Best books on Astrophysics to be Read

High rated books on Astrophysics to Read: 

Name of the Book  -  Astrophysics for the people in Hurry
Author  -   Neil deGrasse Tyson
Published year  -  2017
Total number of pages  -  244
Type  -  Non-science-fiction
Publisher  -  W.W.Norton & Company
Awards  - Neil deGrasse Tyson was awarded Goodreads Choice Awards Best Science & Technology
Google Review  -  4.1/5
About Book  -  It is a wonderful book on astrophysics with simple basic questions 

Name of the Book  -  Death by Black Hole
Author  -   Neil deGrasse Tyson
Published year  -  2007
Total number of pages  -  384
Type  -  Science Fiction
Publisher  -  W.W.Norton & Company
Google Review - 4.1/5
About Book:  It is most amazing popular science fiction written by deGrasse Tyson commonly called Cosmic Quandaries.

Name of the Book  - Hyperspace
Author  -   Michio Kaku
Published year  - 1994
Total number of pages  -  -
Type  -  Popular Science
Publisher  -  Oxford University Press 
Google Review  -  4.2/5
About Book : This is a scientific space odyssey through a parallel space and time wraps.

Name of the Book  -  An introduction to Modern Astrophysics
Author  -   Dale A Ostlie, Bradley W Carroll
Published year  - 1996
Total Number of pages - -
Type -  Science
Publisher - unknown
Google Review  -  4.2/5
About Book : It is a book for basic introduction to modern astrophysics

Name of the Book  -  Black Holes and Time Wraps
Author  -   Kip Throne
Published year  - 1994
Total Number of pages - -
Type - Non Science Fiction
Publisher -W.W.Norton & Company
Google Review  -  4.2/5
About Book : It is Einstein's outrageous legacy in 1994 popular science

Read More

Exoplanet

NASA Artist concept of exoplanet beyond our solar system

What is Exoplanet? 

     Exoplanet ( exo - means outer or outer solar system ) is a planet outside solar system which orbits a star. The concept of exoplanet was made in the early 1917, but the first confirmed scientific discovery was made in 1992. After that 3,710 planets were discovered outside our solar system including 621 planetary systems. These discoveries were made by High Accuracy Radio Velocity Planet Searcher, Kepler Space Telescope and several other ground based telescopes. It has been found that many planet lie in the habitable zone from their native star. Major discoveries was Proxima Centauri-b and Proxima Centauri closest star to our sun.

 Indian Observatory in Exoplanet Detection:

     The first involvement and report of existence of exoplanet was made by William Stephen Jacob at Madras Observatory controlled by English East India Company in 1855. Similarly in the year of 1890 another astronomer Thomas J.J.See from the University of Chicago stated the existence of 70-Ophiuchi system with 36-years of orbital period. Later, astronomer Forest Ray Moulton published a paper on three-body system with their orbital parameters.

 Detection Techniques:

• Direct imaging
• Gravitational microlensing
• Polarimetry
• Astrometry
• Radial velocity
• Pulsar timings variations
• Transit photometry etc..

 Most Amazing Discovery of exoplanet:

TRAPPIST-1 System :  
     
    NASA had made wonderful discovery of Trappist-1 system which is the best discovery of Hubble Space Telescope and NASA. Now, if we want to know more about the existence of life beyond the solar system, we need to know the age of the star. Young stars have frequent releases of high energy radiation called flares that can zap their planets. If a new planet is born then the orbit of that planet would be unstable.On the other hand, planets orbiting older stars have survived the spate of youthful flares, but have also been exposed to the ravages of stellar radiation for a longer period.

Now NASA's Scientists have a good estimate for the age of one of the most intriguing planetary systems discovered to the date called Trappist-1 System. A system of 7 earth seized planet orbiting a star which is nearly 40 million light years away from the earth. Researchers said that new study reveals that the star is too old between 5.4 to 9.8 billion years ago.

The seven wonders of TRAPPIST-1 were discovered using Transisting Planets and Infinitesimals Small Telescope (TRAPPIST) in Chile, Spitzer Space Telescope of NASA, and other ground based telescopes.

Trappist-1 is 13.7 billion years old in age than the universe and it is like a slow-burning candle that will shine for about 900 times longer than the current age of the universe.

In 2017, more than 139 exoplanets have been discovered.
Exoplanets discoeverd in 2017.

