MESSENGER Solves Solar Flare Mystery

Antenna Array


In a case of being in the right place at the right time, the MESSENGER spacecraft was able to capture a average-sized solar flare, allowing astronomers to study high-energy solar neutrons at less than 1 astronomical unit (AU) from the sun for the first time. When the flare erupted on Dec. 31, 2007, MESSENGER – on course for entering orbit around Mercury — was flying at about half an AU, said William C. Feldman, a scientist at the Planetary Science Institute. Previously, only the neutron bursts from the most powerful solar flares have been recorded on neutron spectrometers on Earth or in near-Earth orbit. The MESSENGER results help solve a mystery of why some coronal mass ejections produce almost no energetic protons that reach the Earth, while others produce huge amounts.

Solar flares spew high-energy neutrons into interplanetary space. Typically, these bursts last about 50 to 60 seconds at the sun. But MESSENGER’s Neutron Spectrometer was able to record neutrons from this flare over a period of six to ten hours. “What that’s telling us is that at least some moderate-sized flares continuously produce high-energy neutrons in the solar corona.” Said Feldman. “From this fact, we inferred the continuous production of protons in the 30-to-100-MeV (million electron volt) range due to the flare.”
About 90 percent of all ions produced by a solar flare remain locked to the sun on closed magnetic lines, but another population results from the decay of the neutrons near the sun. This second population of decayed neutrons forms an extended seed population in interplanetary space that can be further accelerated by the massive shock waves produced by the flares, Feldman said.

“So the important results are that perhaps after many flare events two things may occur: continuous production of neutrons over an extended period of time and creation of seed populations of neutrons near the sun that have decayed into protons,” Feldman said. “When coronal mass ejections (nuclear explosions in the corona) send shock waves into space, these feedstock protons are accelerated into interplanetary space.”

“There has always been the question of why some coronal mass ejections produce almost no energetic protons that reach the Earth, while others produce huge amounts,” he added. “It appears that these seed populations of energetic protons near the sun could provide the answer, because it’s easier to accelerate a proton that already has an energy of 1 MeV than a proton that is at 1 keV (the solar wind).”

The seed populations are not evenly distributed, Feldman said. Sometimes they’re in the right place for the shock waves to send them toward Earth, while at other times they’re in locations where the protons are accelerated in directions that don’t take them near Earth.

The radiation produced by solar flares is of more than academic interest to NASA, Feldman added. Energetic protons from solar flares can damage Earth-orbiting satellites and endanger astronauts on the International Space Station or on missions to the Moon and Mars.

“People in the manned spaceflight program are very interested in being able to predict when a coronal mass ejection is going to be effective in generating dangerous levels of high-energy protons that produce a radiation hazard for astronauts,” he said.

To do this, scientists need to know a lot more about the mechanisms that produce flares and which flare events are likely to be dangerous. At some point they hope to be able to predict space weather — where precipitation is in the form of radiation — with the same accuracy that forecasters predict rain or snow on Earth.

MESSENGER could provide significant data toward this goal, Feldman observed. “What we saw and published is what we hope will be the first of many flares we’ll be able to follow through 2012,” he said. “The beauty of MESSENGER is that it’s going to be active from the minimum to the maximum solar activity during Solar Cycle 24, allowing us to observe the rise of a solar cycle much closer to the sun than ever before.”

MESSENGER is currently orbiting the sun between 0.3 and 0.6 AU — (an AU is the average distance between the Earth and the sun, or about 150,000 km) — on its way to orbit insertion around Mercury in March 2011. At Mercury, it will be within 0.45 AU of the sun for one Earth year.

Read the team’s paper: Evidence for Extended Acceleration of Solar Flare Ions from 1-8-MeV Solar Neutrons Detected with the MESSENGER Neutron Spectrometer.

