TWIN EARTH: The Possible Candidates
by Vani Chaturvedi
Guided by:
Tafheem Ahmad Masudi and Sukant Khurana
“It’s double the chuckle and double the smirks, and double the trouble if you’re blessed with twins”. The scientific research shows the possible candidates that made our universe blessed with an Earth twin. But what do we mean by Earth twin? The Earth twin refers to a planet or moon having same environmental conditions as of earth. In past there possibility of existence was described by two contrasting themes. The first is mediocrity principle which says that Earth like planets are common in universe and the second is rare earth hypothesis that says they are very rare. And, the discovery led by scientists of exosolarsystem supports rare earth hypothesis. But this will not disappoint cause we the young generation is a techgeek and progressing from a simple bot to a human bot the day will not be far when we will artificially produce an earth twin by terrraforming. Earlier Mars, Venus, Titan were announced as the possible candidates for the twin earth. The discovery of Earth twins are based on certain attributes. The major one is the terrestrial planet. Others are: planet size, surface gravity, star size and type (i.e. solar twin), orbital distance and stability, axial tilt and rotation, similar geography, oceans, air and weather conditions, strong magnetosphere and even the presence of Earth-like complex life. But some of this assumed factors may be different to that of Earth because of it’s own formation history. For example the Earth’s atmosphere was not always oxygen-rich and this is a biosignature from the emergence of photosynthetic life. The formation, presence, influence on these characteristics of the Moon (such as tidal forces) may also pose a problem in discovering an Earth twin.
The first is size: It is generally considered as an important attribute since planets with size similar to Earth are capable of having a terrestrial nature and an earth like atmosphere. According to the size criteria, the closest planetary mass objects by known radius or mass in race to be an earth twin are:
Dealing in terms of habitability it is clearly visible that size alone is not a sufficient criteria. Temperature must also be considered as Venus and the planets of Alpha Centauri B (discovered in 2012), Kepler-20 (discovered in 2011 [4]), COROT-7 (discovered in 2009) and the three planets of Kepler-42 (all discovered in 2011) are very hot, and Mars, Ganymede and Titan are frigid worlds, resulting also in wide variety of surface and atmospheric conditions. The masses of the Solar System’s moons are a tiny fraction of that of Earth whereas the masses of extrasolar planets are very difficult to accurately measure. However discoveries of Earth-sized terrestrial planets are important as they may indicate the probable frequency and distribution of Earth-like planets.
Terrestrial
The second criterion is that an Earth twin must be terrestrial, i.e. it should possess a similar surface geology — a surface composed of similar surface materials. The closest known examples are Mars and Titan and while there are similarities in their types of landforms and surface compositions, there are also significant differences such as the temperature and quantities of ice.
Many of Earth’s surface materials and landforms are formed as a result of interaction with water (such as clay and sedimentary rocks) or as a byproduct of life (such as limestone or coal), interaction with the atmosphere, volcanically or artificially. A true Earth twin therefore might need to have formed through similar processes, having possessed an atmosphere, volcanic interactions with the surface, past or present liquid water and life forms.
Temperature
The next attribute is temperature, there are several factors that can determine planetary temperatures and therefore have several measures that can draw comparisons to that of the Earth in planets where atmospheric conditions are unknown. First is the measure of Equilibrium temperature that is used for planets without atmospheres. Second for planets with atmosphere, a greenhouse effect is assumed. Finally, surface temperature is used. Each of these temperatures is affected by climate, which is influenced by the orbit and rotation (or tidal locking) of the planet, each of which introduces further variables.
Below is a comparison of the confirmed planets with the closest known temperatures to Earth.
Solar analog
Another criterion towards discovering an Earth twin is that it should orbit a solar analog, that is, a star much like our Sun, may be similar photometrically or in terms of spectral type. It follows that the composition of a planet around a solar twin with similar metallicity might have a similar composition to Earth. Also, this would help eliminate stellar extremes and variability that may be applicable to other types of stars.
While planets have been discovered orbiting similar stars to the Sun, most are gas giant or super-Earth sized, and many of these planetary systems have shown to be surprisingly different from our own. This measure is not entirely reliable as Mars and Venus also orbit the Sun but have different compositions and properties.
