CHAPTER 1 Floating Among the Stars Can you imagine living on another world What would it be like to wake up and see the landscape of Mars from your bedroom window How would it feel to float above the clouds of Venus What would it be like to live on a space station in orbit around Earth For centuries people have imagined traveling into space Today astronomers scientists who study space are asking themselves whether this might be possible What would it take for humans to live in space Scientists have been considering the question ever since astronomers first realized Earth was a planet orbiting the Sun As technology developed scientists began figuring out how to leave Earth In the later part of the 20th century people used airplanes to fly toward the very edge of space They learned that space is very different from the surface of our planet Space begins at the top of Earth s atmosphere which is the envelope of gases that surrounds a planet 4
The Race to Space Starting in the second half of the 20th century many scientists took up the challenge of getting people into space Engineers worked to build rockets and other spacecraft that could leave Earth’s atmosphere and safely return Astrophysicists study the behavior of bodies in space They figured out how space objects move in relation to one another and how to send spaceships between two moving planets Astrobiologists are scientists who study life on Earth and potential life elsewhere They wondered what life might be like on other planets and what humans would have to do to make it possible to live on other worlds This illustration imagines living underground as a way to cope with difficult conditions on other planets Thanks to the work of such scientists 12 people have walked on the Moon More than 500 people have spent a combined total of 29,000 days in space We have sent uncrewed missions to all the planets and some dwarf planets in our Solar System Voyager 1 which was launched in 1977 is preparing to leave our Solar System altogether We are a long way from being able to set up permanent colonies in space or on other planets or make space travel common but scientists are working on it During your lifetime you may be able to take a vacation on the Moon 5
Here on Earth Earth provides us with everything we need to survive so why would we leave our planet Some scientists are proposing that we look for other worlds on which we could live because one day we will run out of resources on Earth Resources are food water and energy sources such as coal and oil Our population is growing each year which means that we need more and more resources Future populations will need to find these on other planets Signs of Life When astrobiologists look for signs of life on other planets they look for planets where liquid water can form All life we know about needs water to survive Even cells which are the tiny building blocks of all living things are mostly water Water is so essential for living things that astrobiologists believe all planets that can support life must have water All life on Earth depends on water 6
Habitable Zones Earth is in our Solar System’s Goldilocks Zone This zone is far enough from the Sun that water does not boil away but not so far that all water freezes It is also close enough to the Sun to receive warmth and light from its rays but not so close that the rays scorch life on Earth In these stable conditions ecosystems have built up Plants thrive in the sunlight animals eat the plants and humans eat the plants and animals Earth is so perfect for life that it is called a Goldilocks Planet Humans would need to find a planet very similar to Earth another Goldilocks Planet if they were to survive there Europa a moon of Jupiter releases jets of water that suggest it may have an ocean beneath its surface YOUR MISSION We already know Earth is the only planet in our Solar System where conditions are just right for life to survive If we find another Goldilocks Planet that we could live on we could take plants and animals there from Earth What plants and animals would you choose to take with you to a new Goldilocks Planet 7
