Giant dust storm swallows half of the Red Planet
Posted: July 14, 2001

The largest dust storm to be seen on Mars since NASA's Mars Global Surveyor spacecraft arrived in 1997 is currently raging across about half the planet.

"This is by far the largest storm we've seen during the Mars Global Surveyor mission," said Dr. Philip Christensen of Arizona State University in Tempe, principal investigator for the Global Surveyor's thermal emission spectrometer. The instrument has been monitoring the Martian atmosphere since March 1999. "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," Christensen said.

Mars Global Surveyor Thermal Emission Spectrometer data from June 17 to July 8 showing the dust storm. Photo: NASA/JPL
Daily observations by the instrument are made into maps that allow scientists to determine both the temperature and the amount of dust in the atmosphere.

Scientists first noticed the onset of the storm June 15, 2001 when a region of dust began to appear in the Hellas Basin in the southern hemisphere. A week and a half later, on June 26, 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 be monitoring Mars over the next few months to see how this major storm develops and to test their 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. Odyssey will use repeated passes through Mars' upper atmosphere to slow the spacecraft and lower its orbit around the red planet. "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. Odyssey's orbit height can be adjusted as needed in response to the changing atmosphere as observed by Global Surveyor, he said.

Global Surveyor was launched in November 1996, and Mars Odyssey was launched in April 2001. Both missions are managed by JPL for NASA's Office of Space Science, Washington, D.C. Lockheed Martin Astronautics, Denver, Colo., developed and operates both spacecraft. The thermal emission spectrometers on each spacecraft are operated by Arizona State University. JPL is a division of the California Institute of Technology in Pasadena.