6 oXYGEn Making sure they survive when they get there is an even bigger one and so is being able to return home Both surviving on Mars and getting getting back to Earth require oxygen NASA has a plan for that The Mars Oxygen In-Situ Resource Utilization Experiment called Moxie for short is NASA’s plan for producing oxygen from the atmosphere on Mars A machine would use an electric current to separate the carbon and oxygen atoms that make up the carbon dioxide in the Martian atmosphere The oxygen would then be available for astronauts to breathe and for firing the rockets that would send them back home The word moxie means bold and this is definitely a bold plan It’s also a necessary one if humans are going to do more than make a quick visit to Mars Humans cannot survive for more than a few minutes without oxygen But as important as it is to us now Earth hasn’t always had oxygen oxygen And even after humans came along it took a long time for us to understand what oxygen was Once we did we found a lot of ways to put it to use including firing rockets to get to other planets
1 Finding the Pieces Take Take a deep breath Now take another Breathe slowly Can you taste the oxygen in the air Probably not because oxygen is tasteless odorless and colorless You may not be able to see taste or touch oxygen but it is absolutely essential to life in our world Without it our planet might look more like Mars or the moon dry and lifeless There would be no clouds rain or snow because they each require water and water is nearly 90 percent oxygen Hydrogen accounts for the remaining 10 percent Without oxygen there would be none of the plants and animals that you see every day because oxygen is vital to nearly every organism on Earth Oxygen is an element Elements are made of only one kind of substance substance that cannot be broken down further The elements are the 7
8 oXYGEn building blocks of life If you imagine matter as a giant puzzle the elements are the puzzle pieces really really small puzzle pieces By fitting the pieces together in one way you can create a grain of sand Try a different combination and you can create a drop of water a rock or even a person Scientists have discovered more than one hundred elements Earth is about four and a half billion years old but many of the elements elements were discovered only during the last few hundred years Oxygen was officially discovered by two chemists working independently independently during the eighteenth century Carl Scheele of Sweden and Joseph Priestly of England In 1773 Scheele discovered that whenever he heated nitric acid a colorless liquid that can cause severe burns and is often used in fertilizer a gas was released that made nearby candles burn brighter Scheele wrote that the atmosphere was composed of two gases one that supports combustion or burning which he called fire air and the other that prevents it which he called foul air Carl Scheele of Sweden was one of two scientists to discover oxygen
FIndInG thE PIEcEs 9 A year or so later in England Priestly discovered that the gas released by heating a mixture of mercury and air also made candles candles burn brighter He published his findings in 1775 two years before Scheele and took most of the credit for the discovery of what he called dephlogisticated air Another scientist Antoine Lavoisier gave oxygen its name and realized that it was an essential essential chemical element The Oxygen Puzzle The puzzle pieces are called molecules Molecules are made up of something even smaller atoms An atom is the smallest piece of an element that can unite with other atoms to form a molecule Subatomic Particles Atoms are made up of tiny pieces called subatomic particles particles These particles are protons neutrons and electrons electrons Protons have a positive electric charge electrons have a negative electric charge and neutrons have no charge at all If you were to view an atom Protons Neutrons Electrons Electron Neutron Protons Nucleus Atoms are made up of tiny pieces called subatomic particles These particles are protons neutrons and electrons
