Posted on by Jason Major

How Long is a Day on Mercury?

1/3 the distance from the Sun than Earth, it should be no surprise that a day on Mercury is a real scorcher with temperatures soaring over 400 ºC. But in addition to its solar proximity it also has an extremely slow rotation: a single day on Mercury is 58.6 Earth days long… and you thought your Mondays lasted forever!

To be even more precise, for every 2 Mercury years, 3 Mercury days pass — a 3:2 spin-orbit resonance, caused by the planet’s varying elliptical orbit. (This also makes for some interesting motions of the Sun in Mercury’s sky.)

To illustrate this, UK’s The Open University has published a new video in their 60 Second Adventures in Astronomy series… check it out above (and see more of their excellent and amusing animations here.)

Video: The Open University. Narrated by David Mitchell.

Posted on by Jason Major

Evidence for Active Hollows Formation on Mercury

MESSENGER targeted-observation image of the interior of Eminescu crater

A recent image acquired by NASA’s MESSENGER spacecraft shows the interior of Eminescu, a youngish 130-km (80 mile) wide crater just north of Mercury’s equator. Eminescu made science headlines last year with MESSENGER’s discovery of curious eroded blotches called “hollows” scattered across its interior and surrounding its central peak, and now it looks like the spacecraft may have spotted some of these strange features in their earliest stages of formation along the inner edge of the crater’s rim.

First announced in September 2011, hollows have now been identified in many areas across Mercury. They had showed up in previous images as only bright spots, but once MESSENGER established orbit in March 2011 and began its high-resolution imaging of Mercury’s surface it soon became clear that these features were something totally new.

The lack of craters within hollows indicates that they are relatively young. It was suggested that they may be the result of an ongoing process on Mercury — a suggestion supported by this recent image, acquired on November 19, 2012.

In addition to the hollows seen in the smooth central part of the crater and around the base of the central peak, there are also some small bright spots visible within the knobby terrain extending from the base of the crater wall (see detail at right). These bright spots could well be very young hollows, revealing a process in action that is, as far as we know, unique to the planet Mercury.

It’s thought that hollows are formed by the solar wind constantly blasting Mercury’s surface, scouring away deposits of volatile materials in its crust that have been left exposed by impacts.

The image above shows an area about 42 km across. Read more on the MESSENGER mission site here.

 Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

 

Posted on by Nancy Atkinson

Water Ice and Organics Found at Mercury’s North Pole

A radar image of Mercury’s north polar region is shown superposed on a mosaic of MESSENGER images of the same area. All of the larger polar deposits are located on the floors or walls of impact craters. Deposits farther from the pole are seen to be concentrated on the north-facing sides of craters. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/National Astronomy and Ionosphere Center, Arecibo Observatory

Over 20 years ago, radar-bright materials were seen in the north polar region on Mercury, and since then scientists have postulated that water ice could be hiding there in permanently shadowed regions. The latest data from the MESSENGER spacecraft – now orbiting the planet closest to the Sun – confirms that Mercury indeed does hold water ice as well as organic material within permanently shadowed craters at its north pole. Scientists today said that Mercury could hold between 100 billion to 1 trillion tons of water ice at both poles, and the ice could be up to 20 meters deep in places. Additionally, intriguing dark material which covers the ice could hold other volatiles such as organics.

The MESSENGER team published three papers this week in the journal Science, which present three new lines of evidence that water ice dominates the components inside the craters on Mercury’s north pole.

“Water ice passed three challenging tests and we know of no other compound that matches the characteristics we have measured with the MESSENGER spacecraft,” said MESSENGER Principal Investigator Sean Solomon at a briefing today. “These findings reveal a very important chapter of the story of how water ice has been delivered to the inner planets by comets and water rich asteroids over time.”

MESSENGER arrived at Mercury last year and data from the spacecraft’s neutron spectrometer and laser altimeter were used to make the observations at the planet’s north pole.