So far the scientist’s efforts paid off in finding the closest Earth’s twin or cousin as mentioned in newyork times The planet, known as Kepler 186f, named after NASA’s Kepler planet-finding mission, which detected it, has a diameter of 8,700 miles, 10 percent wider than Earth, and its orbit lies within the “Goldilocks zone” of its star, Kepler 186 of it’s star not too hot, not too cold, where temperatures could allow for liquid water to flow at the surface, making it potentially hospitable for life. Kepler 186f is not a perfect replica, however. It is closer to its star — a red dwarf that is smaller, cooler and fainter than our sun — than the Earth is to it; its year, the time to complete one orbit, is 130 days, not 365. It is also at the outer edge of the habitable zone, receiving less warmth, so perhaps more of its surface would freeze.
“Perhaps it’s more of an Earth cousin than an Earth twin,” Dr. Barclay said.
On the other hand, with its greater mass Kepler 186f could conceivably have a thicker insulating atmosphere to compensate. Red dwarfs emit more of their light at the longer infrared wavelengths, which would be more readily absorbed and trapped by ice and gases like water vapor and carbon dioxide. But what can we say about the intelligent life even if we do discover a TWIN Earth? Talking about microbial life they exists even today they are here for at least 3.5 billion years a very long time when we consider the first rock formation about 3. 8 billion years ago. The chances are more for existence of microbial life on habitable planets within our home galaxy. But the question about more complex life forms existence like insects and planets is still a question.
It’s very hard to say how likely we are to find other intelligent life forms. The oldest fossils of our species, Homo sapiens, are less than 200,000 years old. That’s a geological microsecond, just 0.000057% of the time microbes have been around. If like on Earth intelligent life takes much longer to evolve than microbial life, it might be rare. But some galaxies and solar systems are much older than ours, so maybe other intelligent life has formed; however, it may be long dead. Finding living intelligent beings is a matter of both space and time.
There may be a twin, but they are one of a kind.
References:
1.http://kepler.nasa.gov/Mission/discoveries/kepler20e/ 2.https://web.archive.org/web/20110505000325/http://exoplanet.eu/papers/Kepler-9-d.pdf 3.http://www.nasa.gov/ames/kepler/nasas-kepler-discovers-first-earth-size-planet-in-the-habitable- zone-of-another-star
4. http://www.nasa.gov/mission_pages/kepler/news/kepler-20-system.html Hand, Eric (20 December 2011). “Kepler discovers first Earth-sized exoplanets”.
5. http://solarsystem.jpl.nasa.gov/planets/profile.cfm?Object=Mars&Display=Facts 6. Mallama, A. (2007). “The magnitude and albedo of Mars 7. Mallama, A.; Wang, D.; Howard, R.A. (2006).”Venus phase function and forward scattering from H2SO4"
8.To stellar primary
Photo source: Wikipedia.
Hey!! This is Vani Chaturvedi, a second year undergraduate from IIT KANPUR.I am currently pursuing my Bachelor Of Science (B.S.) degree in Earth Sciences. I don’t know what I want to be in future but I know what I want to do now. A true enthusiasm towards space exploration led me to explore this field. Being a Sherlock fan I am much more oriented towards thinking and solving mysteries of space. Hoping to solve one someday!!
Linkedin: https://linkedin.com/in/vani-chaturvedi-a9168a140/
Gmail: vanichaturvedi@gmail.com
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Guides:
Tafheem is a space enthusiast working in the field of astrobiology and is studying self sustaining environments in outer space. Together with a dynamic research team, he is a establishing a space learning platform. Also he is working towards creating first of its kind subject specific interactive educational gaming modules in various Indian schools.
https://www.linkedin.com/in/tafheemmasudi/
Dr. Sukant Khurana runs an academic research lab and several tech companies. He is also a known artist, author, and speaker. You can learn more about Sukant at www.brainnart.com or www.dataisnotjustdata.com and if you wish to work on blockchain, biomedical research, neuroscience, sustainable development, artificial intelligence or data science projects for public good, you can contact him at skgroup.iiserk@gmail.com or by reaching out to him on linkedin https://www.linkedin.com/in/sukant-khurana-755a2343/.
Here are two small documentaries on Sukant and a TEDx video on his citizen science effort.
