“There is no planet like Earth!” isn’t that a significant statement? But have you ever wondered why it was uttered in the first place? Well, the speaker of this statement surely knew that the life-giving fuel we breathe exists in the air, (yes, I am talking about our beloved oxygen, but wait! Air is a collective term used for the layer of gases found on each planet and we call it as atmosphere) without a suitable atmosphere, no trace of life can ever be seen,  so the study of planetary atmospheres and their potential for life becomes fundamental, especially in this age where with gleaming eyes we are trying to find potentially habitable planets.

1. The Atmosphere in Simple Terms:

Our solar system’s planets and some of its smaller bodies have an outer layer of gas known as the atmosphere. The atmosphere is often found atop a denser, rocky crust or planetary core. Atmospheres may stretch into space for thousands of kilometers.

2. The Planetary Atmosphere and Universal Observations:

The term ‘planētēs’(meaning: “wanderers”) was used by the Greeks to denote the planets.

The primordial atmosphere of Earth had formed due to sulfur compound outgassing, and additional carbon dioxide had evolved due to volcanic activity. Although nitrogen became the dominating component, oxygen did not appear until roughly halfway through our planet’s existence. An outbreak of cyanobacteria caused the Great Oxygenation Event.

The advent of dioxygen in the atmosphere caused an abundance of oxygen in the earth’s biosphere, air, sea, and land, which is required for the development of multicellularity in life on Earth. Oxygen is essential in many biochemical and physiological processes, including cellular respiration.

The range of a planet’s atmosphere contains information on its diverse physical and chemical features, which give crucial insights into many atmospheric processes as well as the planet’s genesis and evolutionary history. Almost a century of spectroscopic observations of solar system planets and moons have yielded a large treasure of knowledge on their variety in all of these features.

The atmospheric variety of the solar system is itself a sight to behold. Venus and Mars are planets that have a relatively thin atmosphere that surrounds a rocky surface. Mars and Venus’s atmospheres are carbon dioxide rich. Jupiter consists of huge storms and NH3 clouds These characteristics illuminate the many processes of atmospheric evolution and finally the unique Earth.

planetary atmospheres and their potential for life
Image by Daniel Roberts from Pixabay/Copyright 2019

3. The Planetary Atmospheres and Their Potential for Life in Our Solar System: is There Hope For Life?

3.1 Mercury’s Atmospheric Composition:

As we all know Mercury is the smallest planet in the Solar System, it is about the one-third size of Earth. This crater-filled, stony planet is hardly bigger than our Moon and is at a distance of 58 million kilometers from the Sun. A day on Mercury is roughly equal to 59 days on Earth. Mercury is one of the rocky worlds of our solar system.

Yet, because of the planet’s sluggish rotation, its bright side experiences extreme temperatures of roughly 450 °C (840 °F) while its dark side experiences temperatures of -180 °C (-290 °F).

According to NASA, Mercury’s atmosphere is a “surface-bound exosphere”, effectively a vacuum. It includes 0.5% Potassium (K), 6% Helium (He), 22% Hydrogen (H), 29% Sodium (Na), and 42% Oxygen (O) with trace quantities of water, argon, nitrogen, carbon dioxide, xenon, neon, and krypton. Due to its low gravity, it is quite a challenge for it to hold onto an atmosphere thereby it is constantly bombarded with solar flares. Therefore, life as we know is quite impossible to exist on Mercury due to solar radiation and extreme temperatures.

Mercury neither has any moons and was named after the swiftest Roman messenger god.

3.2 Venus’s Atmosphere and its Composition:

One day on Venus lasts 243 Earth days. With 154,000 times as much carbon as Earth’s atmosphere, Venus has a thick, toxic atmosphere and an extreme temperature that will make us crisp in a second. Venus is called Earth’s twin rather it is the evil twin and the reason for it will be the runaway greenhouse effect which was triggered by volcanic activity and the loss of water from Venus’s atmosphere. This process condemned Venus to become the hellish landscape it is today.

Venus is just not a little hotter than its twin but it has a whooping temperature which is over 800 degrees F. Earth and Venus are mirror images of heaven and hell.

The Venus atmosphere is drenched with CO2 whereas the Earth’s atmosphere is 78% Nitrogen, 21% oxygen, and 1% everything else. CO2 comes in at a mere 0.039% of the air that we breathe right now and on the other hand, Venus accounts for more than 95% of CO2 as its atmospheric composition.

