Space Exploration

Competencies:

• Develop and use a model to describe the role of gravity in the formation of the universe and the solar system.

• Communicate qualitative/quantitative scientific and technical information about evolution of the universe, stars, solar system, and planets.

• Use the information and communication technologies to enhance the conceptual understanding of space exploration, space technology and their purposes.

Scope:

The Universe (Scope:The Newton’s law of universal gravitation and its role, the origin and evolution of the universe: Solar system, galaxies, stars, planets)

Space explorer (Scope: human space exploration, rovers, spacecrafts)

Astronomy (Scope: space observation, astronomical instruments)

Purpose of space exploration (Scope: evidence of life elsewhere - Mars)

Objectives:

1. Demonstrate the law of universal gravitation using interactive simulation.

2. Communicate qualitative or quantitative scientific and technical information about evolution of the universe, solar system, planets, and stars.

3. Describe various types of space exploration and spacecraft used

4. Explain the components and basic operation of astronomical instruments.

5. Design a prototype of spacecrafts or astronomical instruments to explore the universe.

6. Explore the possibility of human survival beyond Earth.

1.Universal Law of Gravitation

Download the pdf file from here

1. Universal Law of Gravitation

The Universal law of Gravitation states that any two bodies having mass attract each other with force directly proportional to the product of their mass and inversely proportional to the square of distance between them. The force acts along the line joining the centres of the objects.

Here, G is Universal gravitational constant = 6.673 × 10^-11 Nm² kg^-2. The value of G was found out by Henry Cavendish.

NOTE:

1. If mass of object is large, force will be more. If mass of object is small, force will be less. If distance between two object is more, force exerted will be less and vice versa.

2. If the masses of two bodies are doubled, keeping the distance fixed, the gravitational force between them becomes four times the initial value.

3. Both the bodies attract each other with equal force but lighter body will be pulled towards the heavier body.

4. The gravity of the Moon is less than the Earth as the Moon has less mass than Earth.

5. As the distance between two bodies become larger, the force of gravity becomes smaller.

6. If the distance between two bodies is doubled, the force of gravity becomes one-fourth.

Importance of Gravitational Force:

• It binds us to Earth.

• Moon revolves around Earth due to gravitational force.

• Planets revolve around Sun due to gravitational force.

• Tides in seas are caused due to gravitational force of moon on earth.

• Maintains the shape of the solar system.

Acceleration due to gravity:

• The mass of an object which gives rise to its gravitational force of attraction on other object is gravitational mass. The more gravitational mass of the body, stronger the attraction of other bodies towards it.

• Force of attraction due to the gravitational mass, the weight is defined by relation F=mg

• Weight of an object is equal to the force exerted on the object by the Earth's gravitational field.

mg=G(Mm/R²), therefore g=G(M/R²).......in some text, letter d is also used in place of R

Where,
M is the mass of the Earth (5.98 x 10²⁴ kg)
R is the mean radius of the earth (6.38x10⁶ m)
m is the mass of the object.
G is the universal gravitational constant ( 6.67x10^-11 Nm²kg^-2)

Placing the values in g=G(M/R²) we get value for g =9.80 ms^-2
It has the value of 9.78039 ms^-2 at the equator and 9.83217 ms^-2 at the poles (since the Earth is slightly flattened at the poles).

Numerical Problem:

1. What is the gravitational force of attraction between two people, one of mass 80 kg and the other 100 kg if they are 0.5 m apart?

2. Calculate the gravitational force acting between the Earth, with mass m1 = 5.98x10²⁴ kg, and the Moon, with mass m2 = 7.35 x 10²² kg. (G = 6.67 x 10^-11 Nm²kg^-2, mean Earth-Moon distance = 3.84 x 10⁸ m.)

3. The American space agency, NASA, plans to send a manned mission to Mars later this century. Mars has a mass 6.42 x 10²³ kg and a radius 3.38 x 10⁶ m. G = 6.67 x 10^-11 Nm²kg^-2.

i. The mass of a typical astronaut plus spacesuit is 80 kg. What would be the gravitational force acting on such an astronaut standing on the surface of Mars?

ii. State whether an astronaut on Mars would feel lighter or heavier than on Earth.

2. Evolution of the universe, stars, solar systems, and planets

Download the pdf file from here

2. The Evolution of the Universe

Some 15 billion years ago the universe emerged from a hot, dense sea of matter and energy. As the cosmos expanded and cooled, it spawned galaxies, stars, planets and life

(By P. James E. Peebles, David N. Schramm, Edwin L. Turner, Richard G. Kron)

At a particular instant roughly 15 billion years ago, all the matter and energy we can observe, concentrated in a region smaller than a dime, began to expand and cool at an incredibly rapid rate. By the time the temperature had dropped to 100 million times that of the sun’s core, the forces of nature assumed their present properties, and the elementary particles known as quarks roamed freely in a sea of energy. When the universe had expanded an additional 1,000 times, all the matter we can measure filled a region the size of the solar system.

