Super earths- how much probability of colonization of life is there?
Authors_:Rupak Bhattacharya1 , Pranab Kumar Bhattacharya2,*, Upasana Bhattacharya3 , Ritwik Bhattacharya4 , Rupsa Bhattacharya5 , Dalia Mukherjee6 , Ayshi Mukherjee7 , Debasis Mukherjee8
1B.Sc (Calcutta University), M.Sc (Jadavpur University), Kolkata 110, West Bengal, India 2MBBS (Calcutta University), MD (Calcutta University), FIC Path (India), Now Professor of Pathology (on Deputation) , Calcutta School of Tropical Medicine, Kolkata, West Bengal, India; also, Professor in Department of Pathology at Murshidabad District Medical College, Berhampore station Road, Murshidabad, West Bengal, India 3 Student, Kolkata-110, WestBengal, India 4B.com, Calcutta University, Kolkata, West Bengal, India 5Student, Kolkata-110, WestBengal, India 6B.A. (Hons.), (Calcutta University), Kolkata, West Bengal, India 7Student, Kolkata, West Bengal, India 8BSc (Calcutta University), West Bengal, India
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Journal of Aerospace Engineering & TechnologyISSN: 2231-038X (Online), ISSN: 2348-7887 (Print)Volume 9, Issue 1www.stmjournals.com
On January 4th, 2009 American Astronomical Society in Washington D.C, the Kepler team announced that it had identified first new exo-planet and after that up to 2013, Kepler had identified nearly 4034 exoplanets or Super earth outside our solar system where some chemical conditions that the pre-biotic earth had might have prompted life, at least in form of microbes. Scientists so far announced the lists of earth-sized 4034 exo-planets with a duration of orbit around their stars from 6 hours to 632 days and from the list, Kepler team singled up to 20 candidates most likely to have characteristics necessary to sustain life. Of such planets are HD 1461 (76 light years away); GJ 1214b(40 light years away), GJ 452 b ( Which is one and half time sized in the earth and is around 40 light years away); Gliese 581 c and another is KOI -7923.01. This last Exoplanet is 97% of the size of our earth has an orbit period of 395 days of our earth days, likely surrounded by a cold atmosphere. Super-earth Wolf -1061 C is however habitable planet outside our solar system and could support also alien life. It is only 14 light years away from the earth. Statistics suggest that our own galaxy harbors at least 100 billion such exoplanets including planetesimals. Of the world’s found, today few closely resembles the earth. Instead, they exhibit truly enormous diversity, varying immensely in the orbit, their size, composition and circling a wide variety of stars including one significantly smaller than our sun. Diverse features of those exo-planets suggested us (the authors) and also to many others that earth may not be only where close to the pinnacle of habitability. In fact, some exo-planets are quite different from our own, could have much higher chances and can maintain stable biosphere. Of course our planet the earth possesses a number of properties at first seems to be ideal for evolving life, that earth revolves around a sedate middle-aged star, that has shined steadily for billions of years, giving life plenty of times to arose and evolved from RNA worlds to microbe worlds to prokaryotic to eukaryotics to multicellular organism life to modern planets, reptiles mammals, human through a process called Darwinian evolution. It has oceans of life-giving water, largely because it orbits within suns habitable zone, life-friendly size, big enough to hold a substantial atmosphere with its gravitational field but small enough to ensure gravity does not pull a smothering, opaque shroud of gas over the planet earth size its rocky composition, its volcanoes also gave rise to other boosters of habitability of life Wolf 1061 C is the closest Super-earth from our planet, only 14 light years away. But it has more than 4 times the mass of earth and the planet sits within the habitable zone, possible for water and life to exist. Others are in the habitable zone of cool dwarf star known as TRAPPIST -1 which is 39 light years away from earth and the planets have a surface temperature from zero to 100 degree Celsius - the temperature, which is perfect for supporting life. Earth-sized planets those are rocky, those are watery, NH3 has methane, and volcanoes can support the origin of life. The amonia methane, HCN and water are an essential components for the origin of life in any planet
