Scientists poring over their first close-up data from Mercury in almost 33 years say they're delighted by some new discoveries and astonished by the remarkably sharp view of the planet captured by NASA's Messenger spacecraft during its flyby earlier this week.
"We're just jumping up and down as each new image gets examined and new data comes down," said Messenger's principal investigator, Sean Solomon of the Carnegie Institution in Washington.
"Even on the side of Mercury [that] Mariner 10 was able to view 30 years ago, we're seeing things for the first time," he said.
As Messenger flew within 124 miles of Mercury on Monday, its computers spat out pre-programmed commands for more than 1,200 photographs and observations by the craft's cameras, spectrometers and other instruments.
It all went perfectly, and the data arrived Tuesday at the mission's Science Operations Center, at Johns Hopkins University's Applied Physics Lab.
"I was shocked at the quality -- much better than Mariner 10," said Robert G. Strom, a University of Arizona expert on craters and a Mariner 10 project veteran who has written two books on Mercury. "We're going to have to go back and look at the entire planet all over again."
A close-up image displayed a 300-mile-wide swath of Mercury's crater-scarred surface.
To the layman it looked like the moon, but Solomon said Mercury's brightness, colors and topography are quite different. And there have been surprises.
"Mariner 10 saw these big, big cliff-shaped faults that have been interpreted as indicating the planet contracted -- shrank" -- as it cooled, Solomon said. That theory predicted similar faults would be found on the opposite side, which Mariner couldn't see.
"We are seeing them, but there's a greater diversity of tectonic features than expected," he said.
Scientists are also seeing craters with mysterious dark halos around them, he said, "as if the craters had excavated through superficial material and brought up materials of some different composition."
Data from Messenger's spectrometers should identify the minerals and map them. Other instruments have reported on the planet's magnetic field, thin atmosphere and other features as scientists seek answers to larger questions about Mercury's origins and evolution.