May 15

Fire and Ice: A MESSENGER Recap

Source: NASA Science News


NASA's MESSENGER spacecraft crashed into Mercury on April 30th, ending a years-long mission that made many unexpected discoveries about the innermost planet. Today's story summarizes some of MESSENGER's most surprising finds. (learn more)

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Dec 14

Public Contest to Name Craters on Planet Mercury

Source: IAU Newsletter


The MESSENGER Education and Public Outreach (EPO) Team is launching a competition this week to name five impact craters on Mercury in conjunction with the IAU. (learn more)

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May 13

MESSENGER Completes Its 2,000th Orbit of Mercury

Source: MESSENGER Press Release

Artist's impression  of the MESSENGER Spacecraft.
Image credits: NASA /MESSENGER.

MESSENGER Completes Its 2,000th Orbit of Mercury, Provides Data on Solar Magnetic Field

MESSENGER began its 2,000th orbit around Mercury earlier this week, on May 22. The spacecraft completed its primary mission on March 17, 2012, and its first extended mission on March 17, 2013. The team is awaiting word from NASA on a proposal for a second extended mission. In the meantime, instruments aboard the spacecraft continue to gather new data on Mercury and its environment.

From May 6 to May 14, MESSENGER traversed a superior solar conjunction, during which the spacecraft was on the far side of the Sun from Earth. Scientists used the opportunity to measure the characteristics of the solar magnetic field from the Faraday rotation of its radio-frequency carrier.

“We found the orientation of the magnetic field within a coronal mass ejection (CME) that crossed the line of sight on May 10,” says Elizabeth Jensen, of the Planetary Science Institute in Tucson, Arizona. “We saw the rotation of the plane of polarization of MESSENGER’s radio-frequency signal as it moved deeper into the corona, giving information on the Sun's magnetic field configuration on May 11; and on May 12, we saw magnetohydrodynamic waves, a very important mode of energy transfer in the corona.”

Solar storms cause communications disruptions, expose spacecraft and personnel in airplanes to radiation, and threaten electrical grids. Jensen says that the observations of the CME demonstrate the utility of this technique to predict the threat of solar storms headed toward Earth almost immediately after they erupt.

“Understanding the accuracy of models for the solar magnetic field and solar wind generation requires testing,” she says. “Although other methods can be used in active regions, Faraday rotation is the only way to test the magnetic field models in the largest part of the corona where the solar wind is accelerating.”

At its closest point to Mercury, MESSENGER will be about 447 kilometers (277.8 miles) above a point near 83.1° N latitude. Since its most recent orbit-correction maneuver on April 20, 2012, the spacecraft has completed three orbits of Mercury every day. At this rate, says mission trajectory lead James McAdams of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, the spacecraft will reach its 3,000th orbit around Mercury on April 20, 2014.

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Nov 12

MESSENGER Finds Unusual Groups of Ridges and Troughs on Mercury


Image credits: MESSENGER

MESSENGER has discovered assemblages of tectonic landforms unlike any previously found on Mercury or elsewhere in the Solar System. The findings are reported in a paper led by Smithsonian scientist Thomas Watters, “Extension and contraction within volcanically buried impact craters and basins on Mercury,” published in the December issue of the journal Geology and available online at http://geology.gsapubs.org/content/40/12/1123.full.

The surface of Mercury is covered with deformational landforms that formed by faulting in response to horizontal contraction or shortening as the planet’s interior cooled and surface area shrank, causing blocks of crustal material to be pushed together. Contraction from cooling of Mercury’s interior has been so dominant that extensional landforms caused by fault formation in response to horizontal stretching and pulling apart of crustal material had not been previously documented outside of the interiors of a few large impact basins.

The MESSENGER spacecraft, in orbit around Mercury since March of last year, has revealed families of extensional troughs, or graben, that are encircled by contractional wrinkle ridges arranged in circular rings. The troughs can form complex patterns varying from the outlines of polygons inside the ridge rings to arcs that parallel the bounding ridges.