for RNA and DNA. To develop most earliest microbes it need methane-rich oxygen-poor mud at bottoms of river and lakes as microbes live on a diet of methane and nitrogen oxides like nitrites and nitrates or by other pathways like photosynthesis, bacterial reduction of chlorates and enzymatic conversion of reactive oxygen species and directly energy from methane through a chemical process linked denitrification which releases nitrogen and oxygen from nitrogen oxides. So life can begin in any of twenty super-earths where methane exists as free gas in the atmosphere or in the river or as a lake or asthe ocean. In such an environment, alien microbes can use any of the pathways to leave off carbon and energy supplied by methane. The bacteria may be called methanotrophs. Keywords: Gliese 581 c, glycine RNA/DNA life, habitable zone, HCN, HD 1461, KOI - 7923.01, methane, methanotrophs, Miller Urey experiment, super earh, TRAPPIST-1 volcanos, water, Wolf 1061 C *Author for Correspondence E-mail: profpkb@yahoo.co.in
Are "Super-Earths" common around other star systems also in our universe? Are these planets habitable, particularly suitable for the human colonization? Quite possibly there are many Super Earths. Astronomers also found a handful of new planets around sun-like stars beyond our sun and our galaxy [total of known such extra solar planets today is probably more than 400.], some may be only 29 light years away. Astronomers have discovered hundreds of Jupiter-like planets in our galaxy too. In a study published in Nature journal, by a team, led by David Charbonneau of
And is abou t6.55M. times as massive as earth. It is the second smallest planet discovered outside of our solar system to date, trailing behind only CoRoT-7b, which is 1.7 times Earth's size and about five times as massive. Charbonneau's team thinks GJ 1214b is likely a water world with a solid center. Moreover, the planet has a thick surrounding atmosphere of hydrogen and helium. But scientists think the thick atmosphere of GJ 1214b creates a high pressure environment that keeps water on the surface in a liquid state .That's just speculation, however If life exists there, it would probably be well adapted to swim in 400-degree oceans (and actually it may be cooler than than, depending on the planet’s albedo].
. Super earth had been found in our nearby stars also. Six such "super-Earths" had been found orbiting our sun-like neighbor stars in our galaxy. The smallest of the bunch weighs in at about five times the mass of Earth and orbits a star known as 61 Virginis, which is visible with the naked eye in the constellation Virgo. The star is 28 light-years from Earth and closely resembles the sun in size, age and other attributes. Two other newly detected planets -- each about the size of Neptune -- are part of 61 Virginis' family. Another planet that is 7.8 times larger than Earth orbits HD 1461, a sun-like star located 76 light-years away in the constellation Cetus. Super Earths are thus very common all over the universe.In general, Super-Earths are defined exclusively by their mass, and the term does not imply temperatures, compositions, orbital properties, or environments similar to Earth's. A variety of specific mass values are cited in definitions of super-Earths. Super Earths are planets- so named however for their size, - which ranges from about 2 to 10 times that of Earth masses - may be superior to the Earth, when it comes to the questions of sustaining life. Super earths have terrestrial surfaces or liquid oceans that however can support life as we know it. Astrobiologists, thinks, we are more likely to find a life on rocky planets with liquid water, though not an single super earth has been detected so far with life or ocean like earth planet .They estimated that there could be a hundred million such habitable Super Earth planets just in our Milky Way galaxy. They predict that we’ll find more 50 to 100 Super Earth planets in the next 5 years. The Super Earth are traced by the detection of the stellar light reflected by that planet or of the thermal photons emitted by the planet. Both approaches are however valid and may provide a complementary information. The planetary properties those are observed and scientists are interested in observing and constraining are: the size (mass and radius), the atmosphere (chemical composition, clouds, seasonal variations, thermal inertia), the surface (type -rocks, ice, water, “vegetation”-, inhomogeneities), rotation (period, atmospheric dynamics) and environment (rings).Reflected light and/or thermal emission may be used to study these planetary characteristics. The former approach relies on the information that can be extracted from the stellar light reflected by the planet as a function . The NASA will start The Super-Earth Explorer Coronagraphic Off Axis Space Telescope (SEE-COAST) mission in 2016.
