Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast – March 19-25, 2012

NGC 2539 - Credit: Palomar Observatory Courtesy of Caltech

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Greetings, fellow SkyWatchers! The week starts off with new Moon and the perfect opportunity to do a Messier Marathon. The planets continue to dazzle as we not only celebrate the Vernal Equinox, but the March Geminid meteor shower as well! If that doesn’t get your pulsar racing – nothing will. It’s time to get out your binoculars and telescopes and meet me in the backyard!

Monday, March 19 – Right now the Moon is between the Earth and the Sun, and you know what that means…New Moon! Tonight we’ll start in northern Puppis and collect three more Herschel studies as we begin at Alpha Monoceros and drop about four fingerwidths southeast to 19 Puppis.

NGC 2539 (Right Ascension: 8 : 10.7 – Declination: -12 : 50) averages around 6th magnitude and is a great catch for binoculars as an elongated hazy patch with 19 Puppis on the south side. Telescopes will begin resolution on its 65 compressed members, as well as split 19 Puppis – a wide triple. Shift about 5 degrees southwest and you find NGC 2479 (Right Ascension: 7 : 55.1 – Declination: -17 : 43) directly between two finderscope stars. At magnitude 9.6 it is telescopic only and will show as a smallish area of faint stars at low power. Head another degree or so southeast and you’ll encounter NGC 2509 (Right Ascension: 8 : 00.7 – Declination: -19 : 04) – a fairly large collection of around 40 stars that can be spotted in binoculars and small telescopes.

Tuesday, March 20 – Today is Vernal Equinox, one of the two times of the year that day and night become equal in length. From this point forward, the days will become longer – and our astronomy nights shorter! To the ancients, this was a time a renewal and planting – led by the goddess Eostre. As legend has it, she saved a bird whose wings were frozen from the winter’s cold, turning it into a hare which could also lay eggs. What a way to usher in the northern spring!

With the Moon still out of the picture, let’s finish our study of the Herschel objects in Puppis. Only three remain, and we’ll begin by dropping south-southeast of Rho and center the finder on a small collection of stars to locate NGC 2489 (Right Ascension: 7 : 56.2 – Declination: -30 : 04). At magnitude 7, this bright collection is worthy of binoculars, but only the small patch of stars in the center is the cluster. Under aperture and magnification you’ll find it to be a loose collection of around two dozen stars formed in interesting chains.

The next are a north-south oriented pair around 4 degrees due east of NGC 2489. You’ll find the northernmost – NGC 2571 (Right Ascension: 8 : 18.9 – Declination: -29 : 44) – at the northeast corner of a small finderscope or binocular triangle of faint stars. At magnitude 7, it will show as a fairly bright hazy spot with a few stars beginning to resolve with around 30 mixed magnitude members revealed to aperture. Less than a degree south is NGC 2567 (Right Ascension: 8 : 18.6 – Declination: -30 : 38). At around a half magnitude less in brightness, this rich open cluster has around 50 members to offer the larger telescope, which are arranged in loops and chains.

Congratulations on completing these challenging objects!

Are you up for another challenge? Then test your ability to judge magnitude as Mars has now dimmed to approximately -1.0. Does it look slightly different in size and brightness than it did a week or so ago? Keep watching!

Wednesday, March 21 – Take your telescopes or binoculars out tonight to look just north of Xi Puppis for a celebration of starlight known as M93 (Right Ascension: 7 : 44.6 – Declination: -23 : 52). Discovered in March of 1781 by Charles Messier, this bright open cluster is a rich concentration of various magnitudes that will simply explode in sprays of stellar fireworks in the eyepiece of a large telescope. Spanning 18 light-years of space and residing more than 3400 light-years away, it contains not only blue giants, but lovely golds as well. Jewels in the night…

Thursday, March 22 – Today in 1799 Friedrich Argelander was born. He was a compiler of star catalogues, studied variable stars and created the first international astronomical organization.

Tonight let’s celebrate no Moon and have a look at an object from an alternative catalog that was written by Lacaille, and which is about two fingerwidths south of Eta Canis Majoris.

