MESSENGER mission to Mercury

[Rick]

The Messenger probe is nearing the halfway point of 7.9 billion kilometre journey, which when completed will make it the first man-made object to orbit the planet Mercury.

During the craft's first three years and three months in space since its launch in August, 2004, Messenger has flown by Earth once and Venus twice. Now Messenger is nearing the goal of its mission, when it will pass the closest planet to the Sun three times before attempting to lock into orbit.

More: http://www.theregister.co.uk/2007/11/21/mercury_probe_halfway_mark/

[Rick]

NASA's Messenger has beamed back the first picture of Mercury's hitherto unseen side, snapped from a distance of about 17,000 miles after its first fly-by of the planet yesterday.

NASA explains: "The image shows features as small as six miles in size. Similar to previously mapped portions of Mercury, this hemisphere appears heavily cratered. It also reveals some unique and distinctive features. On the upper right is the giant Caloris basin, including its western portions never before seen by spacecraft. Formed by the impact of a large asteroid or comet, Caloris is one of the largest, and perhaps one of the youngest basins in the solar system."

More: http://www.theregister.co.uk/2008/01/16/mercury_hidden_hemisphere/

[Rick]

he smallest planet in the Solar System has become even smaller, studies by the Messenger spacecraft have shown.

Data from a flyby of Mercury in January 2008 show the planet has contracted by more than one mile (1.5km) in diameter over its history.

Scientists believe the shrinkage is due to the planet's core slowly cooling.

More: http://news.bbc.co.uk/2/hi/science/nature/7489557.stm

[Ian]

to start with I thought the IAU were having another pop at Pluto. But then, that's not a planet anymore. Unless it puts on a growth spurt...

[mickw]

Volcanoes on Mercury Solve 30-year Mystery

More:   http://www.space.com/scienceastronomy/080703-mercury-messenger.html

It might have just sprung a leak 

[mickw]

A NASA probe has begun beaming back stunning new images from its successful second flyby of Mercury, the planet closest to the sun.

NASA's MESSENGER probe captured never-before-seen views of the Mercury during its encounter on Monday. The spacecraft zipped past Mercury for the second time this year and used the planet's gravity to adjust its path as it continues en route to become the first probe to orbit the planet in March 2011.

More:   http://www.space.com/scienceastronomy/081007-messenger-mercury-flyby.html

[Rick]

The Mercury Messenger probe has returned another batch of stunning pictures of the innermost world.

The Nasa spacecraft swept over the surface of the planet on Tuesday, passing just 200km above the rocky terrain at closest approach.

Some 1,200 images were obtained - many of regions never before been seen up close by a probe.

The flyby also gave Messenger the gravity tug it needed to get on to the right path to go into orbit in 2011.

More: http://news.bbc.co.uk/2/hi/science/nature/7659250.stm

[Rick]

NASA's Messenger has delivered its second set of postcards from Mercury, following a successful low-altitude fly-past on Monday which saw the spacecraft swoop to within 125 miles (200km) of the planet's surface, snapping furiously as it went.

More: http://www.theregister.co.uk/2008/10/08/messenger_mercury/

...and earlier: http://www.theregister.co.uk/2008/10/02/messenger_mercury/

[Rick]

NASA's Messenger spacecraft has now imaged 80 per cent of the surface of Mercury following its second fly-past of the planet on 6 October, meaning that around 95 per cent has been revealed by various missions, the agency reports.

More: http://www.theregister.co.uk/2008/10/30/messenger_mercury_imaging/
NASA: http://www.nasa.gov/mission_pages/messenger/main/index.html

[mickw]

Mercury should have trouble hanging on to its atmosphere. It is the closest planet to the sun , its searing daytime temperatures top 800 degrees Fahrenheit (450 degrees Celsius and its gravity is weak, only about 38 percent of Earth's. These conditions don't hold air.

New clues to why Mercury does have a thin atmosphere have been discovered by the MESSENGER spacecraft.

"Mercury's atmosphere is so thin, it would have vanished long ago unless something was replenishing it," James Slavin of NASA's Goddard Space Flight Center, Greenbelt, Md., said in a statement.

