Thursday, September 23, 1999, wasn’t a good day for NASA. At 5:01 a.m. EDT, the Mars Climate Orbiter, a $125 million (U.S) space probe intended to observe Martian weather for two years, fired its engines to enter orbit around Mars and dove behind the planet. It never reappeared.
After several hours of study, NASA announced that the probe entered orbit only 60 kilometres above Mars instead of the planned 150 kilometres–so close it must have burned up in the Martian atmosphere. It was an ignominious end to a 286-day voyage, but over the next few years, many more missions will visit our most interesting planetary neighbor.
Popular interest in Mars burgeoned to the late 19th century thanks to Italian astronomer Giovanni Schiaparelli, who reported in the 1870s that he had observed “canali”–Italian for “channels”–on Mars, and American businessman and amateur astronomer Percival Lowell, who got quite excited about Shciaparelli’s announcement, founded an observatory in Arizona, and convinced himself and many other people that Mars was covered by “canals” dug by intelligent beings. Around the turn of the century, even popular songs spoke of signaling to Mars, H.G. Wells had written about Martians invading Earth, and Edgar Rice Burroughs had populated the planet with green-skinned warriors and princesses and renamed it “Barsoom.”
When we finally got spaceships there, alas, the romance faded. The canals proved to be optical illusions. Mars was covered with craters and looked very much like our own moon. And the Viking landers found no princesses, nor any other signs of life.
Martian exploration essentially ended for almost 20 years. But two years ago, the public imagination was re-captured by the Mars Soujourner mission, with its robotic rover that beamed pictures back to Earth–and onto the World Wide Web. Right now, Mars Global Surveyor is orbiting Mars, sending back the highest-resolution pictures ever had before. And, as noted, many more missions are planned. So what’s so interesting about Mars?
Of all the planets in the solar system, Mars is most like Earth–yet also very unlike. By understanding the differences between the two planets, we learn more about our own. Scientists want to know how the composition of Mars is different from Earth, and how and why Mars’s climate has changed. Did it once have a dense atmosphere? Did lakes and oceans once cover part of its surface? Did those lakes and oceans hold life? Could life still be lingering there, underground, perhaps?
Viking, you see, may have been looking in the wrong place. Oon Earth microscopic life lives in places as inhospitable as the dry, frozen rocks of Antarctica and the scalding, poison-drenched waters around deep-sea volcanic vents. The recent discovery of a meteorite from Mars that may contain traces of ancient microbes has also re-ignited the search for Martian life. Discovering life on another planet would be strong evidence that life must be abundant throughout the universe.
The next mission to touch down on Mars will tell us more about Mars’s climate history. The Mars Polar Lande will land on December 3. Before it lands, it will crash two probes onto the Martian surface at 200 meters per second. The probes will punch two metres deep, to see if there is ice locked in the rocks beneath the Martian surface.
The Polar Lander itself will take pictures, dig for soil samples and analyze them for water and carbon dioxide. One interesting instrument on board is the Mars Microphone, which will be able to send back to Earth, for the first time, the actual sounds of the Martian surface.
On March 30, 2001, the Mars Surveyor 2001 Orbiter is scheduled to launch, to arrive on October 20, 2001. It will study Martian mineralogy, measure radiation levels, and look for hydrogen (a key compound for life). On April 20, 2001, the Mars Surveyor 2001 Lander will launch. It will take pictures of the surface during its descent on January 22, 2002, and will carry a rover similar to the Mars Sojourner rover. It will also test technologies needed by a manned mission to Mars. For instance, it will try to produce rocket propellant using gases in the Martian atmosphere.
More long-range plans include sending a lander to scoop up samples of Martian soil and return them to Earth for study–and, eventually, to send human beings to Mars.
The Red Planet still fascinates us, even without canals and green-skinned princesses. Despite the loss of the Mars Climate Observer, we’ll have plenty of opportunity to feed that fascination in the next few years.