Tags: Exoplanet | Space facts

More Links:
 Top 5 high cited research papers on Exoplanet:

• Borucki, William J., et al. "Kepler planet-detection mission: introduction and first results." Science 327.5968 (2010): 977-980.
•  Charbonneau, David, et al. "Detection of planetary transits across a sun-like star." The Astrophysical Journal Letters 529.1 (1999): L45.
• Charbonneau, David, et al. "Detection of an extrasolar planet atmosphere." The Astrophysical Journal 568.1 (2002): 377. 
• PHASE, COMMISSIONING. "Setting new standards with HARPS." The Messenger 114 (2003): 20  
• Charbonneau, David, et al. "Detection of thermal emission from an extrasolar planet." The Astrophysical Journal 626.1 (2005): 523.

Credits:

 

Image Credit : NASA

Journal Credits : google scholar

Text References : Exoplanet ( wikipedia) retrived 2017 

Read More

Great Red Spot - Juno Depth Analysis

GIF Format Image of Jupiter's Great Red Spot       Image Credit: Juno Mission-NASA-New Frontiers Program

     NASA's Juno mission provided a depths of Jupiter's great red spot. From the data collected from Juno spacecraft in July of 2017 reveals the iconic feature of the great red spot and other information include the existence of radiation zones. It had found that the giant storm prevailing for years is almost 300 kilometers wide which is equal to the half of our earth, so that it penetrates into the spot. This identification was made by one of the Juno instrument called Juno's Microwave Radiometer. The instrument has capacity to observe and collect data deep below the clouds of the Jupiter. It has been providing excellent information about the great red spot since its launch.

Red-spot:

      Jupiter's great red spot is a giant cloud of crimson-coloured located in the southern hemisphere. It rotates at greater speed in anticlockwise direction. Data from Juno showed that the width of the red-spot is about 16,000 kilometers (normally equals to 1.3 times the width of our Earth). It also found that the res-spot is 50-100 times deeper than the oceans.The storm in this red-spot has been prevailing since 1830, that is more than 350 years. Earlier NASA missions like Voyager-1 and Voyager-2 visited the Jupiter and its red-spot in 1979, these twin spacecraft reported that the red-spot was two times the width of our Earth. The great red-spot will appear like deminishing in size, the future of this red-spot in mystery.

Radiation Zone:

     Juno also detected new radiation zone near the equator which is just above the giant atmosphere. The zone contains mostly of hydrogen, oxygen and sulfur ions circulating at a speed of light. This new radiation zone was detected by Juno's Jupiter Energetic Particle Detector instrument (JEDI). The energetic particles are moving fast and have no electric charges. The zone have high-energy ion population which was detected and monitored by Juno's Stellar Reference Unit-1 star camera. Large amount of images and data were collected.

About Juno Mission:

     Juno spacecraft was launched on 5 August 2011, from Cape Canaveral Air force station, Florida.  After few years it arrived Jupiter on 4 July 2016. From its arrival it had completed nine science pass around the Jupiter. The last science pass was on 16 December 2017. During its flybys Jupiter's clouds, atmosphere, great red-spot and radiation zone was explored including its magnetosphere. Juno mission is a part of NASA"s New Frontiers Program and the spacecraft was built by Lockheed Martin Space Systems, part of Jet Propulsion Laboratory, Caltech in Pasadena, California.

More Information:

• https://www.nasa.gov/juno
• https://www.missionjuno.swri.edu/

Credits:

Information Credit: Juno Mission | NASA
Image Credit : Juno Spacecraft | NASA Mission

Read More

Most distant black hole in early universe

NASA Found a most distant black hole in the early universe Image Credit: NASA

     Scientists have discovered a supermassive black hole ; the farthest known black hole ever.Its matter-eating beast is about 8000000000 (8 x 10^9) times the mass of the sun, which is extremely large for its young age. Researchers have published their findings in the "journal of Nature" This black hole grew very fast then expected by the scientists, it started to become black hole within 690 million years after the great Big-Bang challenging the theories of black hole formation.

Observation:

     Scientists used the data from WISE ( Wide-field Infrared Survey Explorer) with ground based surveys to study this black hole. It was also observed by Carnegie observatory and Magellan Telescopes in Chile. Carnegie astronomer Eduardo Banados led his full efforts to identify the object out of million objects through the data from WISE. It had been found that, to follow the black hole with Magellan Telescope will be better than WISE.

Formation:

     The formation of black hole in s short age is a mystery. Scientist predict that for a large black hole in the early stage of universe, there must be some special condition to allow the rapid growth of this black hole. It may be the result of a quasar. 

