Tag Archives: Messenger

Mercury MESSENGER mission scores 100%

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Global maps of Mercury. Half the globe is shown in black & white, the other in color. Each map is composed of thousands of images. Click this and any of the other photos for hi-res versions. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Nice job MESSENGER! After two years in orbit, the entire planet of Mercury has been mapped. Can a cellphone map app be far behind? Prior to MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging), human eyes had seen less than half of the planet up close. No spacecraft had dropped by the solar system’s innermost planet since Mariner 10 sent us the first detailed images of Mercury during three brief flyby loops executed in 1974-75.

Craters (from left) Tolkien, Tryggvadottir and Chesterton are located close to the planet’s north pole and have permanently shadowed floors. MESSENGER found evidence for ice in all three. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Over the past two years the probe has taken more than 168,000 pictures of Mercury’s numerous craters, ridges and enigmatic “hollows”, mapped its topography and determined the makeup of minerals on its surface through examination of the light they reflect from the sun.The probe also revealed water ice coated with organic materials within permanently shadowed craters at the planet’s north pole.

The 20.5-mile-diameter crater Kertesz, named for photographer Andre Kertesz. Mercury craters are named for artists. Kertesz’s floor is pocked by enigmatic “hollows” which could be material boiled off by the sun’s heat and radiation. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

With the probe’s original mission extended from one to two years, it’s now coming to an end. Unless a further extension is approval, March 17 would be the last for data gathering. Principal investigator, Sean Solomon of Columbia University’s Lamont-Doherty Earth Observatory, has submitted a proposal that would keep MESSENGER and mission control in business for another two years, about the time it runs out of fuel and crash lands on Mercury.

Waters crater was recently named in honor of blues legend “Muddy Waters” (a.k.a. McKinley Morganfield). The “mud” pouring out below it is melted rock from the impact. A color image at upper right shows it’s appropriately blue-toned. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Keeping the mission running would let scientists continue targeted studies of various features and shoot photos at incredibly high resolution as MESSENGER’s decaying orbit carries it closer and closer to the surface. Not only that, but the spacecraft is ideally placed to study and photograph Comet ISON when it makes it grazes the sun later this fall.

An oblique view of a 174-mile-long escarpment cutting through a crater. The slope is a geologic fault resembling an “overbite” that formed when the planet shrunk due to cooling of its interior. The left side is 1.2 miles higher than the right. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

To celebrate MESSENGER’s milestone, I thought you’d enjoy a selection of images from recent photo shoots.We’ll know in April whether the mission will continue once a science commission makes its decision. Click HERE to browse more photos in the archive.

A closeup view of hollows in an unnamed crater. The pits almost always occur within or surrounding impact features. They’re about 100 feet to a couple miles wide and lack rims. Hollows might be volcanic vents or created when sulfur and other volatile materials escape from the surface during solar wind bombardment. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Curiosity’s history-making discovery a big misunderstanding

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Bite mark left in the sand dune after Curiosity retrieved soil sample. It’s similar to lava rock found in Hawaii and contains feldspar, pyroxene and olivine. Other materials found in the sample will be revealed next week. Credit: NASA/JPL-Caltech

Do you want the good news or bad news first? OK, the bad news. Remember when we learned last week that Curiosity had made a “history changing” discovery in a Martian soil sample? Many of us speculated that the rover had detected the first organic, carbon-containing compounds on Mars.

Well, it turns out it was just a big misunderstanding between the MPR reporter and Mars Science Laboratory (MSL) project scientist John Grotzinger. During the original interview, Grotzinger explained to reporter Joe Palca that Curiosity had analyzed the first soil sample in its Sample Analysis at Mars instrument. While SAM can detect organics, Grotzinger’s reference to the discovery being “one for the history books” was actually a reference to the entire Mars mission, not a specific finding.

Panoramic view of Curiosity’s digs at the Rocknest site in Gale Crater on Mars. One barren-looking landscape! The photo is a composite of images taken in October and November. Click to enlarge. Credit: NASA-JPL/Caltech

Somehow the NPR reporter misinterpreted the excitement surrounding the first soil analysis with Grotzinger’s description of the mission as history-making. Each thought the other was talking about a different thing. Indeed at the time of the interview, the first sample had only begun to be analyzed, so NASA scientists wouldn’t have even known the details of its chemical contents. Results, described as “interesting” rather than earth-shaking, will be presented next week at a meeting of the American Geophysical Union in San Francisco. More on the topic HERE.

