WHAT MAKES OUR MOTHER EARTH SO UNIQUE TO HOST LIFE?

WHY ONLY EARTH HOSTS LIFE IN OUR SOLAR SYSTEM ? (By Sanjeevi Ramamoorthy)

Size of the Observable Universe is > 90 Billion Light Years ( Age of Universe is only 13.8 Billion Years). We  are yet to calculate the size of Total Universe. It is being estimated that there are 200 billion Galaxies in the observable universe and each and every galaxy is having more than 100 billion Stars and 99 % of these stars have at least 1 Planet in it's orbit. But, why we are still not able to find any alien life so far?What makes earth so unique to host a complicated life form like Humans?

WHAT IS LIFE?

There is no consensus among scientist community regarding the definition for Life. All we know / Assume  is that All Life (as we know)  had evolved from the Last common Universal Ancestor (LUCA) which is estimated to have lived approx around 3.8 Billion Years Ago.

What science doesn't know is that whether this LUCA had originated on earth or  some where outside ( Interstellar Cloud / Molecular Cloud / Intergalactic Medium).

Life as we know requires following three things to get evolved on its own / from LUCA

1. One Solvent ( not Necessarily Water)  in Liquid Form. ( Life on earth use water as solvent)

2. One Oxidation Agent ( Co2 / O2 / etc.,)

3. One Energy Source ( Sun / Tidal Warming / Geo Thermal Energy etc.,)

Myth of  Goldilocks zone / Cir cum Stellar Habitable Zone: 

Researchers hypothesized that planets in the Goldilock Zone / Habitable Zone ( particular region around star where Solar Radiations allows water to be present in liquid Form) are more likely to host complex life forms like Humans. Is it So? Then Why Mars & Venus are hostile to any kind of Life in our Solar System?

If liquid can only be present in Habitable Zone, how Titan ( Saturns Largest Moon) has ocean of Hydro Carbon on its surface) and Enceladus ( Satrun's 6th Largest Moon) & Europa ( Jupiter's Moon )have sub surface ocean of Liquid Water?

Scientists strongly suspect that Mars was once hosting life like earth ( 2 Billion Years Ago) and water was flowing on its surface like earth. Then what happened in between which made it as barren land? Will earth also face same fate like Mars?

Why Venus which absorbs less sunlight than earth ( Fact!!!!!)  is so warm and hostile to life?

                                               (Nova Documentary on Alien Planets)


SO WHAT MAKES EARTH SO UNIQUE TO HOST LIFE?

Answer to this question is to find out what went wrong with  Mars & Venus.


WHY MARS HAS LOST ITS LIQUID WATER?

Planets need dense atmosphere to hold water in liquid form on its surface. But, atmosphere of Mars is less than 1% thick than earth. OOPS!!!!!!!!! Why?  How Mars Lost most of its atmosphere resulting in the evaporation of liquid water from its surface?

 Culprit is the Solar Wind. Solar Wind is the stream of particles ( Proton, Electron & Neutrons) released from upper atmosphere of our sun. It has the tendency to react with atmosphere of the planets and will slowly erode it away into the outer space. But, How earth Survived this fate?

Earth survived because of its magnetosphere produced by liquid lava flowing inside our earth. This magnetosphere reflects 99.99 % of solar wind into outer space protecting our atmosphere which keeps water in liquid form on our earth.

Mar's Magnetosphere is not strong enough to reflect all solar wind into outer space because of its small size compared to earth. Planet Need critical mass ( roughly 1 Earth Mass) in order to produce strong magnetic field to protect its atmosphere from dangerous Solar Wind.

Mars Lost of most of its atmosphere to solar wind which led liquid water to either freeze or evaporate resulting in waste barren land. EARTH SURVIVED FROM THIS FATE BECAUSE OF ITS SIZE.

If Size really matters for planet Habitability, how our twin planet Venus which weighs almost same as earth  has become hostile to any life form.

WHY VENUS HAS NO LIFE?

Story of Venus is totally opposite to Venus. Density of its atmosphere is 99 times thicker( 99 Bar Pr) than earths atmosphere ( 1 bar Pressure). This dense Atmosphere is strong enough to keep liquid water on its surface and its mass is also more than enough to produce strong magnetic field to protect its atmosphere from solar wind. Then Why It has become hostile for any life form?