But are these super earths will be habitable for the life or sustaining for life? More the massive a planet is, the hotter is its interior. Tectonics is one of the key features of our planet which however made once life possible here. If not for tectonics, carbon was highly needed by life would stay locked within rocks. Our life is carbon based RNA/DNA life. Super Earths, with a larger and hotter interior, would have a thinner planetary crust placed under more stress. This probably would result in faster tectonics, as well as more earthquakes, volcanism, and other geologic upheavals. Earth has a circular orbit 150 million kilometers away from the Sun, a yellow dwarf star. This helps keep conditions warm enough so that our oceans don’t freeze over, but cool enough so that we don’t lose all our water through evaporation. Let us consider how life evolved in the planet the earth [2]
The Earth was considered to develop out of interstellar gas and dusts somewhat 4.6 billion years ago and from the fossil records, we know that origin of life happened soon after 4.0billion years ago that was either in ocean or in ponds or in the rocks of the primitive earth. At about 4.5 billion years ago ( Ga) a portion of interstellar cloud attained a critical density after which it underwent collapse phenomenon to form the Star “Nebula”. This Solar Nebula was a rotating disk with a central bulge. Half or more of the mass of that solar nebula was concentrated into solar mass, and this central mass subsequently evolved to our Sun. In the extended disk, outside the central condensation, a portion of tiny fraction of the nebular mass, that was in the form of solid grains settled out of nebular gas to form a dust rich layer in the central plane of that disk. In the inner portion of the disk, which was much warmer portion of the disk, the dusts consisted of grains of nickel, iron and silicate metals. In the outer portion, which was cooler portion of the disk, abundant grains of ice and organic compound accumulated along with augmented layers of solid matter. The solid matter within these dense, dirty layer, grains, water, ice, agglomerated to form clumps. The clumps continued to accrete, until much of the solid matter was tied up in kilometer-sized planetesemals. Gravitational forces became important at this scale and larger bodies of hundred to thousands kilometer size or more were formed further by accumulation of these formed up planetesemals. At some points of this process, a few of these bodies began to grow very rapidly at expenses of their smaller neighbors and formed embryonic planets. The nebula from which such embryonic planets were formed had same composition to the sun, mostly hydrogen, and helium and a small sprinkling amount of heavier elements, Oxides, and hydrides of heavier elements, that must had condensed into particles and accreted to form final planets. The Jovian planets then were able to retain substantial amount of gas as well. Their satellite and their ring system [like that of Jupiter, sat tern] also contained ice,water and rocks [oxides and hydrides of heavier elements]. The terrestrial elements were mainly rocks and small amount of icy material. This icy material appeared on the atmosphere of earth planet or on the other planets also but much on earth planet and later helped to form ocean. The original dust grains then accreted by a process, which is still not very well understood into bigger and bigger objects. It is assumed that there were about 500 of these planetesemals roughly of the size of moon.
The merging of these planetesemals gave birth to planets in the region, now occupied by terrestrial planets. So the planets found although different in each run must have a general resemblance to what we find in the solar system. After the planets were formed each planets were too hot. Then there occurred “thermal escape”. Thermal escape process is the classical example of light gas also. It is then known as “Jeans escape”. The basic idea of jeans escape was that above some critical level, we call it “Exobase’ atoms were in high velocity tail of Max William distribution and must escaped, if they were directed upward at or above the escape velocity, was for earth 11.2 Km/second. The exo base level for the earth was500-600 kilometer. Thermal
escape phenomenon explains explain us that the most massive bodies of solar system had dense and denser atmosphere. Thermal escape also says that atmosphere were generally deficient atmosphere in light atoms such as hydrogen and helium. Thermal escape also suggests that heavy gases, even nitrogen (N) must be stable for planet earth and planetesemal moon. But Thermal escape Phenomenon theory later on found unattractive before the scientist because of following reasons that