Since it’s still very early in the mission, we shouldn’t be too bothered if some sort of Holy Grail moment has yet to happen. Look at what Curiosity’s found so far – an ancient stream bed filled with water-rounded cobbles, layered buttes of sedimentary rock like a postcard from the Grand Canyon and a most amazing assortment of wind-sculpted rocks. And don’t forget – we got there in the first place and Curiosity couldn’t be healthier.

Does anyone doubt that handfuls of history-making discoveries lie ahead? My only frustration is that NASA didn’t attempt to correct the misunderstanding sooner through one of its many press releases.

View of Mercury’s north pole seen from above. Red denotes areas of permanent shadow as seen by the MESSENGER probe to date. The polar ice deposits imaged by Earth-based radar are in yellow. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/National Astronomy and Ionosphere Center, Arecibo Observatory

Now for the good news. Mercury, a planet with a surface temperature hot enough to melt lead has been confirmed by MESSENGER probe to have ice deposits in its polar regions. What the heck? Given that it’s the closest planet to the sun, you’d think it an unlikely place for ice, but the little planet’s axis is tipped less than one degree, so areas around its poles are never exposed to sunlight. Since Mercury has no substantial atmosphere to capture and distribute heat, its surface temperature ranges from 800 degrees F in sunlight to 200 below in the polar regions.

While radio-bright areas likely due to ice have been detected from Earth by the giant Arecibo radio telescope in Puerto Rico as long ago as 1991, new data from NASA’s orbiting MESSENGER spacecraft confirm that water ice is indeed present both exposed on the surface as well as buried beneath dark, tar-like deposits.

The probe uses neutron spectroscopy to measure hydrogen concentrations within Mercury’s radar-bright regions. Based on the amount of hydrogen seen, scientists can estimate the volume of water ice present, because water, or H2O, is two parts hydrogen.

“The new data indicate the water ice in Mercury’s polar regions, if spread over an area the size of Washington, D.C., would be more than 2 miles thick,” said David Lawrence, a MESSENGER participating scientist.

The dark material could be a mix of organic compounds delivered by carbon-rich comets and asteroids several billion years ago during the solar system’s youth. Astronomers believe that Earth was similarly enriched by water and organics. I like the connection, and I like that polar opposites – excuse the pun – find a home together on a most unlikely planet. To read more about the discovery, click HERE.

Mercury makes its move into the evening sky

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Three planets and a crescent moon will light up the western sky shortly after sunset this evening (Feb. 22). Created with Stellarium

Move over Jupiter. Move over Venus. It may be the smallest planet, but Mercury is on its way up into the evening sky. Beginning tonight – and with the help of a very young crescent moon – observers with clear skies and a wide open western horizon can seek the innermost planet alongside the 1-day-old moon. As always, take your binoculars to help in case the sky is less than ideal.

The duo will be well below the Venus-Jupiter line just five degrees or three fingers held together at arm’s length above the west-southwest horizon. The best time to look is starting about 20 minutes after sunset.  Don’t wait too long or they’ll set before you get the chance to see them.

As we move into late February and early March, the moon will move up and away from Mercury and pass near Venus  on the 25th and Jupiter on the 26th. Mercury also moves up and away from the sun and will soon become much easier to see. I’ll keep you posted on good viewing opportunities coming up.

Two nearly complete maps of the planet Mercury made from pictures taken by the MESSENGER spacecraft in orbit around the planet. The black and white map is more detailed than the color version, which highlights different types of minerals and terrains. Credit: NASA

NASA’s Mercury MESSENGER (Mercury Surface, Space ENvironment, GEochemistry, and Ranging) mission has nearly completed its initial mission goal of mapping the planet in color and black and white. It’s also made quite a few discoveries including:

* Most of Mercury’s mass – 60-70% vs. 32% for Earth is in the form of metal in its core. Lighter materials were either boiled away from intense solar heat and solar wind bombardment or from heating caused by a major impact long ago.  Mercury is 36 million miles from the sun or 2.5 times closer than the Earth. Surface temperatures are as hot as 800 degrees and sunlight 6.5 times more intense than on Earth.