More:   http://www.space.com/missionlaunches/090608-mm-mercury-tornadoes.html

[mickw]

A NASA spacecraft that completed its third and final flyby of the planet Mercury yesterday, snapping new pictures of the innermost planet, had a small data hiccup that has delayed release of the images, mission engineers said today.

The MESSENGER probe skimmed just 142 miles (228 km) above Mercury at its closest approach as it whipped around the planet during the flyby, the last of three designed to guide the spacecraft into orbit around the planet in 2011.

The spacecraft did snap several new images of the rocky planet on the inbound leg of its close approach.

"We do have some new science from the flyby," said MESSENGER project scientist Ralph McNutt of Johns Hopkins University Applied Physics Laboratory.

More:   http://www.space.com/scienceastronomy/090930-messenger-hiccup.html

[mickw]

During its most recent flyby of Mercury, NASA's MESSENGER spacecraft caught another glimpse of the innermost planet's mysterious bright spot.

The MESSENGER probe skimmed just 142 miles (228 km) above Mercury at its closest approach as it whipped around the planet during the flyby, the last of three designed to guide the spacecraft into orbit around the planet in 2011.

The $446 million probe snapped several new images of Mercury during the flyby, despite a minor data hiccup that delayed the downlink of some of the images.

One of the new images shows a bright spot on the planet's surface, a feature that scientists cannot yet explain.

The new view was the third of the spot, which was first seen in telescopic images of Mercury obtained from Earth by astronomer Ronald Dantowitz. The second view was obtained by the MESSENGER Narrow Angle Camera during the spacecraft's second Mercury flyby Oct. 6, 2008. At that time, the bright feature was just on the planet's limb (edge) as seen from MESSENGER.

More:   http://www.space.com/scienceastronomy/091001-mercury-bright-spot.html

[mickw]

A NASA spacecraft has spotted what appears to be changing seasons on Mercury and found much more iron on the surface of the small, rocky planet than previously thought.

The MESSENGER probe made the observations during its third flyby of Mercury on Sept. 29, when it took a host of measurements and images of the innermost planet's surface and atmosphere. Only about half of the planned measurements were made because of a data glitch that affected the spacecraft during the flyby.

The $446 million probe's third flyby brought it within 142 miles (228 km) of Mercury's surface to cover more uncharted terrain, leaving 98 percent of the planet now mapped. The flyby was also a gravity assist meant to guide the spacecraft into orbit around the planet in 2011.

Tenuous exosphere

Mercury's atmosphere is what scientists call an "exosphere," and is made up of atoms kicked up from the surface. It is very tenuous and has a very low density, meaning atoms in the atmosphere rarely run into each other. It also has a tail that streams away from the planet in the opposite direction of the sun.

MESSENGER looked at differences in three atoms in the exosphere — sodium, calcium and magnesium — between the probe's three flybys. They detected much less sodium during the third flyby than they had during the second.

"While this is dramatic, it isn't totally unexpected," Vervack said. This is because radiation pressures from the sun change as Mercury moves through its orbit, which changes the amount of sodium liberated from the surface.

In essence, Mercury's atmosphere experiences seasonal effects during the planet's orbit.

More:   http://www.space.com/scienceastronomy/091103-mercury-new-images.html

[Rick]

It is only now thanks to the Messenger spacecraft that researchers have the imagery necessary to construct a truly global map of the innermost planet.

The probe's latest pictures added to those of the earlier Mariner 10 mission give near-total coverage.

Mapping experts at the US Geological Survey have been working to piece together all of these images in their possession into a giant mosaic.

More: http://news.bbc.co.uk/1/hi/sci/tech/8415421.stm

[mickw]

Here:   Mercury

[Rick]

MESSENGER Navigates Second Hot Season, Executes Third Orbit-Correction Maneuver

MESSENGER Mission News
September 7, 2011

Today 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.

This hot season began on August 9 and lasted nearly one month. During that time, the closest approach of the spacecraft to Mercury was on the sunlit side of the planet. MESSENGER's sunshade reached temperatures as high as 350°C during this season, and its solar panels had to be turned off the Sun for short periods during each orbit to protect them from overheating.

More: http://messenger.jhuapl.edu/news_room/details.php?id=181

[Rick]

MESSENGER Finds New Evidence for Water Ice at Mercury's Poles

New observations by the MESSENGER spacecraft provide compelling support for the long-held hypothesis that Mercury harbors abundant water ice and other frozen volatile materials in its permanently shadowed polar craters.