“The pattern of winkle ridges and graben resembles the raised edge and cracks in a pie crust,” said Watters of the Center for Earth and Planetary Studies at the National Air and Space Museum. The “pie crust” analogy also fits another notable aspect of these collections of tectonic landforms – their association with “ghost” craters. Ghost craters are impact craters that have been flooded and buried by lava flows. The thin volcanic deposits overlying the rim of a fully buried impact crater serve to concentrate contractional forces, leading to the formation of a ridge ring that reveals the outline of the buried crater.

“The special arrangement of the wrinkle ridges and graben in many of the ghost craters on Mercury is due to a combination of extensional forces from cooling and contraction of unusually thick lava flow units and contractional forces from cooling and contraction of the planet’s interior,” says Sean Solomon of the Columbia University’s Lamont-Doherty Earth Observatory, coauthor and principal investigator of the MESSENGER mission. The eruption and rapid accumulation of very fluid lava flows into thick cooling units on a planet undergoing a high rate of global contraction may be why these systems of tectonic landforms in ghost craters on Mercury have not been seen elsewhere in the Solar System.

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Mar 12

MESSENGER App Now Available

Source: MESSENGER Press Release

Artist's impression  of the MESSENGER Spacecraft.
Image credits: NASA /MESSENGER.

The MESSENGER team has launched a free app that brings you inside NASA’s history-making study of Mercury – the first images of the entire planet, along with the detailed data on Mercury’s surface, geologic history, thin atmosphere, and active magnetosphere that MESSENGER sends back every day.

Now available in the iTunes App Store, "MESSENGER: NASA's Mission to Mercury" brings users the latest news and pictures from the mission, as well as details on the spacecraft and science instruments, and offers access to educational programs and activities.

Circle the innermost planet aboard MESSENGER, the first mission to orbit Mercury. Examine a detailed view of the MESSENGER spacecraft and its science instruments, browse the latest news and images, or trace the spacecraft’s path over Mercury as it scans the scorched surface of the Sun’s closest planetary neighbor. Can you take the heat?

Main Features Include:

Get up-to-the-minute reports from the MESSENGER Web News Center and Twitter feed.


Have the “Mercury Image of the Day” sent straight to your device; flip through hundreds of stunning pictures of Mercury taken by the spacecraft’s cameras; watch videos that trace MESSENGER’s 4.9-billion mile journey to Mercury that included six planetary flybys and 15 trips around the Sun.


Tour the robust MESSENGER spacecraft and science payload; see what MESSENGER was designed to learn about Mercury; pick up some quick facts about the mission and its planetary target.


Follow MESSENGER as it loops around Mercury; pinpoint its location over the surface; see how much time remains in its current, 12-hour orbit.

 Education (iPad only)

Use the interactive QuickMap to view areas on Mercury observed or targeted for hi-resolution observation by MESSENGER instruments, locate craters and other “named” surface features, and explore detailed global and regional images

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Mar 12

MESSENGER Provides New Look at Mercury's Landscape, Metallic Core, and Polar Shadows

Source: MESSENGER Press Release

Artist's impression  of the MESSENGER Spacecraft.
Image credits: NASA /MESSENGER.

MESSENGER completed its one-year primary mission on March 17. Since moving into orbit about Mercury a little over one year ago, the spacecraft has captured nearly 100,000 images and returned data that have revealed new information about the planet, including its topography, the structure of its core, and areas of permanent shadow at the poles that host the mysterious polar deposits.

The latest findings are presented in two papers published online in Science Express today, and in 57 papers presented this week at the 43rd Lunar and Planetary Science Conference in The Woodlands, Texas. Team members at the meeting will also preview MESSENGER’s extended mission, set to run to March 2013. The event, scheduled for 12:30 p.m. CDT (1:30 p.m. EDT), will be streamed live on the Web at http://www.livestream.com/lpsc2012. Presentation materials are available online at http://messenger.jhuapl.edu/news_room/presscon11.html.

