Mission to Mars

On July 4, 1997, space exploration took a huge step. On that day, a spacecraft called Pathfinder landed on Mars. The National Aeronautics and Space Administration (NASA) sent Pathfinder to discover new information about the Red Planet.

The mission was a complete success. After landing, Pathfinder sent a small rover (漫游机器人), Sojourner, onto the planet's surface. Sojourner explored more than 250 square meters of Mars. Together, designed Sojourner to last for only seven days, but little vehicle ran twelve times longer! Pathfinder surprised scientists, too. It sent back information for almost three months. That was three times longer than it was built to last.

Because Pathfinder and Sojourner ran for so long, scientists got more information than they ever dreamed of getting. For one thing, they discovered that Mars is very sandy. Pictures of sand dunes around the land site hint that Mars once had water. Scientists know that water means life. Was there ever life on Mars? We don't know yet. In addition, the Pathfinder mission told scientists that Mars is dusty. Huge "dust devils" on Mars spit enormous amounts of dust into the Martian air. Pathfinder also discovered frosty Martian temperatures at 200 degrees below zero Fahrenheit. At that temperature, a glass of water would freeze solid in just a few seconds.

In October, scientists lost Pathfinder's signal because the spacecraft's battery had run down. They tried to revive the signal but had no luck. The mission officially ended on November 4.

Scientists hope to use the knowledge from these missions to better understand how life on earth began. They will also use it to plan future Mars missions.

Are we humans alone in space? Scientists have been working on this question for a long time. And recently, new discoveries offer more hope that some form of life existed on Mars in the past, and perhaps is still there at present.

According to a new report in the book Science, the Mars Explorer Curiosity has found more methane (甲烷) in the Martian air. It might suggest the possibility of life.

During the last 20 months, Curiosity has found methane many times, and four of them, it tested at a level 10 times higher than usual. “It’s a great increase,” said Christopher Webster, the lead scientist.

This new finding has made a big change. In September 2013, Curiosity found almost no sign of methane on Mars. Just weeks later, however, the explorer picked up the gas.

Methane is also found in Earth’s air, and comes from animal and plant life, as well as from the environment itself. If there’s methane in Mars’ air, where is it coming from? Scientists aren’t sure.

“There are many possible sources, such as actions between water and rock,” guessed Sushil, a scientist of the Curiosity team.

But the scientists have left the possibility open that microbes (微生物) could be the methane’s source. Also, for the first time, Curiosity found other organisms (有机物) in the rocks of Mars. Organisms are thought to be the basis to form life. Scientists aren’t sure where these organisms come from. They could either have formed on Mars or landed on Mars by meteorites (陨石).

For the next three years, Curiosity will keep looking for more organisms in rocks and exploring Mars.