Three independent lines of evidence support this conclusion: the first measurements of excess hydrogen at Mercury's north pole with MESSENGER's Neutron Spectrometer, the first measurements of the reflectance of Mercury's polar deposits at near-infrared wavelengths with the Mercury Laser Altimeter (MLA), and the first detailed models of the surface and near-surface temperatures of Mercury's north polar regions that utilize the actual topography of Mercury's surface measured by the MLA. These findings are presented in three papers published online today in Science Express.

More: http://www.nasa.gov/mission_pages/messenger/media/PressConf20121129.html

[Rick]

MESSENGER Completes Its First Extended Mission at Mercury

On March 17, 2013, MESSENGER successfully completed its year-long first extended mission in orbit about Mercury, building on the groundbreaking scientific results from its earlier primary mission. Today the team is poised to embark on a second extended mission that promises to provide new observations of Mercury's surface and interior at unprecedented spatial resolution and of the planet's dynamic magnetosphere and exosphere at high time resolution during the peak and declining phase of the current solar cycle.

More: http://messenger.jhuapl.edu/news_room/details.php?id=237

[Rick]

MESSENGER's First Images of Comets Encke and ISON

As the new comet C/2012 S1 (ISON) and the well-known short-period comet 2P/Encke both approach their closest distances to the Sun later this month, they are also passing close to the MESSENGER spacecraft now orbiting the innermost planet Mercury. Just this week, both comets have brightened sufficiently to be captured in images by MESSENGER's wide-angle camera.

More: http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=1296

(Link tested on all the systems and browsers I have available, and works fine on all. If you're having trouble with it, please put details in this thread in Updates and Upsets.)

[Rick]

A Tale of Two Comets: MESSENGER Captures Images of Encke and ISON

n November 18, NASA's Mercury-orbiting MESSENGER spacecraft pointed its Mercury Dual Imaging System (MDIS) at 2P/Encke and captured this image of the comet as it sped within 2.3 million miles (3.7 million kilometers) of Mercury's surface. The next day, the probe captured this companion image of C/2012 S1 (ISON), as it cruised by Mercury at a distance of 22.5 million miles (36.2 million kilometers) on its way to its late-November closest approach to the Sun.

MESSENGER's cameras have been acquiring targeted observations of Encke since October 28 and ISON since October 26, although the first faint detections didn't come until early November. During the closest approach of each comet to Mercury, the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) and X-Ray Spectrometer (XRS) instruments also targeted the comets. Observations of ISON conclude on November 26, when the comet passes too close to the Sun, but MESSENGER will continue to monitor Encke with both the imagers and spectrometers through early December.

The spacecraft has a view of the comets very different from that of Earth-based observers. "MESSENGER imaged Encke only a few days before its perihelion when it was at its brightest," explains Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory, who is leading MESSENGER's comet-observation campaign. "That we are so close to the comet at this time offers a chance to make important observations that could shed light on its asymmetric behavior about perihelion."

More: http://messenger.jhuapl.edu/news_room/details.php?id=246
APOD: http://apod.nasa.gov/apod/ap131123.html

[Rick]

Mercury's Contraction Much Greater Than Thought

New global imaging and topographic data from MESSENGER show that the innermost planet has contracted far more than previous estimates. The results are based on a global study of more than 5,900 geological landforms, such as curving cliff-like scarps and wrinkle ridges, that have resulted from the planet's contraction as Mercury cooled. The findings, published online today in Nature Geoscience, are key to understanding the planet's thermal, tectonic, and volcanic history, and the structure of its unusually large metallic core.

Unlike Earth, with its numerous tectonic plates, Mercury has a single rigid, top rocky layer. Prior to the MESSENGER mission only about 45% of Mercury's surface had been imaged by spacecraft. Old estimates, based on this non-global coverage, suggested that the planet had contracted radially by about 1/2 to 2 miles (0.8 to 3 kilometers), substantially less than that indicated by models of the planet's thermal history. Those models predicted a radial contraction of about 3 to 6 miles (5 to 10 kilometers) starting from the late heavy bombardment of the Solar System, which ended about 3.8 billion years ago.

