Earth and Moon from 114 Million Miles.Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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A new image to add to the family photo album! The MESSENGER spacecraft is working its way to enter orbit around Mercury in March of 2011, and while wending its way, took this image of the Earth and Moon, visible in the lower left. When the image was taken in May 2010, MESSENGER was 183 million kilometers (114 million miles) away from Earth. For context, the average separation between the Earth and the Sun is about 150 million kilometers (93 million miles). It’s a thought provoking image (every one of us is in that image!), just like other Earth-Moon photos — Fraser put together a gallery of Earth-Moon images from other worlds, and this one will have to be added. But this image was taken not just for the aesthetics.
This image was taken as part of MESSENGER’s campaign to search for vulcanoids, small rocky objects hypothesized to exist in orbits between Mercury and the Sun. Though no vulcanoids have yet been detected, the MESSENGER spacecraft is in a unique position to look for smaller and fainter vulcanoids than has ever before been possible. MESSENGER’s vulcanoid searches occur near perihelion passages, when the spacecraft’s orbit brings it closest to the Sun. August 17, 2010 was another such perihelion, so if MESSENGER was successful in finding any tiny asteroids lurking close to the Sun, we may hear about it soon.
A double-ring basin named Rachmaninoff reveals young volcanism on Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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Younger volcanoes, stronger magnetic storms and a more intriguing exosphere: three new papers from data gathered during the MESSENGER spacecraft’s third flyby of Mercury in September of last year provide new insights into the planet closest to our Sun. The new findings make the science teams even more anxious for getting the spacecraft into orbit around Mercury. “Every time we’ve encountered Mercury, we’ve discovered new phenomena,” said principal investigator Sean Solomon. “We’re learning that Mercury is an extremely dynamic planet, and it has been so throughout its history. Once MESSENGER has been safely inserted into orbit about Mercury next March, we’ll be in for a terrific show.”
The closest look ever at some of Mercury’s plains suggests the planet’s volcanic activity lasted much longer than previously thought. From new images, researchers identified a 290-kilometer-diameter peak-ring impact basin, among the youngest to be observed on the planet. Named Rachmininoff, the region is characterized by exceptionally smooth, sparsely cratered plains, which formed later than the basin itself, likely from volcanic flow.
“We interpret these plains to be the youngest volcanic deposits yet found on Mercury,” said lead author Louise Prockter, from Johns Hopkins University Applied Physics Laboratory, one of MESSENGER’s deputy project scientists. “Moreover, an irregular depression surrounded by a diffuse halo of bright material northeast of the basin marks a candidate explosive volcanic vent larger than any previously identified on Mercury.
These observations suggest that volcanism on the planet spanned a much greater duration than previously thought, perhaps extending well into the second half of solar system history.”
A depression northeast of the basin is surrounded by a halo of bright mineral deposits, which Prockter and her team propose to be the largest volcanic vent identified on Mercury so far. Both of these findings mean that volcanism continued well into the second half of our Solar System’s history.
A double-ring basin named Rachmaninoff reveals young volcanism on Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
During the third fly-by, the team was able to take measurements of Mercury’s magnetic field, and this happened to occur during a time when the planet was being hit by a strong solar wind. MESSENGER’s Magnetometer documented for the first time the substorm-like build-up, or “loading,” of magnetic energy in Mercury’s magnetic tail. The tail’s magnetic field increased and decreased by factors ranging from two to 3.5 during very brief periods of just two to three minutes.
“The extreme tail loading and unloading observed at Mercury implies that the relative intensity of substorms must be much larger than at Earth,” said lead author James A. Slavin, a space physicist at NASA’s Goddard Space Flight Center and a member of MESSENGER’s Science Team. “However, what is even more exciting is the correspondence between the duration of tail field enhancements and the Dungey cycle time, which describes plasma circulation through a magnetosphere.”
Substorms on Earth are powered by similar processes—except that the loading of our planet’s magnetosphere is ten times weaker and occurs over the course of a full hour. Therefore, the team said, Mercury’s substorms must release more energy than terrestrial ones.