Source: PSI

More New Looks at Mercury from MESSENGER

[/caption]More new images were released today from the MESSENGER spacecraft’s third flyby of Mercury. I asked astrophysicist Dr. Jeff Goldstein (doctorjeff on Twitter), (who was on hand at the mission operations center to blog and Tweet about the flyby) which image the science team found most intriguing, and he replied that it was really hard to tell, as they were oohing and aahing at every image! But one of the most interesting was this shot of a bright spot on the planet closest to the sun. MESSENGER’s Narrow Angle Camera also saw this spot during the spacecraft’s second Mercury flyby on October 6, 2008, but the bright feature was just on the planet’s limb (edge) from the spacecraft’s vantage point. This time, however, the geometry of MESSENGER’s flyby provided a better look at this feature. Surprisingly, at the center of the bright halo is an irregular depression, which may have formed through volcanic processes. Color images from MESSENGER’s Wide Angle Camera reveal that the irregular depression and bright halo have distinctive color. This area will be of particular interest for further observation during MESSENGER’s orbital operations starting in 2011.

Craters form a paw print on Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Craters form a paw print on Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

If you like seeing a little pareidolia, here’s a fun one: a paw print! Mercury’s surface is covered with craters in many sizes and arrangements, the result of impacts that have occurred over billions of years. In the top center of the image, outlined in a white box and shown in the enlargement at upper right, is a cluster of impact craters on Mercury that appears coincidentally to resemble a giant paw print. In the “heel” are overlapping craters, made by a series of impacts occurring on top of each other over time. The four “toes” are single craters arranged in an arc northward of the “heel.” The “toes” don’t overlap so it isn’t possible to tell their ages relative to each other. The newly identified pit-floor crater can be seen in the center of the main image as the crater containing a depression shaped like a backward and upside-down comma.

For more of the latest images from the third flyby, check out the MESSENGER flyby page.

MESSENGER Went Into Safe Mode Approaching Mercury

The MESSENGER spacecraft went into safe mode just before its closest approach of Mercury on Sept. 29. Although the instruments were taking data as the spacecraft came near the planet during this third flyby of the mission, after going into safe mode, no further data or pictures were obtained. This means the expected science investigations from the flyby were not executed. However, as Emily Lakdawalla pointed on in the Planetary Blog, the most important purpose of this flyby was the last gravity assist that will allow MESSENGER to enter orbit in 2011, and to that end, the flyby was a complete success. Additionally, the images taken during the approach are of the 5% of Mercury that was previously unseen, as in the image above of this unnamed basin. See more images from the approach below.

A High-resolution Look over Mercury's Northern Horizon. Credit: MESSENGER team
A High-resolution Look over Mercury's Northern Horizon. Credit: MESSENGER team

MESSENGER skimmed just 142 miles (228 km) above Mercury at closest approach, and then whipped behind the planet for the gravity assist. During the operation, five MESSENGER “fellows” or master teachers were reporting the flyby live via Twitter. Gene Gordon (Porchdragon on Twitter) reported that unexpectedly, the signal dropped from MESSENGER before the expected signal blackout while flying on the other side of Mercury: “Suddenly room got quiet and people hovering near computers. Unexpected signal drop just occurred. Sense of nervousness seems to have happened.”

Read Gene Gordon’s blog post about his experiences.

The MESSENGER team had to wait over 50 minutes until the spacecraft emerged from behind Mercury, and were relieved to be able to resume contact. As of Wednesday morning, the spacecraft was operating normally, and the reason for the signal drop was unclear. At a briefing, MESSENGER team members said the spacecraft went into safe mode when it entered Mercury’s shadow and tried to switch to battery power. The team is still looking into why this anomaly occurred.

A little less than half of the”extra” science goals for the flyby were accomplished. See our previous article on the science goals for the flyby. Following this flyby. only the polar regions of Mercury have never been seen.

Previously unseen side of Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Previously unseen side of Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

MESSENGER made its closest approach on Tuesday at about 5:55 p.m. EDT (2155 GMT), zooming at speeds of about 12,000 mph (19,312 kph). Mercury’s gravity was expected to slow MESSENGER by about 6,000 mph (9,656 kph) during the flyby and place it on track to enter orbit of Mercury in March 2011.

See all the images acquired by the third flyby here.

Learn more about MESSENGER and the two previous flybys which occured in 2008 here.

Lead image caption: his unnamed impact basin was seen for the first time yesterday during MESSENGER’s third flyby of Mercury. The outer diameter of the basin is approximately 260 kilometers (160 miles). This basin has a double-ring structure common to basins with diameters larger than 200 kilometers (about 125 miles).

