| Now it is true that the sun is the center of the solar | | | | when observed from Earth. Indeed, when unmanned |
| system. It is true that Mercury and Venus are closer to | | | | space craft explored its surface, it did appear very red |
| the sun than is Earth. It is true that Jupiter is the largest | | | | and very dry. Two unmanned rovers first landed on |
| planet in the solar system. It is true that Uranus is a | | | | Mars in 2004 for a three-month mission. They |
| ringed planet that turns very differently on its axis than | | | | continued to send information even five years later. |
| the other planets. Indeed, since the United States put a | | | | Most of the efforts have been centered on finding |
| man on the moon in 1969, the country has | | | | water. No water has been found â at least in |
| concentrated on unmanned exploration of the solar | | | | the way we think of water. There has been recent |
| system. What we have learned in the last thirty years | | | | evidence of a white material beneath the surface |
| is far more than we learned throughout history. But | | | | layer of soil. Some speculate that it is ice but most |
| whether you are 17 or 71, what you learned about the | | | | scientists believe it is salt or a briny deposit. The next |
| solar system in school is now out-of-date. | | | | Mars mission will focus on habitability instead of |
| This is true with Mars, the fourth planet from the sun, | | | | searching for water. Are there places on the planet |
| known as the red planet, Mars has a reddish glow | | | | where life might have been possible? |