Mercury’s Hydrogen Tail
Release Date: February 1, 2008



This plot shows Lyman-alpha emission at 121.6 nm associated with neutral hydrogen in the near vicinity of Mercury. This is the first detection of hydrogen tail emission at Mercury and the first time that neutral hydrogen and sodium atoms have been observed in the tail simultaneously. This emission is about 100 times less intense than the sodium emission. As with the sodium emission, discovering the true spatial distribution requires more analysis. The similar asymmetries in hydrogen, derived from the solar wind, and the much heavier sodium nonetheless suggest that solar-wind interactions with Mercury’s magnetosphere have played a strong role in supplying tail material at the time of MESSENGER’s flyby.

Observing the Lyman alpha emission line, deep in the ultraviolet, is possible only from space. Such hydrogen emissions were also observed by Mariner 10 but only on the subsolar limb.

Calcium was detected in the near-Mercury exosphere by MESSENGER and has also been observed telescopically from Earth. Other species are expected to be seen in Mercury’s exosphere as well, but the orbital phase of the mission offers better opportunities to observe them.


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

Source: JHUAPL - MESSENGER - Gallery

MESSENGER Approaches Mercury
Release Date: February 1, 2008



Click here to watch this movie.

On January 13, 2008, beginning 30 hours before MESSENGER's closest approach to Mercury, the Wide Angle Camera, part of the Mercury Dual Imaging System (MDIS), began snapping images as it approached the planet. Over this period, MESSENGER imaged the planet once every 20 minutes to produce this approach sequence, which has been compiled into a movie. At the start of the movie, the MESSENGER spacecraft is about 630,000 kilometers (about 390,000 miles) from Mercury. The movie ends when MESSENGER is about 34,000 kilometers (about 21,000 miles) from Mercury and about 100 minutes before its closest approach, when it passed a mere 200 kilometers (124 miles) above Mercury's surface.

In the approach movie, Mercury appears as a sunlit crescent. During the encounter, MESSENGER passed over the night side of the planet, experienced its closest approach with Mercury, and then emerged into daylight. This encounter was the first of three flybys of Mercury planned for the MESSENGER mission.


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

Source: JHUAPL - MESSENGER - Gallery

MESSENGER Departs Mercury
Release Date: February 1, 2008



Click here to watch this movie.

As MESSENGER completed its successful flyby of Mercury, the Narrow Angle Camera (NAC), part of the Mercury Dual Imaging System (MDIS), took images of the planet as the spacecraft departed. Beginning on January 14, 2008, about 100 minutes after MESSENGER's closest pass by the surface of Mercury, until January 15, 2008, about 19 hours later, the NAC acquired one image every four minutes. In total, 288 images were snapped during this time and were compiled sequentially to produce this movie. At the start of the movie, MESSENGER is about 34,000 kilometers (about 21,000 miles) from Mercury, and the first image has a field of view of about 950 kilometers (about 590 miles) in width. At the end of the movie, the MESSENGER spacecraft is a distance of about 440,000 kilometers (270,000 miles) from Mercury.

This movie shows the end of MESSENGER's first encounter with Mercury. MESSENGER will fly by Mercury two additional times during the mission, in October 2008 and September 2009. In March 2011, MESSENGER will enter into an orbit around Mercury and begin a year-long scientific investigation of the planet.


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

Source: JHUAPL - MESSENGER - Gallery

Mercury's Geological Architecture
Release Date: February 6, 2008



As MESSENGER sped by Mercury on January 14, 2008, the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) captured this image before its closest approach with the planet. The scene is near Mercury's terminator (the line between the sunlit day side and dark night side of the planet), where shadows are long and height differences accentuated, revealing rising crater walls that tower over the floors below. The large crater situated on the right side in the bottom half of the image is Sullivan crater, a structure about 135 kilometers (84 miles) 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 honor finds a fitting home in Mercury's ancient geological architecture.

Mission Elapsed Time (MET) of image: 108821402


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

Source: JHUAPL - MESSENGER - Gallery

MESSENGER Mission News
February 6, 2008
_http://messenger.jhuapl.edu

MESSENGER Team Begins Planning for Second Mercury Encounter

Little more than three weeks after MESSENGER’s first historic flyby of Mercury, the team this week began mapping out its trajectory and observation plans for the probe’s second pass of the planet this fall. On October 6, 2008, at 4:39 a.m. EST, the spacecraft will once again fly 200 kilometers (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 spacecraft’s full suite of instruments will be operating.

• The Mercury Dual Imaging System will gather color observations of Mercury’s surface in 11 filters, and its Narrow Angle Camera will image high-resolution monochrome measurements near the equator.
• The Magnetometer and the Energetic Particle and Plasma Spectrometer will explore the planet’s magnetosphere at low altitude, near Mercury’s equator.
• The ultraviolet and visible spectrometer on the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) will make observations of chemical species in the exosphere and tail, and the MASCS visible and infrared spectrograph will make spectral measurements of Mercury’s surface.
• The Neutron Spectrometer will make measurements of the neutron flux that may yield estimates of iron and thallium abundances near MESSENGER’s ground track.
• The Mercury Laser Altimeter (MLA) will acquire another topographic profile of Mercury’s surface, shedding light on the planet’s geographic history.
• The X-Ray Spectrometer (XRS) and Gamma-Ray Spectrometer will measure X-ray and gamma-ray emissions from the surface of Mercury and look for characteristic “signatures” in those emissions to determine its elemental composition.

“Observations during this second MESSENGER flyby will almost complete the first high-resolution viewing of Mercury, adding another one-third of the planet surface to the 21% of territory not seen by Mariner 10 and first imaged by MESSENGER in January 2008,” says MESSENGER Project Scientist Ralph McNutt. “This second flyby will also provide an important new view of the time-variable exosphere and magnetosphere, adding to our knowledge of how Mercury responds to its variable interplanetary environment as a system.”

MESSENGER is now approximately 0.35 Astronomical Units (AU) from the Sun (1 AU equals 93 million miles) and will reach its next local maximum Sun distance of 0.70 AU at the end of March. Most of the instruments are still on, but they will all be turned off in preparation for the second in-flight main processor software load scheduled for February 27, 2008. The first software load was conducted on October 24, 2005.

“This load – planned more than a year ago – will execute the third Deep Space Maneuver on March 19 using new software,” explains MESSENGER Operations Manager Andy Calloway. He adds: “In addition to these two top priorities and the second Mercury flyby planning, the team will be focusing on orbital operations with a third ‘day in the life’ test. This will be the first test using the latest science planning software and will include orbital eclipse operations along with hot planet fly-over constraints.”

Meanwhile, MESSENGER’s science team is busy analyzing data from the first flyby in preparation for almost two dozen presentations planned to be given at the 39th Lunar and Planetary Science Conference in early March.

”Our second flyby will occur one and a half Mercury solar days after our first, and as a result the nightside we flew over in January will be in daylight in October,” says MESSENGER Principal Investigator Sean Solomon. “Once again, we will be seeing territory never before viewed at close range. Three weeks ago we were reminded how many surprises Mercury has in store for us. We expect to be surprised again this October.”


MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as principal investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.

Source: JHUAPL - MESSENGER - Status Report

One Month Ago…
Release Date: February 14, 2008



One month ago, on January 14, 2008, MESSENGER became the first spacecraft in over three decades to visit Mercury, snapping images of a large portion of Mercury's surface previously unseen by spacecraft. As the spacecraft proceeds on its journey, the science team continues to study the 1213 images returned from the mission's historic first flyby. The probe’s trajectory will bring it to a second Mercury flyby on October 6, 2008.

MESSENGER’s Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) captured this image during the flyby one month ago. The Sun is illuminating this region at a low angle, accentuating the modest ridges and other low topography on these nearly flat plains. Low ridges trend from the top-center of the image to the left edge (white arrows). The ghostly remains of craters are visible, filled to their rims by what may have been volcanic lavas (red arrows). The faint remnant of an inner ring within the large crater in the bottom half of this picture can be seen (blue arrow); the area interior to this ring was also flooded, possibly by lava, nearly to the point of disappearance. Clusters of secondary craters on the floor of the large crater and elsewhere (yellow arrows) formed when clumps of material were ejected from large impacts beyond the view of this image, which is about 350 kilometers (220 miles) across.


Image Mission Elapsed Time (MET): 108826972


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

Source: JHUAPL - MESSENGER - Gallery

Craters with Dark Halos on Mercury
Release Date: February 21, 2008



As MESSENGER flew by Mercury, the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) captured this view on January 14, 2008. Two of the larger craters in this image appear to have darkened crater rims and partial “halos” of dark material immediately surrounding the craters. Both craters appear to have nearly complete rims and interior terraced walls, suggesting that they formed more recently than the other nearby shallower craters of similar size. There are two possible explanations for their dark halos: (1) Darker subsurface material may have been excavated during the explosions from the asteroid or comet impacts that produced the craters. (2) Large cratering explosions may have melted a fraction of the rocky surface material involved in the explosions, splashing so-called “impact melts” across the surface; such melted rock is often darker (lower albedo) than the pre-impact target material. In either case, the association of the dark material with relatively recently formed craters suggests that the processes that gradually homogenize Mercury’s surface materials have not yet had time to reduce the contrast of these dark halos. The crater with associated dark material in the lower-left part of this image is about 100 km (60 miles) in diameter, and the crater with patches of dark material in the upper right is about 70 km (40 miles) across. These dark-halo craters, located near Mercury's south pole, are also visible in the previously released false-color image created from three Wide Angle Camera (WAC) frames.

Information from images taken in the 11 different color filters of the WAC will help MESSENGER scientists to understand the nature of the dark material associated with the craters shown in this image and will determine whether they reveal the presence of subsurface material of a different composition, are examples of impact melt, or perhaps have some other explanation.

Image Mission Elapsed Time (MET): 108828161


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

Source: JHUAPL - MESSENGER - Gallery

Craters in Caloris
Release Date: February 27, 2008



As MESSENGER sped by Mercury on January 14, 2008, the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) captured this image, which includes the edge of the planet against the blackness of space. Much of the foreground shows a portion of Caloris basin, one of the largest impact basins in the solar system. The two large craters near the bottom of this image can be identified on the northwestern floor of the basin on the mosaicked image of Caloris released at MESSENGER's NASA press conference on January 30. The large crater in the bottom middle of this image has a diameter of about 70 kilometers (40 miles).

Caloris basin is an area of particular interest to the MESSENGER science team, since understanding its formation can lead to insights about the nature of large impacts in the early solar system and the results of these catastrophic events. In a false-color image of Mercury, also released on January 30, Caloris basin is visible in the northern hemisphere of the planet as a large, light-colored, roughly circular feature; the floor of the basin may have some differences in its composition compared with the darker surrounding surfaces. The two large craters shown in today's released image are each surrounded by a "halo" of dark material, like the craters shown in our release of February 21. The smaller of the two craters has an unusual pattern of bright, highly reflective material on its floor. The fact that both of these craters, which show different material characteristics, are located within Caloris basin provides information about the variety and complexity of processes that have shaped Mercury's surface.

Image Mission Elapsed Time (MET): 108826622

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

Source: JHUAPL - MESSENGER - Gallery

Making a Mosaic
Release Date: March 5, 2008



During MESSENGER's flyby of Mercury on January 14, 2008, the Mercury Dual Imaging System (MDIS) acquired images to create eight different mosaics. Shown here is an image context sheet with small thumbnail versions of the MDIS Narrow Angle Camera (NAC) images that were captured as the spacecraft approached the planet and used to create a high-resolution mosaic of Mercury. The MDIS instrument is mounted on a pivot, which enables the camera to point in different directions and see different portions of the surface. Both small motions of the spacecraft and movement of the pivot were used to take the images that compose this mosaic sequence. This mosaic has images in 5 columns by 11 rows, but images of just black space or of the unlit, dark planet are not shown on this context sheet.

MDIS started this mosaic 55 minutes before MESSENGER's closest pass by Mercury. The first image of the mosaic was taken in the lower left corner, and images were subsequently acquired by moving across a row and then up to start the next row. An image where Mercury's surface fills the image is about 500 kilometers (310 miles) across. Image names, which are abbreviated under each image in this context sheet, are derived from the mission elapsed time (MET) when the image was taken, which is approximately the time in seconds since launch. The mosaic was planned to have about 10% overlap between neighboring images, to ensure that a mosaic could be formed without any gaps. The resulting mosaic is ultimately created by using the time of each image and corresponding information about the spacecraft location and viewing geometry at that time to place all of the images onto a common map of Mercury.

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

Source: JHUAPL - MESSENGER - Gallery

Making a Mosaic - Part II
Release Date: March 11, 2008



As MESSENGER approached Mercury on January 14, 2008, the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) snapped images of the nearing planet in a sequence that covered the entire sunlit portion of the surface. This mosaic was made from these images, shown as thumbnails on the image context sheet released last week.

This mosaic is shown in a cylindrical equidistant (also known as equirectangular) projection, which simply is a map with longitude lines being vertical and equally spaced and latitude lines being horizontal and equally spaced. The mosaic covers the entire approach crescent view of Mercury, so the vertical extent of the mosaic is comparable to Mercury's diameter of 4880 kilometers (about 3030 miles). Surface features on the right side of the mosaic show long shadows that accentuate height differences because these images were taken near Mercury's terminator, the transition between the sunlit dayside of the planet and the dark night side; the previously released image of the crater Matisse is an example of one of these near-terminator images used in the mosaic. Features near the left side of the mosaic are looking toward the limb of the planet, and this very low viewing geometry and higher Sun angle do not provide much detail about the surface structures; the previously released image looking at Mercury's horizon is an example of such a view that was used to create this mosaic.

This low-resolution version of the mosaic is only 8% of the resolution of the full mosaic and contains only one pixel for approximately every 156 pixels in the original images.