Shallow, flat-bottomed pits on Mercury may be caused by subatomic particles from the sun zapping away at sulfur-laden minerals. Credit: NASA

* Like Earth, Mercury is surrounded by a magnetic field, but it’s offset far to the north of the planet’s center and fluctuates over time. Compared to the planet’s small size (3032 miles or about 1.5 times the size of the moon), this offset is far more than any other planet. Scientists are still at a loss to explain why.

* A vast expanse of volcanic plains with lavas as thick as 1.2 miles surround the north polar region. According to James Head of Brown University, the deposits appear to be flood lavas or huge volumes of solidified molten rock similar to those  in the Columbia River basin in the northwest United States. “Those on Mercury appear to have poured out from long, linear vents and covered the surrounding areas, flooding them to great depths and burying their source vents,” said Head.

* New, unexpected landforms called ‘hollows’ have been discovered inside some of the planet’s craters. The shallow, rimless pits range from about 100 feet to 2 miles wide are often seen in clusters. They’re very reflective and appear quite fresh. Scientists believe the intense solar wind felt at Mercury’s distance may be eating away at exposed sulfur deposits on the surface to create the depressions.

* Mercury’s surface may look like the moon, but its rocks contain lots more potassium and sulfur than the lunar variety.

If you’d care to learn more about the new findings and see additional photos of Mercury, check out the MESSENGER website. And don’t forget to go out and see the planet with your own eyes in the next few weeks.

Picture perfect Mercury lineup

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The planet Mercury, looking like a bright star, lies directly north of the sun yesterday at 6:06 p.m. Central time. The photo was taken with the LASCO C2 coronagraph on SOHO. A metal disk blocks the brilliant sun (center white circle) allowing us to see not only the planet but also the beautiful rays of the sun's outer atmosphere called the corona. Credit: NASA/ESA

Yesterday evening the planet Mercury lined up directly over the sun in an event called superior conjunction. Don’t worry if you missed it. No one except the coronagraph aboard the space-based Solar and Heliospheric Observatory (SOHO) witnessed the lineup. Around 6 p.m. Central time, Mercury was less than one degree north of the sun. Prior to that, it was slightly west of the sun and officially in the morning sky.

Today the speedy planet is slightly east of the sun, and will soon come into view in the evening sky at the end of this month. We’ll update you with directions and maps when the fleet planet reappears in the west after sunset.

19th century composer Johannes Brahms would be surprised to learn he has a spectacular crater named after him on Mercury. Credit: NASA/JHUAPL/Carnegie Institution of Washington

Superior conjunction occurs when Mercury lines up with the sun on the far side of its orbit. Picture the planet in the background behind the sun. At the time the photo was taken, Mercury was 123 million miles from Earth. On the flip side, when Mercury passes between the sun and Earth at inferior conjunction, it’s only 58 million miles away. Because it orbits so quickly, we see several inferior and superior conjunctions a year.

62-mile-diameter Atget crater lies within the even larger Caloris Basin. Credit: NASA/JHUAPL/Carnegie Institution of Washington

Since Mercury is the closest planet to the sun, it takes only 88 days to circle around it. The Greeks called it Hermes, the messenger of the gods. Our name comes from the Roman god of travel and commerce. After all, when it comes to business, we don’t want any dillydallying.

With daytime highs of 800 degrees Fahrenheit and nighttime lows of 300 below, Mercury’s surface temperature is as extreme as it gets. And get this – the sky is clear all the time, because there’s next to nothing for an atmosphere. The few atoms present were blasted from the surface by the solar wind. At 3,032 miles across, the planet is the smallest in the solar system, only half again as big as our moon. It’s a tough, little world out there!