 “The first year of MESSENGER orbital observations has revealed many surprises,” says MESSENGER Principal Investigator Sean C. Solomon, of the Carnegie Institution of Washington. “From Mercury’s extraordinarily dynamic magnetosphere and exosphere to the unexpectedly volatile-rich composition of its surface and interior, our inner planetary neighbor is now seen to be very different from what we imagined just a few years ago. The number and diversity of new findings being presented this week to the scientific community in papers and presentations provide a striking measure of how much we have learned to date.”


Mercury’s Landscape

Ranging observations from MESSENGER’s Mercury Laser Altimeter (MLA) have provided the first-ever precise topographic model of the planet’s northern hemisphere and characterized slopes and surface roughness over a range of spatial scales. From MESSENGER’s eccentric, near-polar orbit, the MLA illuminates surface areas as wide as 15 to 100 meters, spaced about 400 meters apart.

The spread in elevations is considerably smaller than those of Mars or the Moon, notes MESSENGER Co-investigator Maria T. Zuber, author of one of the papers published in Science Express According to Zuber, of the Massachusetts Institute of Technology, the most prominent feature is an extensive area of lowlands at high northern latitudes that hosts the volcanic northern plains. Within this lowland region is a broad topographic rise that formed after the volcanic plains were emplaced.

At mid-latitudes, the interior of the Caloris impact basin — 1,500 kilometers wide — has been modified so that part of the basin floor now stands higher than the rim, Zuber says. “The elevated portion of the floor of Caloris appears to be part of a quasi-linear rise that extends for approximately half the planetary circumference at mid-latitudes,” she writes. “Collectively, these features imply that long-wavelength changes to Mercury’s topography occurred after the earliest phases of the planet’s geological history.”

A Surprising Core

Scientists have also come up with the first precise model of Mercury’s gravity field which, when combined with the topographic data and earlier information of the planet’s spin state, shed light on the planet’s internal structure, the thickness of its crust, the size and state of its core, and its tectonic and thermal history.

Mercury’s core is huge for the planet’s size, about 85% of the planetary radius, even larger than previous estimates. The planet is sufficiently small that at one time many scientists thought the interior should have cooled to the point that the core would be solid. However, subtle dynamical motions measured from Earth-based radar combined with parameters of the gravity field, as well as observations of the magnetic field that signify an active core dynamo, indicate that Mercury’s core is at least partially liquid. “MESSENGER’s observations of the gravity field have let us peer inside Mercury and get the first good look at its largest component — the core,” says Case Western Reserve University’s Steven A. Hauck II, coauthor of one of the papers published in Science Express.

Scientists sought to unravel the mystery of the size and state of Mercury’s core by studying its effect on long-wavelength variations in the planet’s gravity field, and recent results point to a much different interior structure for Mercury from that expected.

“Mercury’s core may not look like any other terrestrial planetary core,” Hauck says. “The structure certainly is different from that of Earth, which has a metallic, liquid outer core sitting above a solid inner core. Mercury appears to have a solid silicate crust and mantle overlying a solid, iron sulfide outer core layer, a deeper liquid core layer, and possibly a solid inner core.”

These findings will have implications for how Mercury’s magnetic field is generated and for understanding how the planet evolved thermally, Hauck adds.

Polar Shadows

A chief goal of MESSENGER’s primary mission was to understand the nature of the radar-bright deposits at the poles of Mercury. The leading proposal since the deposits were discovered has been that radar-bright material consists dominantly of frozen water ice.

“We’ve never had the imagery available before to see the surface where these radar-bright features are located,” says Nancy L. Chabot, instrument scientist for MESSENGER’s Mercury Dual Imaging System (MDIS) at the Johns Hopkins University Applied Physics Laboratory (APL). “MDIS images show that all the radar-bright features near Mercury’s south pole are located in areas of permanent shadow, and near Mercury’s north pole such deposits are also seen only in shadowed regions, results consistent with the water-ice hypothesis.”

This finding is not definitive proof that those deposits are water ice, says Chabot, who is presenting her results at LPSC. And some of the radar-bright deposits are located in craters that provide thermally challenging environments to the water-ice theory. For instance, for the radar-bright material in many of the craters to be water ice would require that there be a thin layer of insulation to keep it colder than the surface, Chabot says.