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

Source: JHUAPL - MESSENGER - Gallery

Exploring the Evolution of the Caloris Basin
Release Date: March 19, 2008



As MESSENGER approached Mercury on January 14, 2008, the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) snapped images of the nearing planet in a sequence that covered the entire sunlit portion of the surface. This mosaic was made from these images, shown as thumbnails on the image context sheet released last week.

The Caloris basin on Mercury is one of the youngest large impact basins in the Solar System, and MESSENGER images are enabling scientists to study it in ways not previously possible. This image, acquired by the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS), was taken on January 14, 2008, and shows an area that is about 280 kilometers across (about 170 miles) on the floor of the basin. Bright rays from a young impact crater extend into the image from the top right corner. This bright-rayed crater is located slightly left of the center of the basin and is easily spotted on the previously released image that shows the entire Caloris basin.

The spectacular fractures seen cutting the floor of the basin, as visible in this image, show that extensional (pull-apart) forces deformed Mercury's crust in the ancient past. Impact craters can be observed on top of the fractures and the fractures do not deform the craters, indicating that the fractures are ancient. The fractures are observed in the smooth plains material that fills the Caloris basin, are found near the outer edges of the basin, and are oriented roughly concentric with the basin’s rim. This orientation is in contrast to a series of radial fractures located in the center of the Caloris basin. The fractures were likely formed when the floor of the basin was uplifted, causing horizontal stretching and breaking apart of the material that filled the basin. Similar concentric fractures were observed on the eastern side of the basin that was photographed by Mariner 10. By mapping out the extent of these fractures and other tectonic features, MESSENGER scientists are exploring how Mercury's great Caloris basin evolved after it formed.

Image Mission Elapsed Time (MET): 108826817

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

Source: JHUAPL - MESSENGER - Gallery

MESSENGER Mission News
March 19, 2008
_http://messenger.jhuapl.edu

Critical Deep-Space Maneuver Targets MESSENGER for Its Second Mercury Encounter
The MESSENGER spacecraft delivered a critical deep-space maneuver today – 64 million miles (103 million kilometers) from Earth – successfully firing its large bi-propellant engine to change the probe’s trajectory and target it for its second flyby of Mercury on October 6, 2008. This was the first trajectory-correction maneuver (TCM) to test the continuous slow rotation of the spacecraft throughout the burn, essential for the March 18, 2011, Mercury orbit-insertion (MOI) maneuver.

“Every propulsive event in this complex mission is an important step toward our ultimate goal – placing the first spacecraft into orbit about the innermost planet,” offers MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. “Today’s deep-space maneuver is a crucial milestone that points us cleanly toward our next close look at Mercury in October.”

The 149-second maneuver began at 3:30 p.m. EDT. Mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of the maneuver about 5 minutes 42 seconds later, when the first signals indicating spacecraft thruster activity reached NASA’s Deep Space Network tracking station outside Goldstone, California.

The continuous rotation of the spacecraft occurred during the 90-second firing of the large bi-propellant engine, the main part of the 149-second TCM, and was less than 4° – about 11% of the turn required for the mission-critical MOI. The total change in velocity of 72.2 meters per second (161.5 miles per hour) achieved during the maneuver will increase the spacecraft’s speed relative to the Sun.

This was the third of five deep-space maneuvers that will help the spacecraft reach Mercury orbit. The first, on December 12, 2005, positioned the probe for its October 2006 flyby of Venus; the second, on October 17, 2007, targeted MESSENGER for its first flyby of Mercury this January.

DSM-4 on December 6, 2008, will position MESSENGER for Mercury flyby 3, scheduled for September 30, 2009. And the final deep-space maneuver on November 29, 2009, will target the probe for Mercury orbit insertion.

The next maneuver, TCM-24, is currently scheduled for April 24 and will be used to further fine-tune the trajectory for the second Mercury encounter. “There are also several instrument and subsystem calibrations this spring and summer, and even an instrument flight software load in July,” says MESSENGER Mission Operations Manager Andy Calloway of APL. “The MESSENGER team will also continue to focus on the Mercury Flyby 2 sequence planning and testing, as well as orbital operations planning in parallel with the ongoing flight operations.”


MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as principal investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.

Source: JHUAPL - MESSENGER - Status Report

Appreciating Mozart in a New Light
Release Date: March 27, 2008



When Mariner 10 flew by Mercury in 1974, morning sunlight was just striking Mozart crater so that most of the feature was hidden in darkness near the terminator. During MESSENGER's Mercury flyby on January 14, 2008, Mozart was in full sunlight, allowing the crater to be seen in detail for the first time, as shown in this image snapped by the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS). Named in honor of the classical composer Wolfgang Amadeus Mozart, Mozart is the large crater near the center of the image. The crater’s diameter is about 225 kilometers (140 miles). The arc of dark hills visible on the crater's floor probably represents remnants of a central peak ring, similar to that shown in the January 30 image release. Clues to the origin of the dark material on the peak ring and the curious dark streaks radiating outward from the crater will be provided by 11-color image data collected by the spacecraft’s Wide Angle Camera (WAC). A close inspection of the area around Mozart crater shows many long chains of secondary craters, formed by impact of material thrown out during the formation of the main crater. Mozart crater is located just south of the Caloris basin and can be identified in the false color image previously released. Members of the MESSENGER Science Team are currently studying and characterizing the small craters on Mercury in order to provide new insight into the cratering process as it operates on the different planets in the Solar System.

Image Mission Elapsed Time (MET): 108830250

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

Source: JHUAPL - MESSENGER - Gallery

Mercury Laser Altimeter (MLA) Images Mercury from 4 Million Kilometers
Release Date: March 31, 2008



From a distance of approximately 4 million kilometers (2.5 million miles), MESSENGER's Mercury Laser Altimeter (MLA) imaged the half-moon shape of Mercury one week after the January 14, 2008, flyby of the planet. This image was produced by recording the noise counts in the MLA detector as the spacecraft scanned slowly across the face of the planet. Higher counts are shown as red in this image and lower counts as blue. The scale of the image is given in milliradians (mrad), a unit of angular size, relative to the calculated center of Mercury. At a distance of 4 million kilometers, 1 mrad covers a size of about 4000 kilometers (2500 miles).

This activity was coordinated with scans conducted by the Mercury Dual Imaging System (MDIS) and the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) instruments (shown as the wider patterns near the bottom of the image) in order to co-align the instruments and the spacecraft inertial reference frame. The crosshairs show the calculated position of Mercury, while the circle is a fit to the crescent shape of the planet as determined by the MLA measurements. The offset between the crosshairs and the center of the circle is only roughly 0.05 mrad, which is well within the 0.4-mrad field of view (FOV) of the MLA detector, shown in the top left corner of the image. The MLA detector FOV is designed to allow the altimeter receiver to cover the 0.08-mrad-diameter laser spot when the instrument is within a range to the planet of 1800 kilometers (1100 miles), so it produces a somewhat blurry image at the much greater distance of this image. Observations such as this one continue to improve the calibration of the MESSENGER spacecraft and its science payload.