A layer of water ice several meters thick is illustrated in white. Abundant hydrogen atoms within the ice stop the neutrons from escaping into space. A signature of enhanced hydrogen concentrations (and, by inference, water ice) is a decrease in the rate of MESSENGER’s detection of neutrons from the planet. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Neutron spectroscopy measures average hydrogen concentrations within Mercury’s radar-bright regions, and scientists were able to derive the water ice concentrations from the hydrogen measurements.

“The neutron data indicate that Mercury’s radar-bright polar deposits contain, on average, a hydrogen-rich layer more than tens of centimeters thick beneath a surficial layer 10 to 20 centimeters thick that is less rich in hydrogen,” said David Lawrence, a MESSENGER Participating Scientist based at the Johns Hopkins University Applied Physics Laboratory and the lead author of one of the papers. “The buried layer has a hydrogen content consistent with nearly pure water ice.”

This image shows sunlight that reaches the Prokofiev crater floor and rim. The north-facing portions of the rim and interior remain in perpetual shadow, as do those of numerous other craters. Click on the image watch a movie which simulates approximately one half of a Mercury solar day (176 Earth days) and uses the digital terrain model derived from MLA measurements. Credit: NASA Goddard Space Flight Center/Massachusetts Institute of Technology/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

Data from MESSENGER’s Mercury Laser Altimeter (MLA) — which has fired more than 10 million laser pulses at Mercury to make detailed maps of the planet’s topography — corroborate the radar results and Neutron Spectrometer measurements of Mercury’s polar region. Gregory Neumann of the NASA Goddard Flight Center, lead author of the second paper said the team used topographic data to develop illumination models for Mercury north polar craters, revealing irregular dark and bright deposits at near-infrared wavelength near Mercury’s north pole.

“The real surprise is that there were dark areas surrounding bright areas that were more pervasive than radar bright areas,” said Neumann at Thursday’s briefing. “They are a blanket that protects the bright volatiles that lie underneath.”

Neumann said that impacts of comets or volatile-rich asteroids could have provided both the dark and bright deposits, a finding corroborated in a third paper led by David Paige of the University of California, Los Angeles.

Paige and his colleagues provided 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 MLA. The measurements “show that the spatial distribution of regions of high radar backscatter is well matched by the predicted distribution of thermally stable water ice,” he said.

A map of “permafrost” on Mercury showing the calculated depths below the surface at which water ice is predicted to be thermally stable. The grey areas are regions that are too warm at all depths for stable water ice. The colored regions are sufficiently cold for subsurface ice to be stable, and the white regions are sufficiently cold exposed surface ice to be stable. The thermal model results predict the presence of surface and subsurface water ice at the same locations where they are observed by Earth-based radar and MLA observations. Credit: NASA/UCLA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

According to Paige, the dark material is likely a mix of complex organic compounds delivered to Mercury by the impacts of comets and volatile-rich asteroids, the same objects that likely delivered water to the innermost planet. The organic material may have been darkened further by exposure to the harsh radiation at Mercury’s surface, even in permanently shadowed areas.

This dark insulating material is a new and intriguing piece of the story of Mercury that MESSENGER is seeking to unravel, said Solomon, and raises questions about what types of organics could be found there. Solomon added that Mercury may now become an object of interest for astrobiology, but said in no uncertain terms that none of the scientists think there is life on Mercury. This could, however, provide information about the rise of organics on Earth.

Additionally, the scientist said there is zero chance of liquid water on Mercury, even though temperatures in some regions would be conducive to liquid water. But with no atmosphere on Mercury, water wouldn’t stick around for long. “It would be ice or vapor really fast,” said Paige.

This schematic of MESSENGER’s orbit illustrates some of the challenges to acquiring observations of Mercury’s north polar region. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Solomon said that obtaining these measurements has not been easy and has not been quick. “Even at highest latitudes reached by MESSENGER, the spacecraft must look at an oblique angle to look at the north polar regions,” he said.

During its primary orbital mission, MESSENGER was in a 12-hour orbit and was at an altitude between 244 and 640 km at the northernmost point in its trajectory. Since April 2012, MESSENGER has been in an 8-hour orbit, shown above, and it has been at an altitude between 311 and 442 km at the northernmost point in its trajectory. Even from these high-latitude vantages, Mercury’s polar deposits fill only a small portion of the field of view of many of MESSENGER’s instruments.

But despite the challenges, Solomon said, the one and a half years of MESSENGER in orbit have now yielded clear results.

See more images and videos from the briefing here.

Sources: MESSENGER, NASA

Posted on by Jason Major

Lighting Up Mercury’s Shadowy North Pole

Part of a stereographic projection of Mercury’s north pole

Talk about northern exposure! This is a section of a much larger image, released today by the MESSENGER team, showing the heavily-cratered north pole of Mercury as seen by the MESSENGER spacecraft’s Mercury Dual Imaging System (MDIS) instrument.

See the full-size image below:

Many MDIS images were averaged together to create a mosaic of Mercury’s polar region, which this stereographic projection is centered on. MESSENGER is at its lowest altitude as it passes over Mercury’s northern hemisphere — about  200 kilometers (124 miles), which is just a little over half the altitude of the ISS.

The largest centrally-peaked crater near the center is Prokofiev, named after a 20th-century Russian composer. Approximately 110 km (68 mi.) in diameter, its permanently-shadowed interior is home to radar-bright deposits that are thought to contain water ice.

Even though Mercury is almost three times closer to the Sun than Earth is and hosts searing daytime temperatures of 425ºC (800ºF), there’s virtually no atmosphere to hold or transmit that heat. Nighttime temperatures can reach as low as -185ºC (-300ºF), and since a day on Mercury is 176 Earth days long it gets very cold for quite a long time!

Also, because Mercury’s axis of rotation isn’t tilted like Earth’s, low elevation areas near the poles receive literally no sunlight. Unless vaporized by a meteorite impact any ice gathered inside these deep craters would remain permanently frozen.

Here’s an orthographic projection of the image above, showing what the scene would look like on Mercury — that is, if it was ever fully lit by the Sun, which it isn’t.

Many of the craters on Mercury’s north pole have recently been named after famous artists, authors and composers, such as Kandinsky, Stieglitz, Goethe, and even one named after J.R.R. Tolkien. You can see an annotated image showing the names of Mercury’s north polar craters here.

Read More: “The Hobbit” Author Gets a Crater on Mercury

On November 29, NASA will host a news conference at 2 p.m. EST to reveal new observations from MESSENGER, the first spacecraft to orbit Mercury. The news conference will be carried live on NASA Television and the agency’s website… you can tune in on NASA TV here. 

Image credits: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Posted on by Jason Major

Mercury’s Surface is Full of Sulfur

The southern portion of Mercury’s Vivaldi basin and outlying rugged terrain

Named for the 17th-century Venetian composer, the southern half of Mercury’s Vivaldi basin is seen in this image acquired on August 26 by NASA’s MESSENGER spacecraft. The 213-km (132-mile) -wide crater’s smooth floor is contrasted by the incredibly rugged terrain beyond its outermost ring — a result of the ejected material that was flung out from the impact site and emphasized by the low angle of illumination.

The floor of the crater remained relatively smooth due to molten material that erupted in the wake of the impact event, flooding the basin.

Recent findings from the MESSENGER mission have revealed variations in Mercury’s surface composition due to volcanism that occurred at different times, as well as a surprising concentration of elements like magnesium and sulfur — much more so than any of the other terrestrial planets.

In results to be published in the Journal of Geophysical Research, scientists report that Mercury’s volcanic smooth plains differ in composition from older surrounding terrains. The older terrain has higher ratios of magnesium to silicon, sulfur to silicon, and calcium to silicon, but lower ratios of aluminum to silicon, suggesting that the smooth plains material erupted from a magma source that was chemically different from the source of the material in the older regions, according to Shoshana Weider of the Carnegie Institution of Washington, the lead author on the paper.

Mercury’s surface was also found to be high in magnesium and sulfur-enriched minerals.

“None of the other terrestrial planets have such high levels of sulfur. We are seeing about ten times the amount of sulfur than on Earth and Mars,” Weider said. “In terms of magnesium, we do have some materials on Earth that are high in magnesium. They tend to be ancient volcanic rocks that formed from very hot lavas. So this composition on Mercury tells us that eruptions of high-temperature lavas might have formed these high-magnesium materials.”

Read: MESSENGER Reveals Mercury’s Colors

The data was gathered with MESSENGER’s X-Ray Spectrometer (XRS) — one of two instruments designed to measure the abundances of many key elements in the top 2mm of Mercury’s crust. XRS detects emissions from elements in the 1-10 kiloelectron-volt (keV) range – specifically, magnesium, aluminum, silicon, sulfur, calcium, titanium, and iron.

Read more on the MESSENGER mission site here.

Inset image: A global mosaic of Mercury from MESSENGER (2011). Image credits: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Posted on by Nancy Atkinson

The Moon from Earth As You’ve Never Seen it Before

The Morteus region on the Moon, taken from the suburbs of Paris, France. Credit: Thierry Legault. Used by permission.

Think this is an orbital view of the Moon? Guess again. Astrophotographer Thierry Legault took this image from his backyard in the suburbs of Paris, France! He’s taken a series of images of the Moon the past few nights that will blow your mind when you consider they were taken from Earth, within the confines of the metropolis of Paris (largest city in France, 5th largest in the EU, 20th largest in the world). Thierry used a Celestron C14 EdgeHD (356mm) and Skynyx2.2 camera. You definitely want to click on these images for the larger versions on Thierry’s website, and he suggests using a full-HD screen in subdued surroundings.

Additionally, Thierry also recently took images of Mercury and Uranus that include incredible detail.

Plato, Mons Pico and Montes Teneriffe as seen on Sept 8th, 2010, from the suburbs of Paris, France. Credit: Thierry Legault. Used by permission.

The clarity and detail are just tremendous. See all of Thierry’s recent lunar images at this link. He has a collection of twelve different images of various regions on the Moon and all are stunning.

Below are his images of Mercury and Uranus. In the image of Mercury, surface details are visible, and the cloud belts are even visible on the images of Uranus:

Incredibly detailed view of Mercury on August 23, 2012, as seen from Blancourt, France. Credit: Thierry Legault. Used by permission.

Uranus, as seen on September 9, 2012 from Blancourt, France. Credit: Thierry Legault. Used by permission.

Thanks, as always, to Thierry Legault for sharing his images and allowing us to post them. Check out his website: http://legault.perso.sfr.fr/ for more wonderful images and information about how he does his amazing astrophotography.

Posted on by Jason Major

“The Hobbit” Author Gets a Crater on Mercury

Here’s a little something to please fans of space, art and fantasy alike (and those who enjoy all three): on August 6 the International Astronomical Union approved names for 9 craters on Mercury, one of which is named for J.R.R. Tolkien, revered author of The Hobbit and The Lord of the Rings (among other seminal fantasy works.)

The crater Tolkien is approximately 30 miles (48 km) in diameter. All 9 newly-named craters are located in Mercury’s north polar region and exhibit radar evidence of water ice hidden in their shadowy pocketses.

IAU procedure for craters on Mercury has them named after “deceased artists, musicians, painters, and authors who have made outstanding or fundamental contributions to their field and have been recognized as art historically significant figures for more than 50 years.” Find out who all 9 new craters are named for after the jump:

Egonu, for Uzo Egonu (1931-1996), a Nigerian-born painter who at 13 was sent to England to study art, first at a private school in Norfolk and later at the Camberwell School of Arts and Crafts. Exile, alienation, and the pain of displaced peoples were recurrent themes in his work.

