ES8

• Satellites: With the development of artificial satellites around the Earth, scientists have developed many uses for them on Earth. Global Positioning System (GPS) is used for aviation, shipping and personal satnav devices. Weather satellites give us information to carry out detailed weather forecasts. Television signals, the internet and some types of telephones use satellite technology to relay information.

• Efficient solar panels: Space stations such as the International Space Station require efficient solar panels to generate electricity to power the many systems necessary for the survival of humans on these space stations. This technology is used today on Earth as sustainable source of electricity for buildings and electronic devices.

• Battery technology: The International Space Station relies on efficient battery technology to keep its system working in the absence of sunlight. Advanced battery technology is needed today on Earth to store electricity generated by solar panels and for electric cars.

• New materials: Materials such as memory foam, scratch-proof glass and Teflon-coated fiberglass were originally developed for use in space. We have many uses for these materials on Earth today.

• Water purification systems: On the International Space Station, all water has to be recycled from sweat, respiration, perspiration, urination and wshing. This needs to be converted into drinking water by water purifcation systems. This technology has been adapted for use in the developing world, where there is a lack of clean water to drink.

Space travel has been taking place since 1945. The year 1957 was a landmark in space exploration, as the Russians succeeded in putting an artificial satellite into orbit around the Earth (Sputnik 1) and sent a dog into orbit (Sputnik 2). This showed that it was possible for human beings and animals to survive in space. Since then, space travel has become more commonplace. However, many hazards still exist today.

• Explosion: Launching rockets into space is similar to carrying out a controlled explosion and accidents have happened In 1967, Apollo 1 caught on fire during ground testing, killing three astronauts. In 1986, the Space Shuttle Challenger exploded shortly after take-off, killing all seven people on board. Sometimes space probes carry nuclear reactors, which could spread radioactivity if they were explode on take-off.

• Burning up: When a spacecraft is travelling back to surface of the Earth (Re-entry), the outside of the aircraft can reach temperatures in excess of 9,000°C. Spacecraft are designed to withstand this heat during re-entry. If the spacecraft is damaged in any way, the heat can cause the spacecraft to burn up. This is what happened to NASA's Space Shuttle Columbia in 2003, killing all seven astronauts.

• Space debris: Hundreds of thousands of pieces of human-made debris are orbiting the Earth. These range from flecks of paint to entire satellites. You might wonder what harm a fleck of paint would do in space. However, if it was moving at 6,600 meters per second, it would be like a lower-powered bullet. Space debris can damage spacecraft and spacesuits used by astronauts when working outside the International Space Station. Natural space debris, such as pieces of rock can also strike spacecraft at enormous speeds, which could cause fatal damage.

• Cosmic radiation: The Earth is protected from cosmic radiation by its magnetic field. In space, this radiation comes from the sun and other sources. It damages DNA, which can cause cancer and other diseases. This is a major problem for any proposed trip to Mars. Airline pilots and cabin crew are also exposed to this radiation during flights. The amount of time they can spend in the air is controlled to protect their health and safety.

• Mechanical failure: If a spacesuit or spacecraft were to leak for any reason, the drop in pressure would cause the astronaut to suffocate, as happened in Soyuz 11 in 1971. In addition, exposure to the sun would subject an astronaut to temperatures more than 100°C or -180°C in the shade. Astronauts depend on machines to produce water and air to breathe. Failure of any of these systems can lead to death. This is of special importance for missions that may take years to travel to other places.

• Lack of gravity: The lack of gravity can cause muscle and bone weakness over time. When an astronaut returns to Earth, it can take them several weeks to recover their strength. This also causes the heart to weaken, as it does not have to work as hard pumping blood against gravity. Other effects inculde bulging neck veins, a puffy face and sinus and nasal congestion. In the pat, some astronauts collapsed when they returned to Earth. Now astronauts do a lot of resistance training to maintain their fitness.

• Psychological effects: Lack of sleep, maintaining high performance while under public scrutiny, an extreme change of environment, living and working in cramped, noisy conditions with people from very different cultures who speak different languages as well as isolation from peers and family can lead to anxiety and depression in astronauts.

• Emergency: Astronauts may not be able to quickly return to Earth or receive medical supplies equipment or personnel if a medical emergency occurs. The astronauts may have to rely for long periods on their limited existing resources and medical advice from the ground.

Over the past 20 years, most space missions have taken place using spacecraft without crews on board. It is likely that most missions in the future will also take place this way, with remotely controlled technology such as satellites and robots to carry out investigations.

• Some people argue that it is unethical to send astronauts on a hazardous one-way journey to Mars without access to hospital care or any prospect of returning to their families.

• Space exploration is expensive and it may be difficult to justify spending public money on such research while people at home die from poverty and lack of appropriate health care.

• Planet Earth supports life because it is not too hot, not too cold and has liquid water. Scientists hope to one day find a planet with similar conditions that may also be home to living organisms. If anything were to destroy life on planet Earth, the human race could be wiped out unless we travel into space.

• Space exploration will continue to develop technologies that will be of benefit to this world, as it did in the past. New technologies for rocket propulsion may be used as sources of energy on Earth in the future.

• There will need to be more international co-operation to maximize the benefits of space research. In addition, as more human activity in space is likely, rules and laws will be needed to say what can and cannot be done in space. Humans have succeeded in doing a great amount of damage to this planet and should avoid doing the same to space.