Universe:

    The universe started to began after 400,000 years after the big-bang, the particles and masses from big-bang spread apart in the universe. These particles were cooled and turned into hydrogen gas, but still it prevailed dark universe without any source of light. After that the gases in the space get ionised so that the light can travel. Thus the universe become transparent to light. Scientists predict that whole sky contains 20 to 100 quasars as bright and distant. 

Collaborative Mission:

     A mission called European Space Agency's Euclid Mission and NASA's Wide-field Infrared Survey Telescope are deeply involved in finding the distant objects in the sky. We will have several facilities and technologies to predict exciting discoveries in the early universe in coming up years as stated by Stern, NASA.

More Information:

• https://www.nasa.gov/feature/jpl/found-most-distant-black-hole

Read More

Proxima Centauri

Proxima Centauri Star. Image Source : wikipedia.org

Proxima Centauri:

     Proxima Centauri is the nearest star to our Earth and also near to the "Centaurus Star". It is located in the constellation of Centaurus which is nearly about 1.52 light years away from our Sun. It was first observed and discovered by Scottish astronomer Robert Innes in the Union Observatory in South Africa. It forms a third component for the Alpha Centauri Binary Star system. The orbital period of this star is 550,000 years.

     Mass of proxima centauri star is eighth of the mass of Sun and the density of the star is about 40 times larger than sun. Its changes in flare is due to the action of magnetic activity and the luminosity is very low, it cannot be clearly seen through our naked eye, because it is a flare star. The distance between the sun and proxima centauri is same as the distance between the sun and alpha centauri, this was calculated by Dutch astronomer Joan Voute (parallax method). In 2016, the European Southern observatory found that the star has a orbiting planet called Proxima-b and it is orbiting the star at a distance of 0.05 AU.

Proxima Centauri planetary system with proxima-b planet

     Proxima is a red dwarf, because it belongs to the Hertzsprung-Russell's M6 spectral class. It has a mean density of 1.411 x 10^3 kg/m^3 observed by Optical Interferometry Large Telescope in 2002. It has been observed by many observatories across the world. It is noted that its 85% of the energy is emitted as Infrared Radiation. The photometric variation of this star is 83.5 days as stated by a study in 1998. Like the sun, it is estimated that all the fuel of proxima will be consumed before the thermonuclear fusion comes to an end. The temperature measure is about 270,000,000 Kelvini and it is too hot emit x-ray. The estimated age of the star is 4.85 x 10^9 years. 

List of Observatories that observed Proxima Centauri:

• European Southern Observatory
• Union Observatory Jahannesburg
• Einstein Observatory
• XMM-Newton Observatory
• Chandra Observatory 
• Hubble Space Telescope 

Satellites which observed Proxima:

• EXOSAT
• ROSAT 

 Mostly cited Research Papers in referred journals:

1.  Anglada-Escudé, Guillem, et al. "A terrestrial planet candidate in a temperate orbit around Proxima Centauri." Nature 536.7617 (2016): 437-440.
2. Benedict, G. Fritz, et al. "Interferometric Astrometry of Proxima Centauri and Barnard's Star Using HUBBLE SPACE TELESCOPE Fine Guidance Sensor 3: Detection Limits for Substellar Companions." The Astronomical Journal 118.2 (1999): 1086.
3. Wood, Brian E., et al. "Observational estimates for the mass-loss rates of α Centauri and Proxima Centauri using Hubble Space Telescope Lyα spectra." The Astrophysical Journal Letters 547.1 (2001): L49.
    

Read More

Light Year

What is light year?

      The term "light year" most commonly used to denote the distances between stars, galaxies, and from a point to far point of the universe. In astronomy, the familiar term to express distances is "Par-sec" which is equal to 3.26 light years.

Why it is light year?

     Because, one light year distance is equal to the distance traveled by light throughout a year. i.e; speed of light x year x 1 day in hours x 1 hour in minutes x 1 minute in seconds. It can be mathematically expressed as:

Distances of Some nearest object in light year:

    In the table below, distances of some nearest object from earth measured in light year.

* Gliese 581 Red Dwarf

** It is A0620-00 the nearest black hole i.e; 3000 light years away from Earth

Importance:

    The unit of distances between stars and galaxies are measured in light year. It have been in practical use since 1984.But now the modern astronomers use parsec , light years also popularly used to express distances between interstellar and intergalactic distance.