But the MDIS images, combined with ongoing analysis of data from MESSENGER’s Neutron Spectrometer and the MLA, will provide a more complete picture of the nature of the deposits.

Extending the Discoveries

MESSENGER’s second year at Mercury will build upon these and other results from the primary mission phase, emphasizes MESSENGER Project Scientist Ralph L. McNutt Jr., of APL. “The second year of orbital operations will not be a simple continuation of the primary mission,” he says. “Extended mission themes will include more comprehensive measurement of the magnetosphere and exosphere during a period of more active Sun, greater focus on observations at low spacecraft altitudes, and a greater variety of targeted observations.”

“MESSENGER has already fundamentally changed our view of this innermost planet,” he adds. “With the extension of the MESSENGER mission, many more discoveries can be expected.”

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Mar 12

MESSENGER Completes Primary Mission at Mercury, Settles in for Another Year


Image credit: NASA/MESSENGER.

On March 17, 2012, MESSENGER successfully wrapped up a year-long campaign to perform the first complete reconnaissance of the geochemistry, geophysics, geologic history, atmosphere, magnetosphere, and plasma environment of the solar system’s innermost planet. The following day, March 18, 2012, marked the official start of an extended phase designed to build upon those discoveries. What MESSENGER has accomplished since its launch in August 2005 is “amazing,” says MESSENGER Mission Systems Engineer Eric Finnegan, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.

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Mar 12

MESSENGER Team Delivers Data from First Full Mercury Solar Day to Planetary Data System

Source: MESSENGER Press Release

Artist's impression  of the MESSENGER Spacecraft.
Image credits: NASA /MESSENGER.

Data collected during MESSENGER’s third through sixth month in orbit around Mercury were released to the public today by the Planetary Data System (PDS), an organization that archives and distributes all of NASA’s planetary mission data. With this release, data are now available to the public for the first full Mercury solar day of MESSENGER orbital operations.

Calibrated data from all seven of MESSENGER’s science instruments, plus radio science data from the spacecraft telecommunications system, are included in this release. The science results have shed light on many aspects of Mercury, including its global magnetic field, the dynamics of its exosphere, its surface composition, its geological evolution, and its interior structure.

The images included in this release provide monochrome views at 250 meters per pixel and eight-color image sets at 1 kilometer per pixel. Apart from small gaps, many of which have already been filled by subsequent imaging, these images cover the entire planet under lighting conditions ideal either for assessing the form of Mercury’s surface features or for determining the color and compositional variations across the planet.

For more than two decades, 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. The PDS includes eight university/research center science teams, called discipline nodes, each of which specializes in a specific area of planetary data. The contributions from these nodes provide a data-rich source for scientists, researchers, and developers.

The data for this delivery are archived and available online at http://pds.nasa.gov/subscription_service/SS-20120308.html, and all of the MESSENGER data archived at the PDS thus far are available at http://pds.nasa.gov. As of this release, MESSENGER will have delivered 1.7 terabytes of raw and calibrated data to the PDS, including more than 62,355 images (of which 49,275 are from orbit). The team will submit four more PDS deliveries at six-month intervals from MESSENGER’s primary orbital mission and its extended mission.

The MESSENGER team has created a software tool with which the public can view data from this delivery. ACT-REACT-QuickMap provides an interactive Web interface to MESSENGER data. Developed by Applied Coherent Technology Corporation, the software allows users to examine global mosaics constructed with high-resolution images from this and previous PDS deliveries.

The tool also provides weekly updates of coverage for surface-observing instruments, as well as the status of specially targeted MDIS observations. Information is also available that can be used to locate MESSENGER data products at the PDS. QuickMap can be accessed via links on each of the MESSENGER websites at http://messenger.jhuapl.edu/ and http://www.nasa.gov/messenger. The MDIS mosaics can be downloaded from http://messenger.jhuapl.edu/the_mission/mosaics.html.

