its six-month planned mission!

Though over the next couple of months, the orbiter completed its mission objectives, it had enough fuel to remain operational, and its mission was extended. It continues to collect and transmit data to date, even on its seventh year in Mars orbit! Over this period, thanks to its autonomous functioning capabilities, Mangalyaan overcame an extended communications “blackout” in 2015 when Mars went out of the Earth’s sight behind the Sun in a solar conjunction, and a communications “whiteout” in 2016 when the Earth came in between the Sun and Mars with the solar radiation making it difficult for the spacecraft to receive signals from the Earth. Mangalyaan’s contribution to advancing the Indian space mission has been acknowledged in a unique way - a sketch of the spacecraft that features on the new Indian 2,000-Rupee note! It was also listed as one of the 25 best inventions of 2014 in Time magazine.

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What were the major phases of the Mangalyaan mission?

Have you seen a film hero leap out of a moving car, and dash across the platform to board a running train? Don’t ever do it, because nothing can be more dangerous! For our spacecraft, they have no other choice. Because both their home and destination planets are racing around the Sun without ever stopping! To execute such a terrifying transit, different spacecraft use different manoeuvres. Mangalyaan did it in three phases - geocentric, heliocentric and areocentric phases.

In the first phase, Mangalyaan was carried by its rocket into an orbit around the Earth. Then by firing the spacecraft’s main engine in seven, carefully-planned stages, Mangalyaan’s orbit was made more and more elliptical, until it broke free of the Earth’s gravitational pull. The final firing launched Mangalyaan on a Sun-centric curved path to Mars, tangential to both planets. This space cruise stage from the Earth to Mars formed the second phase of the mission. The third phase began about ten months later with a precisely-timed manoeuvre, called Mars Orbit Insertion (MOI). The engines were fired once again to reduce the velocity of Mangalyaan just enough so that the gravitational field of Mars would pull the spacecraft into an orbit around it.

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What were the mission objectives of Mangalyaan? What were the challenges Mangalyaan was designed to overcome?

The Mars Orbiter Mission (MOM), or Mangalyaan, was not just a scientific mission. It was also a chance to showcase the capabilities of Indian-made spacecraft, rockets and other instruments in the field of space technology!

As a technology demonstrator, Mangalyaan was to successfully cover all stages of an interplanetary journey - first go around the Earth in increasingly elliptical orbits, then cruise through space for the planned number of days, reach Mars and fall into an orbit around the planet, and continue orbiting it for the mission duration. The second goal of Mangalyaan was to image Mars, and collect data about its atmosphere and mineral composition. For this, Mangalyaan carried five payloads - Mars Colour Camera (MCC), Methane Sensor for Mars (MSM), Lyman Alpha Photometer (LAP), Mars Exospheric Neutral Composition Analyzer (MENCA), and Thermal Infrared Imaging Spectrometer (TIS).

While designing Mangalyaan, the Indian Space Research Organisation (ISRO) planned for all challenges it could foresee. Its engine was designed to restart smoothly after its ten-month space cruise.

Another aspect taken care of was the deep space communication system. The large distances separating the Earth and Mars mean that the Round-Trip Light Time, or RTLT (the time taken for a signal from Earth to travel to a spacecraft and back), will be anywhere between 6 and 43 minutes! So, it was also designed to independently manage many in-flight situations!

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What makes Mangalyaan unique?

On 24 September 2014, India joined the exclusive club of nations with a presence on a planet other than the Earth. The Indian Space Research Organisation’s (ISRO) first interplanetary attempt - Mars Orbiter Mission (MOM), also called Mangalyaan made it possible!

Built in a record time of just 15 months, Mangalyaan was launched on 5 November 2013 from the Satish Dhawan Space Centre at Sriharikota Range (SHAR), Andhra Pradesh. The rocket used for lift-off was a Polar Satellite Launch Vehicle (PSLV). The total project expense came only to around Rs.450 crores, a fraction of what it cost other nations to deploy a Mars orbiter, making Mangalyaan the least-expensive mission to Mars!

The success of Mangalyaan gave us a lot more “firsts” - it made India the first country in Asia with a presence on Mars, and the first nation in the world to succeed in a Mars mission at the very first attempt. Also, ISRO is the fourth space agency to reach Mars after the Soviet Union (present-day Russia), the U.S. National Aeronautics and Space Administration (NASA), and the European Space Agency (ESA).

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What do we know about NASA’s latest missions to Mars?

Within the last 20 years, the U.S. National Aeronautics and Space Administration (NASA) sent four missions to Mars - Mars Science Laboratory (MSL) mission (2011) which landed the Curiosity rover; Mars Atmosphere and Volatile Evolution (MAVEN) orbiter mission (2013); InSight mission (2018); and Mars 2020 mission (2020) that carried the Perseverance rover and the Ingenuity helicopter. All the four are operational to date.