Credit: NASA/Goddard Space Flight Center/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Source: JHUAPL - MESSENGER - Gallery

Discovering New Rupes on Mercury
Release Date: April 8, 2008



When MESSENGER flew by Mercury on January 14, 2008, the Mercury Dual Imaging System (MDIS) snapped images of a large portion of Mercury's surface that had not been previously seen by spacecraft. On these images, new examples of long cliffs were identified and viewed for the first time. This image, taken by the Narrow Angle Camera (NAC), shows one of those cliffs in the bottom right corner. The cliff can be followed from the bottom edge of the image, cutting through and deforming an impact crater, and curving out of the image frame on the middle right edge. This cliff is the northern continuation of the cliff visible in the images previously released on January 16 and January 27. This image shows an area of Mercury's surface about 200 kilometers (125 miles) across, and by tracing this cliff through the three images, it can be seen that it extends for hundreds of kilometers.

Cliffs that mark geologic escarpments on Mercury are called "rupes," which is simply the Latin word for cliff. On Mercury, rupes are named after the ships of famous explorers, and names include Discovery Rupes, for a ship of Captain Cook, Santa Maria Rupes, for a ship of Christopher Columbus, and Victoria Rupes, for a ship of Ferdinand Magellan. (The word rupes is both singular and plural). Of course, this new rupes discovered by MESSENGER is currently unnamed, but its impressive extent makes it a prime candidate for an addition to the list of the named rupes on Mercury. The MESSENGER team has proposed to the International Astronomical Union, which has the final say on all names of landforms on planets and satellites, that this cliff be named the Beagle Rupes, after the ship on which naturalist Charles Darwin sailed around the world.

Image Mission Elapsed Time (MET): 108827037

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

Source: JHUAPL - MESSENGER - Gallery

Now Introducing: Eminescu
Release Date: April 17, 2008



Last week, the MESSENGER team learned that the impact crater seen in the middle of this Narrow Angle Camera (NAC) image has been officially named Eminescu. The crater was named in honor of Mihai Eminescu, an accomplished and influential poet who is still considered the national poet of Romania. The MESSENGER team proposed the name to the International Astronomical Union (IAU), the authority that officially names surface features on planetary bodies.

Eminescu crater is 125 kilometers (78 miles) in diameter and can be seen just at the top of the image previously released on January 30. The image shown here was acquired by the Mercury Dual Imaging System (MDIS) on January 14, 2008, and shows a portion of Mercury's surface unseen by spacecraft prior to MESSENGER's historic flyby. Eminescu is a particularly interesting crater for several reasons. Eminescu formed more recently than most of the craters on Mercury, on the grounds that there are very few later craters superposed on it. Moreover, impressive chains of secondary craters, formed by material ejected by the impact explosion that formed the crater, radiate away from Eminescu. The central peaks within the crater are arranged in a circular pattern; geologists call this a “peak ring.” The bright peaks inside Eminescu exhibit unusual color characteristics in the 11-color Wide Angle Camera (WAC) images, which the MESSENGER Science Team is currently studying. They show up with a bluish tinge in the previously released false-color image of the entire planet; Eminescu is just north of the equator, near the day/night “terminator” in that image.

Image Mission Elapsed Time (MET): 108828468

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

Source: JHUAPL - MESSENGER - Gallery

New Names for Features on Mercury
Release Date: April 28, 2008



The International Astronomical Union (IAU) recently approved new names for features on Mercury that were all seen for the first time in images taken by MESSENGER during the spacecraft’s first flyby of the planet. Read the full press release for additional details about the naming process and the origin of the names, and visit the U.S. Geological Survey website, the Gazetteer of Planetary Nomenclature, to learn about all of the named planetary features in the Solar System.

This image, produced by mosaicking many Narrow Angle Camera (NAC) images together, shows the locations of the newly named features, along with the craters Basho, Mozart, and Tolstoj, first seen by the Mariner 10 mission. Close-up views of many of these features are available in the MESSENGER website image gallery. In particular, look at these previous releases for NAC high-resolution images of Apollodorus, Beagle Rupes, Eminescu, Mozart, Neruda, Pantheon Fossae, Raditladi, and Sander.

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

Source: JHUAPL - MESSENGER - Gallery

Mercury’s First Fossae
Release Date: May 5, 2008



“The spider” now has an official name: Pantheon Fossae. As first presented at the NASA press conference on January 30, when MESSENGER flew by Mercury on January 14, 2008, the Mercury Dual Imaging System (MDIS) snapped images of an intriguing and previously unknown feature on the surface of Mercury. Near the center of the Caloris basin, a set of troughs (called graben by geologists) was observed to radiate outward in a pattern unlike anything ever seen on Mercury. The Science Team nicknamed this unique feature “the spider.” The International Astronomical Union (IAU) recently approved the official name of Pantheon Fossae, as detailed in the MESSENGER press release issued last week.

The word fossa is Latin and means trench. The term is used in planetary geology to name features that are long, narrow, shallow depressions. Fossae, the plural of fossa, have been named on planetary bodies including Mars, Venus, and the Moon, but Pantheon Fossae are the first to be named on Mercury. The name is taken from the Pantheon in Rome, an ancient temple with a classic domed roof. The dome of the Pantheon has a series of sunken panels that radiate from a central circular opening at the top of the dome, and Mercury’s Pantheon Fossae is reminiscent of this pattern. Consequently, the crater near the center of Pantheon Fossae is now named Apollodorus, who is credited by some as being the architect of the Pantheon. Apollodorus, shown in the middle of this Narrow Angle Camera (NAC) image, has a diameter of 41 kilometers (25 miles). MESSENGER scientists are debating whether Apollodorus played a role in the formation of Pantheon Fossae or whether the crater is simply from a later impact that occurred close to the center of the radial pattern.

Image Mission Elapsed Time (MET): 108828901

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

Source: JHUAPL - MESSENGER - Gallery

The University of Illinois at Urbana-Champaign press release is reproduced below:

5/7/08

James E. Kloeppel, Physical Sciences Editor
217-244-1073; kloeppel@uiuc.edu


CHAMPAIGN, Ill. — New scientific evidence suggests that deep inside the planet Mercury, iron “snow” forms and falls toward the center of the planet, much like snowflakes form in Earth’s atmosphere and fall to the ground.

The movement of this iron snow could be responsible for Mercury’s mysterious magnetic field, say researchers from the University of Illinois and Case Western Reserve University. In a paper published in the April issue of the journal Geophysical Research Letters, the scientists describe laboratory measurements and models that mimic conditions believed to exist within Mercury’s core.


Click photo to enlarge
Photo by L. Brian Stauffer

Jie "Jackie" Li, a professor of
geology, and graduate student
Bin Chen have concluded that
deep inside the planet Mercury,
iron “snow” forms and falls toward
the center of the planet, much like
snowflakes form in Earth’s
atmosphere and fall to the ground.
The movement of this iron snow
could be responsible for Mercury’s
mysterious magnetic field.

“Mercury’s snowing core opens up new scenarios where convection may originate and generate global magnetic fields,” said U. of I. geology professor Jie "Jackie" Li. “Our findings have direct implications for understanding the nature and evolution of Mercury’s core, and those of other planets and moons.”