History:

    The usage of light year came into existence when famous astronomer Friedrich Bessel in 1838 measured the distance between a star and earth was calculated. The star was called 61-Cygni.

Read More

Ornament Nebula

Ornament Nebula | NGC 5189  Image Credit : NASA

Ornament Nebula:

    Ornament nebula which is NGC 5189 nicknamed as Spiral Planetary Nebula. It can be located in the constellation of Musca over the night sky. This nebulae was first discovered by James Dunlop on 1 July 1826. He catalogued this nebula as 252. After many years of this discovery, it was thought to be a bright emitting nebula. But in the year 1967 a astronomer called Karl Gordon Henize who described this nebula as NGC 5189 as spectral emissions like quasi planetary model.

Visibility:

      It can be seen through the telescopes, it will have shape like "S" with barred spiral galaxy. For a long time, it hinted astronomers that there must be a central star present at the center of this nebula. 

Observations:

     Astronomers from Southern African Large Telescope have found that it has a central star called NGC 5189 or Wolf-Rayet type central star and another white dwarf which rotates around the central star every 4.04 day. It is estimated to be at 1,780 light years away from our Earth and having 546 parsec. Measurements from other observatories have shown that the nebulae is about ~3000 light years away from Earth and having 900 parsecs.

More Information:

1. Phillips, J. P., and N. K. Reay. "Ansae and the precession of central stars in planetary nebulae-The cases of NGC 5189 and NGC 6826." Astronomy and Astrophysics 117 (1983): 33-37.
2. Blanco, V., et al. "Spectrum of the Central Star in NGC 5189." The Astrophysical Journal 152 (1968): L135.
3. Reay, N. K., P. D. Atherton, and K. Taylor. "Kinematic structure of planetary nebulae–III. Condensations in NGC 5189." Monthly Notices of the Royal Astronomical Society206.1 (1984): 71-75.

Credits:
Journal Credits : Google Scholar
Image Credit : NASA
Text Credit : Wikipedia

Read More

Gravitational Waves

Gravitational Waves from two neutron stars. Image Credit : LIGO

     Gravitational waves are the ripples in the space-time fabric, which are caused by the violent and energetic process of the universe. These waves are produced from the collision of neutron stars, massive acclerating black holes, stellar cores, supernovas, coalescing neutron and white dwarfs. Famous physicist Albert Einstein predicted the existence of gravitational waves in 1916, he proved by his mathematical expression. After 20 years of prediction of gravitational waves, scientists detected the gravitational waves from binary pulsar star in 1974. 

Detection:

     In 1974, two astronomers working at Arecibo Radio Observatory in Puerto Rico discovered a binary pulsar two extremely dense and heavy stars in orbit around each other. This was similar to the theory of relativity in which the body radiates gravitational waves from the source in a space-time fabric. The study had continued for 40 years about the binary pulsar star. In 14 September 2015, Laser Interferometer Gravitational Wave Observatory (LIGO), first time detected the distortion in the space-time fabric. the distortion was due to the collision of fast rotating black holes nearly 1.3 billion light years away. LIGO made a huge achievement after detecting the waves. When it was detected, the sound was like a "bird chirp".

Need to detect Gravitational Wave:

     Gravitational wave can only be detected by LIGO observatory, because it was designed in such a way that it can detect any small or tiny distortion in the fabric of space time. Similar to the discovery of gravity, the gravitational wave will change the view of space science and will help us to understand the origin of the universe in a effective manner.

Data in gravitaional wave:

     Astronomers and data scientists stated that gravitational waves are not like electromagnetic radiation, it is quite different from the EM wave. It carry information and data of cosmic object in space-time, and it travel at a speed of light in the universe. They interaction between the dark matter and gravitational wave in space is very weak.

Souces of waves:

• Neutron stars
• Binary neutron stars
• Binary black holes

LIGO:

LIGO - Gravitational Observatory, Hanford, USA

     LIGO stands for Laser Interferometer Gravitational Wave Observatory is a observatory established in Hanforn and Livingston in the shape of "L". They are of 4km x 4km of length, It was constructed to act as antenna for the detection of gravitational waves.It can detect waves at a wavelength of 30 Hz to 7 kHz.

Observatories and Collaborations:

     Many scientists and engineers are involved in the detction of  gravitational wave outside the Hanford,Livingston,Caltech and MIT. They are all part of scientific collaboration of LIGO.

