Earth is the only known planet that sustains life. Its atmosphere provides us with oxygen, protects us from the Sun’s radiation, and creates the barometric pressure needed so water stays liquid on our planet.
But while Earth’s atmosphere stretches for about 10,000 km (6,200 miles) above the planet’s surface, only a thin layer is actually habitable.
This graphic, inspired by Andrew Winter, shows just how small Earth’s “habitable zone” is, using the state of Florida as a point of reference.
Earth’s Like an Onion: It Has Layers
Our planet’s atmosphere is made up of a unique cocktail of gases—roughly 78% nitrogen and 21% oxygen, with trace amounts of water, argon, carbon dioxide, and other gases.
It’s separated into five different layers:
- Exosphere: The uppermost layer of our atmosphere that melds into outer space.
- Thermosphere: Begins at around 80 km (50 miles) above sea level and extends to approximately 600 km (372 miles), reaching temperatures as high as 2,000°C (3,600°F).
- Mesosphere: Around 30 km (19 miles) in range, meteors burn as they pass through this layer, creating “shooting stars.”
- Stratosphere: Home to the ozone layer, which is responsible for absorbing a majority of the sun’s radiation.
- Troposphere: The closest layer to ground. It stretches about 7–15 kilometers (5–10 miles) from the surface.
The troposphere makes up approximately 75-80% of the atmosphere’s mass, as it’s where most of the dust, ash, and water vapor are stored. But only a part of this layer is suitable for human life—in fact, the atmosphere’s habitable zone is so small, several mountain ranges extend beyond it.
Reaching Into Earth’s Atmosphere: Extremely High Altitudes
Elevations above 5,500 meters (18,000 ft) are considered extremely high altitude and require special equipment and/or acclimatization in order to survive. Even then, those who choose to venture to extreme heights run the risk of getting altitude sickness.
When it comes to the world’s tallest mountain ranges, the Himalayas are the highest. At their peak, Mount Everest, the Himalayas reach 8,848 m (29,000 ft) above sea level.
Despite the dangers of extreme altitude, hundreds of mountaineers attempt to climb Mount Everest each year. On Everest, the region above 8,000 m (26,000 feet) is referred to as the “death zone,” and climbers have to bring bottled oxygen on their trek in order to survive.
Life Beyond Earth
Earth is the only known planet with an atmosphere we can survive in. And even on Earth, certain areas are considered dead zones.
But there may be other life forms out in the galaxy that we haven’t discovered. Recent research in The Astrophysical Journal predicts there are at least 36 intelligent civilizations throughout the galaxy today.
So life may very well exist beyond Earth. It just might look a bit different than we’re used to.