Also known as Collinder 140, Lacaille’s 1751 catalog II.2 “nebulous star cluster” is a real beauty for binoculars and very low power in telescopes. More than 50% larger than the Full Moon, it contains around 30 stars and may be as far as 1000 light-years away. When re-cataloged by Collinder in 1931, its age was determined to be around 22 million years. While Lacaille noted it as nebulous, he was using a 15mm aperture reflector, and it is doubtful that he was able to fully resolve this splendid object. For telescope users, be sure to look for easy double Dunlop 47 in the same field.

Now, kick back and enjoy a spring evening with two meteor showers. In the northern hemisphere, look for the Camelopardalids. They have no definite peak, and a screaming fall rate of only one per hour. While that’s not much, at least they are the slowest meteors – entering our atmosphere at speeds of only 7 kilometers per second!

Far more interesting to both hemispheres will be the March Geminids which peak tonight. They were first discovered and recorded in 1973 and then confirmed in 1975. With a much faster fall rate of about 40 per hour, these slower than normal meteors will be fun to watch! When you see a bright streak, trace it back to its point of origin. Did you see a Camelopardalid, or a March Geminid?

Friday, March 23 – Today in 1840, the first photograph of the Moon was taken. The daguerreotype was exposed by American astronomer and medical doctor J. W. Draper. Draper’s fascination with chemical responses to light also led him to another first – a photo of the Orion Nebula.

Our target for tonight is an object that’s better suited for southern declinations – NGC 2451 (Right Ascension: 7 : 45.4 – Declination: -37 : 58). As both a Caldwell object (Collinder 161) and a southern skies binocular challenge, this colorful 2.8 magnitude cluster was probably discovered by Hodierna. Consisting of about 40 stars, its age is believed to be around 36 million years. It is very close to us at a distance of only 850 light-years. Take the time to closely study this object – for it is believed that due to the thinness of the galactic disk in this region, we are seeing two clusters superimposed on each other.

With the Moon out of the picture early, why not get caught up in a galaxy cluster study – Abell 426. Located just 2 degrees east of Algol in Perseus, this group of 233 galaxies spread over a region of several degrees of sky is easy enough to find – but difficult to observe. Spotting Abell galaxies in Perseus can be tough in smaller instruments, but those with large aperture scopes will find it worthy of time and attention.

At magnitude 11.6, NGC 1275 (Right Ascension: 3 : 19.8 – Declination: +41 : 31) is the brightest of the group and lies physically near the core of the cluster. Glimpsed in scopes as small as 150 mm aperture, NGC 1275 is a strong radio source and an active site of rapid star formation. Images of the galaxy show a strange blend of a perfect spiral being shattered by mottled turbulence. For this reason NGC 1275 is thought to be two galaxies in collision. Depending on seeing conditions and aperture, galaxy cluster Abell 426 may reveal anywhere from 10 to 24 small galaxies as faint as magnitude 15. The core of the cluster is more than 200 million light-years away, so it’s an achievement to spot even a few!

Saturday, March 24 – Today is the birthday of Walter Baade. Born in 1893, Baade was the first to resolve the Andromeda galaxy’s individual stars using the Hooker telescope during World War II blackout times, and he also developed the concept of stellar populations. He was the first to realize that there were two types of Cepheid variables, thereby refining the cosmic distance scale. He is also well known for discovering an area towards our galactic center which is relatively free of dust, now known as “Baade’s Window.”

Just after sunset, you really need to take a look out your western window for a really beautiful bit of scenery. As the sky darkens, look for the very tender crescent Moon lit with “Earthshine”. Above it you will see bright Jupiter. Above that you will see blazing Venus. And, if that’s not enough, just a little higher will bring you to the Pleiades! What a great way to start a weekend evening!

With the Moon so near the horizon, we have only a short time to view its features. Tonight let’s start with a central feature – Langrenus – and continue further south for crater Vendelinus. Spanning 92 by 100 miles and dropping 14,700 feet below the lunar surface, Vendelinus displays a partially dark floor with a west wall crest catching the brilliant light of an early sunrise. Notice also that its northeast wall is broken by a younger crater – Lame. Head’s up! It’s an Astronomical League challenge.