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Mar 12

MESSENGER Modifies Orbit to Prepare for Extended Mission

Source: NASA Messenger Press Release
Image credit: NASA/MESSENGER

MESSENGER successfully completed an orbit-correction maneuver this evening to lower its periapsis altitude — the lowest point of MESSENGER’s orbit about Mercury relative to the planet’s surface — from 405 to 200 kilometers (251 to 124 miles). This is the first of three planned maneuvers designed to modify the spacecraft’s orbit around Mercury as science operations transition from MESSENGER’s primary orbital mission to its extended mission.

MESSENGER’s orbit around Mercury is highly eccentric, taking it from 200 kilometers (124 miles) above Mercury’s surface to 15,200 kilometers (9,445 miles) altitude every 12 hours. Since orbit insertion nearly one year ago, spacecraft operators at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, conducted five earlier maneuvers to counter the perturbing forces that pull MESSENGER away from its preferred observing geometry, including those arising from solar gravity and Mercury’s slight oblateness (the flattening of its spherical shape at the planet’s poles).

For this latest orbit adjustment, MESSENGER was 148 million kilometers (92 million miles) from Earth when the 171-second maneuver, which used all four of the medium-sized monopropellant thrusters on the deck opposite most of the science instruments, began at 8:44 p.m. EST. APL mission controllers verified the start of the maneuver 8 minutes and 12 seconds later, when the first signals indicating spacecraft thruster activity reached NASA’s Deep Space Network tracking station near Canberra, Australia.

In mid-April the team will conduct two additional maneuvers designed to reduce the period of MESSENGER’s orbit around Mercury from 12 to eight hours. According to MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington, “This reduction in orbital period will mean that MESSENGER spends a greater fraction of its time close to Mercury’s surface than during the primary mission that is now nearing a successful completion. Moreover, the accomplishment of the global mapping carried out during the primary mission will free many of MESSENGER’s instruments for a new mix of measurements to address a fresh set of scientific objectives that address questions raised by the findings from orbital observations to date.”

“The eight-hour orbit will provide 50% more low-altitude observation opportunities of Mercury’s north polar regions, including permanently shadowed craters,” explains MESSENGER Mission Design Lead Jim McAdams of APL. “A one-third reduction in maximum altitude relative to the 12-hour orbit will enable higher-resolution imaging of the southern hemisphere.”

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Feb 12

Software Enables Efficient Planning of MESSENGER Observations

Source: MESSENGER Press Release

SciBox, a scientific planning software package, has proven critical to the success of the MESSENGER mission to Mercury. With completion of the design of all primary-mission observations — including more than 70,000 images and millions of spectral observations — the SciBox software tool has substantially increased, relative to original expectations, the scientific return from the first year of Mercury orbital observations. The spacecraft team is now adapting the system to develop the best plan for MESSENGER’s extended mission, which begins next month.

Software engineers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., designed SciBox for the simulation and planning of mission scientific operations and for the generation of spacecraft and instrument commands. “It is a flexible, adjustable suite of mission-simulation and command-generation tools that models spacecraft performance with high fidelity,” explains APL’s Teck Choo, the creator and architect of SciBox.

SciBox developers worked with the scientists responsible for MESSENGER’s investigations to insert the requirements for all scientific observations into the software’s decision routines. During a planning run, SciBox examines the entire mission, locating the best opportunity for each scientific observation. Then, using a set of intertwined priorities constructed to minimize interference among observations, SciBox schedules the full set of observations for the entire mission.

Once the science and engineering teams verify the plan, SciBox produces the instrument commands, which are combined with telecommunication and power commands and then converted to binary format for transmission to the spacecraft. Because spacecraft pointing is integral to the observation plan, SciBox also plans attitude control maneuvers and produces those commands.

The SciBox planning system has increased the scientific return from MESSENGER in several ways. First, it has reduced the complexity involved in combining the more than 30 different sets of observations from the seven instruments and radio science. “By hand, this intractable problem—to find a fully integrated schedule that accommodates all observations — would be nearly impossible to solve,” states Mark Perry, the science lead for SciBox development. “With SciBox, the scientists can levy any and all types of requirements and constraints on the observations, no matter how intricate, and the SciBox implementation team can create an observing sequence to satisfy them.”

