CONTENTS Chapter 1 ARE WE ALONE 4 Chapter 2 THE BEGINNING OF LIFE ON EARTH 10 Chapter 3 LIFE ON VENUS AND MARS 16 Chapter 4 FINDING EXTRATERRESTRIALS 22 Chapter 5 EXTRATERRESTRIALS IN THE SOLAR SYSTEM 28 Chapter 6 BEYOND THE SOLAR SYSTEM 34 Be a Space Scientist ANSWERS 44 Glossary and Further Reading 46 Index 48
Chapter 1 ARE WE ALONE The ancient Greeks believed that Earth was the center of the universe with the sun moon and planets all rotating around our planet In the fourth century BC the philosopher Aristotle 384 bc 322 bc wrote about the world as he saw it He said there could be no other worlds or aliens For centuries this is what people believed Other Worlds Aristotle’s writings may have very influential but in 1277 the teaching of some of his work was banned One of the newly banned ideas from Aristotle’s work was that God was unable to create many worlds All of a sudden people were allowed to consider worlds other than our own but most still thought that any God would probably not bother to create other worlds Later the philosophers Nicholas of Cusa 1401 1464 and Giordano Bruno 1548 1600 argued for the likelihood of other worlds More importantly they imagined them having life just like human beings or perhaps even more intelligent 4
If advanced alien life exists then it is outside the solar system If any aliens ever visit us they will be more technologically advanced than us They will have to have technology that allows them to travel between the stars This is ALH 84001 the meteorite from Mars In the center is a worm-like structure that scientists believed may have been a fossil Martian microbe Imagining Aliens Fiction has always been ahead of science when it comes to alien life The Syrian Greek writer Lucian ad 120 c 180 wrote True History in the second century In it people travel to the moon and are swept up into a war between the kings of the moon and the sun It also has aliens including dog faced men When H G Wells 1866 1946 wrote The War of the Worlds between 1895 and 1897 space exploration was 60 years away and people were able to imagine aliens from Mars invading us Now that probes have explored all the planets we know there are no intelligent aliens in our solar system But that has not stopped scientists from looking for more primitive life When the US National Aeronautics and Space Administration NASA announced possible fossil microbes in a meteorite from Mars in 1996 the news shocked the world Most scientists now discount this discovery and it became yet another shattered dream of finding alien life 5
