SPACE FACTS

Because the space environment is beyond the normal experience of those of us who have spent our whole lives on planet Earth, it is easy to get confused about what it is really like to live, work and play on the moon, in spacecraft and other places. Some terms can be confusing. Popular media like the internet, television, and movies sometimes give us ideas that are not correct. Hopefully this will help you separate science fiction from space fact.

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Comets, Meteoroids, and Asteroids
Gravity Facts
Life on the Moon Facts
Spacecraft Facts

This artist's rendering represents a concept of possible activities during future space exploration missions.

Comets, Meteoroids, and Asteroids

• Comets are composed of ice and orbit the Sun.
• Comets follow an orbit that take them from beyond Uranus and back around the Sun, following the same path. Some comets pass the sun on a regular basis. The best known comet is Halley's Comet that appears about every 76 years.
• The nucleus of a comet is composed of rock and ice. As a comet gets close to the Sun, the ice begins to heat and starts to vaporize. This causes the nucleus to break apart and throws dust up which then forms a coma. The force exerted on the coma by the Sun's radiation and solar wind causes an enormous tail to form which points away from the Sun.
• Here is a picture of Comet Soho.
• Here is a picture of Comet Hale-Bopp.
• Asteroids are composed of rocky and/or iron-nickel material and most of them orbit between Mars and Jupiter.
• Asteroids are known as minor planets and vary in size from large rocks down to the size of small pebbles. An asteroid named Ceres has a diameter of 1000 km.
• Asteroids can be covered with craters and dust as a result of collisions from other objects. Some asteroids orbit each other like the Earth and the Moon.
• Meteoroids are small particles in space. When they fall through the atmosphere, they are called meteors and if they land on Earth, they are called meteorites.
• Meteoroids are sometimes confused with comets but there are several differences. Meteoroids are much smaller than comets and are usually the size of pebbles. Some are the result of impacts with other asteroids, while others are caused by comets, the Moon or even Mars.
• A meteor is a meteoroid that reaches the Earth and falls through the atmosphere, where it starts to burn up. When people see the flash, they call it a shooting star or falling star.
• A meteorite is a meteoroid that has hit the Earth. It is made up of rock and/or metal.
• A meteor shower occurs when the Earth passes through a comet's orbit. The planet encounters the dust stream left by the comet's tail. Due to the large number of dust particles burning up in the Earth's atmosphere, there are so many flashing meteors that it is called a shower.

Gravity Facts

• There is gravity in space, including the moon.
  • There is a gravitational attraction between all objects in our universe. Gravity keeps the moon (and various spacecraft) in orbit moving around the Earth, the Earth in orbit moving around the Sun, our solar system in its place within the Milky Way, and the Milky Way in its place among the other galaxies
  • Massive objects like a star or a planet have more pull than objects with less mass.
  • Distance also affects the strength of the gravitational attraction between objects; closer objects have more pull. Gravity pulls you down toward the Earth instead of toward the much more massive Sun because it is much further away.
  • Compared to the Earth, gravity is weaker on some planets and moons and stronger on others, depending on their mass and size. On the moon's surface, gravity is about one sixth of that on the Earth's surface.
• There is gravity within spacecraft.
  • Although there seems to be no gravity on the Space Shuttle and the International Space Station, it is almost the same as on the surface of the Earth. It's only about 10% less because those spacecraft are always close to the Earth.
  • It doesn't seem like there is gravity when the motion of a spacecraft (or any other object) follows gravity's downward pull. That is what happens with a spacecraft except for when it is on the ground and durng the short times when the rockets fire. In other words, the spacecraft is falling, but it doesn't seem to be because of its high speed.
  • Astronaut float in space because their motion is following gravity's downward pull. In other words, floating astronauts are really falling. It just doesn't seem like they are falling because their spacecraft is falling too. For the same reason, you can feel weightless on roller coasters (at the top of “fast” hills) and other amusement park rides.
• Even on the moon, gravity makes objects fall.
  • Although the gravity on our moon is much weaker than on the Earth, our moon does have gravity that pulls astronauts and objects to the ground.
  • The weaker gravity on the moon does make objects fall more slowly than on Earth, but they still fall.
• Astronauts can't jump off and away from the moon.
  • Although it is weaker than on Earth, lunar gravity is still much too strong for astronauts to jump off and away from the moon.
  • However, it is possible that astronauts could jump away from a small object (with low mass) like an asteroid.
• Zero gravity chambers have not been invented.
  • Gravity is not well understood and scientists don't know if antigravity is possible or how gravity could be turned off. Such a scientific breakthrough could be an important step forward in enabling faster-than-light space travel.
  • However, a lack of gravity can be simulated in a chamber by letting it move following gravity's downward pull. For example, NASA trains astronauts in research aircraft by flying them like roller coasters.
• Gravity can be simulated by rotating a spacecraft.
• In space, artificial gravity normally refers to the rotation of a spacecraft to simulate gravity. This is similar to the force that you feel in a car when it makes a sharp turn and you feel pulled in the opposite direction.
• Higher gravity could be simulated on the Moon within a rotating chamber, but the chamber would need to be rotating quickly (and ideally be large), and the gravity would seem to be outward instead of downward.
• Thus far, simulating gravity with magnets is normally only practical for small objects, and Velcro™ is a much more common approach for that purpose within spacecraft.