1) The escape was from a level with low density 11) The principal term in the Jean escape equations was e –GMm/KTr where G was the Newton
or from water vapor on planet earth, which could be photo dissociated or react with hydrocarbons or with crustal iron. The solar heat then to run this flow were ionizing one and less then~100nm which contained ~ 1x10-5 of present solar spectral power. So to drive a suitable flow of Hydrogen from earth would require ~100 times as much as short wave length radiation decay over a period of few hundred million years. G. W. Wetherill[3]] suggested that earth formed 10010 million years and earth’s interior was initially very hot as a result of large asteroids or commentary or planetesemals impact events Watherill[3] suggested that earth’s core was probably formed simultaneously with accretion As a result iron, nickel were removed from earth’s upper mantle. As early as 4.5 billions years ago (Ga) volcanic gases started to release and had been relatively oxidized. Moreover many of earth’s volatile gases were probably released on impact. These process might have formed a steam atmosphere during at least in a part of accreatory period. Simultaneously the escape phenomenon went on with H and H2 Rapid hydrodynamic escape of hydrogen could drag the other gases with it particularly lighter isotopes, which were carried off more easily then heavier one. Hydrodynamic escape however became difficult after 4.5 Ga in post accretion era, because after ~4.5 Ga the solar ultraviolet flux were lower and energy available to fuel up the escape process phenomenon were greatly reduced.Further more the escape rate became limited by diffusion once hydrogen became minor component of accreatory atmosphere, as a consequence of reduction of water by in falling metallic iron rich planetesemals or asteroids as impacts. The water or ice vaporized due to heat generated by in fall of impact on earth’s surface as huge bombardments from space.
Then started the Rainy atmosphere. Once the main accreatory phase had ended, the surface heatflux of the earth had come down much and the steam atmosphere were rained out for 0.3 Ga with heavy lightening on sky of Earth. Ocean was thus formed on earth’s surface. The remaining atmosphere would probably then dominated by carbon and nitrogen compounds, mainly in form of CO2, CO, N2, NO. Next to water carbon atom was most abundant in the volatile form in earth’s atmosphere & in surface. Most of the carbon atom was in relatively nonvolatile form in the carbonate rock, under the ocean. The estimated crustal abundance of carbon was~1023, which was sufficient to produce 60-80 bars, were all of it present in atmosphere of earth as CO2. Moreover as much as 15% of these carbon resided in the atmosphere before continents of earth started to grow in the ocean and carbonates rocks began to accumulate on earth surface. This type of atmosphere was for first several hundred millions years. The mean surface temperature of earth was then~850C. Even after the main accretion period ended the earth surface environment under went further rapid changes. Significant numbers of large impactors [>100Km in diameter] continued to hit the both the earth’s and moon surface, until at least 3.8 billion years ago (3.8Ga). Some of these imp actors were of commentary of carbonaceous chondrite composition and quiet substantial amount of water and Ice were brought on earth surface for a period Of 0.7 billion years through these commentary bombardments, as if comets were used as vehicle for organic compounds as well water for earth, from space. These impacts also did effected earth’s atmosphere composition by providing
source of CO&NO. CO could have been also produced by oxidation of organic carbon in carbonaceous impacts or by reduction of ambient atmospheric CO2 by iron rich impactors. NO would have been also generated by shock heating atmospheric CO2 &N2. The heavy bombardments of impacts on earth’s surface at about3.8Ga. 3.5 Ga as evidenced by presence of microfossils and stromatolites probably started life in the ancient samples[4]. The narrow window of time between 3.8Ga and3.5 Ga was the most probable time for the life to be originated on earth’s surface. Before 3.8Ga the uppermost layer of ocean on earth’s surface would probably had been evaporated several times & repeatedly by the large impacts. Impacts however larger then 440 Kilometer in diameter could have vaporized water from entire ocean in earth sterilizing the planet with possible exception living in sediments and submarine hydrothermal region for some hundred years. Events of these magnitudes were possiblebefore 3.8 and probably before 4.5 Ga.
