The first picture of Mars taken from Earth orbit by the Hubble Space Telescope has been released by the Space Telescope Science Institute in Baltimore.
The picture, snapped Dec. 13 when Mars was 53 million miles from Earth, is the start of a long-term project to monitor and photograph the planet's changing weather, its atmosphere and surface features.
The photo shows a variety of features across the full face of Mars, including a thick canopy of clouds over the planet's north pole and thin clouds in the southern hemisphere. There also are dusty, light-colored features, and dark, volcanic surfaces in between.
Astronomer Philip James of the University of Toledo, lead scientist on the Mars project, said he was impressed with the picture.
"We've done considerable amounts of Mars photography from observatories in Mona Kea [Hawaii] and Cerro Tololo [in Chile], and some of those pictures were among the best ever obtained from terrestrial observatories. And this is clearly better," he said.
"Unfortunately, it still isn't as good as Hubble might originally have done" because of defects in its primary mirror, James said. But, after all the gloom that followed the discovery of Hubble's defects, "I really had expected much worse."
He was particularly struck by the clarity of the Martian atmosphere.
"This picture was taken at the tail end of one of the big dust-storm periods on Mars, and the atmosphere seems real clear of dust," he said. "If there had been a big storm recently, we would have seen more dust hanging around."
"Then I was sort of interested in the clouds at the south polar region. Very little is known about the south polar clouds," he said.
James said additional pictures of comparable quality were taken in January and February, and more are scheduled for March and May. After that, the observations will end for a year because Mars will be too close to the sun.
The picture released today is actually a composite of three separate pictures shot at 12-minute intervals through red, green and blue filters by Hubble's Planetary Camera. Put together, they yield a full-color portrait of Mars in midwinter in its southern hemisphere.
Because of defects in the telescope's primary mirror, scientists at the Space Telescope Science Institute had to process the images through computers that subtracted, or "deconvolved," most of the distortions.
The picture shows surface features as small as 30 miles across, as compared with 90 miles with the best ground-based telescopes on their best days.
James expressed confidence that scientists will gradually get better at processing Hubble images, yielding clearer pictures.
More detailed pictures, of course, have been taken from unmanned planetary spacecraft such as Mariner 9 in 1971, and the Viking Mars landers in 1976.