"This is by far the largest storm we've seen during the Mars Global Surveyor mission," said Philip Christensen of Arizona State University in Tempe, principal investigator for the probe's thermal emission spectrometer.
"We expect that the storm will continue to grow -- perhaps becoming a global storm of the type that was seen during the Mariner 9 and Viking missions in the 1970s."
Mars Global Surveyor began mapping the Red Planet in March 1999. The planet's climate is dominated by
.Scientists first noticed the storm June 15, when a region of dust began to appear in the Hellas Basin in the southern hemisphere.
A week and a half later, the storm began to intensify and expand. Since then, the storm has dramatically grown in size and severity. The dust storm has expanded well into the northern hemisphere and has wrapped more than halfway around the planet, Christensen said.
This storm also began earlier than normal for Martian dust storms. In the past when a large storm has occurred early in the season, there are usually several large storms during the year. NASA scientists will monitor Mars over the next few months to see how this storm develops and to test predictions of more storms to come.
The storm should not have a major impact on the planned arrival of another spacecraft, the 2001 Mars Odyssey, in October, Christensen said. Like Mars Global Surveyor, Odyssey will use repeated passes through Mars' upper atmosphere to slow down and lower its orbit around the Red Planet.
Mars Global Surveyor and Odyssey will team up during this crucial phase of the newer orbiter's mission.
"We'll use the instruments on Global Surveyor to monitor the atmosphere on an hourly basis, providing the Odyssey spacecraft team the information they need to keep Odyssey at the proper height where it can safely fly through the atmosphere," Christensen said.
Mars Global Surveyor encountered some difficulties when it first entered Mars' atmosphere in 1997 as friction was stressing a malfunctioning hinge on one of the probe's solar wings. Mission engineers solved the problem by slowing the schedule for the craft's dips into the atmosphere, thereby lessening pressure on the hinge so it wouldn't break and leave the probe with just one solar wing.
Odyssey's orbit height can be adjusted as needed in response to the changing atmosphere as observed by Global Surveyor, Christensen said.
Global Surveyor was launched in November 1996, and Mars Odyssey was launched in April 2001. Both missions are managed by JPL NASA. Lockheed Martin Astronautics, of Denver, developed and operates both spacecraft.
The thermal emission spectrometers on each spacecraft are operated by Arizona State University.
advertisement