After a precision landing in the Gale Crater in 2012, Curiosity has been collecting data about the Martian climate and geology, and searching for biosignatures on the planet. The rover found proof of an ancient mega-flood and organic chemicals in the crater.

The MAVEN orbiter has been zipping around Mars gathering details of the past and present of the Martian atmosphere since 2014. Meanwhile, the InSight lander, has been studying whatever goes on underneath! It does this by monitoring “marsquakes”, and using them to map the interior of the planet. Finally, Perseverance is also looking for signs of life on Mars.

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What makes Mars Global Surveyor and Mars Pathfinder stand out from other Mars missions of the decade?

The last decade of the 20th century saw more mission failures than successes. Major among them were Mars 96 by Roscosmos (the space agency of the then-newly-constituted Russia) and Nozomi by Japan’s Institute of Space and Astronautical Science, or JAXA.

But the decade was saved by NASA’s Mars Global Surveyor or MGS (1996) and Mars Pathfinder (1996)! The MGS reached Mars in 1997, and by the time its mission ended in 2006, this orbiter had long achieved its primary goal of mapping Mars. It imaged potential landing sites for future missions.

The lander-rover mission, Mars Pathfinder, was a great achievement for two more reasons. Executed within three years, with a total cost of only 265 million dollars, the project was a success for NASA’s Discovery Program, which aimed to make space missions “cheaper, faster and better.” Additionally, on July 5 1997, Pathfinder’s rover, Sojourner, became the first to operate on a planet other than the Earth!

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What made the Viking mission remarkable?

The launch window of 1973 was dominated by the Soviet Union’s missions to Mars. By that time, the Space Race had also come to an end, and it was slowly replaced by growing cooperation between the two countries. In 1975, while the Soviet Union waited it out, the U.S. National Aeronautics and Space Administration (NASA) sent out a pair of identical missions to Mars, Viking 1 and Viking 2, together known as the Viking program.

Viking 1 was launched on 20 August 1975, and Viking 2 followed on 9 September. Both contained an orbiter and a lander each. While all four were successful, the lander of Viking 1 which touched down in the Martian terrain on 20 July 1976 became the first lander to successfully operate on the planet! Previous landers had all failed, except perhaps that of the Soviet Union’s Mars 2. But it too stopped working 110 seconds after landing, and transmitted only a partial image of the planet.

The pictures of Martian valleys captured by the Viking orbiters gave evidence of the massive floods that once used to flow across Mars, and completely changed the way we saw the planet. The landers, on either side of the planet (Viking 1 in Chryse Planitia, and Viking 2 in Utopia Planitia), collected data about the atmosphere and conducted experiments with the soil. They looked for biosignatures in the soil, but the results were not conclusive.

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What was special about the Mariner 9 mission?

After the launch failure of its Mariner 8 spacecraft on 9 May 1971, the U.S. National Aeronautics and Space Administration (NASA) launched Mariner 9 on the 30th of the same month. It was a late start compared to the Soviet Union’s (present-day Russia) Mars 2 and Mars 3 missions launched on 19 and 28 May, respectively. But Mariner 9 overtook them and became the first spacecraft to orbit another planet! It entered the orbit of Mars on 14 November 1971, with a lead of 13 days over its contender, Mars 2 of the Soviet Union.

But it was not ribbons and confetti that greeted the winner; it was a full – “blown” Martian dust storm that had hidden almost the entire planet from view! Imaging, therefore, was postponed for about two months by re-programming Mariner 9 from the Earth. Unfortunately, this was not an option for the Soviet Union’s Mars 2 and 3, and these orbiters wasted data resources by merely taking photographs of dust clouds that revealed none of the features of Mars.

In contrast, Mariner 9 out-performed its target of covering 70 per cent of the Martian surface by imaging 85 per cent instead! The whopping 7,329 photographs it took, including those of the most prominent features on Mars such as the Olympus Mons, Valles Marineris, and many other volcanoes and flow channels, improved our knowledge of the Red Planet by leaps and bounds! Mariner 9 also captured the Martian moons, Deimos, and Phobos. In fact, the Valles Marineris canyon is named in honour of the spacecraft!

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How did Mariner 6 and Mariner 7 revolutionize our perception of Mars?

Riding on the success of Mariner 4, the U.S. National Aeronautics and Space Administration (NASA) planned a dual mission to the Red Planet for the near-Earth phase of Mars in 1969. The identical flyby missions were launched accordingly - Mariner 6 on 25 February 1969, and Mariner 7, just a month later, on 27 March 1969. On the 31st of July of the same year, Mariner 6 made its closest approach of Mars, passing by at a distance of around 3,400 kilometres from the surface. Just five days later, Mariner 7, which had caught up with its predecessor, also made its closest approach keeping about the same distance from Mars!

Mariner 6 and Mariner 7 took about 201 images, covering nearly 20 per cent of the surface of Mars! Some of them showed Martian craters containing ice, outlines of an ice cap at the South Pole, and dark features that had previously been mistaken for canals by astronomers. Data from the devices on the spacecraft also revealed that the atmosphere of Mars is thin, and made up of mainly carbon dioxide (about 98 per cent) and a small percentage of water vapour. They also detected minerals that indicated that the planet may have held liquid water in the past.