At that time, the free quarks became confined in neutrons and protons. After the universe had grown by another factor of 1,000, protons and neutrons combined to form atomic nuclei, including most of the helium and deuterium present today. All of this occurred within the first minute of the expansion. Conditions were still too hot, however, for atomic nuclei to capture electrons. Neutral atoms appeared in abundance only after the expansion had continued for 300,000 years and the universe was 1,000 times smaller than it is now. The neutral atoms then began to coalesce into gas clouds, which later evolved into stars. By the time the universe had expanded to one fifth its present size, the stars had formed groups recognizable as young galaxies.

When the universe was half its present size, nuclear reactions in stars had produced most of the heavy elements from which terrestrial planets were made. Our solar system is relatively young: it formed five billion years ago, when the universe was two thirds its present size. Over time the formation of stars has consumed the supply of gas in galaxies, and hence the population of stars is waning. Fifteen billion years from now stars like our sun will be relatively rare, making the universe a far less hospitable place for observers like us.

Our understanding of the genesis and evolution of the universe is one of the great achievements of 20th-century science. This knowledge comes from decades of innovative experiments and theories. Modern telescopes on the ground and in space detect the light from galaxies billions of light-years away, showing us what the universe looked like when it was young. Particle accelerators probe the basic physics of the high-energy environment of the early universe. Satellites detect the cosmic background radiation left over from the early stages of expansion, providing an image of universe on the largest scales we can observe.

Our best efforts to explain this wealth of data are embodied in a theory known as the standard cosmological model or the big bang cosmology. The major claim of the theory is that in the large scale average the universe is expanding in a nearly homogeneous way from a dense early state. At present, there are no fundamental challenges to the big bang theory, although there are certainly unresolved issues within the theory itself. Astronomers are not sure, for example, how the galaxies were formed, but there is no reason to think the process did not occur within the framework of the big bang. Indeed, the predictions of the theory have survived all tests to date.

Yet the big bang model goes only so far, and many fundamental mysteries remain. What was the universe like before it was expanding? (No observation we have made allows us to look back beyond the moment at which the expansion began.) What will happen in the distant future, when the last of the stars exhaust the supply of nuclear fuel? No one knows the answers yet.

Our universe may be viewed in many lights—by mystics, theologians, philosophers or scientists. In science we adopt the plodding route: we accept only what is tested by experiment or observation. Albert Einstein gave us the now well-tested and accepted Theory of General Relativity, which establishes the relations between mass, energy, space and time. Einstein showed that a homogeneous distribution of matter in space fits nicely with his theory. He assumed without discussion that the universe is static, unchanging in the large-scale average.

In 1922 the Russian theorist Alexander A. Friedmann realized that Einstein’s universe is unstable; the slightest perturbation would cause it to expand or contract. At that time, Vesto M. Slipher of Lowell Observatory was collecting the first evidence that galaxies are actually moving apart. Then, in 1929, the eminent astronomer Edwin P. Hubble showed that the rate a galaxy is moving away from us is roughly proportional to its distance from us.

The existence of an expanding universe implies that the cosmos has evolved from a dense concentration of matter into the present broadly spread distribution of galaxies. Fred Hoyle, an English cosmologist, was the first to call this process the big bang. Hoyle intended to disparage the theory, but the name was so catchy it gained popularity. It is somewhat misleading, however, to describe the expansion as some type of explosion of matter away from some particular point in space.

That is not the picture at all: in Einstein’s universe the concept of space and the distribution of matter are intimately linked; the observed expansion of the system of galaxies reveals the unfolding of space itself. An essential feature of the theory is that the average density in space declines as the universe expands; the distribution of matter forms no observable edge. In an explosion the fastest particles move out into empty space, but in the big bang cosmology, particles uniformly fill all space. The expansion of the universe has had little influence on the size of galaxies or even clusters of galaxies that are bound by gravity; space is simply opening up between them. In this sense, the expansion is similar to a rising loaf of raisin bread. The dough is analogous to space, and the raisins, to clusters of galaxies. As the dough expands, the raisins move apart. Moreover, the speed with which any two raisins move apart is directly and positively related to the amount of dough separating them.

The evidence for the expansion of the universe has been accumulating for some 60 years. The first important clue is the redshift. A galaxy emits or absorbs some wavelengths of light more strongly than others. If the galaxy is moving away from us, these emission and absorption features are shifted to longer wavelengths—that is, they become redder as the recession velocity increases. This phenomenon is known as the redshift.

Source: https://www.scientificamerican.com/article/the-evolution-of-the-universe

The End of the Universe

Will the universe continue expanding? Will it just stop or even begin to contract? The answer depends on the amount of mass that the universe contains. If the universe's mass exceeds a certain crucial value, then gravity should eventually stop everything from flying away from everything else.