• LIGO's Dual detectors
• LIGO-India (planned joint work with India)
• Virgo, GEO and KAGRA   

More Information:

• LIGO - Caltech
• LIGO -  Hanford Observatory
• LIGO - Livingston Observatory
• LIGO - MIT
• Press Releases - LIGO - Gravitational wave detection: 
• Detection on 16 October 2017
• Detection on 27 September 2017
• Detection on 01 June 2017
• Detection on 15 June 2016
• Detection on 11 February 2016 

Research Papers on Gravitational Wave Detection:

1.  Eberle, Tobias, et al. "Quantum enhancement of the zero-area Sagnac interferometer topology for gravitational wave detection." Physical review letters 104.25 (2010): 251102.
2.  Harry, Gregory M., and LIGO Scientific Collaboration. "Advanced LIGO: the next generation of gravitational wave detectors." Classical and Quantum Gravity 27.8 (2010): 084006.
3.  Abbott, B. P., et al. "LIGO: the laser interferometer gravitational-wave observatory." Reports on Progress in Physics 72.7 (2009): 076901.
4. Abadie, Jea, et al. "Predictions for the rates of compact binary coalescences observable by ground-based gravitational-wave detectors." Classical and Quantum Gravity 27.17 (2010): 173001. 
     

Credits:

  

Image Credit : LIGO

Journal Credit : Google Scholar

 

Read More

Dark Matter and Dark Energy

Dark matter and dark energy universe Image Credit : NASA's Hubble space telescope

     Dark matter and dark energy is a hypothesized theory which was widely accepted around the world. In the field of astronomy and cosmology, dark energy is a unknown form of energy which widely distributed in the universe. This dark matter and dark energy is responsible for the brief expansion and acceleration of the universe. It was mostly accepted hypothesis since 1990. According to the modern concept of cosmology, the total universe constitutes 68.3% percent of dark matter and the remaining are neutrinos and photons. It is very difficult for the scientist in defining and explaining the dark matter by experiments, however it may be proved in upcoming generations.

Discovery:

     Most familiar scientists Alan Guth and Alexei Starobinsky were the one who firstly proposed the dark matter in early 1980 and that could drive the inflation of universe. (Infilation is nothing but , some kind of repulsive force which resulted in expansion of the universe after the great Big-Bang (Giant explosion of dark matter to form universe). It is very interesting that, big-bang took with higher density(sum of dark matter and energy) of universe, it was likely to end within a second.

Hubble Constant:

    During 1980s, when they proposed the theory, they found that 95% of universe consist of cold dark matter and 5% of ordinary matter which is nothing, but the baryons. The discovery led to many difficulties in defining to the value acquired by the Hubble (Hubble constant). This difficulties became very stronger after the COBE Spacecraft of 1992 discovered the anisotropy. The first evidence of dark matter was observed from a supernova explosion in 1998, this was observed by Riess and Perlmutter.

Evidences of dark matter:

     Scientists provided indirect evidences for the existence of dark matter from the independent sources

1. By measuring the distances and relating it to the redshift
2. Theoretically, it is not a dark matter to form flattened universe
3.  By measuring the wave patterns and mass density form various sources of the universe

First Observed Supernova:

     In the year 1998, a team called Hihg-Z Supernova Search Team published their observation on Type-A Supernova. In 1999, Nobel Prize in Physics was awarded to Saul Perlmutter, Brian P.Schmidt and Adam G.Riess for their discovery suggesting the expansion and acceleration of the universe (Supernova Cosmology Project).

Research Papers Published in the high profile referred journals:

      High rated and cited research paper on Dark Matter in google scholar from 1980 to 2000.

1) Smith, P. F., & Lewin, J. D. (1990). Dark matter detection. Physics Reports, 187(5), 203-280.
2) Freese, K., Frieman, J., & Gould, A. (1988). Signal modulation in cold-dark-matter detection. Physical Review D, 37(12), 3388.
3)  Savage, Christopher, et al. "Compatibility of DAMA/LIBRA dark matter detection with other searches." Journal of Cosmology and Astroparticle Physics 2009.04 (2009): 010.
4) Munoz, Carlos. "Dark matter detection in the light of recent experimental results." International Journal of Modern Physics A 19.19 (2004): 3093-3169.

5) Spiro, Michel. "Dark matter." Nuclear Physics B-Proceedings Supplements 43.1-3 (1995): 100-107.