NASA calls this Rock Lobster - The 21-mile-diameter crater's central peak is shaped like a lobster claw. Credit: NASA/JHUAPL/Carnegie Institution of Washington

Looking at the photos, which were all taken by the orbiting MESSENGER probe, you’ll be reminded of the moon’s cratered landscape – with a few differences. Except for the Caloris Basin, a huge impact basin 963 miles in diameter, Mercury has few of the ‘seas’ or dark, lava-filled basins that form the face of the ‘man in the moon’. Its sun-baked globe is also crossed by huge ridges or escarpments, some a couple hundred miles long and over a mile high. They presumably formed when the planet’s large core cooled and shrunk, causing the crust to buckle and break.

NASA will host a news conference at noon on Thursday, June 16, to reveal new images and science findings from the MESSENGER probe at Mercury, so stay tuned.

A ramble over the hot rocks of Mercury

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An animation of T Pyxidis using photos taken before and after its outburst. Credit: Ernesto Guido and Giovanni Sostero

The wind nearly tore my ears off last night, but I packed the scope and took a southern sojourn to Pyxis the Compass to check out yesterday’s featured star T Pyxidis (PICK-sih-dis). Two days ago this star was only visible in larger amateur telescopes; last night it was bright enough at magnitude 8.6 to be visible in a pair of 10×50 binoculars – in a moonless sky. The bright gibbous moon quashed that possibility, but any scope will now show it plainly.

If you’re an amateur astronomer, finding T Pyx is not difficult. For night sky newcomers it’s another matter. You can use yesterday’s finder chart link to locate the star. Once the moon’s out of the evening sky, I’ll provide you with one of my own.

The MESSENGER spacecraft has been in orbit around Mercury since March 18 snapping photos like a kid with a new cellphone. All kinds of new features, from craters to mountain peaks to odd dark spots, have been seen. Below is a selection of recent images for you to peruse and enjoy. If they whet your appetite for more, click on over to the MESSENGER gallery.

As you look through the photos, you’ll be reminded of the moon. Like the moon, Mercury has virtually no atmosphere. Craters created by bombardment from meteorites and asteroids some four billion years ago are still well-preserved on both worlds. Lack of erosion forces we’re familiar with on Earth like wind, water, and tectonic forces from beneath the crust that rearrange and recycle our planet’s crust are the cause.

No atmosphere also means dramatic swings in surface temperature. Mercury’s ranges from -270 F at night to 800 F during the day. The moon’s ranges from 250 below at night for a typical location to 250 above on a sunny afternoon.

The 43-mile-wide crater Camoes is located in the south polar region. A large ridge or scarp crosses the crater's floor. These giant scarps are believed to have formed when Mercury’s interior cooled and the entire planet contracted or shrunk slightly as a result, causing the surface rocks to fracture and thrust (push) over others along great faults. Credit: NASA/JHUAPL/Carnegie Institution of Washington

The crater 50-mile-diameter crater Debussy (top) sports a striking halo of rays created when material excavated during the formation of the crater rained down to the surface. Credit: NASA/JHUAPL/Carnegie Institution of Washington

Scientists still aren't sure what the dark material is to the left of center. They suspect it's a dark rock type. Perhaps volcanic in nature? Credit: NASA/JHUAPL/Carnegie Institution of Washington

A view of the terrain over Mercury's north polar region. A low sunlight angle reveals lots of details in the landscape reveals numerous curving and intersecting ridges. Understanding the interiors of the craters in Mercury's polar regions and any ices they may contain is one of the main science goals of the MESSENGER mission. Credit: NASA/JHUAPL/Carnegie Institution of Washington

The crater Bec, 20 miles across, is surrounded by a starfish-like pattern of rays. At lower right is Lermentov. Bec's bright rays are indicative of its relative youth; Lermontov's floor is a suspected site of explosive volcanism, with irregular depressions. Credit: NASA/JHUAPL/Carnegie Institution of Washington

Life’s nice with liquid, gas and ice

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A series of remarkable bell-shaped icicles line the underside of an ice shelf over the Brule River this weekend. They were created by a combination of water dripping from the shelf and river water flow. Photo: Bob King

Mud turned to ice under our feet last night as the temperature dropped to 20 F. I spoke before a group of naturalists at the Boulder Lake Environmental Learning Center north of Duluth. After the talk we walked outside and set up a telescope in a parking lot for a tour the spring sky. Our shoes sank in the soft ground at first, but by session’s end, the puddles had solidified into icy patches. We soon were sliding to the telescope as each took their turn at the eyepiece.