Together, the two Mariner spacecraft changed our understanding of the Red Planet. After successfully completing their mission in 1970, they are now spending their retired lives orbiting the Sun!

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Why is the Mariner 4 mission significant in the history of Mars exploration?

In the period after the two World Wars, rivalry between the world’s two super-powers, the Soviet Union (the U.S.S.R. or the present-day Russia) and the U.S. was at its peak. Space was one of the frontiers both nations wanted to dominate, and thus began the Space Race, the golden age of space technology! The first artificial satellite, the first human to space, and the first mission to the Moon were all sent by the U.S.S.R, while the U.S. was the first to land a human on the Moon, and successfully complete a flyby of Venus. Next up for grabs was Mars!

After six failed missions to Mars (five by the Soviet Union, and one by the U.S.), the U.S. National Aeronautics and Space Administration (NASA) finally scored - its Mariner 4 became the first spacecraft to reach Mars! Launched on 28 November 1964, it travelled 112 million kilometres and completed a flyby of the Red Planet on 15 July 1965. The images it sent back became the first close-ups of the Martian terrain.

The absence of surface water on Mars, its heavily-cratered Moon-like surface, and its lack of a magnetic field came as a shock to many scientists of the day. From the data gathered by the mission, even those who thought Mars might have water or vegetation, had to accept that the planet was dry and barren (signs of water were detected only on later missions)!

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How successful are our missions to Mars?

As on date, we have sent 82 spacecraft to Mars spanning over 49 missions. But almost 60 per cent of them ended in failure (or partial failure), sometimes before they could even start collecting useful data. In fact, our first attempt itself ended in a launch failure in 1960; the Soviet Union’s (present-day Russia) Mars 1M No.1 spacecraft, was destroyed after it suffered an equipment malfunction at an altitude of 120 kilometres above the Earth.

Over the first three launch windows (in 1960, 1962 and 1964), we suffered six losses before NASA’s Mariner 4 spacecraft became the first successful mission to Mars after completing a flyby of the planet on 15 July, 1965. But we have had unexpected successes also! NASA’s Mars Exploration Rovers (MER), called Spirit and Opportunity, launched separately in 2003, functioned much beyond their planned durations of operation (90 sols) by over 24 and 57 times! By the time we lost contact with them in 2010 and 2018, respectively, they had collected a wealth of data that are invaluable to our understanding of Mars.

As with everything else, every time a mission to Mars fails, we must let Thomas Edison’s words guide us – “I have not failed. I have just found 10,000 things that do not work!”

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How do we plan missions to Mars?

Technological advancements have virtually brought Mars closer to us step-by-step, first as blurry images through telescopes, then as data collected remotely by flybys and orbiters, and finally as physical observations conducted by landers and rovers that can test the Martian air and terrain for us. Today we are even planning sample return missions, and one day in the near future we will also have our first human on Mars!

But carrying out a mission to Mars is no easy job. Based on the scientific intent of the mission, items of equipment for the spacecraft have to be designed, built, tested and optimized. Since Mars is far away from the Sun, solar energy available on the planet will be limited, and efficient systems will have to be designed to power our equipment. A rocket, best suited to carry its payload, also has to be selected.

Mars is millions of kilometres away from the Earth. The differences between their orbits and orbital speeds mean that the two planets are the closest only for a limited duration. So, to execute the fastest and most efficient mission, we will have to time our rocket to Mars perfectly within a specific period known as the “launch window” which comes only once every two years and two months! Also, it usually takes around six to nine months for a spacecraft to reach Mars! So we have to plan our mission well in advance. And all this must be done keeping in mind the cost of the mission!

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What is special about Robert A. Heinlein’s book, Red Planet?

Robert A. Heinlein (1907 - 1988) was an American naval officer and aeronautical engineer who made a name as a science fiction writer! His works were scientifically accurate and logical to a degree that had never been seen before in science fiction. And thus, a new subcategory of the genre was born - hard science fiction - and it had a lasting influence on the generations of readers and writers of fiction that followed Heinlein!

Among the many novels Heinlein wrote for young adults aged between 12 and 18 is Red Planet, a gripping tale of adventure set in Mars, published in 1949. Years later, it was adapted by Fox Kids and made into a three-episode animated mini-series.

The novel tells the story of two friends, Jim and Frank, who live in a boarding school on Mars, along with Jim’s Martian pet, Willis the Bouncer. One day Willis overhears conversations between the greedy principal of their school, and the corrupt administrator of their Martian colony about a plan which threatens to put all Martian colonists in immediate danger. When the boys get to know about this evil plot, it is up to them to save everyone’s lives!

This book contains a lot of detail about Mars and its terrain. It also features the Martian canals popularized by the American astronomer, Percival Lowell!

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