SciBox also helped the team evaluate options. “With SciBox, scientists and planners can modify the observational parameters and evaluate the effect on the entire mission schedule,” Perry says. “Part of SciBox’s output is an extensive set of reports that includes detailed lists, summary statistics, and hundreds of plots that facilitate evaluation of improvements and modifications. With that valuable information, MESSENGER scientists can conduct trades to identify the best approach.”

SciBox can also respond quickly to changes in the mission or requirements. “SciBox can re-plan an entire mission in three hours, including the re-integration of all observations, the generation of commands, and the completion of reports,” says Choo. “If the orbit is slightly different from that expected, or if an instrument’s optimal observing parameters change during the course of the mission, then we modify SciBox and re-run it.”

These same SciBox features have also reduced the risks involved in achieving overall mission objectives. “By planning all the mission observations at once, scientists need not estimate the long-range effects of their requirements,” Perry says. Many of the observing variables are run-time parameters, enabling trade studies without modifying the SciBox code, he explains. With SciBox, planners can also easily investigate the effects of problems and then modify SciBox to develop a plan that is less sensitive to such problems. This rapid response capability minimizes the effect of mission changes by quick re-planning of the full mission.

The SciBox tool continues to evolve. Indeed, one of its advantages is the ease with which it accommodates changes. During MESSENGER’s yearlong primary mission, as the science team has identified new observing opportunities, capability has been added to generate new and improved observations.

For the extended mission, the team developed a version of SciBox that incorporates all of the extended-mission observing requirements defined by MESSENGER’s science team. The SciBox developers examined strategies for accomplishing the new observations and then worked with the scientists to resolve conflicts and ensure that all requirements are met. The result, endorsed by the science team and scheduled to go into effect in March, is a packed plan that achieves a scientific return that exceeds extended mission requirements.

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Nov 11

NASA Extends MESSENGER Mission

Source: NASA/Messenger

Rembrandt, the second largest impact basin on Mercury discovered during the second MESSENGER flyby.
Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

NASA has announced that it will extend the MESSENGER mission for an additional year of orbital operations at Mercury beyond the planned end of the primary mission on March 17, 2012. The MESSENGER probe became the first spacecraft to orbit the innermost planet on March 18, 2011.

“We are still ironing out the funding details, but we are pleased to be able to support the continued exploration of Mercury,” said NASA MESSENGER Program Scientist Ed Grayzeck, who made the announcement on November 9, 2011, at the 24th meeting of the MESSENGER Science Team in Annapolis, Md.

The spacecraft’s unprecedented orbital science campaign is providing the first global close-up of Mercury and has revolutionized scientific perceptions of that planet. The extended mission will allow scientists to learn even more about the planet closest to the Sun, says MESSENGER Principal investigator Sean Solomon, of the Carnegie Institution of Washington.

“During the extended mission we will spend more time close to the planet than during the primary mission, we’ll have a broader range of scientific objectives, and we’ll be able to make many more targeted observations with our imaging system and other instruments,” says Solomon. “MESSENGER will also be able to view the innermost planet as solar activity continues to increase toward the next maximum in the solar cycle. Mercury’s responses to the changes in its environment over that period promise to yield new surprises.”

The extended mission has been designed to answer six scientific questions, each of which has arisen only recently as a result of discoveries made from orbit:

1.            What are the sources of surface volatiles on Mercury?

2.            How late into Mercury’s history did volcanism persist?

3.            How did Mercury's long-wavelength topography change with time?

4.            What is the origin of localized regions of enhanced exospheric density at Mercury?

5.            How does the solar cycle affect Mercury’s exosphere and volatile transport?

6.            What is the origin of Mercury’s energetic electrons?

“Advancements in science have at their core the evaluation of hypotheses in the light of new knowledge, sometimes resulting in slight changes in course, and other times resulting in paradigm shifts, opening up entirely new vistas of thought and perception,” says MESSENGER Project Scientist Ralph McNutt, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. “With the early orbital observations at Mercury we are already seeing the beginnings of such advancements. The extended mission guarantees that the best is indeed ‘yet to be’ on the MESSENGER mission, as this old-world Mercury, seen in a very new light, continues to give up its secrets.”

