Little more than three weeks after MESSENGERs first historic flyby of Mercury, the team this week began mapping out its trajectory and observation plans for the probes second pass of the planet this fall. On October 6, 2008, at 4:39 a.m. EST, the spacecraft will once again fly 200 kilometres (124 miles) above the surface of the planet. This is the second of three scheduled passes of Mercury, each designed to provide a critical gravity assist needed to keep MESSENGER on track for its March 2011 orbit insertion around the planet. As with the first flyby on January 14, 2008, the spacecrafts full suite of instruments will be operating.
As MESSENGER captured this image before its closest approach with the planet.
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
The scene is near Mercury's terminator. The large crater situated on the right side in the bottom half of the image is Sullivan crater, a structure about 135 kilometres in diameter also seen during the Mariner 10 mission. An influential American architect, Louis Sullivan and his work are often associated with the rise of modern skyscrapers, and this crater named in his honour finds a fitting home in Mercury's ancient geological architecture.
The planet Mercury's magnetic field appears to be strong enough to fend off the harsh solar wind from most of its surface, according to data gathered in part by a University of Michigan instrument onboard NASA's MESSENGER spacecraft. U-M's Fast Imaging Plasma Spectrometer (FIPS) on Jan. 14 took the first direct measurements of Mercury's magnetosphere to determine how the planet interacts with the space environment and the Sun.
MESSENGER skimmed only 124 miles (200 kilometres) over Mercury's surface on Jan. 14, in the first of three passes it will make before settling into orbit March 18, 2011. The photos, released today, include one of a feature the scientists informally call "the spider," which appears to be an impact crater surrounded by more than 50 cracks in the surface radiating from its centre.
This set of departing Narrow Angle Camera (NAC) images has been assembled into a movie, which will be shown tomorrow during a NASA press conference at 1 pm EST.
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Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington This image, taken by the Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS), shows a close view of the previously unseen side of Mercury.
This image, taken by the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS), shows a region of Mercury's surface previously unseen by spacecraft and a large scarp crossing vertically through the scene, on the far right of the image. This scarp is the northern continuation of the one seen in the NAC image released on January 16. The width of this image is about 200 kilometres, showing that these scarps can be hundreds of kilometres long on Mercury.
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
This image was acquired about 94 minutes after MESSENGER's closest approach to Mercury, when the spacecraft was at a distance of about 32,000 kilometres.
The Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) captured this shot looking toward Mercury's north pole.
One of many investigations underway includes identifying and measuring the impact craters on these previously unseen regions. The density of craters on the surface of a planet can be used to indicate the relative age of different places on the surface; the more craters the surface has accumulated, the older the surface.
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By counting craters on different areas of Mercury's surface, a relative geologic history of the planet can be constructed, indicating which surfaces formed first and which formed later. However, this process is also time consuming; Mercury has a lot of craters! This image shows just a portion (276 kilometres wide) of one frame taken with the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS). In this image alone, 763 craters have been identified and measured (shown in green) along with 189 hills (shown in yellow). Altogether, 491 frames were taken by the NAC to create high-resolution mosaics of Mercury's surface.
MESSENGER's Wide Angle Camera (WAC), part of the Mercury Dual Imaging System (MDIS), is equipped with 11 narrow-band colour filters, in contrast to the two visible-light filters and one ultraviolet filter that were on Mariner 10's vidicon camera. By combining images taken through different filters in the visible and infrared, the MESSENGER data allow Mercury to be seen in a variety of high-resolution colour views not previously possible. MESSENGERs eyes can see far beyond the colour range of the human eye, and the colours seen in the accompanying image are somewhat different from what a human would see.
Expand (110kb, 1024 x 768) Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
This colour image was generated by combining three separate images taken through WAC filters sensitive to light in different wavelengths; filters that transmit light with wavelengths of 1000, 700, and 430 nanometers (infrared, far red, and violet, respectively) were placed in the red, green, and blue channels, respectively, to create this image. The human eye is sensitive across only the wavelength range 400 to 700 nanometers. Creating a false-colour image in this way accentuates colour differences on Mercury's surface that cannot be seen in the single-filter, black-and-white images released last week.