Once the Moon has set, revisit M46 in Puppis – along with its mysterious planetary nebula NGC 2438. Follow up with a visit to neighboring open cluster M47 – two degrees west-northwest. M47 may actually seem quite familiar to you already. Did you possibly encounter it when originally looking for M46? If so, then it’s also possible that you met up with 6.7 magnitude open cluster NGC 2423 (Right Ascension: 7 : 37.1 – Declination: -13 : 52), about a degree northeast of M47 and even dimmer 7.9 magnitude NGC 2414 (Right Ascension: 7 : 33.3 – Declination: -15 : 27 ) as well. That’s four open clusters and a planetary nebula all within four square arc-minutes of sky. That makes this a cluster of clusters!

Let’s return to study M47. Observers with binoculars or using a finderscope will notice how much brighter, and fewer, the stars of M47 are when compared to M46. This 12 light-year diameter compact cluster is only 1600 light-years away. Even as close as it is, not more than 50 member stars have been identified. M47 has about one tenth the stellar population of larger, denser, and three times more distant, M46.

Of historical interest, M47 was “discovered” three times: first by Giovanni Batista Hodierna in the mid-17th century, then by Charles Messier some 17 years later, and finally by William Herschel 14 years after that. How is it possible that such a bright and well-placed cluster needed “re-discovery?” Hodierna’s book of observations didn’t surface until 1984, and Messier gave the cluster’s declination the wrong sign, making its identification an enigma to later observers – because no such cluster could be found where Messier said it was!

Sunday, March 25 – Today in 1655, Titan – Saturn’s largest satellite – was discovered by Christian Huygens. He also discovered Saturn’s ring system during this same year. 350 years later, the probe named for Huygens stunned the world as it reached Titan and sent back information on this distant world. How about if we visit Saturn? You’ll find the creamy yellow planet located about a fistwidth northwest of bright, white Spica! Even a small telescope will reveal Titan, but remember… it orbits well outside the ring plane, so don’t mistake it for a background star! While you’re there, look closely around the ring edges for the smaller moons. A 4.5” telescope can easily show you three of them. How about the shadow the rings on the planet’s surface? Or how about the shadow of the planet on the rings? Is the Cassini division visible? If you have a larger telescope, look for other ring divisions as well. All are part and parcel of viewing incredible Saturn!

If you missed yesterday evening’s scenic line-up, don’t despair. Just after the Sun sets tonight – and above the western horizon – you’ll find the young Moon very closely paired with Jupiter. Keep traveling eastward (up) and you’ll encounter Venus. Continue east and the next stop is M45. Watch in the days ahead as the Moon sweeps by, continuing to provide us with a show! Need more? Then check out Leo and Mars! You’ll find a great triangulation of Regulus to the west, Mars to the east and Algieba to the north. If you didn’t know better, you’d almost swear the Lion swallowed the red planet.

Tonight let’s return to our previous studies of the Moon and revisit a challenging crater. Further south than Vendelinus, look for another large, mountain-walled plain named Furnerius, located not too far from the terminator. Although it has no central peak, its walls have been broken numerous times by many smaller impacts. Look at a rather large one just north of central on the crater floor. If skies are stable, power up and search for a rima extending from the northern edge. Keep in mind as you observe that our own Earth has been pummeled just as badly as its satellite.

On this day in 1951, 21 cm wavelength radiation from atomic hydrogen in the Milky Way was first detected. 1420 MHz H I studies continue to form the basis of a major part of modern radio astronomy. If you would like to have a look at a source of radio waves known as a pulsar, then aim your binoculars slightly more than a fistwidth east of bright Procyon. The first two bright stars you encounter will belong to the constellation of Hydrus and you will find pulsar CP0 834 just above the northernmost – Delta.

Unitl next week? May all your journeys be at light speed!