Answer is because of "Green House Effect". Even though, it absorbs  less sun light than earth, its mean surface temperature is 470 Deg C which makes the evolution of complex life almost impossible ( Microbes may still live there). How Earth escaped from this fate?

Earth escaped from this fate because of " Plate Tectonics" ( Movement of Tectonic Plates under earth surface which creates earth quakes and continental drift). These Plate tectonics help planets to trap Green House Gases ( Methane, Water Vapour, Co2) from its atmosphere into subsurface.

Recent Studies have found that "Plate Tectonics" are missing on Venus ( Reason is still unknown.). Venus had failed to trap the Green House Gases from its atmosphere due to the absence of plate tectonic activities resulting in the so called " Run away Green House Effect".

So Second Factor which makes earth so unique from other planets is its "Plate Tectonics".

But these two factors are not major factors. Hebble Telescope have found thousands of earth like planets at our Milkyway Galaxy in the Habitable Zone of the Stars. How our mother earth is different from these new planets?

PRESENCE OF JUPITER:

It seems Weird. How Planet Jupiter can help earth to host life? It can... Planets need relatively Calm Period for complex life to get evolved since process of biological evolution is very slow. Humans had evolved only before 2.5 Lakhs year ago. It took 3.8 billions of years for our earth to create intelligent life like Humans from the Last Universal Common Ancestor. If earth had collided with any bigger asteroid in this period, humans would have not evolved at all.

History teaches us that just 10 KM size Asteroid is more than enough to kill 95 % life on earth instantly. Dinosaure which ruled this world for almost 20 crores years have been wiped out by just a small 10 KM size asteroid. ( Please read my old post titled " How Extinction of Dinosaur helped Human Evolution").

BUT WHAT IS THE ROLE OF JUPITER IN PREVENTING ASTEROIDS?

There is something called Asteroid Belt in between Mars & Jupiter. Jupiter is Very Big Planet in our solar system ( 470 times our earth). Its Huge Gravity only helps to arrest all these irregular & Huge Size ( upto 900 KM) asteroids in between mars and jupiter. In the absence of planet like jupiter in our solar system, there is lot of probability for our earth to get collided with these asteroids. Infact, our moon was created from one of such collision only.

                                                             (Asteroid Belt)

SO PRESENCE OF THE JUPITER IS ONE OF THE MAIN REASONS WHICH KEEPS US ALIVE.



SO SOME OTHER INTERESTING QUESTIONS ARE


1. Whether Moons Like Titan (Saturn's Largest Moon), Encaludus (Saturn's 6 th Largest Moon) and Europa ( Jupiter's Moon ) can host life?

2. What is the future of Earth?

3. Will earth survive Red Giant Phase of Sun?


Lets discuss in the Part 2 of this Article

INDIA'S MARS MISSION: HOW ORBITAL MECHANICS WORKS?

INDIA'S MARS MISSION: HOW ORBITAL MECHANICS WORKS?  (By Sanjeevi Ramamoorthy)

India has become the first nation in the world to have successfully achieved the Mars Mission in its Ist attempt itself. Only 3 Countries (USA, Russia & India) & 1 Continent  (Eurpoean Space Agency) out of 200 countries in the world have so far successfully sent the orbiter to the  mars. There have been 52 attempts by the various nations in last 60 years to send the orbiter to mars. But only 22 missions have become successful. ( Approx. 40 % Success rate).


How Inter Planetary Spaceflight Works?

There are two ways to send the Spacecrafts to the mars. Shortest Way ( Less time Consuming Method)  is called as crow flight method / brutal force method in which spacecraft is sent from the earth orbit to mars against the sun's gravity through the continuous force generated by the burning of rocket fuel as explained in the below image.


          
            (Illustration of Crow Flight Method)

However, it is not practically viable due to the requirement of Huge Fuel ( Since we lack the knowledge of any other method to accelerate Spacecraft in space  except Newton's Third Law and Gravitational Sling Shot ( which is not effective between earth and mars)).

How Hohhman Transfer Orbit works?

Most economical method of sending spacecraft to mars which all nations currently follow is called as Hohhman Transfer Orbit Method.This is the most economical way of sending space craft since it consumes very less fuel but time consuming ( around 9 months to reach Mars).

According to this method, spacecraft will be  transferred from earth's orbit to the Heliocentric orbit ( orbit around sun) first which is marked in green color in the below diagram.