Additional information from Jeff Goldstein on Twitter (doctorjeff) was also used in this article

Third and Final Flyby of Mercury for MESSENGER Next Week

Next week, on September 29, 2009 the MESSENGER spacecraft will fly by Mercury for the third and final time, looking at areas not seen before in the two previous passes. The spacecraft will pass 141.7 miles above the planet’s rocky surface, receiving an a final gravity assist that will enable it to enter orbit about Mercury in 2011. With more than 90 percent of the planet’s surface already imaged, the team will turn its instruments during this flyby to specific features to uncover more information about the planet closest to the Sun.

Determining the composition of Mercury’s surface is a major goal of the orbital phase of the mission.

“This flyby will be our last close look at the equatorial regions of Mercury, and it is our final planetary gravity assist, so it is important for the entire encounter to be executed as planned,” said Sean Solomon, principal investigator at the Carnegie Institution in Washington. “As enticing as these flybys have been for discovering some of Mercury’s secrets, they are the hors d’oeuvres to the mission’s main course — observing Mercury from orbit for an entire year.”

A collage of images from the previous two flybys. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.  Click image for more information
A collage of images from the previous two flybys. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington. Click image for more information

As the spacecraft approaches Mercury, cameras will photograph previously unseen terrain. As the spacecraft departs, it will take high-resolution images of the southern hemisphere. Scientists expect the spacecraft’s imaging system to take more than 1,500 pictures. Those images will be used to create a mosaic to complement the high resolution, northern-hemisphere mosaic obtained during the second Mercury flyby. The first flyby took the spacecraft over the eastern hemisphere in January 2008, and the second flyby took it over western side in October 2008.

“We are going to collect high resolution, color images of scientifically interesting targets that we identified from the second flyby,” said Ralph McNutt, a project scientist at APL. “The spectrometer also will make measurements of those targets at the same time.”

The spacecraft may observe how the planet interacts with conditions in interplanetary space as a result of activity on the sun. During this encounter, high spectral- and high spatial-resolution measurements will be taken again of Mercury’s tenuous atmosphere and tail.

“Scans of the planet’s comet-like tail will provide important clues regarding the processes that maintain the atmosphere and tail,” said Noam Izenberg, the instrument’s scientist at the Johns Hopkins University Applied Physics Laboratory, or APL, in Laurel, Maryland. “The Mercury Atmospheric and Surface Composition Spectrometer will give us a snapshot of how the distribution of sodium and calcium vary with solar and planetary conditions. In addition, we will target the north and south polar regions for detailed observations and look for several new atmospheric constituents.”

For a detailed look at the MESSENGER flyby, see the MESSENGER website; additionally, Emily Lakdawalla at the Planetary Society has posted a detailed overview here.

Mercury in Living Color

The MESSENGER science team released more pictures from the Jan. 14 flyby, including what we’ve all been waiting for, the first one in color! But if you’re looking for spectacular, eye-catching color, well, sorry, its just not part of Mercury’s make-up.

The color image was created by combining three separate images taken through MESSENGER’s Wide Angle Camera (WAC) filters in the infrared, far red, and violet wavelengths (red, green, and blue filters for this image.) MESSENGER’s eyes can see far beyond the color range of the human eye, and the colors seen in this image are somewhat different from what a human would see.

Creating a false-color image in this way brings out color differences on Mercury’s surface that cannot be seen in the black and white images released earlier.

The WAC has 11 narrow-band color filters, in contrast to the two visible-light filters and one ultraviolet filter that were on Mariner 10’s camera. By combining images taken through different filters in the visible and infrared, the MESSENGER data allow Mercury to be seen in a variety of high-resolution color views not previously possible. This visible-infrared image shows an incoming view of Mercury, about 80 minutes before MESSENGER’s closest pass of the planet from a distance of about 27,000 kilometers (17,000 miles).

I love this image of Mercury’s south pole limb. It shows the terminator; the transition from the sunlit, day side of Mercury to the dark, night side of the planet. In the region near the terminator, the sun shines on the surface at a low angle, causing the rims of craters to cast long shadows, which brings out the height differences of the surface features. This image was acquired about 98 minutes after MESSENGER’s closest approach to Mercury, when the spacecraft was at a distance of about 33,000 kilometers (21,000 miles).