Posted on by Ray Sanders

Solving the Puzzle of Apollo 12’s Mysterious Magnetic Moon Rocks

The moon's largest grouping of magnetic anomalies, on the left, is near the northern rim of the South Pole-Aitken basin, which scientists believe was created by the impact of a massive asteroid about 4.5 billion years ago. Image Credit: NASA/LRO/Science/AAAS

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Ever since their discovery by the Apollo 12 crew, scientists have been puzzled by strongly magnetized rocks found on the Moon. Most Moon rocks that were brought back by the Apollo missions have very little iron, and therefore lack the ability to be strongly magnetized. At first, the magnetic oddities didn’t appear to be related to any lunar geology such as craters or lava flows. Over time, additional lunar missions have provided more data showing that only some portions of the Moon’s crust have magnetic fields. A team of scientists now theorize that the magnetized “patches” on the lunar surface may be the remains of an asteroid that crashed into the Moon shortly after its formation nearly 4.5 billion years ago. The impact crater, known as the South Pole-Aitken basin is one of the largest known in our Solar System.

Mark Wieczorek (Paris Institute for Global Physics), describes the South Pole-Aitken basin as, “this huge, whopping crater that’s roughly half the size of the U.S,” and says it may hold the answers to the mystery of the Apollo 12 rocks.

The Apollo 12 landing site as seen by LRO. Credit: NASA/GSFC/Arizona State University

Studies of the basin show that it is elliptical which suggests the impact was by a large object that hit at an oblique angle. Wieczorek speculates that the impactor was 10% to 30% iron by weight and about 100 times more magnetic than the lunar regolith. Interestingly enough, the theorized impact angle would have flung debris from the object in a pattern very similar to the observed magnetic anomalies. The material could have been magnetized as it cooled by a magnetic field that may have existed early in our Moon’s history.

Wieczorek and his team set out to test their theories with computer simulations of different types of impacts. The research led to a scenario where an object struck the Moon at about a 45 degree angle with a velocity of 15 kilometers per second. The team’s best impact model was described as normal by Wieczorek who stated, “We don’t require improbable conditions.”

Now the team needs to address one other question: How and when did a magnetic field develop on the Moon?

Wieczorek offers a simple solution: Go back to the moon and collect samples.

Source: NASA Lunar Science Institute

Posted on by Jason Major

Go On a Grand Tour of the Moon

Take a "peak" into Tycho Crater!


To honor the Lunar Reconnaissance Orbiter’s amazing 1,000 days in science-filled orbit, the LRO team at Goddard Space Flight Center has created a wonderful video tour of the lunar surface like you’ve never seen it before!

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“Tour of the Moon” takes viewers to several breathtaking locations on the Moon, including Orientale Basin, Shackleton crater, Tycho crater, Aristarchus Plateau, Mare Serenitatis, Compton-Belkovich volcano, Tsiolkovsky crater and more. The fully narrated video is above, and clips from each of the stops on the tour are available in many other formats here.

In addition, another video highlighting the dramatic evolution of the Moon was released today… you can view the full narrated version in 2D and stereoscopic 3D here.

iPad owners can also download the NASA Viz app to see this and other NASA stories, updated twice a week.

Credit: NASA Goddard Space Flight Center

Posted on by Jason Major

Revisiting The First Rover

LROC image of Lunokhod 1 (NASA/GSFC/ASU)

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Before there was Curiosity, before Spirit, and Opportunity, and even long before Sojourner, there was Lunokhod 1, the Soviet Union’s lunar rover that explored Mare Imbrium from November of 1970 to September the following year. It was a curious-looking machine, a steampunk fantasy reminiscent of something out of a Jules Verne novel. But until the Mars Exploration Rovers nearly 40 years later, Lunokhod 1 held the record for the longest-operating robotic rover on the surface of another world.

These images from the Lunar Reconnaissance Orbiter Camera (LROC) are the most detailed yet of the now-silent Soviet rover and its lander, Luna 17.

The lander, Luna 17, was launched from Earth orbit on November 10, 1970, and entered lunar orbit five days later. It successfully soft-landed in Mare Imbrium on November 17 and deployed the Lunokhod (“moon walker” in Russian) rover, which was powered by batteries that were recharged via solar power during the lunar day.