The new results, which are based on the first comprehensive survey of the planet's surface, show that Mercury contracted radially by as much as 4.4 miles (7 kilometers) -- substantially more than the old estimates, but in agreement with the thermal models. Mercury's modern radius is 1,516 miles (2,440 kilometers).

More: http://messenger.jhuapl.edu/news_room/details.php?id=254

[Rick]

MESSENGER Modifies Orbit to Prepare for Low-Altitude Campaign

MESSENGER successfully completed the first orbit-correction maneuver of its Second Extended Mission this morning to raise its minimum altitude above Mercury from 113.9 kilometers (70.8 miles) to 155.1 kilometers (96.4 miles). This maneuver is the first of four designed to modify the spacecraft's orbit around Mercury so as to delay the spacecraft's inevitable impact onto Mercury's surface and allow scientists to continue to gather novel information about the innermost planet.

During the primary phase of the MESSENGER mission, the spacecraft's orbit around Mercury was highly eccentric, drifting between 200 and 500 kilometers (124 to 311 miles) above Mercury's surface at closest approach, and between 15,200 and 14,900 kilometers (9,445 to 9,258 miles) above the surface at its farthest point, and completing an orbit every 12 hours. Spacecraft operators at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, conducted several spacecraft maneuvers to counter the perturbing forces that caused MESSENGER's lowest orbital altitude to drift upward, away from its preferred observing geometry, and early in MESSENGER's First Extended Mission conducted a pair of maneuvers to reduce the orbital period to eight hours.

"In this final phase of the mission, the opposite effect is happening," explained the mission trajectory lead Jim McAdams of APL. "To extend the mission, we need to raise the minimum altitude by increasing the Mercury-relative speed of the spacecraft when it is farthest from Mercury."

More: http://messenger.jhuapl.edu/news_room/details.php?id=257

[Rick]

MESSENGER and STEREO Measurements Open New Window Into High-Energy Processes on the Sun

Understanding the Sun from afar isn't easy. How do you figure out what powers solar flares -- the intense bursts of radiation coming from the release of magnetic energy associated with sunspots -- when you must rely on observing only the light and particles that make their way to Earth's orbit? One answer: you get closer.

NASA's MESSENGER spacecraft -- which orbits Mercury, and so is as close as 28 million miles from the Sun versus Earth's 93 million miles -- is close enough to the Sun to detect solar neutrons that are created in solar flares. The average lifetime for one of these neutrons is only 15 minutes. How far they travel into space depends on their speed, and slower neutrons don't travel far enough to be seen by particle detectors in orbit around Earth.

More: http://messenger.jhuapl.edu/news_room/details.php?id=258

[Rick]

MESSENGER Gets Closer to Mercury than Ever Before

On July 25, MESSENGER moved closer to Mercury than any spacecraft has before, dropping to an altitude at closest approach of only 100 kilometers (62 miles) above the planet's surface.

"The science team is implementing a remarkable campaign that takes full advantage of MESSENGER's orbital geometry, and the spacecraft continues to execute its command sequences flawlessly as the 14th Mercury year of the orbit phase comes to a close," said MESSENGER Mission Operations Manager Andy Calloway, of the Johns Hopkins University Applied Physics Laboratory (APL).

More: http://messenger.jhuapl.edu/news_room/details.php?id=259

[Rick]

MESSENGER Provides First Optical Images of Ice Near Mercury's North Pole

NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has provided the first optical images of ice and other frozen volatile materials within permanently shadowed craters near Mercury's north pole. The images not only reveal the morphology of the frozen volatiles, but they also provide insight into when the ices were trapped and how they've evolved, according to an article published today in the journal, Geology.

Two decades ago, Earth-based radar images of Mercury revealed the polar deposits, postulated to consist of water ice. That hypothesis was later confirmed by MESSENGER through a combination of neutron spectrometry, thermal modeling, and infrared reflectometry. "But along with confirming the earlier idea, there is a lot new to be learned by seeing the deposits," said lead author Nancy Chabot, the Instrument Scientist for MESSENGER's Mercury Dual Imaging System (MDIS) and a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.

Beginning with MESSENGER's first extended mission in 2012, scientists launched an imaging campaign with the broadband clear filter of MDIS's wide-angle camera (WAC). Although the polar deposits are in permanent shadow, through many refinements in the imaging, the WAC was able to obtain images of the surfaces of the deposits by leveraging very low levels of light scattered from illuminated crater walls. "It worked in spectacular fashion," said Chabot.

The team zeroed in on Prokofiev, the largest crater in Mercury's north polar region found to host radar-bright material. "Those images show extensive regions with distinctive reflectance properties," Chabot said. "A location interpreted as hosting widespread surface water ice exhibits a cratered texture indicating that the ice was emplaced more recently than any of the underlying craters."

More: http://messenger.jhuapl.edu/news_room/details.php?id=266

[Rick]

Third of Four Planned Maneuvers Extends MESSENGER Orbital Operations

MESSENGER mission controllers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., conducted the third of four maneuvers today to raise the spacecraft's minimum altitude sufficiently to extend orbital operations and delay the probe's inevitable impact onto Mercury's surface until early next spring.

More: http://messenger.jhuapl.edu/news_room/details.php?id=267

[Rick]

Maneuver Successfully Delays MESSENGER's Impact, Extends Orbital Operations

MESSENGER mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., successfully conducted a maneuver today designed to raise the spacecraft's minimum altitude sufficiently to extend orbital operations and delay the probe's inevitable impact onto Mercury's surface until early next spring.

The immediately previous maneuver, completed on October 24, 2014, raised MESSENGER to an altitude at closest approach from 25.4 kilometers (15.8 miles) to 184.4 kilometers (114.6 miles) above the planet's surface. Because of progressive changes to the orbit over time, the spacecraft's minimum altitude continued to decrease.

At the time of this most recent maneuver, MESSENGER was in an orbit with a closest approach of 25.7 kilometers (16.0 miles) above the surface of Mercury. With a velocity change of 9.67 meters per second (21.62 miles per hour), the spacecraft's four largest monopropellant thrusters (with a small contribution from four of the 12 smallest monopropellant thrusters) nudged the spacecraft to an orbit with a closest approach altitude of 105.1 km (65.3 miles).

More: http://messenger.jhuapl.edu/news_room/details.php?id=271

[Rick]

New MESSENGER Maps of Mercury's Surface Chemistry Provide Clues to the Planet's History

The MESSENGER mission was designed to answer several key scientific questions, including the nature of Mercury's geological history. Remote sensing of the surface's chemical composition has a strong bearing on this and other questions. Since MESSENGER was inserted into orbit about Mercury in March 2011, data from the spacecraft's X-Ray Spectrometer (XRS) and Gamma-Ray Spectrometer (GRS) have provided information on the concentrations of potassium, thorium, uranium, sodium, chlorine, and silicon, as well as ratios relative to silicon of magnesium, aluminum, sulfur, calcium, and iron.

Map: http://messenger.jhuapl.edu/news_room/images/magnesium-silicon.jpg

More: http://messenger.jhuapl.edu/news_room/details.php?id=273

[Rick]

Best views yet of Mercury's ice-filled craters

Scientists have obtained the most detailed views yet of ice deposits inside the permanently shadowed craters at Mercury's north pole.

The pictures were taken by Nasa's Mercury Messenger spacecraft, which has been orbiting just tens of kilometres from the planet's surface.

More: http://www.bbc.co.uk/news/science-environment-31917308

[Rick]

MESSENGER's Endgame: Hover Campaign Promises Bird's-Eye View of Mercury's Surface

MESSENGER will not go gentle into that good night. The mission will end sometime this spring, when the spacecraft runs out of propellant and the force of solar gravity causes it to impact the surface of Mercury. But the team initiated a "hover" observation campaign designed to gather scientific data from the planet at ultra-low altitudes until the last possible moment. Engineers have devised a series of orbit-correction maneuvers (OCMs) over the next five weeks -- the first of which was carried out today -- designed to delay the inevitable impact a bit longer.

A highly accurate OCM executed on January 21 targeting a 15-kilometer periapsis altitude -- the lowest to date -- set the stage for the hover campaign, in a short extension of the Second Extended Mission termed XM2-Prime (XM2'). The top science goals for XM2' will be carried out with the Magnetometer (MAG) and the Neutron Spectrometer (NS), and each instrument will target different objectives in different regions, explained MESSENGER Deputy Project Scientist Haje Korth, of The Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md.