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Oct 11

Fourth Orbit Adjustment Stretches MESSENGER’s Orbit around Mercury

Source: MESSENGER Press Release

Image credit: NASA/MESSENGER

The MESSENGER spacecraft successfully completed its fourth orbit-correction maneuver today to increase the period of the spacecraft’s orbit around the innermost planet from 11 hours 46 minutes to a precise 12 hours.

MESSENGER was 198 million kilometers (123 million miles) from Earth when the 159-second maneuver began at 6:12 p.m. EDT. Mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of the maneuver about 11 minutes, 1 second later, when the first signals indicating spacecraft thruster activity reached NASA’s Deep Space Network tracking station outside Goldstone, California.

This is the fourth of five maneuvers planned for the primary orbital phase of the mission to keep orbital parameters within desired ranges for optimal scientific observations. MESSENGER’s orbital velocity was changed by a total of 4.2 meters per second (9.4 miles per hour) to make the corrections essential for continuing the planned measurement campaigns.

Most of the instruments were placed in a passive state during the burn, but the instruments were reconfigured at 7:05 p.m. EDT to resume scientific observations of the planet.

MESSENGER Mission Systems Engineer Eric Finnegan, of APL, said the engine burn was executed as planned. “The team was well-prepared for the maneuver, and MESSENGER is right where it needs to be to continue revealing new details about Mercury,” he said.

The next orbit-correction maneuver is scheduled for December 5.

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Oct 11

The Sleepy Hollows of Mercury

Source: NASA

NASA's MESSENGER spacecraft has discovered strange hollows on the surface of Mercury. Images taken from orbit reveal thousands of peculiar depressions at a variety of longitudes and latitudes, ranging in size from 60 feet to over a mile across and 60 to 120 feet deep. No one knows how they got there.

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Sep 11

Orbital Observations of Mercury Reveal Flood Lavas, Hollows, and Unprecedented Surface Details

Source: Messenger Press Release

Image credit: NASA/MESSENGER

After only six months in orbit around Mercury, NASA’s MESSENGER spacecraft is sending back information that has revolutionized the way scientists think about the innermost planet. Analyses of new data from the spacecraft show, among other things, new evidence that flood volcanism has been widespread on Mercury, the first close-up views of Mercury's "hollows," the first direct measurements of the chemical composition of Mercury's surface, and the first global inventory of plasma ions within Mercury’s space environment.

The results are reported in a set of seven papers published in a special section of Science magazine on September 30, 2011.(read more)

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Sep 11

MESSENGER Team delivers first orbital data to Planetary Data System

Source: MESSENGER Mission

Image credit: NASA/MESSENGER

Data collected during MESSENGER’s first two months in orbit around 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. Calibrated data from all seven of MESSENGER’s science instruments, plus radio science data from the spacecraft telecommunications system, are included in this release. (read more)

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Sep 11

MESSENGER navigates second hot season and performs third orbit-correction maneuver


Image credit: NASA/MESSENGER

Last Wednesday, the MESSENGER spacecraft emerged unscathed from the second of four “hot seasons” expected to occur during its one-year primary mission in orbit around Mercury. Hours later, mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., successfully executed a maneuver to adjust the spacecraft’s trajectory. (read more)

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Aug 11

MESSENGER Marks Seventh Anniversary of Launch

Source: MESSENGER Mission

Image credit: NASA/MESSENGER

Seven years ago, on August 3, 2004, MESSENGER left Earth aboard a three-stage Boeing Delta II rocket to begin a journey that would take it more than 15 laps through the solar system, through six planetary flybys, and ultimately into orbit around Mercury. The spacecraft has travelled 5.247 billion miles (8.445 billion kilometers) relative to the Sun, and the team is one-third of the way through the one-year science campaign to understand the innermost planet. (read more)

To watch an animation of the Sun rise and set on Mercury, go online to http://messenger-education.org/Interactives/ANIMATIONS/Day_On_Mercury/day_on_mercury.php.

