Thanks to the news images sent back to Earth by NASA's Messenger spacecraft the scientists are able to decipher more secrets of the Red planet.

Researchers are amazed by the wealth of images and data that show a unique world with a diversity of geological processes and a very different magnetosphere from the one discovered and sampled more than 30 years ago.

The spacecraft's cameras and other sophisticated, high-technology instruments collected more than 1,200 images and made other science observations. Data included the first up-close measurements of Mercury since the Mariner 10 spacecraft's third and final flyby on March 16, 1975.

"This flyby allowed us to see a part of the planet never before viewed by spacecraft, and our little craft has returned a gold mine of exciting data," said Sean Solomon, MESSENGER's principal investigator, Carnegie Institution of Washington. "From the perspectives of spacecraft performance and maneuver accuracy, this encounter was near-perfect, and we are delighted that all of the science data are now on the ground."

The images revealed that Mercury has impact craters that appear very different from lunar craters. One of the craters puzzled the scientists. This formation, that scientists dubbed "The Spider", the middle of a large impact crater called the Caloris basin and consists of more than 100 narrow, flat-floored troughs radiating from a complex central region.

"The Spider has a crater near its center, but whether that crater is related to the original formation or came later is not clear at this time," said James Head, science team co-investigator at Brown University, Providence, R.I.

Now that the spacecraft has shown scientists the full extent of the Caloris basin, its diameter has been revised upward from the Mariner 10 estimate of 800 miles to perhaps as large as 960 miles from rim to rim. The plains inside the Caloris basin are distinctive and more reflective than the exterior plains. Impact basins on the moon have opposite characteristics. The spacecraft's suite of instruments has provided insight into the mineral makeup of the surface terrain and detected ultraviolet emissions from sodium, calcium and hydrogen in Mercury's exosphere. It also has explored the sodium-rich exospheric "tail," which extends more than 25,000 miles from the planet.

Launched on a Boeing Delta II rocket, MESSENGER lifted off from Cape Canaveral Air Force Station, Florida at 02:15:56 EDT on August 3, 2004 with the goals to determine the chemical composition of Mercury's surface, its geologic history, the nature of the planet's magnetic field, the size and state of the core, the volatile inventory at the poles, and the nature of Mercury's exosphere and magnetosphere.

However, MESSENGER's most important mission is yet to come: its Mercury orbit insertion will be on March 18, 2011, beginning a year-long orbital mission which will see a lot more data sent to Earth.

The space probe is also interesting because its navigation team is lead by KinetX, the first private company to be responsible for navigation of a NASA deep space mission. Their experts are fully responsible for determining all trajectory adjustments throughout the probe's flight through the inner solar system ensuring that MESSENGER arrives at Mercury with the proper velocity for orbit insertion.

Mercury, named after the Roman god Mercurius, is the innermost and smallest planet in the solar system and orbits the Sun every 88 days. The robotic space probe Mariner 10 was the only spacecraft to approach Mercury, and managed to map about 40 percent of its surface. Its mission ran between 1974 and 1975 and was the first spacecraft to make use of an interplanetary "gravitational slingshot" maneuver.