With enough mass, the universe will eventually succumb to the overpowering force of gravity and collapse again into a single point—a theory often called the Big Crunch. But without enough mass, the universe will continue to expand. As of 2001, many scientists concluded that the latter hypothesis appears to be the most likely. In 1998, astronomers found an even more remarkable puzzle: the universe seems to be accelerating while expanding, as if being pulled by some kind of "antigravity" force. Other astronomers have since corroborated this finding using a variety of methods, and have all but confirmed the existence of this mysterious "dark energy."

Source: https://www.scholastic.com/teachers/articles/teaching-content/origin-universe/

Video lesson 1: https://youtu.be/TBikbn5XJhg

Video lesson 2:

3. Life Cycle of a Star

Life Cycle of a Star

Stars go through a natural cycle, much like any living beings. This cycle begins with birth, expands through a lifespan characterized by change and growth, and ultimately leads to death. The time frame in the life cycle of stars is entirely different from the life cycle of a living being, lasting in the order of billions of years. In this piece of article, let us discuss the life cycle of stars and its different stages.

Did you know that some of the stars we see in the sky may already be dead! Their light travels millions and millions of kilometres, and by the time it reaches us, the star would have died. So the distance between our planet and the stars further away is unimaginable, but measurable still. Watch and learn how these distances can be measured and the secrets hiding among the stars.

Seven Main Stages of a Star

Stars come in a variety of masses and the mass determines how radiantly the star will shine and how it dies. Massive stars transform into supernovae, neutron stars and black holes while average stars like the sun, end life as a white dwarf surrounded by a disappearing planetary nebula. All stars, irrespective of their size, follow the same 7 stage cycle, they start as a gas cloud and end as a star remnant.

1. Giant Gas Cloud

A star originates from a large cloud of gas. The temperature in the cloud is low enough for the synthesis of molecules. The Orion cloud complex in the Orion system is an example of a star in this stage of life.

2. Protostar

When the gas particles in the molecular cloud run into each other, heat energy is produced. This results in the formation of a warm clump of molecules referred to as the Protostar. The creation of Protostars can be seen through infrared vision as the Protostars are warmer than other materials in the molecular cloud. Several Protostars can be formed in one cloud, depending on the size of the molecular cloud.

3. T-Tauri Phase

A T-Tauri star begins when materials stop falling into the Protostar and release tremendous amounts of energy. The mean temperature of the Tauri star isn’t enough to support nuclear fusion at its core. The T-Tauri star lasts for about 100 million years, following which it enters the most extended phase of development – the Main sequence phase.

4. Main Sequence

The main sequence phase is the stage in development where the core temperature reaches the point for the fusion to commence. In this process, the protons of hydrogen are converted into atoms of helium. This reaction is exothermic; it gives off more heat than it requires and so the core of a main-sequence star releases a tremendous amount of energy.

5. Red Giant

A star converts hydrogen atoms into helium over its course of life at its core. Eventually, the hydrogen fuel runs out, and the internal reaction stops. Without the reactions occurring at the core, a star contracts inward through gravity causing it to expand. As it expands, the star first becomes a subgiant star and then a red giant. Red giants have cooler surfaces than the main-sequence star, and because of this, they appear red than yellow.

6. The Fusion of Heavier Elements

Helium molecules fuse at the core, as the star expands. The energy of this reaction prevents the core from collapsing. The core shrinks and begins fusing carbon, once the helium fusion ends. This process repeats until iron appears at the core. The iron fusion reaction absorbs energy, which causes the core to collapse. This implosion transforms massive stars into a supernova while smaller stars like the sun contract into white dwarfs.

7. Supernovae and Planetary Nebulae

Most of the star material is blasted away into space, but the core implodes into a neutron star or a singularity known as the black hole. Less massive stars don’t explode, their cores contract instead into a tiny, hot star known as the white dwarf while the outer material drifts away. Stars tinier than the sun, don’t have enough mass to burn with anything but a red glow during their main sequence. These red dwarves are difficult to spot. But, these may be the most common stars that can burn for trillions of years.

Source: https://byjus.com/physics/life-cycle-of-stars/

Video links: Supernova and Supergiant Star Life Cycle: https://youtu.be/XA2tOTuWWzY

4. Solar System

Our solar system includes Sun, planets, satellite etc. but we have other members also which play a very important role in the existence of universe the way it exists today. Let us briefly discuss the other members of the solar system.

The solar system is huge at least 100 Astronomical Units in size (15 trillion km). It is held together by the sun’s immense gravitational pull that keeps objects like the planets and the asteroids in orbit around it.

The sun is the biggest object in the solar system and provides energy to the earth by nuclear reactions that occur in its center. The sun is a star and has a surface temperature of 6000 0C! It is mostly composed of Hydrogen gas along with a small amount of Helium gas.

What does the Solar System consists of?