Moreover, sulfuric acid clouds that are yellow surround it all of the stated facts make it impossible to assume signs of life on Venus.

Exploring Planetary Atmospheres and Their Potential for Life 1
Image by Arek Socha from Pixabay/Copyright 2016

3.3 Earth’s Atmosphere and its Composition:

The only planet in our solar system known to consistently contain surface liquid water bodies is Earth. Earth has carbon-based life as it is the primary component in all life forms on earth.

The spotlight should be on the carbon cycle if we are to comprehend the Earth’s amazingly stable long-term climate. Carbon dioxide is released into the atmosphere by volcanic activity and is ultimately removed by two processes: the first is the physical burial of organic carbon in coal, gas, oil, and shale, and the second is the chemical formation of carbonates in the oceans, such as coral reefs or limestones. Carbonates contain carbon, and their production traps it for lengthy periods.

Along with being in our star’s habitable zone, another reason why the earth is a suitable host is that the earth’s tectonic system is an active one, it gives it proper water and gas cycles and in itself, the tectonic system moves slowly so that it maintains the climate. All these facts together bestowed earth with the gift to support life. The other planets do not have this beauteous combination for the flowering of earth organisms.

The earth also has ozone in the upper atmosphere which protects us from ultraviolet radiation. The infamous hole in the ozone is a major threat to life on earth.

The Earth has stayed habitable for 4 billion years because of the harmonious dance between CO2, temperature, and weathering. We have the privilege to be here because nature decided us to be right here. The primitive life form on earth were microbes.

Another remarkable characteristic of Earth is photosynthesis, it is a process in which light energy is converted into chemical energy.

3.4 Mars Atmospheric Composition:

Mars, a planet that Earthlings are attempting to transform into a habitable planet, however, Mars is hundreds of degrees colder than Earth, has a hundred times less atmosphere, and that atmosphere has little oxygen (source: NASA)

The martian atmosphere is thin and consists of more than 95% Carbon dioxide and if this isn’t a horrifying fact then due to its thin atmosphere, it is hit by higher solar radiations and is quite famous for its dust storms. Thereby it cannot be compared at all to the earth’s life.

There is no liquid water on the surface but The research conducted by a team of scientists led by Edwin Kite at the University of Chicago concluded that once the temperature was warm enough for possibly livable lakes and rivers of water to exist based on trends in the distribution of precipitation-fed rivers.

3.5 Jupiter’s Atmospheric Composition:

Jupiter, the gas giant and also the holder of the title: “the largest planet in the solar system”. One rotation by Jupiter is completed in about 10 hours and it takes around 12 Earth years for completing one revolution.

The atmospheric gases of Jupiter mostly comprise Hydrogen and Helium (quite similar to the composition of our sun) It is an endless stretch of atmosphere i.e there is no surface. The temperature here is so high that it may melt tungsten. Jupiter and Saturn have hydrogen-rich atmospheres.

Jupiter is the planet with the fastest rotation. Jupiter’s famed Great Red Spot is a massive superstorm. The Galileo probe was the only human-made object to enter Jupiter’s atmosphere in 1995; it lasted only 58 minutes before losing contact and being destroyed by the pressure.

Exploring Planetary Atmospheres and Their Potential for Life 2
Image by Reimund Bertrams from Pixabay/Copyright 2012

3.6 Saturn’s Atmospheric Composition:

Standing tall among the giant planets, Saturn is the second largest planet among all the planetary bodies. “Saturn is approximately 75% hydrogen and 25% helium with traces of other substances like methane and water ice” – ESA. Like Jupiter it to doesn’t have a solid surface but it is speculated that it might have a solid core and thereby becomes unfit to be called a habitable world.

.One of the gas giants Saturn rotates on its axis once every 10.7 hours and orbits the sun every 29 Earth years.

NASA discovered that Saturn may be the only planet with a warm polar vortex at both poles. “The vortex is punctured by a compact spot that is the warmest place on the planet”. The storm on the Northern pole is distinctive in that it is shaped like a hexagon.

The form of the Earth’s polar vortex is a little askew, owing to mountains, seas, and other characteristics that impact the passage of air. Yet, because Saturn is a gas giant, there is nothing to destabilize the polar vortex, giving it the benefit of symmetry and the single force regulating the atmosphere.