A third paper analyzed data from specialized instruments on-board the spacecraft to gain a clearer picture of Mercury’s neutral and ionic exospheres. Mercury’s exosphere is a tenuous atmosphere of atoms and ions derived from the planet’s surface and from the solar wind. Notable in the new observations were the differences in altitude of elements like magnesium, calcium, and sodium above the planet’s north and south poles. The team said this indicates that several processes are at work and that a given process may affect each element quite differently
“A striking feature in the near-planet tail ward region is the emission from neutral calcium atoms, which exhibits an equatorial peak in the dawn direction that has been consistent in both location and intensity through all three flybys,” said lead author Ron Vervack, also at the Applied Physics Laboratory. “The exosphere of Mercury is highly variable owing to Mercury’s eccentric orbit and the effects of a constantly changing space environment. That this observed calcium distribution has remained relatively unchanged is a complete surprise.”
The first-ever global mosaic map of Mercury was released today, which will be a critical tool for the MESSENGER mission’s observations of the planet when it enters orbit in 2011. The map was created from images taken during MESSENGER’s three flybys of Mercury – the most recent of which took place in September 2009 — and those of Mariner 10 in the 1970s. “The production of this global mosaic represents a major milestone for everyone on the MESSENGER imaging team,” said Sean Solomon, MESSENGER Principal Investiagor. “Beyond its extremely important use as a planning tool, this global map signifies that MESSENGER is no longer a flyby mission but instead will soon become an in-depth, non-stop global observatory of the Solar System’s innermost planet.”
The map was created by the MESSENGER mission team and cartographic experts from the U. S. Geological Survey. It will help scientists pinpoint craters, faults, and other features for observation.
While creating a mosaic map may seem straightforward – just stitch together multiple images taken by the spacecraft — it was actually quite a challenge to create cartographically accurate maps from images with varying resolution (from about 100 to 900 meters per pixel) and lighting conditions (from noontime high Sun to dawn and dusk) taken from a spacecraft traveling at speeds greater than 2 kilometers per second (2,237 miles per hour).
Small uncertainties in camera pointing and changes in image scale can introduce small errors between frames.
“With lots of images, small errors add up and lead to large mismatches between features in the final mosaic,” said MESSENGER team member Mark Robinson. “By picking control points—the same features in two or more images—the camera pointing can be adjusted until the image boundaries match.”
This operation is known as a bundle-block adjustment and requires highly specialized software. Cartographic experts at the USGS Astrogeology Science Center in Flagstaff, Ariz., picked the control points to solve the bundle-block adjustment to construct the final mosaic using the Integrated Software for Imagers and Spectrometers (ISIS). For the MESSENGER mosaic, 5,301 control points were selected, and each control point on average was found in more than three images (18,834 measurements) from a total of 917 images.
“This mosaic represents the best geodetic map of Mercury’s surface. We want to provide the most accurate map for planning imaging sequences once MESSENGER achieves orbit around Mercury”, said Kris Becker of the USGS. “As the systematic mapping of Mercury’s surface progresses, we will continually add new images to the control point network, thus refining the map”, he says. “It has already provided us with a start in the process of naming newly identified features on the surface.”
In the final bundle-block adjustment the average error was about two-tenths of a pixel or only about 100 meters—which is an excellent match from image-to-image, the team said. Absolute positional errors in the new mosaic are about two kilometers, according to the MESSENGER team. Once the spacecraft enters orbit around Mercury, the team will be able to make even more refinements and the entire planet will be imaged at even higher resolution. The global mosaic is available for download on the USGS Map-a-Planet web site. It is also available at the MESSENGER site.
A presentation on the new global mosaic was given today at the Fall Meeting of the American Geophysical Union in San Francisco.
Even though the MESSENGER spacecraft experienced a “hiccup” during its third and final flyby of Mercury on Sept. 29, scientists are still pleased and surprised by the data garnered. The spacecraft went into safe mode, shutting down temporarily because of a power system switchover during a solar eclipse as it approached the planet and only half of the expected observations were carried out. But the new data – combined with observations from the two previous flybys — provide an almost complete view of Mercury’s surface and offer new, unexpected scientific findings. “Although the area viewed for the first time by spacecraft was less than 350 miles across at the equator, the new images reminded us that Mercury continues to hold surprises,” said principal investigator Sean Solomon.
The most important aspect of the flyby was a critical gravity assist to remain on course to enter into orbit around Mercury in 2011. Additionally, the spacecraft’s cameras and instruments collected high-resolution and color images unveiling another 6 percent of the planet’s surface never before seen at close range. Image coverage map of Mercury after the third MESSENGER flyby. Credit: NASA, Applied Physics Lab
Solomon said at today’s press conference that all the data gathered on Mercury so far are like first few chapters of a novel; we’ve learned much, but much more of the story remains. Approximately 98 percent of Mercury’s surface now has been imaged by NASA spacecraft. After MESSENGER goes into orbit around Mercury, it will see the polar regions, which are the only unobserved areas of the planet.
Many new features were revealed during the third flyby, including a region with a bright area surrounding an irregular depression, suspected to be volcanic in origin. Other images revealed a double-ring impact basin approximately 180 miles across. The basin is similar to a feature scientists call the Raditladi basin, which was viewed during the probe’s first flyby of Mercury in January 2008.
This spectacular 290-km-diameter double-ring basin seen in detail for the first time during MESSENGER’s third flyby of Mercury bears a striking resemblance to the Raditladi basin, observed during the first flyby.
“This double-ring basin, seen in detail for the first time, is remarkably well preserved,” said Brett Denevi, a member of the probe’s imaging team and a postdoctoral researcher at Arizona State University in Tempe. “One similarity to Raditladi is its age, which has been estimated to be approximately one billion years old. Such an age is quite young for an impact basin, because most basins are about four times older. The inner floor of this basin is even younger than the basin itself and differs in color from its surroundings. We may have found the youngest volcanic material on Mercury.”
One of the spacecraft’s instruments conducted its most extensive observations to date of Mercury’s exosphere, or thin atmosphere, during this encounter. The flyby allowed for the first detailed scans over Mercury’s north and south poles. The probe also has begun to reveal how Mercury’s atmosphere varies with its distance from the sun. Comparison of neutral sodium observed during MESSENGER’s second and third Mercury flybys
“A striking illustration of what we call ‘seasonal’ effects in Mercury’s exosphere is that the neutral sodium tail, so prominent in the first two flybys, is 10 to 20 times less intense in emission and significantly reduced in extent,” says participating scientist Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory, or APL, in Laurel, Md. “This difference is related to expected variations in solar radiation pressure as Mercury moves in its orbit and demonstrates why Mercury’s exosphere is one of the most dynamic in the solar system.”
The observations also show that calcium and magnesium exhibit different seasonal changes than sodium. Studying the seasonal changes in all exospheric constituents during the mission orbital phase will provide key information on the relative importance of the processes that generate, sustain, and modify Mercury’s atmosphere. Schematic view of Mercury’s interior showing its large, iron-rich core, which constitutes at least ~60% of the planet’s mass.
The third flyby also revealed new information on the abundances of iron and titanium in Mercury’s surface materials. Earlier Earth and spacecraft-based observations showed that Mercury’s surface has a very low concentration of iron in silicate minerals, a result that led to the view that the planet’s crust is generally low in iron.
“Now we know Mercury’s surface has an average iron and titanium abundance that is higher than most of us expected, similar to some lunar mare basalts,” says David Lawrence, an APL participating mission scientist.
The spacecraft has completed nearly three-quarters of its 4.9-billion-mile journey to enter orbit around Mercury. The full trip will include more than 15 trips around the sun. In addition to flying by Mercury, the spacecraft flew past Earth in August 2005 and Venus in October 2006 and June 2007.
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.
Bright spot on Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
[/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
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.
This unnamed basin was imaged as MESSENGER approached Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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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
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.”
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
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.
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
This enhanced-color image shows the regions targeted for MASCS and MDIS observations during Mercury flyby 3. Click the image for more information.
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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
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.
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).
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.
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.
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.
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.