The solar system also contains 8 planets which are large almost spherical objects that revolve around the sun in elliptical paths known as orbits. The earth is also one of the planets and lies at a distance from the sun such that it is neither too hot nor too cold for life to exist. The planets were formed at least 4.6 billion years ago when discs of dust and gas orbiting around the sun collapsed and clumped together due to gravity. There are two kinds of planets:

1. Rocky planets include Mercury, Venus, Earth, and Mars which are mostly made up of solid rock and metal.

2. Gas giants include Jupiter, Saturn, Uranus, and Neptune which are mostly made up of gases like Hydrogen, Helium, Methane, etc. These planets are very large in comparison to the rocky planets.

The solar system also contains small irregularly shaped objects made of rock, metal, and carbon called asteroids orbiting the sun. Most of these objects lie between the orbits of Mars and Jupiter in the asteroid belt.

Asteroids

These are big chunks of rock or metal that are mostly found orbiting the Sun between Mars and Jupiter. It is believed that these moons did not originally orbit Mars, but were instead a part of the Asteroid belt. The asteroid belt lies between Mars and Jupiter. It contains lumps of rock much smaller than planets. These lumps are called asteroids or minor planets. They are not visible from Earth with the naked eye, but many may be seen through binoculars or small telescopes.

Satellites

Satellites are objects that revolve around planets and are also part of the solar system. The Earth’s satellite is the Moon. Some satellites like Ganymede (orbiting Jupiter) are bigger than Mercury and can have atmospheres.

Artificial satellites are an important part of the solar system too, these satellites are man-made. These satellites revolve around the earth much closer than the Earth’s natural satellite, the moon. Aryabhata is the first artificial satellite of India. Many other satellites have been launched by India some of them are INSAT, IRS, and EDUSAT.

Comets

Comets are small irregularly shaped objects made up of ice. They usually come from the outermost reaches of the solar system beyond Neptune from a region known as the Kuiper Belt. When these objects come close to the sun, the ice vaporizes forming a beautiful tail behind them. Some of these comets appear regularly such as the Halley’s Comet which appears once every 76 years (the next time in year 2061!).

Dwarf planets

Dwarf planets are objects smaller than planets and larger than asteroids that orbit the sun at various places. The nearest dwarf planet to us is Ceres which lies in the asteroid belt. The most famous is Pluto which lies beyond Neptune on the inner edge of the Kuiper belt. In 2014, Pluto and its 5 satellites were visited by a spacecraft named New Horizons for the first time in history capturing images of the icy dwarf planet in high resolution.

Source: https://byjus.com/physics/solar-system/

5. Planet

What is Planet?

The word planet means ‘wanderer’. This is because the planets do appear to wander listlessly across the night sky. The stars also move across the sky east to west but relative to each other, they appear fixed. The planets, on the other hand, seem to move relative to the fixed stars in backward and forwards directions. This is why they were called Wanderers. We can define Planet as:

An astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.

A planet is a large celestial body that revolves around the sun in fixed orbits. Planets do not have any light of their own but reflect the light of the sun. Planets also do not twinkle like stars because they are much closer to us. The earth is also a planet and is the only place we know in the universe which can harbor life.

Planets in order from the Sun

1. Mercury 2. Venus 3. Earth 4. Mars 5. Jupiter 6. Saturn 7. Uranus 8. Neptune

Only the first five planets are visible from earth with the naked eye: Mercury, Venus, Mars, Jupiter, and Saturn. The other two: Uranus and Neptune were discovered only after telescopes were invented.

• The first four planets are made of rock with inner cores made of metal and are called rocky planets.

• The next four are made of gasses like hydrogen and methane and are huge compared to the rocky planets. These planets are called gas giants.

All planets rotate around their own axis just like the earth rotates once in 24 hours. The time a planet takes to revolve around the sun is called it’s period of revolution.

• Jupiter is the fastest spinning planet in our Solar System, rotating on average once in just under 10 hours. That is very fast, especially considering how large Jupiter is. This means that Jupiter has the shortest day of all the planets in the Solar System.

• Venus takes 243 days to rotate. It takes Venus longer to rotate once on its axis than to complete one orbit of the Sun. That's 243 Earth days to rotate once - the longest rotation of any planet in the Solar System - and only 224.7 Earth days to complete one orbit of the Sun.

• For the earth, it is 365.26 days or 1 year to revolve around the sun.

The farther a planet is from the sun, the longer it takes to move around the sun.

Source: https://byjus.com/physics/planet/

6. Difference between Earth and Mars

The difference between Earth and Mars is provided here. Earth and Mars are the two planets along with seven other planets. These two planets in our solar system have a few geological similarities such as Mars is one-half the diameter of the Earth and the amount of dry land surface present on both the planets is the same.

However, there are a few differences between Earth and Mars. For instance, the size, atmosphere and temperature of these planets are different.

What is Earth?

Earth is the third planet from the sun, and it is our home planet. It is the only planet known to harbour life. The Earth’s surface consists of 29% of continents and islands while 71% of the water is in the form of lakes, rivers and freshwater. The radius of the Earth is 3,959 miles, and it is the fifth-largest planet in our solar system. The four layers of the Earth are:

• Solid inner core

• Liquid outer core

• Silicate mantle

• Rocky crust

What is Mars?