The hexagonal pattern was discovered in photographs from NASA’s Voyager 2 spacecraft in 1988, but NASA’s Cassini mission has provided higher-quality images of it.

“Very few missions have visited Saturn: Pioneer 11 and Voyagers 1 and 2 flew by: but Cassini orbited Saturn 294 times from 2004-2017.” -NASA

3.7 Uranus Atmospheric Composition:

uranus’s atmosphere is similar to Jupiter’s and Saturn’s in its primary composition of noble gases: hydrogen (83%) and helium (15%), but it contains more “ices” such as water, ammonia, and methane(2%), along with traces of hydrocarbons. It is the coldest planetary atmosphere in the Solar system with a surface temperature of -353 degrees F.

Uranus has enormous pressure and would crush any life that Earth requires sunlight to provide energy, there is no process inside Uranus, like volcanism on earth, that would give life inside the planet a form of energy.

3.8 Neptune’s Atmospheric Composition:

Neptune’s atmosphere is thick and mostly consists of Hydrogen with little levels of Helium and methane. It is the absorption of red light by methane that gives Neptune its vibrant blue coloration. -373 degrees Fahrenheit is the average temperature of Neptune.

Neptune’s rotation takes place in 16 hours and a complete orbit around the sun takes about 165 earth years.

4. Is There Any Moon That Holds the Chance to Support Life?

Titan, Saturn’s biggest satellite (and the second largest in the solar system after Jupiter’s Ganymede), is an intriguing feature of Saturn. Titan, the most Earth-like object in the solar system, is the only Moon known to have an atmosphere composed of nitrogen and methane. Several ideas about Titan have recently been proven by the Cassini spacecraft and the European-based Huygens probe, including witnessing clouds, signs of rain, and seasonal fluctuations ( comparable to Earth’s water cycle).

4.1 Is Life Possible on Titan?

It would not be a bad estimate to accept the possibility of life on Titan, but the life discovered will not be suitable even for Earthlike microbes. Despite it resembles Earth, it does not enjoy Mars’ (relatively) pleasant temperature. Titan’s shorelines and lakes are filled with methane and ethane rather than water, and the temperature drops to 300 degrees below zero Fahrenheit. As a result, any type of life would be very different from Earth.

It wouldn’t be a wrong guess if one agrees to the existence of life on Titan but the life found will not be a comfy place for Earthlike microbes. Though it looks strikingly like Earth, it doesn’t enjoy the (relatively) balmy climate of Mars. The shorelines and lakes witnessed on Titan are filled with methane and ethane rather than water and the temperature reaches 300 degrees below zero Fahrenheit.

Titan’s atmosphere is mostly nitrogen, with a hint of methane. Titan may also contain an underground ocean of water.

5. Extrasolar Planets:

Studying other planetary systems helps us understand the story of our solar system. It will also aid us in answering one of science’s and philosophy’s most fundamental questions: are we alone? Current or next-generation observatories may be able to locate terrestrial planets in their planets’ liquid water habitable zones that have atmospheric spectra showing the existence of gases that would only exist in certain combinations with the presence of life.

There are chances we might discover instead, life is far more difficult to find than we anticipated. This means that either life is uncommon or we don’t understand its effects on its environment well enough to identify it. Whatever occurs, we will learn a lot about our place in the cosmos.

One-third of exoplanets discovered over the past decades have been called super earth.

Exploring Planetary Atmospheres and Their Potential for Life 3
Image by WikiImages from Pixabay/ Copyright 2011

6. A Few Notable Space-Based Telescopes and Satellites:

6.1 James Webb Space Telescope:

The James Webb Space Telescope (JWST) has the potential to change the way scientists investigate exoplanetary atmospheres. The primary benefits of JWST for exoplanet spectroscopy are obvious: its enormous aperture and hence great sensitivity, as well as its wide spectral spectrum, particularly in the infrared. Much research has been conducted to study the science that can be undertaken using JWST.

JWST is undoubtedly revolutionizing our understanding of big planets, which will be the best in the world to study exoplanet atmospheres as evidenced by current facilities. This is especially evident when one considers that the variety of species that JWST will be able to study in hot Jupiters may outnumber what we know about Jupiter in our solar system, which is now the most studied giant planet. The first series of photos featured star birthplaces and deathbeds, as well as a cosmic waltz of galaxies.

according to NASA the vantage point of JWST’s investigation of exoplanets is “the distant planets/worlds that orbit stars other than the Sun”. “All the prominent molecular species containing the key volatile elements (e.g. O, C, and N) such as H2O, CO, CH4, CO2, HCN, C2H2, and NH3, have strong spectral features in the JWST spectral range”.