further vaporization of upper layer of ocean} in a jar containing CH4- NH3-H-H 2O,the earlyatmospheric gas on earth’s surface. According to Miller Urey subsequent reactions between thesecompounds organized a self replicating RNA molecule- The first life appeared in the earth.Changes in the surface temperature of the earth through out it’s history were very important forunderstanding both the geological development of earth surfaces and origin and development of lifein earth. Carl Sagon and Muller G carried out a theoretical investigation of living term changes in theearth temperature on assumption that major infrared absorbing gases in earth atmosphere had
always been vapor and carbon dioxide[6] [. But inview of accepted boundary condition for early earth, they concluded that original terrestrialatmosphere must also have contained additional absorbing gases. The earth’s early atmosphere musthad gone a significant changes in chemical composition as the postulated additional absorbing agencywas removed. Secondly because any physically probable additional absorber was likely to belong to a chemical species that figured in concerning the origin of life. Sagan & Muller considered “TheAmmonia” to be most probable candidate. The surface temperature could be calculated in twostages The first involved the computation ofeffective temperature of the planet earth Te-S (1-A)=fóTe4 where S= Solar constant, A= the spherical Abedo of earth, f=the flux factor ó =the steafanBlotzman constant. For a rapidly rotating planet, with a thick atmosphere the area of emitting
radiation is taken as 4Ï R2 where R= planetary Radius. Since the area receiving solar radiation as 4ÏR2, the flux factor becomes 4. In case of slowly rotating planets with thin atmosphere the area of emitting radiation is similarly 2Ï R2 and the flux factor f=2. The second stage of their calculation relates Te to the surface temperature Ts by an equation Ts=Te+ÄT whereÄT was the green houseeffect in the earth, which also played a vital role in the appearance of life in this planet. Onthe lifetime of the Earth for the period 4.5 to 4.0 Ga the solar constant (S) had increased by 40-45%,
since the origin of solar system. If this was to fit into the model Ts= TetÄT, then surface temperatureof earth was bellow the freezing point of water during the early phase of earth’s history i.e. the earth had to pass a “Ice cold Stage also”. But the geological evidence suggest the presence of extended sheet of liquid water on earth’s surface was the pre-requisite condition for appearance of life at least3700MYR ago Carl Sagan and Muller.G also suggested that the infant biosphere of earth was warmed by an atmospheric gas which exerted a ‘Green house effect “ by transmittingsunlight while hindering the escape of heat to space. Water vapor made the mostsignificant contribution to the green house effect in that contemporary atmosphere. Asudden fall in temperature could result it an increase in the size of polar ice caps of earth andseasonal snowfields and a corresponding fall in the atmospheric humidity. Both effects would contribute further drop in the temperature. On the other hand a sudden rise in temperature, increased the water vapor content of atmosphere. Sagan and Muller suggested that early atmosphere was very rich in ammonia gas and this ammonia provided the blanket to keep the earth sufficiently warm for life to emerge. Recent works suggested that primordial atmosphere probably contained little ammonia but relatively high partial pressure of CO2. CO2 alsoacted as blanket gas as green house gas. What ever the green house gas, ammonia or CO2, meansurface temperature of earth exceeded that time over 500c with 25% increase in solar heat flux. Now the question stands for CH4 and NH3. However CH4 and NH3 might not have been present in the atmosphere of early earth. Whether methane and ammonia were present or not in primitive earth’s atmosphere were a debatable situation and might depend on whether oxidation state of upper mantleof atmosphere varied over time or not. For that required volcanic sources where from methane andammonia become a significant component of volcanic gas. Yet the volcanic gases were there, themantle could have been oxidized gradually by recycling of water from surface to atmosphere and