Luna 17 and Lunokhod 1's tracks. (NASA/GSFC/ASU)

The 5600 kg (12,345 lb.) Lunokhod 1 boasted a suite of scientific tools for exploring the lunar surface. It was equipped with a cone-shaped antenna, a highly directional helical antenna, four television cameras, and special extendable devices to impact the lunar soil for soil density and mechanical property tests.

An x-ray spectrometer, an x-ray telescope, cosmic-ray detectors, and a laser device were also included.

The super-steampunk Lunokhod 1 rover. (NASA/GSFC)

Operating for nearly 300 days — almost four times longer than planned — by the time it officially ceased operations in October 1971 Lunokhod 1 had traveled 10,540 meters and had transmitted more than 20,000 images, and had conducted over 500 lunar soil tests.

The images above were obtained during a low-altitude pass by LRO, which came within 33 km (20.5 miles) of the lunar surface.

Via the LROC site by Arizona State University.

Luna 17 seen from Lunokhod 1
Posted on by Nancy Atkinson

Watch 4.5 Billion Years of the Moon’s Evolution in 2.5 Minutes

Over time, our Moon has changed from a glowing ball of magma, to being pummeled and pounded by impacts, to evolving to the current constant companion we see in the sky each night. With the Lunar Reconnaissance Orbiter, we’re getting a better understanding of just what has taken place on the Moon over its history. Thanks to the folks at Goddard’s Scientific Visualization Studio, this video provides a look at 4.5 billion years of the Moon in just two and a half minutes.

Posted on by Ken Kremer

Twin NASA Science Probes Start Lunar Gravity Mapping

Twin GRAIL Lunar Probes Ebb and Flow Start Lunar Gravity Science. GRAIL probes use precision formation-flying technique to map Lunar Gravity, as depicted in this artist's rendering. Radio signals traveling between the two spacecraft provide scientists with exact measurements which will result in the most accurate gravity map of the moon ever made. Credit: NASA/JPL-Caltech

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NASA’s twin lunar orbiting GRAIL (Gravity Recovery and Interior Laboratory) spacecraft christened Ebb and Flow have kicked off their science collection phase aimed at precisely mapping our Moon’s gravity field, interior composition and evolution, the science team informed Universe Today.

“GRAIL’s science mapping phase officially began Tuesday (March 6) and we are collecting science data,” said Maria Zuber, GRAIL principal investigator of the Massachusetts Institute of Technology in Cambridge, to Universe Today.

“It is impossible to overstate how thrilled and excited we are !”

“The data appear to be of excellent quality,” Zuber told me.

GRAIL’s goal is to provide researchers with a better understanding of how the Moon, Earth and other rocky planets in the solar system formed and evolved over its 4.5 billion years of history.

NASA’s Dawn spacecraft is currently mapping the gravity field of Asteroid Vesta in high resolution from low orbit.

Despite more than 100 missions to the Moon there is still a lot we don’t know about the Moon says Zuber, like why the near side is flooded with magma and smooth and the back side is rough, not smooth and completely different.

South pole of the far side of the moon as seen as seen in this 1st image from the MoonKAM camera aboard GRAIL mission’s Ebb spacecraft. Credit: NASA/JPL-Caltech

The formation-flying spacecraft will make detailed science measurements from lunar orbit with unparalleled precision to within 1 micron – the width of a human red blood cell – by transmitting Ka-band radio signals between each other and Earth to help unlock the mysteries of the Moon’s deep interior.

“We’ve worked on calibrating the alignment of the Ka-band antennae to establish the optimal alignment. We’ve verified the data pipeline and are spending a lot of time working with the raw data to make sure that we understand its intricacies,” Zuber explained.

The washing-machine sized probes have been flying in tandem around the Moon since entering lunar orbit in back to back maneuvers over the New Year’s weekend. Engineers have spent the past two months navigating the spaceship duo into lower, near-polar and near-circular orbits with an average altitude of 34 miles (55 kilometers), that are optimized for science data collection, and simultaneously checking out the spacecraft systems.