The planets of our solar system are a good place to start, “We will be observing the solar system with the James Webb Space Telescope, and have been doing so,” Milam explained. The JWST team has already published stunning photographs of Mars, Jupiter, and Neptune, as well as views of the DART impact on the asteroid Dimorphos in September 2022.

JWST began its 2023 by confirming an exoplanet. The exoplanet, officially known as LHS 475 b, is almost precisely the size of Earth, measuring 99% of our home planet’s diameter. NASA stated on January 11 that a team of two researchers — Kevin Stevenson and Jacob Lustig-Yaeger of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland — used the JWST to confirm the exoplanet. (Source: The Hindu)

6.2 Nasa’s Kepler Space Telescope:

In this galaxy, we are quite sure the planets are orbiting their stars and with immense dedication, the Kepler telescope was used to study a distant planet.

6.3 Infrared Transmission Spectroscopy:

Infrared transmission spectroscopy is also used to identify and detect exoplanets “by comparing them with high-resolution spectra from atmospheric modeling codes”. This determines the planet’s orbital velocity and aids in determining its real mass and orbital inclination.

6.4 Transiting Exoplanet Survey Satellite:

As per NASA, TESS observes huge regions of the sky, known as sectors, for around 27 days at a time. These extended glances enable the satellite to detect variations in stellar brightness produced by a planet passing in front of its star from our perspective, a phenomenon known as a transit.

6.5 Hubble Space Telescope

The Hubble Space Telescope was named after the renowned astronomer Edwin Hubble. Hubble was deployed in April 1990 and its significance lies in the fact that it was the most advanced telescope since “Galileo’s telescope”. Since its launch in 1990, Hubble has made over 1.2 million observations. Hubble never visits stars, planets, or galaxies. It photographs them as it whirls around the Planet at around 17,000 mph. (source: NASA)

7. A Search for Earth-like Planets:

On our Earth as well as in space there are several observatories and telescopes set up to search for exoplanets and Earth’s twins, To name a few: the Transiting Exoplanet Survey Satellite (TESS), the Kepler Space Telescope, and the James Webb Space Telescope (JWST), and others.

The quest to find Earth 2.0 refers to finding a planet that is quite similar to Earth in terms of composition, size, and distance from its host star, and could also be supporting life as we know it. These planets orbit around their sun-like stars.

YouTube video

8. Potentially Habitable Planets:

8.1 Kepler-452b

Also called KOI-7016.01 is a “super-Earth exoplanet” found orbiting in the border habitable zone of the sun-like parent star: Kepler-452. “It’s around 1,800 light-years (550 pc) away from Earth in the constellation Cygnus”. It is the sole planet identified by Kepler.

8.2 GJ 1002b and GJ1002c

GJ 1002 is a red dwarf star, with barely one-eighth the mass of the sun,” study co-author and IAC researcher, Vera María Passenger, said in the statement”. It’s a chilly, dim star. This suggests that its habitability zone (Goldilocks zone) is quite near to the star. The innermost planet, GJ 1002b, takes around 10 days to orbit the star, whereas the outermost planet, GJ 1002c, takes 21 days.” (source: space.com)

Other extraterrestrial planets like Gliese 667Cc, Kepler-62f, Kepler-69c, Kepler 186f, Kepler 442b, Proxima Centauri and Trappist- 1e are earth-like planets in size especially and provide us hope that there might be life beyond.

By studying the extrasolar planet’s atmosphere and the gases produced by it, scientists can discuss the possibility of life on these distant planets.

9. What do Exoplanets Teach Us?

While exploring the cosmos, we may be approached by the thought that we may or may not be the only ones, but our soul entirely must preserve what has been bestowed upon us, and before venturing onto distant worlds, we must preserve ours right now because global warming has blown our Earth out of proportion, and the last thing we want is to leave behind our haven into a lifeless rocky world.

Conclusion:

To comprehend the beginning and end of the cosmos, as well as the long-term survival of our species, we require a firm grip on the study of planetary atmospheres and their potential for life as well as the ability to express gratitude to Mother Earth for her fond care.

 

Last Updated on by Himani Rawat

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