atmosphere to surface, followed by volcanic out gassing of hydrogen. These process of course couldhave required hundreds of millions billions years to bring the mantle to be it’s present oxidation state .Not by mere0.7 billion years. So in absence of volcanic sources of methane and ammonia gases, the past history of bombardment atmosphere was probably dominated by carbon di oxide and nitrogen gas with traces of CO, H2, NO, N2, reduced sulpher gas. With regard to origin of life, the key and very important question was whether photochemical reaction in such an atmosphercould have generated Formaldehyde (H2CO) and hydrogen cyanide (HCN)? Theformaldehyde was needed to synthesis of backbone sugar molecule of RNA and HCN wasfor synthesis of amino acid for base sequences of RNA nucleotides. Pinto [7] showed that an efficient path way for formaldehyde synthesis existed even in carbon –di- oxide dominated atmosphere, when thesemolecule should have readily available. But formation of HCN was very much and almostdifficult because it would require then breaking up both an Nß N and a CßC triple bond [if it started N2& CO2 to form HCN] both bonds can be severed in very high temperature core of lightening discharge. Yet the resulting N and c atoms are more likely to combine with O2 atoms then with each other unless the atmospheric C:O ratio exceed unity. However Zahnle[8][] showed thatHCN could be formed by ion spherically produced N atoms reacting with photolysis by product of trace elements (1-10ppm) ofCH4. However such a scenario requires an atmospheric source of CH4. So explaining how HCN could have formed is still a major hurdle for theories of origin of Life that rely on atmosphere as a source of starting materials. When one thinks of varied molecular process at the origin of life, one can imagine that the first replicating molecule that brought life in earth was a RNA molecule. Possibly about 4.6 Billion years ago (Ga) lightening and ultraviolet radiation from sun were enough to break up simple hydrogen rich molecule of the primitive atmosphere. The fragments spontaneously then recombined into more and more complex molecules. The products of this early chemistry were dissolved in water of ocean or ponds forming a kind of organic soup, which gradually had an increasing complexity, until one fine day, quiet by an accident? - A molecule arose that was able to make crude copies of itself using buildings blocks of their molecules in that soup- which was the master molecule of life – The DNA. It took approx one million years to develop a DNA molecule from RNA molecule in the earth. It was possible that life was largely confined to sea during the Archaean period. In the ocean the atmospheric partial pressure of Co2 maintained a continuous flux of particulate organic matter for life into the deep ocean. These flux resulted from primary production in the surface layers which was limited by rate of supply of nutrients notably nitrogen and phosphorus, from reverie inputs and from the slow circulation of nutrients-CO2 rich deep ocean water. In 1950 Stainley Muller and Harold Uray did an experiment individually and isolate with all possible primitive gasses present in early atmosphere of earth in an airtight thick non breakable glass bottle and gave constant electrical sparkling discharge at the glass bottle. After 100 minutes of constant sparkling, resulted a product looking like Tar. It was extremely rich in collection of amino acids (constituent parts of protein) and nucleic acid and amino acids. But not the life.
The habitable zones for different types of stars, with our solar system as an example. As a planet is pulled in towards its star, it can be pulled away from the habitable zone.For an amino acid to form, all it would take is organic compounds and liquid water An amino acid glycine, one of the essential ingredients to life on Earth, has been found in a comet in the comet Wild 2, and not the result of terrestrial contamination. But simple the detection of organic compounds will not necessarily mean there's life on a planet, because there are other ways to generate such molecules. It simply means that there are a lot more life-giving chemicals
Gliese 581 e (foreground) is only about twice the mass of our Earth. The Gliese 581 planetary system now has four known planets, with masses of about 1.9 (planet e, left in the foreground), 16 (planet b, nearest to the star), 5 (planet c, centre), and 7 Earth-masses (planet d, with the bluish colour).Credit: ESO
1] New Super-Earth: Hot, Watery, and Nearby at Discover ;Science, Technology and Future Blog 80 beats
2] Rupak Bhattacharya, Professor Pranab kumar Bhattacharya, Ritwik Bhattacharya . Upasana Bhattacharya, Dalia Mukherjee , Aindrila Mukherjee , Tarun Biswas “‘Theory of Pan-spermia as well breaking the symmetry is however essential for development of life in other worlds in other universes too” Comments 14th Published for the featured article by Tom Siegfried “ Infinity Success in coping with infinity could strengthen case for multiple universes” The Science News June 6th, 2009; Vol.175 #12 (p. 26)
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Acknowledgement- To diseased late Mr. Bholanath Bhattacharya and late Mrs.Bani Bhattacharya(parents of of residence 7/51 purbapalli, Po-sodepur Dist 24 parganas(north) , Kolkata-110,WestBengal , India
By Declaration
[This Article has been published previously in Journal Nature, www. bautforum.com (BAD astronomy and Universe Today forum, Science News ]
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