Hooray! On July 4, the Mars Pathfinder arrived on the Red Planet. Scientists were nervous about the tricky crash landing--the spacecraft slammed into the Martian atmosphere at 16,600 miles per hour--but the arrival was nearly perfect. Parachutes and retro-rockets slowed the speeding machine. A cocoon of puffy airbags help cushioned the craft as it struck the surface, bounced 50 feet high, and finally rolled to a stop. Shortly after the landing, a small robot called Sojourner rolled out from the spacecraft. It will spend about a month exploring the planet.
More than 2,000 people watched the incredible touchdown on Independence Day from NASA's Jet Propulsion Laboratory (J.P.L.) in California. The crowd whooped and wept with joy as the first pictures from Pathfinder streamed onto a 25-ft. screen: stunning shots of Mars red, rocky surface.
Now, Sojourner, the coolest remote control car in the galaxy, is busy snapping photos of rocks and examining the dusty soil of Earth's neighbor. A scientist in California controls its slow crawl across the Martian soil using computers and 3-D glasses. The probe, travels at only 2 feet per minute, but it can cover a football-field size area near the lander, and can climb slopes and rocks. Scientists have picked out and nicknamed several formations they'd like Sojourner to investigate. Among the nicknamed rocks: Barnacle Bill, Yogi, Flat Top, Couch and Casper. Eventually, the Sojourner will stop working because of the extreme cold: temperatures dip to -125ƒF at night.
Clues to a Watery Past...
While its weather is chilly, Mars is the hottest planet in the solar system right now. NASA's Pathfinder websites recorded more than 100 million hits from people around the world eager to see the new pictures from Mars. Although it is about half the size of our planet and pocketed with craters as our moon is, Mars is similar to Earth in many ways. It has volcanoes and giant canyons. The area named Ares Vallis, which Sojourner is now exploring, looks like a giant desert, but without cactus plants. Iron-rich dust give Mars a red surface and a pink sky. Parts of the planet that look like dry riverbeds have led scientists to believe that water once flowed on Mars ages ago.
Now, Pathfinder's color photos are showing scientists that a giant flood did once sweep across the Red Planet. A surge of water crashed through the plain of Ares Vallis, giving rocks and ridges their particular shapes and colors which Pathfinder and Sojourner now see. Scientists now guess that the flood came from the southwest portion of the planet, and probably evaporated. But they are still determining whether liquid water could have remained on the surface for any time.
These new images of a watery past are thrilling to researchers--and many others--who have long wondered whether Mars has ever held life. Where there's liquid water, there is the possibility of life. Scientists have thought the possibility of life on Mars was very slim, until last summer. In August 1996, to everyone's amazement, a team of geologists and biologists announced that they had found evidence that life may actually have existed on Mars long ago. They found it inside a Martian rock known as ALH84001.
İİİİ The potato-size rock had been found on Earth, sitting on a sheet of ice in Antarctica. Scientists have found about a dozen rocks from Mars on Earth. They know the rocks are from Mars because they're made of minerals different from anything on Earth (or our moon, asteroids or comets, for that matter), and the gasses trapped in tiny pockets within the rocks matches the gasses which were found in the Martian atmosphere by the Viking probes in 1976. The rocks
probably were blasted into space when an asteroid smashed into Mars. After many years, they fell to Earth.
İİİİ When scientists cracked this particular rock open, they found several interesting things. One was a group of chemicals called polycyclic aromatic hydrocarbons (polly-sik-lik, ah-row-ma-tik, high-dro-car-buns), or PAHS for short. PAHS are created when bacteria die and rot. Using a microscope, scientists also found objects
that look like fossils of bacteria and even tiny worms. Best of all, the
chemicals and objects were found deep inside the rock. If they had come from contact with the Earth, they would be near the surface.
Another promising sign: ALH84001 dates back to between 3 billion
and 4 billion years ago, exactly the time when some scientists believe Martian rivers were flowing.
There's Plenty Left to Prove
The scientists are being very careful, though. They admit the chemicals in the rock still don't prove life once existed on Mars. PAHS are sometimes found in ordinary lifeless meteorites, and the tiny objects inside ALH84001 could just look like worms and bacteria. If similar chemicals and objects can be found in other rocks on Mars,
researchers may be a little more certain.
İİThe Pathfinder lander could last up to a year on Mars, and it will remain on the planet as the Carl Sagan Memorial Station even though it will not be working. But another spacecraft is already on its way to join Pathfinder in the Martian atmosphere probably in September: the Global Surveyor, which began its long trip to Mars last November. Once there, it will orbit Mars and take supersharp pictures of the surface. And at least three other lander-orbiter pairs will journey to the Red Planet in 1998, 2001 and 2003.
Because the Pathfinder mission and other Mars missions that NASA has planned are one-way trips, there's no solid plan to bring back rocks from Mars. And while Sojourner is picking up excellent information about the chemical makeup of Mars, the probes that are going are not designed to test for signs of life. Thanks to ALH84001 and the amazing success of Pathfinder, though, NASA may be making new plans. The space agency is thinking about sending a probe on a round trip to Mars in the year 2005 which would bring back a few precious handfuls of rock and soil. If Congress okays some extra money, it could happen sooner. And if Congress is willing to spend a lot of money, there could even be a Mars trip with humans aboard.
Some scientists believe life may still exist on the Red Planet not on the dry surface but deep underground, where water may be trapped. If so, astronauts with the right equipment could dig down and find it. This would certainly be one of the biggest discoveries
ever.
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