Every parent knows how special the one-year birthday is of their progeny. They remember the sleepless nights worrying about the health of their babies and if they are safe, and the constant amazement of the knowledge one year can bring. JPL scientist are like all parents as they celebrate the one Martian year birthday of their rovers Spirit and Opportunity.
"Spirit was a year old on November 20. Opportunity will be a year old on December 12," said John Callas, deputy project manager of Mars Exploration Rover Project.
A Martian year is equal to 687 Earth days.
"We had a cake and a celebration in observing the birthdays," Callas said.
The rovers are about the size of a golf cart. Spirit has traveled 5,000 meters, or three miles, and Opportunity has traveled 6,446 meters, a little more than four miles. The Rovers have exceeded their original 90 Martian day mission. A Martian day is 24 hours and 40 minutes long. The rovers continue to send data and pictures to Earth.
According to JPL, Spirit has sent back about 70,000 images.
They must not only travel on unexplored foreign soil but must also withstand the extreme Martian weather -- in the day the average temperature is 0 degrees Celsius and at night a negative 100 degrees Celsius.
"They are very robust and resilient," Callas said.
According to JPL, Spirit has been given a longer life thanks to the corporative Martian winds. Scientists concluded from earlier research that large dust storms occurred during the spring through early summer blocked out sunlight needed to power the rovers. These storms have not happened, although many dust devils, which are tornado-like wind storms, have been seen.
Spirit and Opportunity have provided scientist with a huge amount of information, Callas said. The rovers have taught scientists that water played an important role in the development of Mars and that liquid water containing high levels of sulfate was present on the surface.
"It is unlikely that life could have evolved here," Callas said, adding that scientists cannot rule out the possibility of the past existence of life on Mars. "One could hardly determine on two sites on Earth what the entire planet would be."
The rovers are looking at specific areas on Mars. Callas compares it to a spacecraft that would land in some of the desert areas on Earth, that data would not give a true picture of the entire planet. The rovers continue to do geological assessments to help scientist understand the role water played at the site, Callas said.
Spirit has the distinction of being the first explorer to climb a mountain on another planet when it climbed the "Columbia Hills." And Opportunity gave scientist a different look at new Martian landscape.
"All other photos from Mars showed lava-like rocks. Opportunity did not show that," Callas said. He describes blueberry-type rocks all over the surface. The blueberries precipitate out a rich solution of dissolved minerals, Callas said.
Callas cannot pick one rover discovery over another but feel that important data is being discovered from the rovers investigations of Martian craters.
"The craters are time tunnels of Martian history. Going deep into craters is like going back in Martian time," he said.
The rovers will continue to drive across Martian soil, sending back data that will help future travelers including perhaps a human explorer several decades from now, Callas said.
For now JPL scientist are just celebrating the longevity of their rovers. They cannot predict how much longer they will continue.
"There will come a day when we just stop hearing from them," Callas said.
Until that day the rovers will continue to send back data and pictures of a world that has fascinated Earthlings for centuries.