Water vapor is carried around the globe by weather systems. This satellite image shows the distribution of water vapor over Africa and the Atlantic Ocean. White areas have high concentrations of water vapor, while dark regions are relatively dry. Credit and copyright: Eumetsat

In only an hour’s time, water went from fluid to solid literally beneath our feet. And don’t forget the vapor. Though invisible, it permeated the air around us.

Water is the most important chemical to life and can be found in all three of its states – solid, liquid and gas – simultaneously on Earth. Since life depends on water, ours is the most suitable world we know of where it can thrive.

Our group had a joyful time looking at Saturn, always a rave-getter, double stars, galaxies and little bit of everything in the universe.

I kept thinking about that water, though. How many planets around the thousands of stars we saw might be fortunate enough to have the H2O so necessary for life? With the number of known extrasolar planets now at 539 and counting, I’m confident we’ll find one like Earth within our lifetimes, another blue planet in the Goldilocks zone , where liquid water can set up shop, flow where it may and serve as a medium for an extraterrestrial evolution of life.

This image is the first ever obtained from a spacecraft in orbit about Mercury. The dominant rayed crater in at top is Debussy, named after the 20th century French composer. Mercury's south polar region is near the bottom. Credit: NASA/Johns Hopkins U. A. P. L./Carnegie Institution of Washington

Today the first images taken by the MESSENGER spacecraft in orbit around Mercury are being released. The approximately one-year mission will focus on a creating a detailed map of the entire planet in addition to studying its topography, crustal minerals, magnetic field and more.

Claude Debussy circa 1908

It gives me a little thrill that the first image sent back by the probe included the striking crater Debussy, named after Claude Debussy, one of my favorite composers. His atmospheric and impressionistic music stands in stark contrast to the rough-edged, cratered landscape of the solar system’s innermost planet.

According to the International Astronomical Union (IAU) Working Group for Planetary System Nomenclature, craters on Mercury are named after deceased artists, musicians and authors who have been significant figures for more than 50 years. Mountains are named for the word “hot” in various languages and valleys for radio telescope facilities. To learn how other features of the moons and planets of the solar system get their names, click on over the Group’s planetary names page.

The crater near the bottom of the left hand image is a beautiful example of a relatively small, simple, fresh impact feature on Mercury. The image at right is striped by rays of material from another crater outside the frame. Credit: NASA/Johns Hopkins U. A. P. L./Carnegie Institution of Washington

Above are two additional images taken by MESSENGER from orbit released this afternoon. To see more, please click HERE.

Toast a pint o’ green beer to tonight’s Mercury mission

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Artist's view of the MESSENGER spacecraft in orbit about Mercury. The white shield is a special ceramic sunshade to protect the craft and its instruments from the intense heat and radiation near the sun. Credit: JHU-APL

Tonight’s the big night for the Mercury MESSENGER space probe. After more than a dozen loops through the inner solar system that included six planetary flybys, NASA mission controllers will ease the craft into orbit around the innermost planet starting about 8 p.m. Central time.

Around 7  p.m., MESSENGER will be positioned for orbital entry. Then at 7:45, the main thruster will fire for about 15 minutes to slow the probe some 1,929 miles per hour, allowing it to be captured by Mercury’s gravity. The remaining fuel will be used to adjust its orbit during a year-long study of the planet. We should know by 9 p.m. whether the capture was successful. Let’s hope mission control has plenty of green beer on hand to celebrate.

“For the first two weeks of orbit, we’ll be focused on ensuring that the spacecraft systems are all working well in Mercury’s harsh thermal environment,” according to Eric Finnegan, MESSENGER Mission systems engineer.

“Starting on March 23 the instruments will be turned on and checked out, and on April 4 the science phase of the mission will begin and the first orbital science data from Mercury will be returned.”

MESSENGER's arrival at the planet has been a complicated, drawn-out affair due to the need for the spacecraft to come up to Mercury's speed so it can be safely put into orbit around the planet. Credit: NASA/JPL

To arrive at the solar system’s smallest planet, which at 3,032 miles is just half again as big as the moon, MESSENGER’s orbit and speed were shaped by flybys of Earth, Venus and Mercury over the past six years. As of this morning, it’s traveled a total of 4.9 billion miles or 52 times the distance between the Earth and sun.  Why so many miles to travel to a relatively close planet?