Mercury Spectra.  Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/Laboratory for Atmospheric and Space Physics, University of Colorado
And here’s one for the scientist in you: the first data returned from MESSENGER’s Mercury Atmospheric and Surface Composition Spectrometer (MASCS). What the image on the right shows with the bar-graph type lines is a high-resolution spectra of the planet’s surface in ultraviolet, visible, and near-infrared light. The image on the left shows a portion of the ground-track along which the MASCS instrument took over 650 observations of the surface. The area is about 300 kilometers (190 miles) across. For those of you not fluent in spectra-ese, this shows the relative amount of sunlight reflected from the surface at wavelengths from the ultraviolet to the visible (rainbow) to the infrared.

Original News Source: MESSENGER Press Releases

A View of Mercury’s Far Side


Images and data are arriving from MESSENGER’s recent flyby of Mercury. Scientists from NASA and the Johns Hopkins Applied Physics Lab are pouring over high resolution images of the side of the planet that has never before been imaged by a spacecraft. From these images, planetary geologists can study the processes that have shaped Mercury’s surface over the past 4 billion years. Let’s take a look at some of the images snapped by MESSENGER on January 14:

This image was taken just 21 minutes after MESSENGER’s closest approach to Mercury, at a distance of only 5,000 kilometers (3600 miles). It shows a region about 170 km (100 miles) across. Visible are a variety of surface features, including craters as small as about 300 meters (about 300 yards) across. But the most striking part of the image is one of the highest and longest cliffs yet seen on Mercury. About 80 km (50 miles) long, it curves from the bottom center up across the right side of this image. Scientists say that great forces in Mercury’s crust must have thrust the terrain occupying the left two-thirds of the picture up and over the terrain to the right. An impact crater has subsequently destroyed a small part of the cliff near the top of the image.

MESSENGER at Mercury.  Image Credit:  Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
This image shows a previously unseen crater with distinctive bright rays of ejected material from the impact extending outward, providing a look at minerals from beneath Mercury’s surface. A chain of craters nearby is also visible. Studying impact craters provides insight into the history and composition of Mercury. The width of the image is about 370 kilometers (about 230 miles), and was taken about 37 minutes after MESSENGER’s closest approach. This image is the 98th in a set of 99 images that were taken to create a large, high-resolution mosaic of this region of Mercury. Hopefully this anticipated mosaic will be released at a planned press conference on January 30.

MESSENGER at Mercury.  Image Credit:  Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
As MESSENGER approached Mercury on January 14, 2008, about 56 minutes before the spacecraft’s closest encounter, the Narrow-Angle Camera captured this view of the planet’s rugged, cratered landscape illuminated by the Sun. Although this crater has been imaged before by Mariner 10, MESSENGER’s modern camera has revealed detail that was not well seen by Mariner including the broad ancient depression overlapped by the lower-left part of the Vivaldi crater. Its outer ring has a diameter of about 200 kilometers (about 125 miles). The image shows an area about 500 km 9300 miles) across and craters as small as 1 kilometer (0.6 mile) can be seen. It was taken from a distance of about 18,000 km (11,000 miles.)

The MESSENGER (Mercury Surface Space Environment Geochemistry and Ranging) Science Team has begun analyzing these high-resolution images to unravel the history of Mercury, as well as the history of our solar system.

Original News Source: MESSENGER Website

A Winged MESSENGER Flies By Mercury


On January 14 the MESSENGER spacecraft skimmed just 200 kilometers (124 miles) above the surface of Mercury in the first of three flybys of the planet. Today (Jan. 15) the spacecraft will turn back towards the Earth to start down-linking the on-board stored science data it acquired during the flyby. The probe’s equipment gathered data on the mineral and chemical composition of Mercury’s surface, its magnetic field, its surface topography and its interactions with the solar wind. “This was fantastic,” said Michael Paul, a mission engineer. “We were closer to the surface of Mercury than the International Space Station is to the Earth.”

The closest approach was on the planet’s night side, the side facing away from the sun, and the spacecraft flew in the region along the equator. The scientific results will be available for the public at the end of January.