Mercury is the innermost planet in our solar system and, other than Earth, the only terrestrial planet that possesses a global magnetic field. Discovered in the 1970s by NASA’s Mariner 10 spacecraft, Mercury’s magnetic field is about 100 times weaker than Earth’s. Most models cannot account for such a weak magnetic field.

Made mostly of iron, Mercury’s core is also thought to contain sulfur, which lowers the melting point of iron and plays an important role in producing the planet’s magnetic field.

“Recent Earth-based radar measurements of Mercury’s rotation revealed a slight rocking motion that implied the planet’s core is at least partially molten,” said Illinois graduate student Bin Chen, the paper’s lead author. “But, in the absence of seismological data from the planet, we know very little about its core.”

To better understand the physical state of Mercury’s core, the researchers used a multi-anvil apparatus to study the melting behavior of an iron-sulfur mixture at high pressures and high temperatures.

In each experiment, an iron-sulfur sample was compressed to a specific pressure and heated to a specific temperature. The sample was then quenched, cut in two, and analyzed with a scanning electron microscope and an electron probe microanalyzer.

“Rapid quenching preserves the sample’s texture, which reveals the separation of the solid and liquid phases, and the sulfur content in each phase,” Chen said. “Based on our experimental results, we can infer what is going on in Mercury’s core.”

As the molten, iron-sulfur mixture in the outer core slowly cools, iron atoms condense into cubic “flakes” that fall toward the planet’s center, Chen said. As the iron snow sinks and the lighter, sulfur-rich liquid rises, convection currents are created that power the dynamo and produce the planet’s weak magnetic field.

Mercury’s core is most likely precipitating iron snow in two distinct zones, the researchers report. This double-snow state may be unique among the terrestrial planets and terrestrial-like moons in our solar system.

“Our findings provide a new context into which forthcoming observational data from NASA’s MESSENGER spacecraft can be placed,” Li said. “We can now connect the physical state of our innermost planet with the formation and evolution of terrestrial planets in general.”

With Li and Chen, Case Western Reserve University planetary geodynamics professor Steven A. Hauck II was a co-author of the paper.

The work was funded by the National Science Foundation.

Editor’s note: To reach Jie Li, call 217-333-7008; e-mail: jackieli@uiuc.edu.

To reach Bin Chen, call 217-244-8479; e-mail: binchen2@uiuc.edu.

Source: UIUC Press Release

Bright Rays Extending From a Halo of Darkness
Gaze upon Basho
Release Date: May 12, 2008



Though Basho crater is only about 80 kilometers (50 miles) in diameter, its bright rays make it an easily identified feature on Mercury's surface. In addition to the long bright rays, photographs from Mariner 10 showed an intriguing dark halo of material around the crater, which can be seen in the lower right portion of this Narrow Angle Camera (NAC) image snapped by MESSENGER's Mercury Dual Imaging System (MDIS) on January 14, 2008. The MESSENGER Science Team is using the full color data set obtained with the 11 filters of the Wide Angle Camera (WAC) to investigate the nature and composition of this dark material. Basho crater is visible near Mercury's limb in the southeastern portion of the WAC false color image previously released.

The crater is named for the 17th-century Japanese poet Matsuo Basho, renowned for his many haiku. MESSENGER's images of Mercury's striking landscape have inspired at least one poet; read Stuart Atkinson's poem "MESSENGER's Memories."

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

Source: JHUAPL - MESSENGER - Gallery

Xiao Zhao's Rays Paint Mercury's Surface
Release Date: May 19, 2008



Date Acquired: January 14, 2008

Image Mission Elapsed Time (MET): 108828473

Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)

Resolution: 500 meter/pixel (0.3 miles/pixel)

Scale: Xiao Zhao crater is 23 kilometers (14 miles) in diameter

Spacecraft Altitude: 19,760 kilometers (12,280 miles)

Of Interest: Recently named after the 12th century Chinese artist, Xiao Zhao crater on the central left side of this image is small in comparison with many other craters on Mercury and even with many other craters in this scene. However, Xiao Zhao's long bright rays make it a readily visible feature. The fresh, bright rays, which were created by material ejected outward during the impact event that formed the crater, indicate that Xiao Zhao is a relatively young crater on Mercury's surface.

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

Source: JHUAPL - MESSENGER - Gallery

MESSENGER Captures a Shot of Kertész

Release Date: May 27, 2008



Date Acquired: January 14, 2008

Image Mission Elapsed Time (MET): 108826812

Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)

Resolution: 260 meter/pixel (0.16 miles/pixel)

Scale: Kertész crater is 34 kilometers (21 miles) in diameter

Spacecraft Altitude: 10,200 kilometers (6,340 miles)

Of Interest: Located in the western edge of Mercury's giant Caloris basin, Kertész crater (recently named for André Kertész, a Hungarian-born American photographer) has some unusual, bright material located on its floor. Sander crater, located in the northwestern edge of Caloris basin, also shows bright material on its floor. The MESSENGER Science Team is investigating the nature and composition of these bright materials and making comparisons between these two craters both located at the edges of Caloris basin. Just northeast of Kertész, a small crater has very bright rays and ejecta in this image, indicating that the crater is young.

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

Source: JHUAPL - MESSENGER - Gallery

Oh look. Another Space Alien (face). I can see the new threads now!

No it's gotta be one of those fusion reactors, mining operation or factory of some sort...

Voilà! Mercury's Atget

Release Date: June 3, 2008



Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): 108828540
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 520 meter/pixel (0.32 miles/pixel)
Scale: This image shows a scene about 530 kilometers (330 miles) across
Spacecraft Altitude: 20,300 kilometers (12,600 miles)

Of Interest: Recently named for the French photographer Eugène Atget, Atget crater, seen in the middle of the lower portion of this NAC image, is distinctive on Mercury's surface due to its dark color. Atget crater is located within Caloris basin near Apollodorus crater and Pantheon Fossae, which are also both visible in this image to the northwest of Atget. The dark color of the floor of Atget is in contrast to other craters within Caloris basin that exhibit bright materials on their floors, such as the craters Kertész and Sander. Other craters on Mercury, such as Basho and Neruda, have halos of dark material but the dark material does not cover the crater floors. Understanding the variety of bright and dark materials associated with different craters will provide insight into Mercury's composition and the processes that acted on Mercury's surface.

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

Source: JHUAPL - MESSENGER - Gallery

Young Cunningham Crater in Old Caloris Basin

Release Date: June 10, 2008



Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): 108828535
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 520 meters/pixel (0.32 miles/pixel)
Scale: Diameter of Cunningham crater is 37 kilometers (23 miles)
Spacecraft Altitude: 20,300 kilometers (12,600 miles)

Of Interest: Mercury's giant Caloris basin is the best-preserved large impact basin known on Mercury, and the high density of craters on its floor indicates that the basin is fairly old and probably formed about 3.8 billion years ago. This NAC image shows an area on the plains that partially fill the Caloris basin floor. On the right portion of this image, the light-colored rays emanating from Cunningham crater (named for the American photographer Imogen Cunningham) show that this crater is relatively young; bright ejecta rays tend to darken with time, as the ejected material is gradually modified by impacting micrometeoroids and solar particles (a suite of different processes that together are called “space weathering”). Relative age relationships such as this one are used to unravel Mercury's geologic history. The similar-sized Kertész crater is also visible on the left side of this image.