Why it consumes Less Fuel?

It is because of Heliocentric Orbit & Newton's First Law. Burning of Fuel is only needed to transfer  the spacecraft ( to attain the escape velocity to get out from the influence of earth's gravity) from the earth's orbit  to Heliocentric orbit. Once it is done, it will simply start orbiting around the sun in Heliocentric Orbit like earth and all other planets normally do. Newton's First Law allows this space craft to be in constant motion without consuming further fuel.

Hohmaan Transfer orbit is nothing but highly Elliptical Orbit around sun which connect both earth's orbit and destination planet's orbit ( in this case Mars). The above diagram clearly shows the Heliocentric orbit in green color connecting both  earth's and mars orbit.

Most critical aspect of this method is that mars & space craft should exactly reach the apogee ( furthest point of the Heliocentric orbit marked as red dot) in the same time to make the "Mars Orbit Transition (MOI)" possible. It happens only one time in approx. every 2 years. ( 2014, 2016 & 2018).

INDIA'S LIMITATION & HOW IT ENCOUNTERED:

Even though, we have successfully sent the orbiter to the mars, we lack the the powerful rockets like NASA's Atlas V (which can lift upto 18 MT)  to carry the Heavy Spacecraft to space and to achieve the escape velocity ( 11. 2Km /s)  to move out of earth's gravity pull.

Our PSLV can  lift upto 1.3 MT  only and can place the spacecraft only in Low Earth Orbit ( < 500 Km from the earth surface). It lacks the capability to directly inject the mangalyan in Mars Transfer Orbit (HeliocentricOrbit) . Only solution for this problem is to use the Method Called Orbital Maneuvers.

Earth Orbit Maneuvers:

According to the Kepler's 3rd Law, orbital speed of the spacecraft will increase due to the gravity when it reaches perigee ( closest point in the elliptical orbit) and decelerate when it moves towards apogee ( furthest point in the elliptical orbit) .

So If we fire the Liquid Apogee Motor (LAM) exactly when it reaches perigee ( as illustrated in below diagram, we can increase the distance of apogee ( which means that velocity of spacecraft will get increased as per Kepler IIIrd Law when it reaches perigee again). This method is called Earth Orbit Manuevers. See the below video to know exactly how it works.

                                   ( Video Illustration of Earth Orbit Maneuvers Method?)


After 4- 5 earth Maneuvers ( around 1 Lakhs Km apogee distance), mangalyan had attained velocity ( 11.2 Km/s) sufficient enough to escape from earth's gravity and to get transferred into Heliocentric Orbit.. This process is called Trans Mars Injection.

                           
                          ( Mangalyan's  Earth Orbit Maneuver to attain the escape velocity)

Once spacecraft reaches Heliocentric Orbit, newtons first law will help it to reach mars orbit with out consuming fuel.

MARS ORBIT INSERTION:

Once Mars & Space craft reaches the apogee of Heliocentric, next challenge is deceleration.

Challenge in this phase is to decelerate the Spacecraft to a level where it wont escape the gravity of mars. But risk is that deceleration beyond the certain limit will lead the spacecraft to crash in mars surface. Challenges are to get the spacecraft into the capture orbit of Mars ( approx  within 1 Lakh KM) and to decelerate it to < 2Km/ s velocity.

                          ( Isro's simulation video explaining how Mars Orbit Transition Works)


Another efficient method to accelerate and decelerate the spacecraft without consuming fuel is Gravitional Sling Shot in which orbital energy of the planets is being converted to accelerate the body and vice versa. But it is not effective between earth and mars. NASA's Interplanetary missions such as Volyager1, Voyager II, New Horizon have sucessfully used this method to travel to the end of our solar system.

1.HOW GRAVITATIONAL SLING SHOT WORKS? CAN WE USE THIS METHOD FOR INTER GALACTIC TRAVEL?

2.  IS FASTER THAN LIGHT TRAVEL  POSSIBLE?

3. WHETHER "WARM HOLE" IS THE EASIEST WAY TO REACH OTHER GALAXIES?

4. CAN "SPACE - TIME" CAN BE WRAPPED ACCORDING THE EINESTIN'S GENERAL THEORY OF RELATIVITY?

          ( Let's discuss in the Part 2 of this article)