Messenger Sends New Views Of Mercury

NASA's Messenger spacecraft early this morning beamed back new views of Mercury taken Monday during its second close encounter with the planet.

Launched from Cape Canaveral Air Force Station in 2004, Messenger is on target to become the first probe to orbit the innermost planet in 2011.

With data from the second of three planned flybys, scientists at the Johns Hopkins University Applied Physics Laboratory in Maryland hope to map about 30 percent of Mercury's surface that had never been seen by a spacecraft.

That's a land area larger than South America on the solar system's smallest planet, which is slightly larger than Earth's moon.

"When these data have been digested and compared, we will have a global perspective of Mercury for the first time," said Sean Solomon of the Carnegie Institution of Washington, Messenger's principal investigator, in a statement released today.

Most of the terrain being seen up close for the first time is shown in the picture above, to the east of the bright crater near the center of the picture.

The image was taken about 90 minutes after Messenger made its closest approach, skimming about 125 miles above Mercury's surface at 4:40 a.m. Monday.

In all, about 30 hours of science observations were recorded with instruments including cameras, spectrometers and an altimeter. Messenger rotated its instruments toward Earth before 2 a.m. today and began to transmit data from the flyby.

Scientific findings will be discussed during a news conference tentatively scheduled for Oct. 29.

The $426 million Messenger mission seeks to improve understanding of Mercury's composition and magnetic field, and what they say about the formation of the inner solar system.

Messenger made its first flyby of Mercury in January, seeing the opposite side of the planet. A third flyby will occur next September, again using the planet's gravity to help position the probe to enter orbit around Mercury in March 2011.

NOTE ON IMAGES: Click on the spectacular new images of Mercury to enlarge them. They were taken by NASA's Messenger spacecraft on Monday during the second of three planned flybys of the planet. The image above is one of the first to be returned and shows a Wide Angle Camera image of the departing planet taken about 90 minutes after the spacecraft’s closest approach to Mercury. The bright crater just south of the center of the image is Kuiper, identified on images from the Mariner 10 mission in the 1970s. For most of the terrain east of Kuiper, toward the limb (edge) of the planet, the departing images are the first spacecraft views of that portion of Mercury’s surface. A striking characteristic of this newly imaged area is the large pattern of rays that extend from the northern region of Mercury to regions south of Kuiper.

The second Wide Angle Camera image was acquired 9 minutes and 14 seconds after MESSENGER’s closest approach to Mercury, when the spacecraft was moving at 3.8 miles per second. This portion of Mercury’s surface was previously imaged under different lighting conditions by Mariner 10, but this new MESSENGER image mosaic is the highest-resolution color imaging ever acquired of any portion of Mercury’s surface. The largest impact feature at the top of the image is about 83 miles in diameter and is named Polygnotus, after a Greek painter from the 5th century B.C. This basin has a central peak ring and is embayed with smooth plains material, which is very different in texture from the surrounding terrain.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington