This collection of craters, shaped not unlike the iconic head of a certain cartoon mouse, was imaged by NASA’s MESSENGER spacecraft on June 3, 2012.
All together now: C-R-A, T-E-R… M-O-U-S-Eeeeee…
Acquired as part of MESSENGER’s extended mission to map Mercury’s surface in higher detail, the image above isn’t map-projected; that is, it’s not aligned with north as up. In reality the large crater that makes up Mickey’s “head” is north of the two “ears”.
Still, this is one big mouse head — the large crater in the center has a diameter of approximately 105 km (65 miles)!
Read more about this and see many other images of the first rock from the Sun on the MESSENGER mission site here.
Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Mercury (top) and Jupiter by the LASCO C3 instrument on the SOHO spacecraft. Credit: NASA/SOHO
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Here’s a great shot from the Solar and Heliospheric Observatory (SOHO) spacecraft of Mercury (top planet) and Jupiter snuggling up together, along with the Pleiades cluster, all close to Sun, as seen from SOHO’s LASCO C3 instrument (Large Angle and Spectrometric Coronagraph). SOHO has been in space since 1995, and is a workhorse of solar observing, giving us insights into the workings of the Sun, comets and other bodies in the Solar System. Check out the SOHO website for more great images.
Warhol crater, one of 23 recently named craters on Mercury
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As pop art icon Andy Warhol said, “In the future everyone will be famous for fifteen minutes,” and so here’s an image of the crater on Mercury that now bears his name, set up in the style of one of his multicolored silkscreens.
Warhol is one of 23 craters on Mercury to be recently approved for names by the International Astronomical Union (IAU), joining other notable artists, authors and musicians like Gustav Holst, Rene Magritte and Dr. Seuss who now have craters named in their honor on the first rock from the Sun.
95 km (59 miles) in diameter, Warhol crater features a large, elongated central peak, stepped walls and many of the curious erosions known as hollows.
The original image, seen at top left, was acquired by NASA’s MESSENGER spacecraft on October 21, 2011, using its Wide-Angle Camera Mercury Dual Imaging System (MDIS) instrument.
With the new list of 23 named craters, there are now 76 officially (and artistically) titled craters on Mercury since MESSENGER’s first pass of the planet in January 2008.
See the original release by the MESSENGER mission team here.
“I’m bored with that line. I never use it anymore. My new line is “In 15 minutes everybody will be famous.”
– Andy Warhol (1928 – 1987)
Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Alan Shepard on board the deck of the USS Champlain after recovery of Freedom 7. Credit: NASA
51 years ago today, on May 5, 1961, NASA launched the Mercury-Redstone 3 rocket carrying Alan B. Shepard, Jr. aboard the Freedom 7 capsule. Shepard successfully became America’s first man in space, making a brief but historic suborbital test flight that propelled American astronauts into the space race of the 1960s.
The video above is made from photographs taken by a film camera mounted to the Freedom 7 spacecraft and scanned by archivists at Johnson Space Center. It shows the view from Freedom 7 as the Redstone rocket launched it into space, getting an amazing view of Earth’s limb and the blackness beyond before falling back to splash down in the Atlantic.
The video is made from the entire film reel, so at the end there’s also some shots of a light experiment inside the spacecraft. (View the individual scans at ASU’s March to the Moon website here.)
What’s amazing to realize is that, at this point in time, the space surrounding our planet was a very empty place. This was a time before communication and weather satellites, before GPS, before Space Station and space shuttles — and space junk — and student-made weather balloon videos. Just 51 years ago low-Earth orbit was a new frontier, and guys like Shepard (and Gagarin and Glenn, etc.) were blazing the path for everyone that followed.
Even though images of Earth from space are still amazing to look at today, seeing these photos reminds us of a time when it was all just so very new.
Read more about Shepard and the MR-3 launch here.
Images and video: NASA/JSC/Arizona State University
MESSENGER image of Mercury, acquired with its Wide Angle Camera on March 21, 2012.
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The subtle yet surprisingly varied colors of Mercury are revealed in the latest images from NASA’s MESSENGER spacecraft, now in its extended mission and second year in orbit.
The image above, a composite of Wide Angle Camera images acquired in 996, 748 and 433 nanometers for red, green and blue, shows a semi-lit limb of Mercury with the bright rayed crater Debussy visible at left. (The image has been rotated 180 degrees from the original, and color saturation was boosted by 25%.)
Named for the French composer Claude Debussy of “Claire de Lune” fame, the crater itself is approximately 50 miles (80 km) wide. It was first detected by ground-based radar telescopes in 1969 as a bright spot.
Now, 43 years later, we have a spacecraft in orbit sending back images like this. Amazing.
The various colors seen across Mercury are due to different mineral compositions of the geologic regions. The exact compositions are not yet known, and the current puzzle that researchers are trying to solve with MESSENGER is to figure out what materials make up Mercury’s complex, multi-hued surface. That will also give a clue as to what’s inside the planet and how it evolved… as well as how it is currently evolving today.
The image below is from MESSENGER’s Visual and Infrared Spectrograph (VIRS) and shows a map of Mercury’s surface, with RGB colors corresponding to different mineralogical compositions.
Sinusoidal equal area projection map of Mercury from MESSENGER's VIRS instrument.
Younger surface materials that are brighter at visible wavelengths and less affected by space weathering show up in reds, yellows and greens. Materials that may have relatively higher iron contents show up in blue.
These are Mercury’s “other colors”… maybe not what we would see with our own eyes, but beautiful nonetheless to planetary scientists!
See the above image on the MESSENGER website here.
Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Until relatively recently, Mercury was one of the most poorly understood planets in the inner solar system. The MESSENGER mission to Mercury, is changing all of the that. New results from the Mercury Laser Altimeter (MLA) and gravity measurements are showing us that the planet closest to our sun is thin skinned and wrinkled, which is very different from what we originally thought.
The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft was launched back in 2004. It took a long time getting to its destination, completing 3 flybys of Mercury before finally entering orbit a little over a year ago. Currently, the spacecraft is in a highly eccentric polar orbit, approaching the planet much closer in the north than in the south. This allows the northern hemisphere to be probed and imaged at enviably high resolutions, but leaves the southern hemisphere poorly understood.
Even so, the data returned from MESSENGER is showing us some quite unanticipated findings. Two papers from the MESSENGER team, published in today’s issue of Science, are showing some surprising results from the laser altimeter and gravity experiments.
Using NASA’s Deep Space Network, Earth-based radio tracking of MESSENGER has allowed minute changes in the spacecraft’s orbit to be monitored and recorded. From this, Dr. Maria Zuber of MIT and her team calculated a model of Mercury’s gravity. Meanwhile, the on-board laser altimeter has provided invaluable topographic information. Combined together, these data have allowed the MESSENGER team to glean a great deal of information about the planet’s interior workings.
One of the most striking findings is that the iron-rich core of Mercury is very large. A combination of measurements and models suggest that the core has both a solid interior portion and a liquid outer portion. And while it is not certain how much of the core is solid and how much is liquid, it is clear that the total core has a radius of about 2030 km. This is a huge core, representing 83% of Mercury’s 2440 km radius!
The internal structure of Mercury is very different from that of the Earth. The core is a much larger part of the whole planet in Mercury and it also has a solid iron-sulfur cover. As a result, the mantle and crust on Mercury are much thinner than on the Earth. Credit: Case Western Reserve University
Furthermore, these calculations suggest that the layer above the core is much denser than previously expected. Results from MESSENGER’s X-Ray spectrometer indicate that the crust, and by extension the mantle, are too low in iron to explain this high density. Dr. Zuber’s team think that the only way to explain this discrepancy is by the presence of a solid iron-sulfur layer just above the core. Such a layer could be anywhere from 20 to 200 km thick, leaving only a very thin crust and mantle at the top. This kind of interior structure is completely different from what was originally suggested for Mercury, and it is nothing like what we have seen in the other planets!
This striking fact may help explain some unexpected altimeter results, which show that Mercury’s topography has less variation than other planets. The total difference between the highest and lowest elevations on Mercury is only 9.85 km. Meanwhile, the Moon has a total difference of 19.9 km between its highest and lowest points, and on Mars this difference is 30 km. Dr. Zuber and her team speculate that the presence of the core so close to the surface could keep the mantle hot, allowing topographic features to relax. In such a scenario, the lithosphere under tall impact-formed mountains would sink down into a mushy mantle that cannot support their weight. Conversely, the thin lithosphere under impact basins would rebound upwards, taking part of the mobile mantle with it.
In fact, the gravity data shows evidence of exactly this kind of process, in the form of “mascons”. These mass concentrations form when large imacts make the local crust very thin, allowing denser mantle material to rise closer to the surface as the lithosphere rebounds from the impact event. Mascons are well known from studies on the Moon and Mars, and now MESSENGER’s gravity data has revealed three such mascons on Mercury, located in the Caloris, Sobkou, and Budh basins.
The elliptical polar orbit of the MESSENGER spacecraft means that measurements at the North Pole of Mercury are much better than those at the South Pole, or even at the equator. This is evident in the better spatial resolution that can be seen at the high latitudes in this elevation map of the northern hemisphere. Major impact structures are identified by black circles. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Interestingly enough, the mascons in Sobkou and Budh basins are not immediately obvious. They only show up when the effects of a regional topographic high are adjusted for. This topographic feature is a large quasi-linear rise that extends over half the circumference of Mercury in the mid-latitudes. The rise even passes through the northern part Caloris basin (which is large enough that its mascon is not overwhelmed by the rise). Studies of this rise by the MESSENGER team suggest that it is relatively young, having formed well after the formation of the basins, after the volcanic flooding of their interiors and exteriors, and even after some of the later impact craters that cover the flooded surfaces.
Dr. Zuber and her team also identified another young topographically elevated region, the Northern Rise, located in the lowlands surrounding the North Pole. They speculate that these young rises represent a buckling of the lithosphere, which happened when the planet’s interior cooled and contracted. This interpretation is supported by the presence of lobate scarps and ridges that can be seen around the planet, and which represent faulting of the crust when it was compressed.
So, it seems that Mercury is unlike the other planets of the Solar System. It appears to have a disproportionately large core that is covered by a thin skin of mantle and lithosphere. Furthermore, this skin seems to have wrinkled like a raisin’s when the huge core of the planet shrunk as it cooled.
Sources
Gravity Field and Internal Structure of Mercury from MESSENGER, Smith et al., Science V336 (6078), 214-217, April 13 2012, DOI:10.1126/science.1218809
Topography of the Northern Hemisphere of Mercury from MESSENGER Laser Altimetry, Zuber et al., Science V336 (6078), 217-220, April 13 2012, DOI:10.1126/science.1218805
The bright object in the center of this video sequence is the planet Mercury, seen by NASA’s STEREO-B spacecraft as it was pummeled by wave after wave of solar material ejected from the Sun during the week of March 25 – April 2, 2012.
The video above was released by NASA’s Goddard Space Flight Center earlier today. The Sun is located just off-frame to the left, while Earth would be millions of miles to the right.
Proof that it’s not easy being first rock from the Sun!
Named after the 17th-century metaphysical poet, Mercury’s Donne crater was captured in this image by NASA’s MESSENGER spacecraft. The 53-mile (83-km) -wide crater features a large, rounded central peak and numerous lobate scarps lining its floor.
Lobate scarps are found all across Mercury. Visible above as arc-shaped ridges, they are most likely thrust faults resulting from surface compression and contraction.
Donne’s central peak has been well-eroded by impacts into a softly rolling mound. Central peaks are common features of larger craters, thought to be formed when the excavation of material during an impact springs the crater floor upwards — a process called “isostatic rebound”.
This image was acquired by MESSENGER’s Narrow-Angle Camera (NAC) on August 2, 2011.
On March 17 MESSENGER successfully wrapped up a year-long campaign to perform the first complete reconnaissance of the geochemistry, geophysics, geologic history, atmosphere, magnetosphere, and plasma environment of Mercury. The following day, March 18, marked the official start of its extended phase designed to build upon those discoveries.
“Six plus years of cruise operations, capped by a year of nearly flawless orbital operations, with an additional year of scientific return ahead in the harsh environment at 0.3 astronomical units (27,886,766 miles) from the Sun,” said MESSENGER Mission Systems Engineer Eric Finnegan at JHU/APL. All this “achieved with a 1,000 kg satellite, designed, built, and launched in less than four years for a total mission cost of less than $450 million.”
Well “Donne”, MESSENGER!
Read more about the MESSENGER mission’s extension here.
Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.
MESSENGER captured this high-resolution image of an elongated pit crater within the floor of the 355-km (220-mile) -wide crater Tolstoj on Mercury on Jan. 11, 2012. The low angle of sun illumination puts the interior of the pit crater into deep shadow, making it appear bottomless.
Pit craters are not caused by impacts, but rather by the collapse of the roof of an underground magma chamber. They are characterized by the lack of a rim or surrounding ejecta blankets, and are often not circular in shape.
Since the floor of Tolstoj crater is thought to have once been flooded by lava, a pit crater is not out of place here.
The presence of such craters on Mercury indicates past volcanic activity on Mercury contributing to the planet’s evolution.
Mercury's limb. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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Mercury is one of the 5 planets visible with the unaided eye. Even thousands of years ago, ancient astronomers knew that the 5 wanderers were different from the other stars in the sky. The 5 planets visible with the unaided eye are Mercury, Venus, Mars, Jupiter and Saturn. They gave them distinct names, and charted their positions with incredible accuracy. It’s impossible to say “when was Mercury discovered”, since that would have been before recorded history.
But when did astronomers realize that Mercury was a planet? That happened with Copernicus developed his model of a Sun-centered Solar System, published in 1543. With the Sun at the center of the Solar System, and not the Earth, it meant that both the Earth and Mercury were planets. This discovery was confirmed when Galileo first turned his telescope on the planets and realized they matched predictions made by Copernicus. Unfortunately, Galileo’s telescope wasn’t powerful enough to reveal a disk for Mercury, but it did show how Venus went through phases like the Moon.
This model was backed up by Galileo, who pointed his first rudimentary telescope at Mercury in the 17th century. Unfortunately his telescope wasn’t powerful enough to see Mercury go through phases like he saw with Venus.
Because it’s so small and close to the Sun, Mercury was difficult to observe with ground-based telescopes. More powerful telescopes only revealed a small grey disk; they didn’t have the resolution to display features on the planet’s surface, like craters or lava fields.
It wasn’t until the early 1960s when radio astronomers started bouncing signals off the surface of Mercury that more information was finally known about the planet. These signals revealed that Mercury’s day length is about 59 days. Even more detailed observations have been made with the Arecibo telescope, mapping surface features down to a resolution of 5 km.
The most detailed observations of Mercury have come from the exploration from spacecraft sent from Earth. NASA’s Mariner 10 spacecraft swept past Mercury in 1974, capturing images from an altitude of just 327 km. It eventually mapped about half of the planet in unprecedented detail, revealing that the planet looked very similar to the Earth’s moon, with many impact craters and ancient lava fields.
If you’re wondering who discovered the element mercury, nobody knows that either. The element has been known for thousands of years, and was used by the ancient Chinese. Liquid mercury was found in Egyptian tombs closed up almost 4,000 years ago.
