The black and white image, posted on the NASA website Tuesday, shows a surface pocked with craters of varying sizes and shapes. NASA says this was the first of more than 360 images taken and sent back to Earth on Tuesday.

    The images were captured by the unmanned MESSENGER probe, which earlier this month became the first spacecraft to orbit Mercury.

    MESSENGER is expected to continue circling the solar system's innermost planet for at least a year before mission controllers here on Earth allow the little probe to drop through the thin atmosphere and crash on the surface.

    Mission managers say MESSENGER will use high-tech instruments and cameras to collect important data about Mercury that possibly will solve some of the mysteries surrounding the tiny planet.

    They are interested in learning more about Mercury's geologic history and magnetic field, the composition of its core, and learning whether there is frozen water at its poles.   Scientists say knowing more about Mercury will give them a better understanding of the early solar system and how it formed about 4.5 billion years ago.

    The only other man-made probe to reach Mercury was NASA’s Mariner 10,  which photographed the planet on three "fly-bys" in the mid-1970s.

    Mercury is slightly larger than the earth's moon, making it the smallest planet in the solar system.  With an orbit keeping it a mere 58 million kilometers from the sun on average, Mercury is about two-thirds closer to the sun than Earth.(本文由在线英语听力室整理编辑)