Life on the Moon Facts

• Surviving the lunar atmosphere isn't just about oxygen.
• Because the atmosphere on the moon is so thin, the temperatures on the surface are very extreme. The temperature on the moon can range between -250 º F to 250 º F! Spacesuits must protect you against these temperatures, as well as supply oxygen.
• On Earth, the air (and water when swimming) exerts pressure on you. Without such pressure, your body would swell and you'd have some serious health problems. Although spacesuits operate at much lower pressures than our atmosphere on Earth, our bodies do need to be protected from the vacuum of space.
• Micrometeoroids also pose a risk on the moon. On Earth, most meteoroids burn up as they enter the atmosphere. But the moon doesn't have that same shield. Your spacesuit needs to protect you from a potential rock shower. It also protects you from things like radiation and lunar dust (which poses a hazard if you breathe too much of it).
• While NASA plans to put people back on the moon by 2020, a moon base is a ways off.
• When astronauts return to the moon, they will begin to test the technologies needed to support a lunar base. But, it will take a while until everything is in place. To stay on another planet for long durations, people need a source of food, oxygen, and other life support. NASA is already exploring ways of getting the resources from the lunar soil itself. The first astronauts to return may test some of these techniques.
• Constructing a moon base will take some time too. Just like the space station, most materials must be sent from earth. But they have a much longer journey to get there. There also won't be big machines, like you see at a construction sites on earth, to move soil and building materials around. Light weight materials and creative building techniques must be developed.

Spacecraft Facts

• NASA's Space Shuttles can't fly to the moon or other planets.
• At a distance of about 239,000 miles, the moon is a thousand times further from the Earth than the Space Shuttle orbiters normally go. The Space Shuttles were only built to orbit the Earth at an altitude of 100 to 400 miles, but it is rare when they even reach 300 miles. If you look at a globe, the distance across a typical U.S. state (like Ohio) is about how far as the Space Shuttle can get from the Earth.
• To escape the Earth's gravity and fly to the moon or other planets, spacecraft must launch with speeds of at least 25,000 miles per hour (which is roughly 7 miles per second). The Space Shuttle wasn't designed or built to reach that speed, and can only orbit the Earth. Even so, spacecraft like the Space Shuttle must fly at a speed of about 17,500 miles per hour (which is roughly 5 miles per second) to stay in a low Earth orbit.  Objects launching at slower speeds (like a thrown ball) will be pulled back to the Earth by gravity.
• The new Orion spacecraft won't have wings or land on the moon.
• The Orion crew vehicle is new spacecraft that is being designed to carry astronauts to the moon (and the International Space Station). It will be a cone-shaped capsule that will launch on top of a rocket named Ares I. Instead of having wings like the Space Shuttle, the Orion spacecraft will be similar to the Apollo command module. However, the Orion may land on the ground instead of in water like the Apollo capsule.
• Although future astronauts will fly from the Earth to a lunar orbit in the Orion, they will get into the Altair lunar lander to travel to the surface of the moon. The Orion will remain empty while in orbit around the moon waiting for the astronauts to return for their trip back to the Earth.