Jul 14, 2022
Earth: our oasis in space. Our solar system includes seven other planets and many moons and other small worlds. But only Earth has all the ingredients for life as we know it. There is no place like home—at least in our neighborhood.
Imagining Other Worlds
So far scientists have yet to find another world like Earth. But people have long imagined Earth-like planets and alien creatures living on them. They have shared their visions through books, movies, and popular culture. What would it take for people to live on another planet? How are scientists trying to find other habitable worlds?
For hundreds of years people thought life could exist nearly everywhere in our solar system. Discoveries made by spacecraft missions to the planets changed that view—but take a look at some of the imaginative ways people thought about life on other worlds in the gallery below.
Investigating Life on Other Worlds
So—can humans live anywhere else in our solar system?
Only the Moon, Mars, and perhaps some of the larger moons of the giant planets—Jupiter, Saturn, Uranus, and Neptune—might support a long-term colony. The giant planets themselves have no hard surfaces to walk on. It is also impossible to survive on many of their moons.
However, according to a NASA study, along with our Moon and Mars, humans might make long term visits to only two of the gas giants’ larger moons: Jupiter’s Callisto, and Saturn’s Titan. Jupiter’s and Saturn’s other moons are affected by the gas giants’ strong radiation fields, and the smaller moons have such low gravity that an explorer’s muscles would weaken over time.
That leaves us with Mercury and Venus. Mercury is too close to the Sun to support human life. Its surface temperature averages 800°F (430°C) and is bathed by solar radiation. Venus is even hotter than Mercury. The average surface temperature is hot enough to melt lead. The pressure of the atmosphere is crushing—90 times what we experience on Earth!
So is there any possibility of life on other planets? Finding the answer is a large part of what drives space exploration. One thing we know is that planets change. Earth today looks nothing like it did over four billion years ago when life began.
The movement of Earth’s surface by plate tectonics has created the continents we see today. The atmosphere has changed from mostly carbon dioxide to mostly nitrogen and oxygen. Even the saltiness of the oceans has varied over time. These changes have wiped out clues to how life began.
Conductive material at Earth’s core generates the magnetic field that surrounds our planet. The magnetic field protects us from the Sun’s solar wind, which would blow away our atmosphere. Some of the solar particles are deflected harmlessly toward the poles, where they form auroras—like the well-known aurora borealis, or northern lights.
These characteristics which make Earth unique, or some combination of them, may be essential for creating life and for sustaining it long enough to become intelligent. Some of the earliest evidence of life on Earth are stromatolites—mounds with fossil material created by primitive organisms. These organisms consumed carbon dioxide and released oxygen as waste, building up oxygen in Earth’s atmosphere over billions of years. Life that thrived on oxygen evolved.
Despite the fact that we have not yet found life outside of Earth, scientists continue to search for it—in our Museum, NASA centers, and other laboratories worldwide. We’ve also tried to reach out to other life … out there. One of the first things humans sent into space was a metal record, similar to a phonograph. Voyager 1 and 2, which launched from Earth in 1977, both carried these records, along with the needle needed to read it, which contained information about Earth and life on it, including sounds and images of life. Who knows if someone will one day hear it?
We rely on the generous support of donors, sponsors, members, and other benefactors to share the history and impact of aviation and spaceflight, educate the public, and inspire future generations. With your help, we can continue to preserve and safeguard the world’s most comprehensive collection of artifacts representing the great achievements of flight and space exploration.