Two days after NASA's Messenger probe sped past Mercury, a group of Earth-bound scientists are getting their first glimpse of previously undiscovered parts of the scorched planet.

Messenger provides the first look at Mercury's previously unseen side. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Scientists at the Johns Hopkins University's Applied Physics Laboratory reported Messenger's wide- and narrow-angle cameras snapped 1,213 images during about 55 hours of near-continuous science observations.

Four images were posted on the mission's Web site by late Wednesday, including shots of never-before-seen portions of the solar system's innermost planet.

It could take up to a week for all of the 700 gigabytes of data to be sent home. All of the probe's scientific instruments were turned on for the trip past Mercury to study its composition and terrain.

Officials also plan to create at least seven large mosaic images of the desolate world from high-resolution snapshots taken by Messenger's narrow-angle camera in the coming weeks.

Monday's historic fly-by was the first time a robotic spacecraft visited the hostile world since NASA's Mariner 10 probe zoomed past Mercury nearly 33 years ago. Mariner 10 approached Mercury three times during its mission but never entered orbit.

This image shows a previously unseen crater with distinctive bright rays of ejected material extending radially outward from the crater's center. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

But Mariner 10 was only able to study about 45 percent of Mercury's surface, and Messenger was dispatched to fill in the voids from the first round of the planet's exploration three decades ago. Messenger's camera system was able to see about half of the unexplored side of Mercury on Monday.

The highest resolution images from Monday are also giving scientists a more detailed view of known surface features, including a giant 800-mile-wide impact basin named Caloris.

"It is already clear that MESSENGER's superior camera will tell us much that could not be resolved even on the side of Mercury viewed by Mariner's vidicon camera in the mid-1970s," the science team said in a written statement.

The Caloris basin, believed to be one of the youngest large impact craters in the solar system, lied in partial darkness during the Mariner 10 mission.

"The new image shows the complete basin interior and reveals that it is brighter than the surrounding regions and may therefore have a different composition," the science team said.

Messenger's modern camera has revealed detail that was not well seen by Mariner 10, including the broad ancient depression overlapped by the lower-left part of the Vivaldi crater. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Messenger flew within 124 miles of Mercury's singed surface at 2:04 p.m. EST Monday as part of a pinball-like course through the inner solar system to set up for the craft's permanent arrival at Mercury.

Messenger already completed swings past Earth and Venus since its 2004 launch. Two more close approaches to Mercury are planned in October and September 2009 to slow the spacecraft before it maneuvers into orbit around the planet on March 18, 2011.

Scientists plan to operate Messenger for at least a year after its 2011 arrival in an effort to answer key questions about the planet's history and the formation of the inner solar system.

One of the highest and longest scarps (cliffs) yet seen on Mercury curves from the top center down across the right side of this image. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington