For nearly a century, scientists around the world have been searching for signs of alien civilizations, but have found none.
The universe is 93 billion light years old, containing trillions of stars and countless planets. The solar system and the Earth are small and common in the universe, but only the Earth gave birth to a higher intelligent life.
Therefore, scientists take the Earth's environment as a model to search for possible life stars in the universe, such as atmosphere, water, etc., When a planet has one or more of the above characteristics, they will become the object of close attention of astronomers.
The exoplanet Kepler 22b, which is considered the most Earth-like planet in the world, is 638 light-years away from our solar system, making it unlikely that we'll be able to get there for another few hundred years with current technology.
Perhaps we are always looking deep into space and rarely notice the inner planets of our solar system. Have you ever imagined that there might be a leafy world six billion kilometers away from Earth?
January 8th, 1610
Galileo used homemade 20 times refracting telescopes to watch the skies, discovered the moons of Jupiter for the first time. Due to the Galileo used a telescope magnification is very small, so the resolution is very low 39bet-xì dách-phỏm miền bắc-tiến lên miền bắc-xóc đĩa-game bắn cá, Europa and IO at the beginning is regarded as a single dot, record was the same planet, This error was corrected until the next day. If this mistake had not been corrected, we would not have today's protagonist: Europa.
In the past hundred years, as a result of the limitation of the observation technology, Europa's diameter of more than three thousand kilometers, only the size of the area of Africa does not cause the attention of scientists, in the 1960 s, scientists define the Europa to "death star", because it is the entire surface of the earth, which was surrounded by a thick ice package even the most warm equator position average temperature of 163 ℃ below zero only, At the cold poles, the average temperature is as low as -223 ℃.
No known form of life could have thrived in this extreme cold, so scientists have dubbed it the Death Star.
If it's already a Death Star, what's the point of foliage? The turn of events came in 1979, when Voyager 2 made a major discovery that turned a Death Star into a "very likely planet for life."
January 6, 1979
Voyager 1 flew by Jupiter and also took a shot of Europa. In thousands of images sent back to Earth by high-gain antennas, Europa's icy surface is almost crystal clear. It is more than 20 kilometers thick, but the smooth surface is full of dark brown textures, cracks that have led scientists to a bold guess. We'll leave that off the table for now.
Voyager one besides back to image, also detected Europa's thin atmosphere. It is important to note that the main components in atmospheric oxygen, to know that even is endless miles of the earth's life, its main composition is nitrogen atmosphere rather than oxygen. Europa, the extremely cold planet, why will produce large amounts of oxygen?
Europa's surface is full of cracks and crack seems to have a material in a tight fit edges, like the ice after being torn, underground material quickly piled up, and this phenomenon will appear only in the geologically active objects, the scientists also found that Europa impact traces is few, for a existed for billions of years of celestial bodies is very strange, The only explanation is that frequent geological activity would quickly erase the impact marks.
By travelers number two on the IO saw a volcanic eruption, the scientists found that IO, Europa, ganymede and three object in a state of resonance, their gravitational pull each other, the process of rock friction produced a huge quantity of heat, the heat is enough to make close to the rock of the ice to melt, and keep it liquid state, This gives scientists more credence to the idea that Europa might have a warm ocean hidden beneath its icy crust.
In 2013, NASA announced that Europa is a silicate and water planet with an ice sheet about 23 kilometers thick, the same thickness as Earth's crust. Beneath the ice sheet, there's a subsurface ocean 100 kilometers deep, astronomer Jeff Schaefer said. Youde believes this is the most likely place for life other than Earth.
On Europa's surface, the Galileo probe photographed a giant water fountain 20 kilometers high.
And the abundant oxygen in the atmosphere comes from this liquid water being radiated by the sun, evaporating into hydrogen and oxygen. Europa has too little mass for its own gravity to hold on to the hydrogen, so the hydrogen escapes into outer space, while the oxygen, which is a little heavier than the hydrogen, stays on Europa's surface.
In a joint paper published in the prestigious journal NATURE, US and German astronomers said they believed Europa's southern hemisphere should contain large quantities of oxygen and unescaped hydrogen, formed by the sun's radiation from liquid water in fountains.
Europa seems to have all the elements needed for life: water, oxygen and geological activity, so whether life could exist in its oceans will require further exploration.
In 2024, NASA will launch a man-made probe dedicated to exploring frozen planets, with Europe at the top of its list, and perhaps discover our supposed "giants of the deep."