Gaudí­, after Antoni Gaudí­ (1852-1926), a Spanish architect whose work concentrated largely on the Catalan capital of Barcelona. He was very skilled with ceramics, stained glass, wrought-iron forging, and carpentry and integrated these crafts into his architecture.

Kandinsky, for Wassily Kandinsky (1866-1944), a Russian painter and art theorist credited with painting the first purely abstract works.

Petronius, for Titus Petronius (c. AD 27-66), a Roman courtier during the reign of Nero. He is generally believed to be the author of the Satyricon, a satirical novel believed to have been written during the Neronian era.

Prokofiev, for Sergei Prokofiev (1891-1953), a Russian composer, pianist, and conductor who is considered one of the major composers of the 20th century. His best-known works include the ballet Romeo and Juliet — from which “Dance of the Knights” is taken — and Peter and the Wolf.

Tolkien, for John Ronald Reuel (J. R. R.) Tolkien (1892-1973), an English writer, poet, philologist, and university professor, best known as the author of the classic fantasy novels The Hobbit and The Lord of the Rings.

Tryggvadóttir, for Nina Tryggvadóttir (1913-1968), one of Iceland’s most important abstract expressionist artists and one of very few Icelandic female artists of her generation. She primarily worked in painting, but she also created collages, stained glass work, and mosaics.

Qiu Ying, for Shifu Qiu Ying (1494-1552), a Chinese painter who specialized in the gongbi brush technique, a careful realist method in Chinese painting. He is regarded as one of the Four Great Masters of the Ming Dynasty.

Yoshikawa, for Eiji Yoshikawa (1892-1962), a Japanese historical novelist best known for his revisions of older classics including The Tale of the Heike, Tale of Genji, Outlaws of the Marsh, and Romance of the Three Kingdoms.

“These designations expand the opportunities to recognize the contributions to the arts by the most creative individuals from many cultures and eras. The names of those individuals are now linked in perpetuity to the innermost planet.”

– Sean Solomon, MESSENGER Principal Investigator

The craters were imaged by NASA’s MESSENGER spacecraft, currently in extended mission around Mercury. Learn more about the preciousss MESSENGER mission here. (Gollum! Gollum!)

Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington 

Posted on by Elizabeth Howell

A Glimpse of Old Cape Kennedy

I’m a child of the shuttle era, but I grew up reading the tales of Mercury, Gemini and Apollo. That heady time in the 1960s was so foreign to a teenager growing up in the age of personal computers and Internet access: people glued to television sets watching space shots. Newspapers carrying pages upon pages of space content, rather than small mentions.

My favourite book symbolizing what this era was like – at least, from the starry-eyed optimist’s point of view – was This Is Cape Canaveral, a children’s book first published in 1963 and subsequently republished under the names This Is Cape Kennedy and This Is The Way To The Moon.

Writer and illustrator Miroslav Sasek portrays the crowds, era and missile-obsessed businesses with a taste of humour and a keen eye for detail. It’s attention that his audience demanded: “Detail is very important to children,” he said in a 1969 interview. “If I paint 53 windows instead of 54 in a building, a deluge of letters pours in upon me!”

I cracked open my dog-eared copy the other day to play a mini where-are-they-now game with some of the mentioned landmarks and people:

The times change in 50 years, but the good thing is there is no lack of chronicles to tell us what it was like at the time.

Lead image caption: In This Is Cape Canaveral, Miroslav Sasek wasn’t afraid to poke fun at the excitement of the early days of the space program.

Elizabeth Howell (M.Sc. Space Studies ’12) is a contributing editor for SpaceRef and award-winning space freelance journalist living in Ottawa, Canada. Her work has appeared in publications such as SPACE.com, Air & Space Smithsonian, Physics Today, the Globe and Mail, the Canadian Broadcasting Corp.,  CTV and the Ottawa Business Journal.