"With MAG, we will look for crustal magnetic anomalies," he said. "For instance, we have seen hints of crustal magnetization at higher altitudes (~70 kilometers) over the northern rise in Mercury's northern smooth plains. We will revisit this region at lower altitudes during XM2'. There may be other regions where such signals can be observed, and we will be looking for them."

"With NS, scientists will hone in on shadowed craters at northern high latitudes to search for water ice," Korth said. "We have found such evidence previously in the mission, but we hope to find more at low altitudes and spatially resolve the distribution within individual craters if we are lucky."

More: http://messenger.jhuapl.edu/news_room/details.php?id=276

[Rick]

MESSENGER Executes Last Orbit-Correction Maneuver, Prepares for Impact

MESSENGER mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., conducted the last of six planned maneuvers on April 24 to raise the spacecraft's minimum altitude sufficiently to extend orbital operations and further delay the probe's inevitable impact onto Mercury's surface.

With the usable on-board fuel consumed, this maneuver expelled gaseous helium -- originally carried to pressurize the fuel, but re-purposed as a propellant. Without a means of boosting the spacecraft's altitude, the tug of the Sun's gravity will draw the craft in to impact the planet on April 30, at about 8,750 miles per hour (3.91 kilometers per second), creating a crater as wide as 52 feet (16 meters).

The previous maneuver, completed on April 14, raised MESSENGER's minimum altitude above Mercury from 6.5 kilometers (4.0 miles) to 13.3 kilometers (8.3 miles). But because of progressive changes in the orbit over time, the spacecraft's minimum altitude continued to decrease.

At the start of yesterday's maneuver, at 1:23 p.m. EDT, MESSENGER was in an orbit with a closest approach of 8.3 kilometers (5.1 miles) above the surface of Mercury. With a velocity change of 1.53 meters per second (3.43 miles per hour), the spacecraft's four largest monopropellant thrusters released gaseous helium to nudge the spacecraft to an orbit with a closest approach altitude of 18.2 kilometers (11.3miles).

Mission controllers at APL verified the start of the maneuver 9.4 minutes later, when the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network (DSN) tracking station in Goldstone, California. This was the third MESSENGER maneuver designed to adjust the course of the spacecraft using just helium gas.

More: http://messenger.jhuapl.edu/news_room/details.php?id=282

[ApophisAstros]

The first to orbit Mercury, the MESSENGER spacecraft came to rest on this region of Mercury's surface yesterday. Constructed from MESSENGER image and laser altimeter data.......

http://apod.nasa.gov/apod/ap150501.html

roger

[Rick]

NASA Completes MESSENGER Mission with Expected Impact on Mercury's Surface

Mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., confirmed today that NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft impacted the surface of Mercury, as predicted, at 3:26 p.m. EDT this afternoon (3:34 p.m. ground time).

Mission controllers were able to confirm the end of operations just a few minutes later at 3:40 p.m., when no signal was detected by the Deep Space Network (DSN) station in Goldstone, California, at the time the spacecraft would have emerged from behind the planet had MESSENGER not impacted the surface. This conclusion was independently confirmed by the DSN's Radio Science team, who were simultaneously looking for the signal from MESSENGER from their posts in California.

MESSENGER was launched on August 3, 2004, and it began orbiting Mercury on March 18, 2011. The spacecraft completed its primary science objectives by March 2012. Because MESSENGER's initial discoveries raised important new questions and the payload remained healthy, the mission was extended twice, allowing the spacecraft to make observations from extraordinarily low altitudes and capture images and information about the planet in unprecedented detail.

Last month -- during a final short extension of the mission referred to as XM2'-- the team embarked on a hover campaign that allowed the spacecraft at its closest approach to operate within a narrow band of altitudes, 5 to 35 kilometers above the planet's surface. On April 28, the team successfully executed the last of seven orbit-correction maneuvers (the last four of which were conducted entirely with helium pressurant after the remaining liquid hydrazine had been depleted), which kept MESSENGER aloft for the additional month, sufficiently long for the spacecraft's instruments to collect critical information that could shed light on Mercury's crustal magnetic anomalies and ice-filled polar craters, among other features.