Mars is the fourth planet from the sun and is referred to as the “Red planet”. It gets the latter name because of the presence of iron oxide on the surface of Mars, which gives it a reddish appearance. The largest volcano Olympus Mons and the highest mountain Valles Marineris are found on this planet. The radius of Mars is 2,106 miles and is the seventh-largest planet in our solar system.

The internal structure of Mars is similar to the Earth:

• Thin rocky crust

• A mantle

• A metal core

Difference between Earth and Mars

Thus, we can say that it’s the atmosphere and geological parameters that make the Earth warm and worthy for living beings. Meanwhile, Mars is cold, dry and dusty because of its atmosphere and geological parameters.

Source: https://byjus.com/physics/difference-between-earth-and-mars/

7. Difference between Stars and Planets

It is essential to know the key differences between Stars and Planets as they are both celestial bodies located in outer space. It is important to understand the clear distinctions between a star and a planet, a star is a body that possesses a light which causes it to reflect the light on its own. A planet, on the other hand, is simply a celestial body that is fixed and has its own orbit and spins on its own axis, yet reflects the light from an external source. As planets do not have an internal source of light, they only receive light from external sources primarily the Sun. Minkowski space is usually used to calculate for special relativity problems, to obtain solutions.

Difference between Stars and Planets

One of the major key points that differentiate stars from planets is size. Even though in images planets may look gigantic and stars may look distant and small, whereas, in reality, stars are gigantic when compared to planets. For a full comparison between planets and stars, check out the table below.

Source:: https://byjus.com/physics/difference-between-stars-and-planets/

8. Space Exploration

Space exploration is sending people or machines into space to visit other planets and objects in space. Mankind has dreamed of visiting the stars for hundreds of years, but it wasn’t until 1969 that the first person walked on the Moon. Since the first person walked on the Moon, hundreds of satellites have been launched into orbit around the earth, and hundreds of people have been into space on lots of different types of spacecraft. We have also sent machines to investigate objects that are further away in the Solar System.

Different space missions include different types of explorations such as flyby, orbiter, rover, and human space explorations.

Download the pdf file HERE

Flyby Space Missions

For decades now, scientists have been sending up all sorts of spacecraft to gather information about our solar system, like private eyes try and gather information about people on Earth. But not every space mission has been exactly the same, just like every private eye mission is kind of different.

One space mission type is known as a flyby, a space mission where a spacecraft passes by a celestial object but isn't held in orbit by it. As the spacecraft passes by, it uses its instruments to observe its target and it sends the information it collects back to Earth. So, this is like a private eye zooming past a house to take a few pictures to scope out the place they're going to spy on later in more detail. But the private eye doesn't stop, nor does he circle around; he just keeps going past the house.

One advantage of a flyby mission has already been sort of revealed; it's used as a quick initial reconnaissance of something that may later be explored with more expensive and technically difficult missions.

A disadvantage is that once the spacecraft flies past, it can't return for further investigation. So if something important was missed, that's kind of too bad.

Orbiter Spacecraft

Unlike a flyby spacecraft, an orbiter spacecraft is a type of spacecraft that enters and stays in orbit around a planet. Here, the private investigator doesn't do a drive-by; instead, he drives towards the house and then begins circling it over and over again to take pictures and videos, measure distances, use heat sensors to see if anyone is inside, and collect other data.

Anyways, the advantage of an orbiter is that you can collect a lot more data and get more detailed information about the object you're investigating, namely a planet.

A disadvantage is that you can't land the orbiter onto the surface of the planet to conduct some more serious scientific experiments.

Rovers

For a more serious investigation, you can turn to a rover spacecraft, an electrically powered spacecraft that can roam around the celestial object they land on to take detailed pictures, soil samples, and perform other specific tasks for scientific purposes. This would be the same thing as our private eye sending in a robot into the home to take objects inside the house or to swab a surface for DNA - stuff like that.

The advantage to rover spacecraft is that they can do a lot of incredible stuff, including chemical experiments, to give us really detailed insights about a planet.

The disadvantage is cost, estimated to be $2.5 billion for the most recent Mars Exploration Rover Mission.

Human space missions

Human space missions are the programs that send people into space or other celestial objects. The ability to have really good and intelligent pick at other places is one of the advantages of human space missions. But disadvantages are numerous: very costly and possible human death and related disasters.

https://study.com/academy/lesson/space-mission-types-advantages-disadvantages.html

Click on the link to watch video on space exploration https://youtu.be/1dD1sK5i-7I

Top 10 Facts on Space Exploration

1. The first person in space was Yuri Gagarin from the Soviet Union, who travelled into orbit around the Earth in 1961.

2. The first man to walk on the Moon was an American called Neil Armstrong in 1969.

3. The Moon is the only place in space apart from Earth that humans have set foot on.

4. People who fly into space are called astronauts. They have to be very careful about what they eat and what exercise they do to stay healthy while they are in space.