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Jul 11

MESSENGER made another successful orbit adjustment

Source: MESSENGER Mission

Image credit: NASA/MESSENGER

The MESSENGER spacecraft continued to fine-tune its orbit around Mercury yesterday afternoon when mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., successfully executed the second orbit-correction maneuver of the mission.

On July 27, the 3-minute, 8-second engine burn stretched the spacecraft’s orbit around the innermost planet from 11 hours 48 minutes to a precise 12 hours. This second of an expected five maneuvers planned for the mission’s primary orbital phase began at 5:20 P.M. EDT, and used approximately 1.9 kilograms of fuel.

“MESSENGER’s first orbit-correction maneuver, which took place in June, reset the periapsis altitude of the orbit to 200 km, but also shortened the orbital period. This second maneuver has reset the period to its nominal value of 12 hours,” says APL’s Peter Bedini, MESSENGER project manager.

MESSENGER Mission Systems Engineer Eric Finnegan, of APL, said the engine burn was “on target and a sweet success. We’re precisely where we need to be to continue to capture amazing data from Mercury’s surface.” The next orbit-correction maneuver is scheduled for September 7 and will lower the periapsis altitude from about 470 kilometers back to 200 kilometers.

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Jun 11

MESSENGER endures its first hot season

Source: MESSENGER Mission News

MESSENGER Spacecraft. Image credit: NASA/MESSENGER

Yesterday the MESSENGER spacecraft successfully completed the first of four “hot seasons” expected to occur during its one-year primary mission in orbit about Mercury. During these hot seasons, the Sun-facing side of the probe’s sunshade can reach temperatures as high as 350°C.

These hot conditions are the result of two concurrent circumstances, says MESSENGER Mission Systems Engineer Eric Finnegan, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. “Mercury is in an eccentric orbit, and its distance from the Sun varies over 88 days, from 43,689,229 miles to 28,816,300 miles,” he explains. “On May 13, Mercury began heading closer to the Sun in its orbit. The planet reached its closest distance from the Sun on June 12.”

The second contributor to this heat is the geometry of MESSENGER’s orbit relative to the hot dayside of Mercury. The spacecraft is in a highly eccentric orbit around the planet, approaching to within 310 miles of the surface every 12 hours.

“During this hot period, the closest point of approach of the spacecraft to Mercury’s surface occurs on the sunlit side of the planet, so for almost one hour per orbit the spacecraft must pass between the Sun on one side and the hot dayside surface of the planet on the other,” Finnegan says. “To add further extremes, this season is also when the spacecraft passes over the nightside of the planet at high elevations and experiences the longest solar eclipses of the mission. During this period, when eclipses last as long as 62 minutes per orbit, the solar arrays are not illuminated and the spacecraft must derive its power from its internal battery.”

High temperatures are always a risk to mechanical and electronic systems, and the geometry of this portion of the orbit severely constrains the ability of the spacecraft to cool itself by radiating heat to cold space. MESSENGER engineers have taken several steps to ensure that the spacecraft remains safe.

“We rotated the solar arrays off the Sun through some of the hottest points so they do not have a view to either the Sun or the hot, dayside surface of the planet,” Finnegan says. “We are power cycling some of the more sensitive instruments to reduce their internal heat dissipation. In a manner similar to the treatment of the solar arrays, we are also adjusting the attitude of the spacecraft to keep some of the more sensitive parts of the spacecraft from seeing the hottest parts of the planet’s surface.”

All of the instruments have been operating during this period. Finnegan says that there have been times during each orbit when instruments are turned off, however, mostly to conserve power during eclipses.

These conditions are expected to recur approximately every 88 days (i.e., the time it takes Mercury to orbit the Sun). MESSENGER can therefore look forward to three more hot seasons during the course of its primary mission.

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Jun 11

New Spacecraft Orbital Views of Mercury

Source: MESSENGER Mission

First ever image of Mercury from orbit taken by Messenger probe on March 23rd, 2011.
Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

After sending back to Earth the first ever image of Mercury taken by a spaceship in orbit, Messenger has began to create galleries of images of the planet. (view more)

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