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

Source: JHUAPL - MESSENGER - Gallery

Peak Rings on Mercury

Release Date: June 17, 2008



Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): 108821505
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Scale: Dürer crater is about 190 kilometers (120 miles) in diameter
Spacecraft Altitude: 18,300 kilometers (11,400 miles)

Of Interest: MESSENGER snapped this image of Mercury’s horizon about 56 minutes before the spacecraft’s closest pass by the planet. The distinctive peak-ring basin Dürer (named from Mariner 10 photos for the German artist Albrecht Dürer) is visible. The smaller crater Mickiewicz (named for the Polish poet Adam Mickiewicz) can also be seen, with a smaller central peak-ring structure in the middle of its crater floor. Craters form ring structures during the impact process that creates the crater, and the number and characteristics of the rings depend on the crater’s size. Raditladi, imaged for the first time by MESSENGER and recently named, also shows a pronounced peak-ring structure.

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

Source: JHUAPL - MESSENGER - Gallery

By Dawn's Early Light

Release Date: June 23, 2008



Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): 108830334
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 0.8 kilometers/pixel (0.5 miles/pixel)
Scale: The width of this image is about 800 kilometers (500 miles)
Spacecraft Altitude: 30,700 kilometers (19,100 miles)

Of Interest: About 91 minutes after MESSENGER’s closest pass by the planet, MDIS acquired this image of Mercury’s northern surface, which is one in a set of 48 that form a mosaic of the departing planet. In this image, the left portion of the surface fades into darkness at the terminator, the line between the sunlit dayside of the planet and the dark night side. The left-side portions of the surface that are just coming out of the darkness are being hit with the first rays of morning sunlight. Some of the surface to the right of this scene can be viewed in this previously released image looking toward Mercury’s north pole.

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

Source: JHUAPL - MESSENGER - Gallery

Mercury’s Craters from a New Perspective

Release Date: June 30, 2008



Date Acquired: January 14, 2008
Instrument: Mosaic created with images taken by the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 1.5 kilometers/pixel (0.93 miles/pixel)
Scale: This mosaic shows Mercury from the equator nearly to the northern pole, a distance of about one Mercury radius (2440 kilometers, 1516 miles).

Of Interest: As MESSENGER approached Mercury, the NAC acquired images to create a mosaic of the entire planet. The mosaic shown here was created from about half of those images and is shown in an orthographic projection. This view is in contrast to the cylindrical equidistant map mosaic previously released. For this mosaic, an orthographic projection was used to create a view that has the perspective that one would see from deep space. Over three decades earlier, Mariner 10 viewed this portion of Mercury’s surface, and the craters that were named on the basis of those images are labeled on this mosaic. The MESSENGER images of this same territory are allowing scientists to study Mercury’s surface under different illumination conditions, and these complementary views provide new insight into the nature of the geologic features on Mercury.

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

Source: JHUAPL - MESSENGER - Gallery

07.03.08

Credit: NASA/APL
> Larger image

Scientists have argued about the origins of Mercury's smooth plains and the source of its magnetic field for more than 30 years. Now, analyses of data from the January 2008 flyby of the planet by the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft have shown that volcanoes were involved in plains formation and suggest that its magnetic field is actively produced in the planet's core.

Scientists additionally took their first look at the chemical composition of the planet's surface. The tiny craft probed the composition of Mercury's thin atmosphere, sampled charged particles (ions) near the planet, and demonstrated new links between both sets of observations and materials on Mercury's surface. The results are reported in a series of 11 papers published in a special section of Science magazine July 4.

The controversy over the origin of Mercury's smooth plains began with the 1972 Apollo 16 moon mission, which suggested that some lunar plains came from material that was ejected by large impacts and then formed smooth "ponds." When Mariner 10 imaged similar formations on Mercury in 1975, some scientists believed that the same processes were at work. Others thought Mercury's plains material came from erupted lavas, but the absence of volcanic vents or other volcanic features in images from that mission prevented a consensus.

Six of the papers in Science report on analyses of the planet's surface through its reflectance and color variation, surface chemistry, high-resolution imaging at different wavelengths, and altitude measurements. The researchers found evidence of volcanic vents along the margins of the Caloris basin, one of the solar system's youngest impact basins. They also found that Caloris has a much more complicated geologic history than previously believed.

The first altitude measurements from any spacecraft at Mercury also found that craters on the planet are about a factor of two shallower than those on Earth's moon. The measurements also show a complex geologic history for Mercury.

Mercury's core makes up at least 60 percent of its mass, a figure twice as large as any other known terrestrial planet. The flyby revealed that the magnetic field, originating in the outer core and powered by core cooling, drives very dynamic and complex interactions among the planet's interior, surface, exosphere and magnetosphere.

Remarking on the importance of the core to surface geological structures, Principal Investigator Sean Solomon at the Carnegie Institution of Washington said, "The dominant tectonic landforms on Mercury, including areas imaged for the first time by MESSENGER, are features called lobate scarps, huge cliffs that mark the tops of crustal faults that formed during the contraction of the surrounding area. They tell us how important the cooling core has been to the evolution of the surface. After the end of the period of heavy bombardment, cooling of the planet's core not only fueled the magnetic dynamo, it also led to contraction of the entire planet. And the data from the flyby indicate that the total contraction is a least one-third greater than we previously thought."

The flyby also made the first-ever observations of the ionized particles in Mercury's unique exosphere. The exosphere is an ultrathin atmosphere in which the molecules are so far apart they are more likely to collide with the surface than with each other. The planet's highly elliptical orbit, its slow rotation and particle interactions with the magnetosphere, interplanetary medium and solar wind result in strong seasonal and day-night differences in the way particles behave.

> Johns Hopkins Applied Physics Lab Media Telecon website for the MESSENGER Mercury discovery will be available at 2 pm on July 03, 2008.


Source: NASA - Missions - MESSENGER

Beagle Rupes Gives Sveinsdóttir an Uplifting Experience

Release Date: July 7, 2008



Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): 108830230
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 0.77 kilometers/pixel (0.48 miles/pixel)
Scale: This image is about 780 kilometers (490 miles) across; Sveinsdóttir crater is about 120 kilometers by 220 kilometers (75 miles by 140 miles).
Spacecraft Altitude: 30,300 kilometers (18,800 miles)

Of Interest: Named for Júlíana Sveinsdóttir, an Icelandic painter and textile artist, Sveinsdóttir crater superimposed by Beagle Rupes is a distinctive feature on Mercury's landscape. Unusually elliptical in shape, the crater was produced by the impact of an object that hit Mercury’s surface obliquely. More than 600 kilometers (370 miles) long and one of the largest fault scarps on the planet, Beagle Rupes marks the surface expression of a large thrust fault believed to have formed as Mercury cooled and the entire planet shrank. Beagle Rupes crosscuts Sveinsdóttir crater and has uplifted the easternmost portion (right side portion) of the crater floor by almost a kilometer, indicating that most of the fault activity at Beagle Rupes occurred after the impact that created Sveinsdóttir. Crosscutting relationships such as this are used to understand the sequence in time of the different processes that have affected Mercury’s evolution.