Mercury is 3,032 miles across compared to Earth's 7,926 miles. Credit: NASA images

It’s all about gravity and speed. Mercury, being the closest planet to the gravitational grip of the sun, travels fastest with an average speed of 106,000 mph. In order to catch up to it, MESSENGER had to increase its speed by 65,000 miles per hour relative to the sun until it was finally neck-in-neck with Mercury.

Last night I saw the movie “Unstoppable”, a fictional account about a runaway train in Pennsylvania. To get control of the train, they had to get someone aboard it. That meant driving a truck alongside the locomotive to match the train’s speed of 60+ mph. Once their speeds were equal, the conductor could jump from the truck and onto the train. The same technique was used to get MESSENGER to Mercury, only instead of employing the brute “foot-on-gas-pedal method”, the spacecraft increased its speed by robbing a bit of orbital momentum from Earth, Mercury and Venus during its six flybys. Pretty cool, eh?

Mercury's giant Caloris Basin recorded during MESSENGER's first flyby on Jan. 14, 2008. This huge impact scare is 960 miles across, one of the largest in the solar system. Credit: NASA/JPL/JHU/APL

Once in orbit, MESSENGER will fly as close as 124 miles above the planet’s surface. It’s equipped with wide and narrow angle cameras, instruments to measure elements and minerals in the crust, study the planet’s magnetic field (generated by a large iron core), topography, tenuous atmosphere and much more.

Because the sun is 11 times brighter at Mercury than at Earth, the planet’s surface temperature during the day can reach 840 degrees Fahrenheit. To protect its delicate scientific instruments, the probe is equipped with a special ceramic fabric sun shield, a sort of space-age patio umbrella, that shields it from the searing heat of the sun.

I’ll update the blog later tonight with the (hopefully) good news of a successful start of MESSENGER’s new mission.


As long as we’re talking flybys, I came across this bit of eye candy today that made my spine tingle. It’s a short movie clip of a flyby through Saturn’s rings created by Stephen van Vuuren using photos taken by the Cassini Saturn spacecraft. Be sure your sound is turned on, because the music, Sam Barber’s “Adagio for Strings”, is a perfect fit for the journey. Enjoy!

How many planets have YOU seen?

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The eight planets are shown to size relative to each other and the sun. Credit: NASA

Well, let’s count them. Earth is easy enough. Each of us has experienced enough of this planet to give any aliens we might encounter enough information to make them think twice about wanting to deal with us. And I’d be willing to bet many of you have seen Venus, the solar system’s brightest student, Mars, the only red planet, and Jupiter, the big kid on the block. Fewer have spotted Saturn, the planet of a thousand hula-hoops.

Let’s see. That makes a total of five easily visible planets seen by most people knowingly or not. So we have three left: Neptune (too faint), Uranus (ditto) and Mercury.  If you’ve never seen Mercury, the next two weeks will be the best time of year to spot it in the evening sky. Since it would put a big smile on my face to see you add planet #6 to your life list, here are a couple of sky maps to help you find it.

Jupiter and Mercury quickly approach one another during evening twilight in the coming days. They'll be closest next Tuesday. Mercury is seen by few people because, being the innermost planet, it's always near the sun in the sky and sets soon after sunset. Created with Stellarium

The first thing you’ll notice is that you’ve got a friend in Jupiter, which is considerably brighter than Mercury. Now through the next week, the two planets will be within 5 degrees of each other. That’s only three fingers held together at arm’s length. Find Jupiter and you’re almost there.

To increase your chances of spotting them both,  get to a place with a good view to the west, because both planets will be low in the sky. Go out a half-hour to 45 minutes after sunset and look one outstretched fist above and a little to the left of the sunset point to find Jupiter. Mercury will be the only other bright star a few degrees to the lower right of Jupiter. It’s not as bright as the king of planets, but does very well for itself thank you.

Take binoculars too in case you need a little help making a preliminary sighting of Mercury, then look with your naked eye. The later it gets, the brighter Mercury will appear but only to a point. An hour-plus after sunset, it will have faded into the horizon haze.