“The engineers and operators pulled off a tremendous feat, acquiring and locking onto the downlink signal from the spacecraft within seconds, providing the necessary Doppler measurements for the Radio Science team.” said MESSENGER Mission Systems Engineer Eric Finnegan, of the Applied Physics Lab in Laurel, Maryland. “The spacecraft is continuing to collect imagery and other scientific measurements from the planet as we now depart Mercury from the illuminated side, documenting for the first time the previously unseen surface of the planet.”

The signal from the spacecraft is tracked by the Deep Space Network, an international network of antennas that supports space missions.

In addition to Monday’s rendezvous, MESSENGER is scheduled to pass Mercury again this October and in September 2009, using the pull of the planet’s gravity to guide it into position to begin a planned yearlong orbit of the planet in March 2011. By the time the mission is completed, scientists also hope to get answers on why Mercury is so dense, as well as determine its geological history and the structure of its iron-rich core and other issues.

MESSENGER stands for Mercury Surface, Space Environment, Geochemistry and Ranging. Launched in 2004, it already has flown past Venus twice and Earth once on its way to Mercury.

Only one spacecraft has previously visited Mercury. Mariner 10 flew past the planet three times in 1974 and 1975, and mapped about 45 percent of its surface.

With Pluto now considered a dwarf planet, Mercury is the solar system’s smallest planet, with a diameter of 3,032 miles, about a third that of Earth.

A surface feature of great interest to scientists is the Caloris basin, an impact crater about 800 miles in diameter, one of the biggest such craters in our solar system. It likely was caused when an asteroid hit Mercury long ago. Scientists hope to learn about the subsurface of the planet from studying this crater.

True to its name, temperatures on the closest plant to the sun are quite “mercurial,” as Mercury experiences the largest swing in surface temperatures in our solar system. When its surface faces the sun, temperatures hit about 800 degrees Fahrenheit (425 Celsius), but when its faces away from the sun they can plummet to minus-300 Fahrenheit (minus-185 Celsius).

Original News Source: Reuters

MESSENGER and other Significant Mission Events in 2008


Today, the MESSENGER spacecraft will perform a significant task in its mission by making its first flyby of Mercury (see more info below). Additionally, other spacecraft that are out doing their jobs in various locations of our solar system will have significant mission events occur in 2008. Let’s take a look at the big events coming up this year.

January 14: MESSENGER Flyby of Mercury

Messenger, the MEercury Surface Space ENvironment GEochemistry and Ranging spacecraft, will be the first spacecraft to visit Mercury in almost 33 years. It will explore and take close-up images of parts of the planet that we’ve never seen before. This is the first of three flybys of Mercury the spacecraft will take before settling into orbit in 2011. MESSENGER’s cameras and other instruments will collect more than 1,200 images and make other observations during this approach, encounter and departure. The closest approach of the flyby will occur at 19:04:42 UTC (2:04:42 EST), but mission managers said pictures from the event may not be released for up to a week.

March 12: Cassini flies through the plume of Enceladus’ geyser

The Cassini spacecraft will fly extremely close to Saturn’s moon Enceladus at an altitude of only 23 km (14 mi), and actually fly through the plume of an active geyser on the moon’s south pole. How such a cold moon could host an area warm enough to have erupting water vapor is a mystery. Scientists are pondering if Enceladus has active ice volcanism, and if so, is it due to ice sublimating, like a comet, or due to a different mechanism, like boiling water as in Old Faithful at Yellowstone. This flyby will help answer those questions.

Cassini will also have several relatively close flybys this year of the moon Titan. The flybys will occur on Feb. 22, March 25, and May 12.

May 25: Phoenix lands on Mars

Phoenix will land in the north polar region of Mars and will help characterize the climate and geology of the Red Planet, as well as possibly determine if live ever arose on Mars. Pursuing NASA’s “Follow the Water” strategy, the lander will dig through soil to reach water ice with its robotic arm and perform numerous scientific experiments. Phoenix launched on Aug. 4, 2007. University of Arizona’s Phoenix page

September 5: Rosetta flyby of Asteroid Steins

The Rosetta spacecraft is on its way to orbit comet 67P Churyumov-Gerasimenko in 2014, but in the meantime it will pass by Asteroid 2867 Steins. During the flyby, Rosetta will study Steins to determine and characterize the asteroid’s surface composition and morphology. Asteroid Steins is roughly 10 km in diameter.