Published: January 31, 2008
WASHINGTON — The Messenger spacecraft that zipped past Mercury two weeks ago found more evidence of the innermost planet’s turbulent past, including ridges that run hundreds of miles and a unique feature made up of more than 100 troughs radiating in all directions, scientists said Wednesday.

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

This false-color image, taken as Messenger approached Mercury, combined three black-and-white images taken through different color filters More Photos »

A preliminary look at data from the flyby, including 1,213 images, shows a small, cratered planet that superficially looks like Earth’s moon but is very different in reality, they said.

The robot spacecraft, the first to visit the planet in more than three decades, passed 124 miles above Mercury’s surface on Jan. 14 before continuing on a path that is to bring it back three more times in the next three years before settling into orbit.

During the encounter, the Messenger’s seven scientific instruments scanned the planet, its magnetic field and its wispy atmosphere in great detail.

“Our little craft has returned a gold mine of exciting data,” said Dr. Sean C. Solomon of the Carnegie Institution of Washington, the mission’s lead investigator.

“We were continually surprised,” Dr. Solomon said at a NASA news conference. “It was not the planet we expected. It was not the moon.”

Mercury remains a very dynamic planet and is a key to understanding the evolution of the inner solar system and its four rocky planets, including Earth, he said.

NASA’s Mariner 10 spacecraft, which made three flybys of Mercury in 1974 and 1975, mapped about 45 percent of the planet’s surface. The Messenger craft took pictures of another 30 percent during its first visit and should complete the portrait when it returns on its next flyby in October, scientists said.

After that visit and another in September 2009 to slow the craft, the Messenger is to settle into orbit around Mercury on March 18, 2011, for at least a year of studies.

Among the features spotted by the Messenger — short for the $446 million mission’s formal name, Mercury Surface, Space Environment, Geochemistry and Ranging — is one informally called “the spider.” It appears to be an impact crater 25 miles in diameter from which more than 100 flat-bottomed troughs shoot out in all directions, said Louise Prockter, an imaging instrument scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., which built and operates the spacecraft.

“It’s a real mystery, a very unexpected find,” Ms. Prockter said, unlike anything ever observed in the solar system. It is unclear if the impact crater caused the shattered-looking feature or came later, after the troughs formed for another reason, she said.

(Article courtesy of The New York Times: )



Mercury in color - Prockter07.jpg
MESSENGER’S first photo of the unseen side of Mercury.

MESSENGER’s Wide Angle Camera (WAC), part of the Mercury Dual Imaging System (MDIS), is equipped with 11 narrow-band color filters. As the spacecraft receded from Mercury after making its closest approach on January 14, 2008, the WAC recorded a 3×3 mosaic covering part of the planet not previously seen by spacecraft. The color image shown here was generated by combining the mosaics taken through the WAC filters that transmit light at wavelengths of 1000 nanometers (infrared), 700 nanometers (far red), and 430 nanometers (violet). These three images were placed in the red, green, and blue channels, respectively, to create the visualization presented here. The human eye is sensitive only across the wavelength range from about 400 to 700 nanometers. Creating a false-color image in this way accentuates color differences on Mercury’s surface that cannot be seen in black-and-white (single-color) images.

Color differences on Mercury are subtle, but they reveal important information about the nature of the planet’s surface material. A number of bright spots with a bluish tinge are visible in this image. These are relatively recent impact craters. Some of the bright craters have bright streaks (called “rays” by planetary scientists) emanating from them. Bright features such as these are caused by the presence of freshly crushed rock material that was excavated and deposited during the highly energetic collision of a meteoroid with Mercury to form an impact crater. The large circular light-colored area in the upper right of the image is the interior of the Caloris basin. Mariner 10 viewed only the eastern (right) portion of this enormous impact basin, under lighting conditions that emphasized shadows and elevation differences rather than brightness and color differences. MESSENGER has revealed that Caloris is filled with smooth plains that are brighter than the surrounding terrain, hinting at a compositional contrast between these geologic units. The interior of Caloris also harbors several unusual dark-rimmed craters, which are visible in this image. The MESSENGER science team is working with the 11-color images in order to gain a better understanding of what minerals are present in these rocks of Mercury’s crust.

The diameter of Mercury is about 4880 kilometers (3030 miles). The image spatial resolution is about 2.5 kilometers per pixel (1.6 miles/pixel). The WAC departure mosaic sequence was executed by the spacecraft from approximately 19:45 to 19:56 UTC on January 14, 2008, when the spacecraft was moving from a distance of roughly 12,800 to 16,700 km (7954 to 10377 miles) from the surface of Mercury.


Caloris basin labeled.png
Mariner 10’s photomosaic of the Caloris Basin on Mercury, with labels. 


Mercury's 'Weird Terrain'.jpg
The so-called ‘Weird terrain’ on Mercury, at the antipodal point of the en:Caloris Basin. From


Merc fig2sm.jpg

Radar image of Mercury’s North Pole.



Terrestrial planet size comparisons.jpg

This diagram shows the approximate relative sizes of the terrestrial planets, from left to right: Mercury, Venus, Earth, and Mars. Distances are not to scale. A terrestrial planet is a planet that is primarily composed of silicate rocks. The term is derived from the Latin word for Earth, “Terra”, so an alternate definition would be that these are planets which are, in some notable fashion, “Earth-like”. Terrestrial planets are substantially different from gas giants, which might not have solid surfaces and are composed mostly of some combination of hydrogen, helium, and water existing in various physical states. Terrestrial planets all have roughly the same structure: a central metallic core, mostly iron, with a surrounding silicate mantle. Terrestrial planets have canyons, craters, mountains, volcanoes and secondary atmospheres.

(Photos courtesy of Wikipedia.)




1 Comment

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  1. What was the name of the spacecraft that took the pictures of mercury’s cratred surface March 29th 1974. Please contact me on myspace 4 the final answer.


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