Artist's concept of MESSENGER in orbit around Mercury. Credit: NASA

Very soon – on St. Patrick’s Day the 17th matter of fact – NASA scientists will insert the MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging mission)  spacecraft into orbit around Mercury, the first time any craft has orbited the planet. It also might be the most amazing acronym ever devised for a space mission.

To get the solar system’s innermost planet, the spacecraft followed a 6 1/2 year-long path through the inner solar system, including one flyby of Earth, two flybys of Venus, and three flybys of Mercury. This loop-de-loop was necessary in order to shape its orbit and slow the craft down in preparation for its upcoming orbital maneuvers.

Mercury is a crater-scarred world that resembles the moon. It also has some of the most extreme temperatures in the solar system. During the day the surface can reach 840 degrees F, while in shaded craters near the poles it's 350 below! Credit: NASA

We’ll have much more in the coming days about the event, which I hope you agree, is perfectly suited to celebration on St. Patrick’s Day. What a fortunate coincidence that Mercury is out for easy viewing at the same time MESSENGER begins the most ambitious part of its program.

Scientists hope to learn much more about the planet’s magnetic field, its great variety of craters and other landforms and the scanty atmosphere boiled off its surface by the sun’s radiation.

Mercury is a rocky, “terrestrial” planet like Mars, Venus and the Earth. The more we learn about it, the more we’ll understand how rocky planets like ours formed and evolved. Your mission, should you choose to accept it, is to stand face to face with this small, battered world.

My mercurial friend

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“This is bogus.” That’s what one of my co-workers said about International Observe the Moon Night item in yesterday’s blog. “I appreciate the moon every night. It’s a contrived event, but at least there’s no commercial angle to it.” OK, OK, he’s got a point. There’s no special happening on the moon that night, no spacecraft impact or alien check-passing ceremony. But why not go out and pay attention to that special orb? The “event” is more of a reminder to look up and appreciate what we sometimes take for granted. I always need reminders about things, like making sure to catch a good movie in town or having enough socks on hand to get me through the week.

Mercury will be visible low in the eastern sky 35-45 minutes before sunrise or around 6 a.m. It's in the constellation of Leo the Lion not far below the star Regulus. Regulus will be faint in twilight, Mercury brighter and easier. Created with Stellarium

This coming weekend and into next week is the best time of the year to catch the planet Mercury in the morning sky for northern hemisphere observers. With the sun rising later, it’s more likely your schedule will allow you to see the planet without losing much, if any, sleep.

Being the innermost planet, Mercury never strays far from the sun, so we always see it in twilight. When it’s orbit takes it east of the sun, it’s nicknamed the “evening star”. When west of the sun, as it will be in the days ahead, it’s the “morning star”.  People in ancient Greece considered Mercury two separate planets for a time. It was Apollo in the morning sky and Hermes in the evening. Not until around 350 B.C. did the Greeks realize they were looking at the same planet. The Romans gave Mercury the name we use today, which means messenger of the gods. They most likely chose it because the planet moves so quickly from one side of the sun to the other – its year is only 88 Earth-days long. That adds up to four complete evening-morning appearances every year for sky watchers.

The craters Copland (left), named after American composer Aaron Copland, famous for his work "Appalachian Spring", and Debussy, after the French composer Claude Debussy. Copland is 129 miles in diameter. Debussy has an extensive system of rays created from material blasted from the crust upon impact. Credit: NASA/JHUAPL/Carnegie Institution of Washington

Messenger is also the name given to the space probe soon to become the first craft ever to orbit Mercury. Over the past couple years, it’s taken many pictures during two flybys of the planet. Once it settles into orbit next March, you can expect gigabytes more plus a thorough investigation of Mercury’s surface composition, magnetic field and tenuous atmosphere. Because the air is as close to nothing as an atmosphere can be, Mercury has extreme temperatures. On the sunny side, the mercury (excuse the pun) reaches 800 Fahrenheit, while during the mercurial night it plummets to 300 below.