Posted on by Jason Major

Mercury’s Many Colors

Although composited from expanded wavelengths of light, this wide-angle image from NASA’s MESSENGER spacecraft shows the amazing variation of colors and tones to be found on Mercury’s Sun-scoured surface.


This scene lies between Mercury’s Moody and Amaral craters, spanning an area of about 1200 km (745 miles). The patch of dark blue Low Reflectance Material (LRM) in the upper left of the image and the bright rayed crater on the right make this a diverse view of Mercury’s surface. Note the curious small, dark crater just below the bright rayed crater on the right.

Dark LRM material is thought to indicate the presence of a mineral called ilmenite, which is composed of iron and titanium and has been revealed through volcanic, cratering and erosion processes.

More Mercury images: Postcards from the (Inner) Edge

Did you know that until MESSENGER arrived in 2008 half of Mercury had never been seen? And that although Mercury is the closest planet to the Sun there may still be water ice on its surface? Learn more about these and other fascinating facts about Mercury here.

Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

 

Posted on by Jason Major

Postcards From The (Inner) Edge

As the world turns its gaze outward in anticipation of the arrival of Mars Science Laboratory — with its hair-raising “seven minutes of terror” landing — let’s take a moment to look back inward, where MESSENGER is still faithfully orbiting the first rock from the Sun, Mercury, and sending back images that could only have been imagined just a few years ago.

The image above shows the graben-gouged terrain around Balanchine crater, within Mercury’s vast Caloris Basin impact crater. Named for the co-founder of the New York City Ballet, Balanchine crater is 41 km (25.5 miles) in diameter and filled with the curious erosion features known as hollows. Graben — basically sunken troughs in the surface — are the result of extensional forces that have pulled sections of the planet’s upper crust apart.

This image shows the peak-ring structure located within the much larger crater Rustaveli, which is 180 km (112 miles) in diameter. One of the more recently-named craters (the IAU convention for new features on Mercury has them titled after renowned artists, writers and composers from history) Rustaveli is named for a 12th-century Georgian poet who wrote the epic “The Knight in the Panther’s Skin”. The crater that now bears his namesake is located on Mercury’s northern hemisphere.

These two craters — also located within Caloris Basin — don’t yet have names but are no less interesting. Their overlapping positions works like an optical illusion, making the newer,sharper-edged crater on the right seem to almost float above the surface. The false-color of the image highlights the difference in surface composition of the two craters, which are both about 40 km (24 miles) wide. (The Caloris Basin in which they reside, however, is one of the largest known impact sites in our solar system, measuring at 1550 km — 963 miles — across!)

Now we zoom out for a wider view of our solar system’s second-densest planet (Earth is the first) and take a look at an image that’s night and day — literally! This is Mercury’s terminator, the twilit dividing line between night and day. More than just making a pretty picture, data on this transition is valuable to scientists as some atmospheric phenomena can only be observed at the terminator, such as the interaction between surface dust and charged particles from the Sun (which, at less than half the distance to the Sun than we are, Mercury is constantly bathed in.)

And now to zoom back in, we get a good look at an unnamed central-peaked crater about 85 km (52 miles) across in an oblique view  that highlights the hollows and depressions within its floor. Acquired as part of what’s called a “targeted observation”, high-resolution images like this (79 meters/pixel) allow scientists to closely investigate specific features — but sadly there’s just not enough mission time to image all of Mercury at this level of detail.

On March 17, 2011 (March 18, 2011, UTC), MESSENGER became the first spacecraft ever to orbit Mercury. The mission has provided the first data from Mercury since Mariner 10, over 30 years ago. After over 1,000 orbits, 98 percent of Mercury is now imaged in detail, allowing us to know more about our solar system’s innermost world than ever before.

Keep up with MESSENGER updates (and the latest images) on the mission website here.

Image credits: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington