What Is in Their Air?
Earth’s atmosphere is divided into layers:
The troposphere is from the Earth’s surface up to approximately 9 km (30,000 ft) at the polar regions and approximately 17 km (56,000 ft) at the equator, with an average altitude of around 12 km (39,000 ft). It is in the troposphere where all life on Earth exists, aside from a few intrepid aviators, astronauts, and perhaps some micro-organisms blowing in the wind. It is also nearly exclusively where all weather occurs, though some storm clouds can push though into the stratosphere.
The stratosphere, separated from the troposphere by the tropopause, extends up to 50 to 55 km (164,000 to 180,000 ft), and is where you will find the ozone layer. The stratosphere ends at the stratopause, on the other side of which begins the mesosphere.
The mesoshpere is the highest layer in which clouds will form, just below the mesopause which resides at 80 to 85 km (260,000 to 280,000 ft). Within the mesosphere is also where most meteors disintegrate once entering Earth’s atmosphere. Beyond the mesopause begins the thermosphere.
The thermosphere height varies greatly from 500 to 1000 km (1,600,000 to 3,300,000 ft) as a result in variations of solar activity. Temperature in the thermosphere can reach as high as 1773 K (1500 °C, 2700 °F), however, the atmosphere is so thin at this altitude that heat energy doesn’t transfer efficiently at all, and you would never feel that heat by putting down the window and sticking your hand out. Though other bad things would most likely happen. Within the thermosphere are the auroras, ionosphere, and the International Space Station.
And finally, past the thermopause, or a.k.a. the exobase, is the exosphere which extends out to about 10,000 km (33,000,000 ft). Most artificial Earth satellites orbit within the exosphere, and the auroras will peek in occasionally.
But is Earth’s atmosphere unique?
Arguably, even Earth’s moon has an atmosphere. Of sorts. Outgassing from within the moon itself provides a thin amount of “lunar atmosphere” which is so sparse, the surface of the moon is considered to exist in a vacuum. But it is there, and was once, about 3 to 4 billion years ago, twice the density of the current Mars atmosphere.
The Sun? Yes, the Sun has an atmosphere, which consists of four layers. The Chromosphere begins at about 500 km up to roughly 2500km. The temperature within the chromosphere increases from about 4100 K to around 20,000 K. Beyond the chromosphere is the Transition Region where the temperature jumps to 1,000,000 K. The most recognizable of the layers is the Corona, without the lime. The corona boasts an average 1,000,000 K to 2,000,000 K, with its highest temperatures reaching 8,000,000 K to 20,000,000 K. Now that will sufficiently roast a hot dog. And the final layer of the solar atmosphere is the Heliosphere, extending out to 50 AU. One AU, or Astronomical Unit, is the radius of Earth’s orbit, about 150,000,000 km. This means we exist well within the atmosphere of the sun, which is why we feel the warmth so well.
The Messenger possesses nearly no atmosphere, though what is there contains hydrogen, helium, oxygen, sodium, calcium, potassium and, surprisingly, water vapor. Due to Mercury’s eccentric orbit being so close to the Sun, solar wind pressures are significant enough to produce a cute little tail, similar to that of a comet.
This beauty’s atmosphere is anything other than beautiful, consisting almost entirely of carbon dioxide, with a little nitrogen. Clouds on Venus are sulfuric acid, not water, obscuring the planets surface from outside its atmosphere. The temperature at the surface is about 740 K, and the pressure is equivalent to being 900 m or 3000 ft below the water surface here on Earth.
Similar to Venus, the God of War has an atmosphere consisting mostly of carbon dioxide, with a little argon, as well as, again, nitrogen. The layers are the easily remembered lower atmosphere, middle atmosphere, upper atmosphere, and exosphere.
The largest atmosphere in our star system has layers, troposphere, stratosphere, thermosphere, and exosphere, similar to Earth, though no mesosphere. The Jovian troposphere, the visible portion we associate with Jupiter, is comprised of mostly of Hydrogen and Helium, with only slight amounts of methane, ammonia, hydrogen sulfide and water, with clouds of ammonia crystals. As Jupiter has no solid surface, the lower levels of the troposphere gradually condense into liquid hydrogen and helium. Without a solid surface, the generally accepted surface of Jupiter is based on where the atmospheric pressure is 100 kPa. Furthermore, this atmosphere’s layers are described in pressure more so than altitude. Jupiter’s troposphere is nearly 143,000 km wide. That is more than 22 Earth’s.
Similar to Jupiter, Saturn is also a gas giant, though not quite as giant. Less is known of Saturn’s atmosphere, though again, it is much as Jupiter’s. Mostly hydrogen, with much less helium. Saturn’s clouds are also made up of ammonia crystals. This visible cloud portion of Saturn is over 120,000 km, nearly 20 Earth’s wide.
Giggle all you like, but this ice giant is similar to Jupiter and Saturn in so much as it’s atmosphere is primarily Hydrogen and some helium. However, due to average temperatures as low as 49 K, there is substantially more water, ammonia, and methane, existing in the form of ice.
Another ice giant, and like Uranus, Neptune’s atmosphere is made up of hydrogen and helium, as well as significant amounts of ice from water, ammonia and methane.
Notice how the amount of information decreases the further out from the center of the solar system we go? Few missions have been sent to our distant neighbors, who still reside in our own galactic back yard.
What about those planets we have detected even farther away?
It should be no surprise that we know even less about atmospheres residing outside of our star system. That we are at all aware of atmosphere light-years away on its own is impressive. Observations of these atmospheres have been mostly of gas giants similar to Jupiter and Neptune, though 55 Cancri e is a Super Earth, only approximately 8.63 times the mass of Earth. Exoplanet atmospheres contain in varying amounts, hydrogen, helium, sodium, carbon monoxide, carbon dioxide, methane, and even water, depending on the planet.
But why is water so important, and from where does it originate?
Source information provided by NASA.