Credits:

Journal credits : Google Scholar 
Image Credit : NASA's Hubble Space Telescope

Tags: dark matter | space facts | universe | relativity 

Read More

NASA's upcoming two missions to Saturn's Moon Titan

     National Aeronautics Space Administration have planned for two selected missions to the largest moon of planet Saturn, which had been previously explored by Rosetta mission. These missions were planned to launch in the middle of 2020 and it include a sample return mission and robotic drone spacecraft. It was categorized under the NASA's New Frontiers Program. (Preceding mission of this new frontiers program was New horizons to Pluto, Juno mission to Jupiter and the OSIRIS-Rex mission to the asteroid Bennu). This project will get funded for further development in end of 2019.

Mission No.1 - Comet Astrobiology Exploration Sample Return (CAESAR)

     This CAESAR mission is a sample return mission from 67P/ Churyumov-Gerasimenko, which is a comet that was previously explored by Rosetta spacecraft.

Mission No.2 - Dragonfly

      This is a robotic drone spacecraft that will explore the whole comet, chemistry and habitability on Sturn's moon Titan.

More Information:

• New Horizons - Pluto Mission
• Juno Mission
• OSIRIS-REx Mission
• NASA's Strategic Plan 2014
• New Frontiers Program
• Planetary Missions - NASA
• Rosetta Mission
• Official page of this post

Read More

Mars missions timeline

Introduction:

     Since earlier times scientists and explorers are very interested in exploring outer planets and in search for life beyond earth. when it comes to "make survival of human on other planet" the only possibility of life beyond earth on another planet is "Mars". It is because Mars lies after the habitable zone (i.e Earth) and it may provide suitable temperature for the formation of life on its surface. Recently, scientists have discovered the ice and water under the soil surface ( Curiosity Rover discovery). From 1960 to recent times, we have been exploring Mars by several missions. This mission includes orbiters, landers, rovers and penetrators. 

Orbiter:

     An orbiter is a robotic spacecraft that explores another planet by orbiting around the planet in its trajectory. It operates by the command programmed by the scientists and further responses according to the commanding signal received from the earth station. It uses its solar panels to power and have several instruments to measure various parameters. 

Lander:

     Similarly, a lander also a robotic spacecraft having arms and cameras, that comes to rest or lands on the surface of Mars. It performs various experiments as programmed by the scientists. It uses its arm to take and analyse the soil composition, its cameras used to image the surface and colour of the soil surface.

Rover:

    A Rover is a moving spacecraft having wheels, example - curiosity rover. It moves on the surface of Mars and performs several experiments. It chooses different location to perform drill practices and soil analysis. It moves very slow as compared to the earth vehicles.

Mars Mission Timeline:

Flybys:-

• Mars 1M No.1
• Mars 1M No.2
• 2MV-4 No.1
• 2MV-4 No.2
• Mariner-3
• Mariner-4
• Zond-2
• Mariner-6
• Mariner-7
• Mars-6
• Mars-7

Orbiters:-

• 2M No.521
• 2M No.522
• Mariner-8
• Kosmos-419
• Mars-2
• Mars-3
• Mariner-9
• Mars-4
• Mars-5
• Viking-1-orbiter
• Viking-2-orbiter
• Phobos-1
• Phobos-2
• Mars Observer
• Mars Global Surveyor
• Mars-96
• Nizomi
• Mars Climate Orbiter
• Mars Odyssey
• Mars Express
• Mars Reconnaissance Orbiter
• Fobos-Grunt
• Yinghuo-1
• Mars Orbiter Mission
• MAVEN
• ExoMars Trace Gas Orbiter

Landers:-

• 2MV3-No.1
• Mars-2 
• Mars-3 
• Mars-6 
• Mars-7
• Viking-2
• Phobos-1
• Phobos-2
• Mars Pathfinder
• Mars Polar Lander
• Beagle-2
• Phoenix
• Schiaparelli

Penetrators:-

• Mars-96
• Deep Space-2

Rovers:-

• Prop-M-rover
• Sojourner
• Spirit
• Opportunity
• Curiosity

Gravity assist probes:-

• Rosetta
• Dawn

Active Mars Missions:

• Mars Odyssey
• Mars Express
• Opportunity Rover
• Mars Reconnaissance Orbiter
• Curiosity Rover
• Mars Orbiter Mission
• MAVEN
• ExoMars Trace Gas Orbiter

Conclusion:

     Out of several missions, only 8 missions are currently active in exploring Mars. Curiosity rover discoveries changes the view of Mars since its launch. Space agencies have many future proposals for mars missions. One of the space agency called space-x is currently working on Human Mars Mission which is a part of Making Life Multiplanetary. 

Read More