With no way to increase its altitude, MESSENGER was finally unable to resist the perturbations to its orbit by the Sun's gravitational pull, and it slammed into Mercury's surface at around 8,750 miles per hour, creating a new crater up to 52 feet wide.

More: http://messenger.jhuapl.edu/news_room/details.php?id=284

[Rick]

MESSENGER Finds Evidence of Ancient Magnetic Field on Mercury

Mercury's magnetic field, generated by a dynamo process in its outer core, has been in place far longer than previously known, a paper by MESSENGER Participating Scientist Catherine Johnson reports.

About 4 billion years ago, Mercury's magnetic field could have been much stronger than today, as indicated by low-altitude observations made by NASA's MESSENGER spacecraft that revealed evidence of magnetization of ancient crustal rocks on Mercury.

The MESSENGER spacecraft crashed onto Mercury last week after running out of fuel, but the mission provided a trove of new information on the planet closest to the Sun.

More: http://messenger.jhuapl.edu/news_room/details.php?id=285

[Rick]

Mercury Gets a Meteoroid Shower from Comet Encke

The planet Mercury is being pelted regularly by bits of dust from an ancient comet, a new study has concluded. This has a discernible effect in the planet's tenuous atmosphere and may lead to a new paradigm on how these airless bodies maintain their ethereal envelopes.

The findings are to be presented at the annual Meeting of the Division of Planetary Sciences of the American Astronomical Society at National Harbor, Maryland, this week, by Apostolos Christou at the Armagh Observatory in Northern Ireland, Rosemary Killen at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and Matthew Burger of Morgan State University in Baltimore, working at Goddard.

Earthlings are no strangers to the effects of cometary dust on a planet and its environment. On a clear, moonless night we witness the demise of countless such dust grains as they burn up in the Earth's atmosphere in the form of meteors or "shooting stars." At certain times of the year, their numbers increase manyfold, creating a natural fireworks display: a meteor shower. This is caused by the Earth passing through a stream of dust particles left behind by certain comets.

More: http://www.nasa.gov/feature/goddard/mercury-gets-meteoroid-shower-from-comet-encke

[Rick]

MESSENGER Data May Reveal the Remains of Mercury's Oldest Crust

Mercury's surface is unusually dark, an observation that until recently had planetary scientists mystified. But in a new study published March 7 2016 in Nature Geoscience, a team of researchers provides evidence that the darkening agent is carbon, a finding that offers important clues to the nature of the planet's original crust.

Patrick Peplowski, a research scientist at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, and lead author of the paper, explains that earlier measurements of the chemistry of Mercury's surface only added to this mystery because they indicated that Mercury's surface has low abundances of iron and titanium, important constituents of the most common darkening agents on the Moon and other silicate bodies.

"A process of elimination led prior researchers to suggest that carbon may be the unidentified darkening agent, but we lacked proof," he said. "Spectral modeling of MESSENGER color imaging data suggested that weight-percent levels of carbon, likely in the form of graphite, would be required to darken Mercury's surface sufficiently. This level is unusually high, given that carbon is found at typical concentrations of only ~100 parts per million on the Moon, Earth and Mars."


More: http://messenger.jhuapl.edu/news_room/details.php?id=291

[Rick]

Researchers Trace Mercury's Origins to Rare Enstatite Chondrite Meteorite

Around 4.6 billion years ago, the universe was a chaos of collapsing gas and spinning debris. Small particles of gas and dust clumped together into larger and more massive meteoroids that in turn smashed together to form planets. Scientists believe that shortly after their formation, these planets — and particularly Mercury — were fiery spheres of molten material, which cooled over millions of years.

Now, geologists at MIT have traced part of Mercury's cooling history and found that between 4.2 and 3.7 billion years ago, soon after the planet formed, its interior temperatures plummeted by 240 degrees Celsius, or 464 degrees Fahrenheit.

They also determined, based on this rapid cooling rate and the composition of lava deposits on Mercury's surface, that the planet likely has the composition of an enstatite chondrite — a type of meteorite that is extremely rare here on Earth.

More: http://news.mit.edu/2016/mercury-origins-rare-meteorite-0627