5. A spacecraft needs to travel at 11,000 miles per hour to get into orbit around the Earth.

6. Spacecraft use huge rockets to carry them into space.

7. The most famous type of spacecraft was the Space Shuttle. There were five Space

8. Shuttles and one prototype – between them they flew 135 missions into space.

9. Out of billions of people who live on Earth, only 535 have been into Orbit, and only 12 have ever walked on the Moon.

10. The International Space Station is the biggest space station ever built. It can hold a crew of six people.

11. In 2012 a machine made by NASA called ‘Curiosity’ landed on Mars to see if it could find evidence of any creatures or plants having ever lived there.

Did you know?

• The first man to walk on the moon was Neil Armstrong. He was an American who travelled there in 1969 on NASA’s Apollo 11 mission. As he stepped onto the Moon he said, “That's one small step for man, one giant leap for mankind.”

• A satellite is what we call a machine that is launched into orbit around the Earth. Some satellites do things like taking photographs or broadcasting TV channels, and others are used by scientists.

• The first satellite was called Sputnik I and was launched by the Soviet Union in 1957. It circled the Earth for three months.

• When a space mission includes people, we call it a manned space expedition. When it only includes machines, we call it an unmanned expedition.

• Nobody has ever stepped on any object in space apart from the Moon, but we have sent machines to investigate Mars, Jupiter, Saturn and many other places.

• There is no air in space, so astronauts have to take air with them from Earth so that they can breathe. If they want to go outside their spacecraft, they have to wear special airtight clothes called a space suit.

• A space station is a place built in space so that astronauts can live and work in space.

• There is so little gravity in orbit around the Earth that instead of walking on the ground, astronauts in the space shuttles or on the International Space Station float in the air. This is called weightlessness.

• Astronauts have to exercise every day to keep their muscles strong while they are in space. They also have to eat specially prepared foods that are nutritious, easy to prepare and don’t make a mess when you eat them in space. Ice cream is too messy to eat in space so astronauts have to have it freeze-dried so that they can eat it for dessert!

Supplementary Reading

1. All About Mars: https://spaceplace.nasa.gov/all-about-mars/en/

2. The Mars Rovers: Perseverance: https://spaceplace.nasa.gov/mars-2020/en/

3. The Mars Rovers: Curiosity: https://spaceplace.nasa.gov/mars-curiosity/en/

4. The Mars Rovers: Spirit and Opportunity: https://spaceplace.nasa.gov/mars-spirit-opportunity/en/

5. The Mars Rovers: Sojourner: https://spaceplace.nasa.gov/mars-sojourner/en/

6. Everyday benefits of space exploration: https://www.asc-csa.gc.ca/eng/about/everyday-benefits-of-space-exploration/default.asp

7. 10 Reasons Why Space Exploration Matters to You: https://science.howstuffworks.com/10-reasons-space-exploration-matters.htm

Source: https://www.theschoolrun.com/homework-help/space-exploration

9. Space Observation and Astronomical Instruments (Telescopes)

Telescopes are meant for viewing distant objects and produce an image that is larger than the image produced in the unaided eye. Telescopes gather far more light than the eye, allowing dim objects to be observed with greater magnification and better resolution. Telescopes were invented around 1600, and Galileo was the first to use them to study the heavens, with monumental consequences. He observed the moons of Jupiter, the craters and mountains on the moon, the details of sunspots, and the fact that the Milky Way is composed of a vast number of individual stars.

Click HERE to download complete notes to read in details.(pdf)

10. Evidence of life elsewhere

Origin of Life?

Within our solar system, Mars has always been in the forefront of our search for alien life. As missions shed new light on the Red Planet, we have new hopes for uncovering the fundamental conditions for life.

Scientists believe that life on Earth may have begun as microscopic organisms in extreme underwater hydrothermal environments

The new scientific field of astrobiology formed to investigate the origins, evolution, distribution, and future of life on Earth and beyond. Astrobiologists strive to address three questions:

• How does life begin and evolve?

• Is there life elsewhere in the universe?

• What is the future of life on Earth and beyond?

Through our efforts to understand how life began and evolved on Earth, we hope to determine where and how to best look for it elsewhere. The scientific field of astrobiology embraces the search for life both close to home (Earth) and far beyond. From laboratory and field investigations on Earth, to the exploration of Mars, the outer planets, and planets beyond our solar system, scientists are studying the potential for life to adapt and thrive beyond our home planet. This research requires partnerships among many fields of science, including molecular biology, ecology, planetary science, astronomy, information science, and space technologies.

1. How is NASA searching for life?

In 1998, in a concerted effort to address the challenges in finding life beyond Earth, the National Aeronautics and Space Administration (NASA) established the NASA Astrobiology Institute (NAI), competitively selected teams across the country that incorporate astrobiology research and training in their programs.