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

Source: JHUAPL - MESSENGER - Gallery

MESSENGER Discovers Volcanoes on Mercury

Release Date: July 11, 2008



Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): 108826877
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 270 meters/pixel (0.17 miles/pixel)
Scale: This image is about 270 kilometers across (170 miles)
Spacecraft Altitude: 10,500 kilometers (6,500 miles)

Of Interest As reported in the July 4, 2008, issue of Science magazine, volcanoes have been discovered on Mercury’s surface from images acquired during MESSENGER’s first Mercury flyby. This image shows the largest feature identified as a volcano in the upper center of the scene. The volcano has a central kidney-shaped depression, which is the vent, and a broad smooth dome surrounding the vent. The volcano is located just inside the rim of the Caloris impact basin. The rim of the basin is marked with hills and mountains, as visible in this image. The role of volcanism in Mercury’s history had been previously debated, but MESSENGER’s discovery of the first identified volcanoes on Mercury’s surface shows that volcanism was active in the distant past on the innermost planet.

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

Source: JHUAPL - MESSENGER - Gallery

Caloris Basin – in Color!

Release Date: July 15, 2008



Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): 108827278-108827328
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 2.3 kilometers/pixel (1.4 miles/pixel)
Scale: Caloris basin is about 1,550 kilometers in diameter (960 miles)
Spacecraft Altitude: 13,000 kilometers (8,000 miles)

Of Interest This false-color image of Mercury, recently published in Science magazine, shows the great Caloris impact basin, visible in this image as a large, circular, orange feature in the center of the picture. The contrast between the colors of the Caloris basin floor and those of the surrounding plains indicate that the composition of Mercury’s surface is variable. Many additional geological features with intriguing color signatures can be identified in this image. For example, the bright orange spots just inside the rim of Caloris basin are thought to mark the location of volcanic features, such as the volcano shown in this previously released Narrow Angle Camera (NAC) image. MESSENGER Science Team members are studying these regional color variations in detail, to determine the different mineral compositions of Mercury’s surface and to understand the geologic processes that have acted on it. Images taken through the 11 different WAC color filters were used to create this false-color image. The 11 different color images were compared and contrasted using statistical methods to isolate and enhance subtle color differences on Mercury’s surface.

Credit: Image produced by NASA/Johns Hopkins University Applied Physics Laboratory/Arizona State University/Carnegie Institution of Washington. Image reproduced courtesy of Science/AAAS

Source: JHUAPL - MESSENGER - Gallery

Craters Deformed and Shortened

Release Date: July 23, 2008



Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): A: 108827037. B: 108825899, 108825904, 108825994, 108825999. C: 108828317.
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)

Of Interest: Numerous examples of craters that have been deformed and shortened by younger faults have been identified on images returned from MESSENGER’s first flyby of Mercury. In three cases shown here (arrows), portions of the floor and rim of a crater were buried when a large block of crust was thrust over the crater during the formation of a prominent fault scarp or cliff. By comparing the estimated size and shape of the original, undeformed crater with the crater’s current geometry, scientists can infer the amount of movement between the two crustal blocks on either side of the fault. This figure was recently published in Science magazine. For each of the three examples of deformed and shortened craters shown here, movement on the faults buried at least a kilometer of the original crater. A: 17-kilometer (11-mile) diameter crater (arrows) shortened by Beagle Rupes. B: 5-kilometer (3-mile) diameter crater deformed near the rim of an older, larger crater, shown enlarged in the box on the lower left. C: 11-kilometer (7-mile) diameter crater (arrows) shortened by a northwest-southeast-trending fault scarp.

Credit: Figure 3 from Solomon et al., Science, 321, 59-62, 2008.S

Source: JHUAPL - MESSENGER - Gallery

A Closer Look at Albedo and Color Variations on Mercury

Release Date: July 23, 2008



Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): A: 108828233. B: 108826687. C: 108827022. D: 108828337, 108828342. E, F: 108829678-108829728.
Instrument: (A-D) Narrow Angle Camera (NAC) and (E-F) Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)

Of Interest: MESSENGER images have revealed intriguing albedo and color variations on Mercury, providing insight into the compositional differences in the rocks found on Mercury’s surface and the processes that have acted on them. The term albedo simply refers to the fraction of light reflected by a material. For example, charcoal has a very low albedo while snow has a very high albedo. This figure, recently published in Science magazine, highlights some of these variations.

A: The bright rays of Basho crater (diameter about 80 kilometers, 50 miles) likely are made of immature material, while the darker material near the rim is thought also to be immature material but of a different composition. Surface materials on Mercury are believed to change color and albedo over time as a result of bombardment by micrometeoroids and energetic particles from the solar wind. They eventually reach an unchanging, “mature” state. If the surface is disturbed, for instance by a cratering impact, underlying material is freshly exposed on the surface. It is termed “immature” if the disturbance was sufficiently recent that there hasn’t yet been time for the exposed material to gain maturity.

B: Two craters within Caloris basin have dark crater walls, and the crater at upper right, Sander (diameter about 50 kilometers, 30 miles), has bright patches on its floor. Unlike the rays of Basho crater, the bright areas are not believed to be immature but are inherently bright.

C: Mozart crater (diameter about 220 kilometers, 140 miles) shows linear dark streamers (unlabeled arrows), which are thought to be material excavated from depth during the crater-forming impact. Similarly colored dark patches can also be seen in the crater wall (arrows labeled W) and in the central peak (arrow labeled P) and may be derived from the same underground layer.

D: The smooth plains (labeled SP) interior to Tolstoj basin are superimposed on the darker areas shown with unlabeled arrows. Materials with these two color and albedo characteristics are common on Mercury’s surface. This image is 825 kilometers (513 miles) wide.

E: This image was generated by comparing and contrasting WAC images taken in 11 different color filters and choosing a color scheme to highlight differences on Mercury’s surface. The image shows the dark streamers of Mozart crater (white arrows) and a young impact crater with fresh, immature rays (black arrow). The image is about 800 kilometers (500 miles) wide.

F: Using a similar color scheme, this image of a segment of the edge and rim of Caloris basin (white arrows) clearly shows that the rocks present on the basin’s floor differ from those exterior to the basin. This image is about 600 kilometers (370 miles) wide.

Credit: Figure 2 from Robinson et al., Science, 321, 66-69, 2008.

Source: JHUAPL - MESSENGER - Gallery

MESSENGER Mission News
August 4, 2008
_http://messenger.jhuapl.edu

Sharing the Wealth: MESSENGER Team Delivers Mercury Flyby 1 Data to Planetary Data System

Data from MESSENGER’s first flyby of Mercury have been released to the public by the Planetary Data System (PDS), an organization that archives and distributes all of NASA’s planetary mission data.