The planet Mercury as seen by Messenger. Credit: NASA

This broiling hot/bitter cold world is a rocky body like the Earth but only 1 1/2 times the size of the moon. Its surface is covered in craters and lava-filled basins; signs of volcanism, including peculiar crater pits, abound. Mercury’s craters are named for famous deceased artists, musicians and authors. Mozart has a lovely hole of his own up there as do Debussy and Picasso.

While Mercury’s year is 88 days long, its day is double that. That means a day on the planet lasts two Mercury-years! If there was ever a challenge for calendar makers, I don’t know a better one. Now, imagine how brutal the heat must be under the sun for so long. It wouldn’t set for nearly three months. Not to mention that it’s three times larger and 11 times brighter than when seen from Earth. Messenger’s instruments are protected by a special fabric shield to keep them operating at room temperature. Definitely a place for the hard-core adventurer.

Our double planet captured from afar

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The Messenger spacecraft, on its mission to study the planet Mercury, took this photo on May 6 this year of Earth and moon against the starry blackness of space. The probe was looking for "vulcanoids" at the time. Credit: NASA/JHUAPL/CIW

This week NASA released a photo of Earth and moon in space taken by the Mercury Messenger spacecraft from a distance of 114 million miles.  This is how our “double planet” would appear to someone on Venus with a pair of binoculars. There’s nothing like the perspective afforded by a pair of distant, robotic eyes to stir our thoughts and fire our imaginations about where we fit in the scheme of things. This view reminds of looking at double stars through the telescope. The similarity is no coincidence — the moon is so large in relation to our planet, the Earth-moon system is often considered a “double planet”.

The character Spock from the planet Vulcan in the Star Trek TV series. Credit & copyright: Paramount Pictures

NASA’s reason to take the provocative photo was not connected to a higher purpose on this occasion. It was a delightful byproduct of a search for “vulcanoids”, small rocky asteroids that may be orbiting between Mercury and the sun. What, you say? NASA looking for Spock’s planet? Well, not really. No vulcanoids have been discovered yet, so they’re still hypothetical. The glare of the sun prevents easy hunting from Earth, so NASA directed the spacecraft, which is much closer and has a better view, to seek out this potential new class of solar system bodies. May it live long and provide prosperous imagery.

A scarp or fault from the shrinking moon has deformed or partially covered small ~125-foot craters (arrowed). The fault carried near-surface crustal materials up and over the craters, burying parts of their floors and rims. About half of the rim and floor of a 60-foot-diameter crater shown in the box has been lost. Since small craters only have a limited lifetime before they are destroyed by newer impacts, their deformation by the fault shows the fault to be relatively young. Credit: NASA/Goddard/Arizona State University/Smithsonian

There was more NASA news this week from the Lunar Reconnaissance Orbiter Mission (LRO) of the discovery of lobate scarps on moon. These cliffs on the lunar crust point to a moon that’s been shrinking, and not four billion years ago, but as recently as a couple hundred million years ago. The moon won’t be crunching itself into a tennis ball anytime soon since the total shrinkage is only on the order of 300 feet. Compared to its 2,160 mile diameter that’s a tiny fraction, but the consequences are evident on its surface. Even more intriguing, we’re waking up to a moon that’s not as dead as once thought. Since the Apollo missions, we’ve learned the moon has water ice embedded at many sites across its surface; now it also appears to have been geologically active in recent times.

These hills in the moon's Taurus-Littrow Valley, near the Apollo 17 landing site (arrowed), were thrust up when the moon contracted. Credit: NASA/Goddard/ASU/Smithsonian

After its formation some 4 billion years ago, the moon was mostly molten rock. As it cooled, the outer crustal rock solidified first. Later, magma beneath the crust also began to cool and solidify. As the molten materials went from a liquid to solid state, their density increased. If you take a certain volume of rock and increase its density, the amount of space or volume it occupies drops. As the moon cooled and grew denser, its internal rock slowly cooled and compressed itself into a smaller ball. The outer crust responded in the only way it could — it broke into faults and slid over itself in an attempt to form a tight fit over the ever-shrinking mantle and core. We see the results of this adjustment in the numerous lobate (rounded or lobed) scarps or cliffs hither and yon across the moon. And we know some are recent because they partially cover small, relatively fresh craters.

To learn more about the discovery, click HERE for the complete story or HERE to watch a short video.