Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington - “MESSENGER’s First Look at Mercury’s Previously Unseen Side“

A heavily cratered side of the planet Mercury never before seen has been revealed by the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft. A single image was released by NASA this evening after the successful flyby of the innermost planet on Monday. Featuring rayed craters, a portion of one of the largest basins in the solar systems, and rings of dark material, the new image is one of over 2000 captured during the first flyby of Mercury in thirty-three years.

More data is expected to arrive on the Earth on Wednesday after MESSENGER’s scheduled contact over the Deep Space Network was postponed due to unexpected problems with other missions and a shift in priorities.  In addition to the global wide-angle image released this evening,  these data include approach and departure images that will be turned into movies and high resolution narrow-angle images taken from only 200 kilometers above Mercury’s surface during closest approach.

In 1975 Mariner 10 successfully completed its third and final flyby of Mercury after imaging less than 50 percent of the planet’s surface.  MESSENGER will complete this mapping task between yesterday’s flyby and two more flybys scheduled for October 06, 2008 and September 29, 2009.  Then, on March 18, 2011, MESSENGER will enter orbit around Mercury for a planned year-long science phase.

The data returned by MESSENGER are expected to answer several longstanding questions about Mercury.  MESSENGER will use its array of instruments protected by a sunshade to search for evidence of water ice trapped in deep and dark craters at the planet’s poles, a potentially counter intuitive finding given Mercury’s close proximity to the Sun.   Scientists will study the planet’s surface and composition as well as its inner structure.  Mercury has a dense core of iron thought to compose a more significant portion of the planet than the cores of the other inner planets do.  Why this should be the case is complicated by the presence of a magnetic field around Mercury.  Magnetic fields are thought to depend on molten cores, but models of Mercury indicate that due to its small size its core should have solidified by now.

More Information

• MESSENGER Website
  • Press Release and Image: “MESSENGER’s First Look at Mercury’s Previously Unseen Side“

NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft was successfully launched this morning at 11:15:56 a.m. PST. The spacecraft will be the first mission to the planet Mercury in 30 years and will be the first spacecraft to ever orbit the innermost planet of our solar system.

When falling toward the Sun, like falling toward the Earth without a parachute, an object begins to accelerate. The fuel requirements for a direct flight to Mercury are cost prohibitive, so MESSENGER will take a looping route using the gravity of the Earth and Venus to slow itself down to the appropriate speed to be captured by Mercury. MESSENGER will arrive at the planet in 2011 to begin a one year mission. Only 40 percent of the planet has been photographed, and most of the images are low resolution.

Because the spacecraft will be operating so close to the Sun, a sunshade is required. The instruments behind the sunshade will enjoy room temperature.

The launch of MESSENGER, the first mission to Mercury since 1974, has just been delayed until after June 30, 2004. The planetary gravity-assist flyby schedule has changed because of the delay. MESSENGER will now fly once around the Earth, twice around Venus, and three times around Mercury before entering orbit around Mercury in March 2011 (delayed from 2009).

By the way, the image you see at the top of your screen is of Mercury (not the Moon) taken thirty years ago by Mariner 10. To date there have been no other missions to Mercury. Thanks to NASA/JPL for public access to many of their mission images.