2. What is Life?

Astrobiologists need a working definition of life — a set of criteria for something to be considered alive —in order to search for life. Defining life is not easy. Nonliving examples like viruses and computer programs display one or more of these same characteristics as life (such as making copies of themselves and using energy). Scientists have collaborated to develop a set of general characteristics of life:

1. Life stores and uses energy

2. Life engenders more life (reproduces and/or grows)

3. Life responds to its environment (external stimuli)

4. Life changes (evolves and adapts) over time

All Earth life is organized in essentially the same way: it is based on the chemistry of the element carbon, it requires liquid water, it engenders further life via DNA and/or RNA, it uses phosphate molecules to store energy, and it uses protein molecules to respond to and affect (influence) its environment. All life on this planet adheres to these basic principles.

3. What Does Life Need?

Life as we know it needs an energy source, nutrients (something to eat or consume), protection from the elements, and liquid water. These four main requirements have been the focus of our search for life in the universe. Scientists are looking for places in our solar system — and beyond — that have all the things that we know life needs.

Of the four identified necessities for life, the presence of liquid water is considered to be one of the most important and perhaps useful to scientists. We have only found living organisms where liquid water exists. Pure water is a liquid over a fairly wide range of temperatures — between 32°F (0°C) and 212°F (100°C). Under special circumstances, however, water can remain a liquid beyond this range: at high pressures (like at the bottom of the ocean or deep in the Earth’s crust), water can remain a liquid at higher temperatures, and saline water (water containing salt, like our ocean water) can remain a liquid at lower temperatures. Scientists are interested in identifying locations in the universe that possess water — especially liquid water — to better narrow their search for life beyond Earth!

All organisms require some form of energy to run their life processes (like growing, moving, and reproducing). The organisms that we are familiar with primarily use light energy or chemical energy. Plants get their energy from light. Light energy diminishes with a planet’s distance from the Sun, and with distance below a planet’s surface. If light energy is absent, then there must be an alternate energy source. Microbes at Earth’s deep-sea vents get their energy by breaking down chemical compounds dissolved in water.

All organisms also require nutrients, the minerals and other chemicals used to maintain and grow their bodies and structures. Plants get nutrients from soils and the atmosphere. Animals get their nutrients as food by eating plants or other animals. Life must have a continuing source of nutrients, not only for an individual plant or animal, but over long periods of time so that the plant-animal communities can continue.

Finally, all organisms require protection from the extremes of the environment. This protection may provide the environmental stability necessary for the development and continuation of life. Rock layers and deep water can protect life from dangerous radiation from the Sun and some impacts; many organisms on Earth live underground or deep in the ocean. A planet’s atmosphere can provide some protection from hazards (like ultraviolet radiation and extreme temperature variations) and allows access to sunlight as a major source of energy. However, to serve as an effective shield or insulator, an atmosphere has to be fairly substantial, such as those on Earth, Venus, or Saturn’s moon Titan. A small￾sized body such as Pluto or Earth’s Moon has too little gravity to hold onto a significant atmosphere, making life on or near the surface difficult. On Mars there is very little atmosphere to protect living things from the Sun’s radiation.

4. What can life tolerate? Extremophiles

Much of the research taking place in astrobiology emphasizes the environment and habits of extremophiles — organisms that thrive in conditions that we would consider “extreme” and life￾threatening (e.g., very high or low temperatures, very salty or acidic water). Extremophiles can live where most organisms cannot because they have adapted special mechanisms for survival. Any life beyond Earth may be found in harsh conditions. By studying analog sites on Earth — places that have similar environmental conditions to those beyond Earth (such as Mars) — scientists are exploring the processes that allow these resilient organisms to survive.

Extreme environments may include extreme depths, pressures, alkaline or saline waters, or severe radiation conditions. The majority of these extremophiles are microbes which closely resemble fossilized remains of earliest life on Earth and thrive in environments very similar to the conditions that scientists think fostered the origin of life as we know it.

5. Life on Mars?

All life as we know it requires liquid water. There is good evidence that liquid water once flowed and ponded on the surface of Mars, so it is possible that life could have become established there. The first evidence for life on Earth is in rocks that formed about 3.5 billion years ago. Life may have taken up to a billion years to become established on Earth, although it may have happened more quickly, and so scientists consider this to be a reasonable timeline for Mars as well.

Conditions on much of Mars would have been suitable for life for about a half billion years, before the martian environment changed to colder and drier. However, Mars’ features suggest that there were occasional warmer and wetter periods after the first half billion years, and there may have been refuges for life, such as moist areas near warm volcanic regions. Given the harsh conditions, and lack of evidence, it is unlikely that life evolved into complex multicellular forms, like it did on Earth between 1 and 500 million years ago. Life on Mars — if it exists or existed in the past — would most likely have been in the form of microbes.

In the 1990s NASA scientists announced the presence of organic molecules, mineral features that could have been formed by biological activity, and possible microscopic fossils of primitive, bacteria-like organisms in a martian meteorite. They interpreted the features to have formed on Mars more than 3.6 billion years ago, and to be evidence that life existed on Mars. The results have been hotly debated in the scientific community. Many scientists believe the structures could have been formed by chemical processes, rather than biologic; such chemically formed features are known to exist. Others suggest that the organic signature is contamination from Earth. At present, few scientists are convinced that the features are evidence of life. Debate is a healthy part of the scientific process, and it has served an additional purpose — it has helped scientists better identify the “signals of life” and develop more tools in the identification process being used by astrobiologists today.

Losing the Atmosphere

Early Mars probably had a thicker atmosphere with more carbon dioxide and water vapor, provided by vigorous volcanic activity. This Mars was warmer and wetter, and the higher atmospheric pressure permitted flowing water at the surface. However, by about 4 billion years ago, Mars’ environment became cold and dry, as it is now. As Mars’ interior cooled, the gases and water vapor from the volcanism gradually dwindled and the magnetic field disappeared. Left unprotected, the atmosphere was worn away by the solar wind, and the martian surface was bathed in radiation.

6. Disappearing Water

Early Mars was wetter and warmer. Images obtained by Mars orbiters have revealed that the ancient southern highlands are covered by networks of stream channels similar to gently meandering river channels on Earth. The Mars Exploration Rovers and the Curiosity rover have found structures in the rocks that are created by flowing water, and minerals formed in salty, acidic water.

Some scientists have calculated that Mars may have had a global layer of water that was about 394 feet (120 meters) thick. About 4 billion years ago, things changed; Mars became cooler and drier. The thinatmosphere and low air pressure no longer permitted liquid water to exist at the surface, and the water may have been sequestered underground, either as a liquid or as ice. Occasional warm periods in Mars’ history resulted in melting of the subsurface ice and gigantic floods, recorded by outflow channels which form from catastrophic floods of water.

Much of Mars’ water is underground, either as a liquid or as ice. Mars’ northern and southern ice caps also contain water ice, as well as carbon dioxide ice. Mars’ northern ice cap is mostly water ice.

7. Missions to Mars: The Search for Signs of Life — Past and Present

Scientists will continue to work to identify where the conditions might be right for life on Mars. NASA has successfully conducted both orbital and lander missions to the Red Planet. The first successful missions, Mariner 4, 6, 7, and 9, launched over the course of the 1960s and early 1970s, were the first spacecraft to acquire and return close range images of Mars.

In the 1960s, a group of NASA scientists, engineers, and technicians designed an ambitious robotic mission to Mars, named Viking. The Viking mission was composed of four spacecraft (two orbiters and two landers) whose principal objective was to look for evidence of life. The landers dug soil samples from the frozen surface and looked for signs of respiration –– an indication of biological activity. Although the initial results were thought promising, Viking found no conclusive signs of life. However, it is important to note that these experiments were not very sensitive by modern standards.

Following the successes — and disappointments (no confirmed life) — of the Viking mission, NASA’s Mars Exploration program sent a series of missions to explore the surface features and history of Mars as well as its geology and water, but these missions did not search for signs of life.

The Mars Exploration Rovers, named Spirit and Opportunity, landed on the Red Planet in January 2004 as a part of three-month missions to look for signs of past water activity on Mars. Both rovers far exceeded their mission goals and expectations, making important discoveries about wet environments on Mars in the past and possibly at the present.

The mission to Mars, Mars Science Laboratory (MSL), is looking for the precursors (building blocks) of life and evidence of past habitable environments. MSL’s Curiosity rover is studying rocks, soils, and the local geologic setting in order to detect chemical building blocks of life (e.g., forms of carbon) on Mars in order to assess what the martian environment was like in the past.

The Mars Science Laboratory rover, Curiosity, is continuing the exploration of Mars and is specifically searching for signs that habitable environments existed on Mars in the past. Future missions include Mars 2020, a rover that will collect soil and rock samples in preparation for return to Earth by a future mission.

The Perseverance rover touched down on the Martian surface at 20:55 GMT (15:55 ET) on Thursday 18 February 2021.

The robot is designed to hunt for signs of past microbial life, if it ever existed. It is the first Nasa mission to hunt directly for these "biosignatures" since the Viking missions in the 1970s. The rover will collect samples of rock and soil, encase them in tubes, and leave them on the planet's surface to be returned to Earth at a future date. Perseverance will also study the Red Planet's geology and test how astronauts on future Mars missions could produce oxygen from CO2 in the atmosphere.

This oxygen could be used for breathing and rocket propellant. In addition, a drone-like helicopter will be deployed to demonstrate the first powered flight on Mars. Perseverance will explore Jezero Crater, near the planet's equator, for at least one Martian year (about 687 Earth days).

Source:

https://www.lpi.usra.edu/education/explore/LifeOnMars/background/

https://www.lpi.usra.edu/education/explore/LifeOnMars/background/

Mars landing: Nasa's Perseverance rover in 'great shape' - BBC News

Notes for download: click here Evidence of Life Elsewhere

Supplementary Reading Materials

Supplementary Reading on The Origin of the Universe

Supplementary Reading on Telescopes parts

Supplementary Reading on Types-of-Telescopes