>Exámenes selectividad inglés resueltos Andalucía
People have been walking on the surface of Mars for more than a century, in fantasy. Now, however, the possibility is so real that many people think the question is not whether humans will go to Mars, but when they will go, how they will get there and who will go first.
Although there is growing agreement that reaching Mars will be some kind of multinational effort, a prosperous nation, like the United States, seems capable of such an achievement by itself. For the US it is a political priority. The cost of the project has been estimated at $60 billion, about double the price of the Apollo Moon project.
Of all the other planets in the solar system, Mars is the most like Earth. With about half the Earth's diameter, with one-third of the gravity and only one percent of the atmosphere, space vehicles have found that Mars hides an important amount of water under its surface and in its frozen poles. While Venus is closer, with an average temperature of about 850 degrees, it is hostile.
From the presence of water and a relatively moderate climate comes another powerful attraction. The fascination with Mars centres around the issue of life. Mars is key to answering that critical question:
Is there life somewhere other than on Earth?