“This delivery, while not the first for the MESSENGER mission, represents a significant milestone,” says MESSENGER Mission Archive Coordinator Alan Mick, of the Johns Hopkins University Applied Physics Laboratory. “We had delivered data from MESSENGER to the PDS before, but not Mercury data,” he says. “This delivery was particularly significant — the first MESSENGER flyby of Mercury was mankind’s return to this planet after an absence of over three decades. In this one flyby we imaged previously unseen areas of Mercury’s surface, greatly improved the resolution in areas already covered, and made observations of a kind that had never been made before.”

Calibrated data from three of the probe’s science instruments — the Magnetometer (MAG), the Mercury Atmospheric and Surface Composition Spectrometer (MASCS), and the Mercury Dual Imaging System (MDIS) — are included in this release. “The science results from these instruments have already shed light on questions about Mercury that have lingered for more than three decades,” says MESSENGER Project Scientist Ralph McNutt of APL.

For instance, analyses of data from MDIS have shown that volcanoes were involved in plains formation, and MAG results confirm that the planet’s magnetic field is actively produced in the planet’s core and is not a frozen relic. The MASCS instrument has provided new insights into the extent and complexity of the planet’s tenuous exosphere. “The availability of these data via PDS will allow scientists around the world to study the data and begin making even more connections and discoveries,” McNutt adds.

Since the mid-1990s, NASA has required all of its planetary missions to archive data in the PDS, an active archive that makes available well-documented, peer-reviewed data to the research community. “An essential element of the implementation of NASA missions is the dissemination of collected data to the science community at large,” explains Marilyn Lindstrom, NASA Program Scientist for MESSENGER. “It’s critical to maintain a planetary data archive that will withstand the test of time so that future generations of scientists can access, understand, and use pre-existing planetary data.”

The PDS includes eight university/research center science teams, called discipline nodes, each of which specializes in specific areas of planetary data. The contributions from these nodes provide a data-rich source for scientists, researchers, and developers. Steven Joy of the University of California, Los Angeles, is MESSENGER’s PDS liaison. His challenge was to coordinate the efforts of the nodes responsible for validating the various datasets before they could be released. “The PDS validation process needs to be comprehensive and unforgiving to ensure that only high-quality, well-documented data are released for use by the science community,” Joy says. “The data archives do not need to be perfect, but they do need to be documented well enough that future users, unfamiliar with how the data were acquired, can understand the data and apply them to new problems.”

The “formal” public release makes mission data available for several applications, including the MESSENGER Mercury flyby visualization tool, available online at http://messenger.jhuapl.edu/encountersactual/. “The tool now includes actual, unprocessed images from the narrow-angle and wide-angle cameras, taken during the January flyby,” says APL’s James McAdams, who designed MESSENGER’s trajectory. “Viewers will see the same images that told the team that the cameras were not only on target, but were revealing Mercury as it had never been seen before.”

In addition, the “Science on a Sphere” exhibit at NASA’s Goddard Space Flight Center’s Visitor Center has now incorporated MESSENGER images into its collection of Solar System displays. This exhibit utilizes four video projectors to display three-dimensional data onto the surface of a six-foot, suspended sphere. “It’s a unique opportunity to project high-resolution NASA data for educational purposes,” notes MESSENGER Education and Public Outreach Project Manager Stephanie Stockman.

MESSENGER Principal Investigator Sean Solomon says it took high level of dedication for the team to pull this off. “Many members of the MESSENGER team devoted long hours and weekends to ensure that the project met the goal of releasing all of our Mercury data six months after the flyby. We are delighted to share these historic data with the scientific community and the public, and we hope that their availability will foster interest everywhere in the mysteries of the Sun’s closest planetary neighbor.”


Happy Anniversary, MESSENGER!

It’s been four years since MESSENGER was launched atop a Delta II rocket on August 3, 2004, and they have been busy years. Since it began its odyssey, the spacecraft has travelled 4.33 billion kilometers (2.69 billion miles) relative to the Sun. It has executed four planetary flybys (one of Earth on August 2, 2005; two of Venus, on October 24, 2006, and June 5, 2007; and one of Mercury, on January 14, 2008), three deep-space propulsive maneuvers, and 15 smaller trajectory-correction maneuvers. Up next are two more passes by Mercury (October 6, 2008, and September 29, 2009) and then on March 18, 2011, MESSENGER will become the first spacecraft to enter into orbit around the innermost planet.


MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as principal investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.

Source: JHUAPL - MESSENGER - Mission News

Wrinkle-Ridge Rings on Mercury and Mars

Release Date: August 6, 2008



Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): A: 108826972
Instrument: A: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Mars Image: B: Mars Express High-Resolution Stereo Camera nadir image h2660_0001

Of Interest: Planetary scientists commonly compare and contrast the geologic features found on different planetary bodies, to learn about the similar processes that operated throughout the Solar System and to understand how each planet is different and unique. This figure, recently published in Science magazine, shows wrinkle-ridge rings on both Mercury (upper image) and Mars (lower image) that look quite similar. Wrinkle ridges arrayed in such a ring are interpreted to trace the rim of an impact crater that was nearly or completely flooded by lavas prior to ridge formation. Wrinkle ridges are created by forces that compress the crust horizontally. A buried crater rim can concentrate the near-surface forces and cause the wrinkle ridges to form a ring. The presence of wrinkle-ridge rings is thus good evidence that volcanism helped to shape the surfaces of both Mars and Mercury.

Credit: Figure 3 from Head et al., Science, 321, 69-72, 2008.

Source: JHUAPL - MESSENGER - Gallery

Rupes, Rupes, Every Where

Release Date: August 13, 2008



Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): Mosaic of images from 108821370, 108821375, 108821397, and 108821402
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)

Of Interest: Giant scarps (cliffs), called rupes, are believed to have formed when Mercury’s interior cooled and the entire planet shrank slightly as a result. This figure, recently published in Science magazine, shows one of these scarps (white arrows) that is about 270 kilometers (170 miles) long. This portion of Mercury’s surface was seen during the Mariner 10 flybys, but this scarp, despite its large size, was not visible in the Mariner 10 photos because the Sun was nearly overhead at the time and, consequently, the scarp did not cast a discernable shadow. In contrast, MESSENGER acquired a mosaic of this area before the spacecraft’s closest approach to the planet, when this portion of the surface was near the terminator, the line between the sunlit dayside and the dark night side of the planet. Such lighting produced long shadows, enabling this rupes to be recognized for the first time.

Credit: Figure 4 from Solomon et al., Science, 321, 59-62, 2008.

Source: JHUAPL - MESSENGER - Gallery

Mapping a Volcano

Release Date: August 19, 2008



Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): Mosaic of 108826812 and 108826877
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Spacecraft Altitude: 10,500 kilometers (6,500 miles)

Of Interest: MESSENGER Science Team members are busy studying in detail the newly discovered volcanoes on Mercury. This figure, recently published in Science magazine, shows a NAC mosaic of the largest volcano currently identified on Mercury and a geologic sketch map of the major features in the surrounding area. The “irregularly-shaped depressions” are believed