NASA announced Monday that , armed with an array of six analysis instruments, flew 125 miles above the planet's at 4:40 Eastern Monday morning. This is the spacecraft's second of three passes over Mercury. It made its first flyby in January.

While Messenger was taking photos and collecting other data from the planet, it used Mercury's gravity to give it a "critical" assist to keep the probe on course. NASA scientists hope to move the spacecraft into position to actually begin orbiting Mercury in March 2011.

NASA hopes that Messenger becomes the first spacecraft to orbit the planet, which is only 58 million kilometers from the sun. In comparison, the Earth is 149,600,000 kilometers from the sun.

Part of Messenger's mission is to help scientists figure out whether there is ice hidden on the poles of Mercury. Finding ice there would be a major discovery, since the planet is so close to the sun, its surface is 11 times brighter than Earth's. NASA noted in online documents that while Mercury's surface temperatures can reach about 840 degrees Fahrenheit, deep craters near its poles are in the shade, and there the temperature can plummet to minus 350 F.

Ice was one of the major discoveries that the this summer on the Martian north pole. Instruments on several tests on soil dug up by and discovered what scientists had been hoping to find -- elements that could .