GRAIL A and B gravity mappers rocket to the moon atop a Delta II Heavy booster on Sept. 10 from Cape Canaveral, Florida. View to Space Launch Complex 17 gantry from Press Site 1. Credit: Ken Kremer

Ebb and Flow were launched to the Moon on September 10, 2011 aboard a Delta II rocket from Cape Canaveral, Florida and took a circuitous 3.5 month low energy path to the moon to minimize the overall costs. The Apollo astronauts reached the Moon in just 3 days.

I asked Zuber to describe the team’s activities putting the mirror image probes to work peering to the central core of our nearest neighbor in unprecedented detail.

“Last Wednesday (Feb. 29) we achieved the science orbit and on Thursday (March 1) we turned the spacecraft to ‘orbiter point’ configuration to test the instrument and to monitor temperatures and power.”

“When we turned on the instrument we established the satellite-to-satellite radio link immediately. All vital signs were nominal so we left the spacecraft in orbiter point configuration and have been collecting science data since then. At the same time, we’ve continued performing calibrations and monitoring spacecraft and instrument performance, such as temperatures, power, currents, voltages, etc., and all is well,” said Zuber.

Measurements gathered over the next 84 days will be used to create high-resolution maps of the Moon’s near side and far side gravitational fields that are 100 to 1000 times more precise than ever before and that will enable researchers to deduce the internal structure and composition of our nearest neighbor from the outer surface crust down to the deep hidden core.

As one satellite follows the other, in the same orbit, they will perform high precision range-rate measurements to precisely measure the changing distance between each other. As they fly over areas of greater and lesser gravity caused by visible features such as mountains, craters and masses hidden beneath the lunar surface, the distance between the two spacecraft will change slightly.

“GRAIL is great. Everything is in place to get science data now,” said Sami Asmar, a GRAIL co-investigator from NASA’s Jet Propulsion Lab in Pasadena, Calif. “Soon we’ll get a very high resolution and global gravity map of the Moon.”

The data collected will be translated into gravitational field maps of the Moon that will help unravel information about the makeup of the Moon’s core and interior composition.

GRAIL will gather three complete gravity maps over the three month mission which is expected to conclude around May 29. If the probes survive a solar eclipse in June and if NASA funding is available, then they may get a bonus 3 month extended mission.

Ebb and Flow - New Names for the GRAIL Twins in Lunar Orbit
4th Grade Students from Montana (inset) win NASA’s contest to rename the GRAIL A and GRAIL B spacecraft. Artist concept of twin GRAIL spacecraft flying in tandem orbits around the Moon to measure its gravity field Credit: NASA/JPL Montage: Ken Kremer

NASA sponsored a nation-wide student contest for America’s Youth to choose new names for the twin probes originally known as GRAIL A and GRAIL B. 4th graders from the Emily Dickinson Elementary School in Bozeman, Montana submitted the winning entries -Ebb and Flow. The new names won because they astutely describe the probes movements in orbit to collect the science data.

The GRAIL twins are also equipped with a very special camera dubbed MoonKAM (Moon Knowledge Acquired by Middle school students) whose purpose is to inspire kids to study science.

By having their names selected, the 4th graders from Emily Dickinson Elementary have also won the prize to choose the first target on the Moon to photograph with the MoonKAM cameras, which are managed by Dr Sally Ride, America’s first female astronaut.

“MoonKAMs on both Ebb and Flow were turned on Monday, March 5, and all appears well, Zuber said. “The Bozeman 4th graders will have the opportunity to target the first images a week after our science operations begin.”

Posted on by Jason Major

Best Views Yet of Historic Apollo Landing Sites

LROC image of the Apollo 11 landing site, acquired Nov. 5, 2011 (NASA/GSFC/Arizona State University)

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Just over 42 years after Neil and Buzz became the first humans to experience the “stark beauty” of the lunar surface, the Lunar Reconnaissance Orbiter captured the remnants of their visit in the image above, acquired Nov. 5, 2011 from an altitude of only 15 miles (24 km). This is the highest-resolution view yet of the Apollo 11 landing site!

The Lunar Module’s descent stage, a seismic experiment monitor, a laser ranging reflector (LRRR, still used today to measure distances between Earth and the Moon) and its cover, and a camera can be discerned in the overhead image… as well as the darker trails of the astronauts’ bootprints, including Armstrong’s jaunt eastward to the rim of Little West crater.

The crater was the furthest the Apollo astronauts ventured; in fact, if you take the total area Neil and Buzz explored it would easily fit within the infield of a baseball diamond!

Neil Armstrong’s visit to the crater’s edge was an unplanned excursion. He used the vantage point to capture a panoramic image of the historic site:

Panorama of the Apollo 11 site from Little West crater. (NASA)

“Isn’t that something! Magnificent sight out here.” Armstrong had stated before he was joined by Aldrin on the lunar surface. “It has a stark beauty all its own. It’s like much of the high desert of the United States. It’s different, but it’s very pretty out here.”

Previously the LROC captured the Apollo 15 landing site, which included the tracks of the lunar rover — as well as the rover itself! And, just yesterday, the LROC site operated by Arizona State University featured the latest similarly high-resolution view of the Apollo 12 site. This location has the honor of being two landing sites in one: Apollo 12 and the Surveyor 3 spacecraft, which had landed on April 20, 1967 – two and a half years earlier!

The Apollo 12 landing site in Oceanus Procellarum. (NASA/GSFC/Arizona State University)

Even though the US flag planted by Apollo 12 astronauts Pete Conrad and Alan Bean isn’t itself visible, the shadow cast by it is.

Apollo 12 was the only mission to successfully visit the site of a previous spacecraft’s landing, and it also saw the placement of the first Apollo Lunar Surface Experiments Package (ALSEP), which included a seismometer and various instruments to measure the lunar environment.

Read more about this image on the LROC page here, and check out the video tour below of the Apollo 12 site.

Images and video courtesy of NASA/GSFC/Arizona State University

Posted on by Jason Major

Why Are Lunar Shadows So Dark?

A lunar boulder peeks out into the sunlight. (NASA/GSFC/Arizona State University)

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A lunar boulder catches the last edge of the setting sunlight in this image from the Lunar Reconnaissance Orbiter Camera. The boulders litter the floor of an unnamed 3.5 km wide (2.17 mile wide) crater located within the much larger crater Lobachevskiy. The smaller crater’s rim casts its shadow along the left side of the image, and raises the question: why are shadows on the Moon so dark?

On Earth, air scatters light and allows objects not in direct sunlight to be still well-lit. This is an effect called Rayleigh scattering, named for the British Nobel-winning physicist Lord Rayleigh (John William Strutt.) Rayleigh scattering is the reason why the sky is blue, and (for the most part) why you can still read a magazine perfectly well under an umbrella at the beach.

On the Moon there is no air, no Rayleigh scattering. So shadows are very dark and, where sunlight hits, very bright. Shadowed areas are dramatically murky, like in the LROC image above, yet there’s still some light bouncing around in there — this is due to reflected light from the lunar surface itself.

Buzz was well-lit by reflected light, even in Eagle's shadow. (NASA/Apollo Image Archive)

Lunar regolith is composed of fine, angular particles of very reflective dust. It tends to reflect light directly back at the source, and will illuminate objects within shadows as well — as seen in Apollo mission photographs. Astronauts within the shadow of the landing modules were still visible, and their suits were well illuminated by reflected light from the lunar surface. Some people have used this as “proof” that the landings were actually filmed on a sound stage under artificial lights, but in reality it’s all due to reflected light.

Here’s a great run-though of the lunar landing photos and how lighting on the Moon works.

So even though air isn’t scattering the sunlight on the Moon, there’s still enough reflection to sneak light into the shadows… but not much. It gets dark — and quickly cold — in there!

And if you’re one of those who likes to get a better look into the shadows, here’s the same image above with the dark areas brightened enough to see details:

Shadow world revealed! (NASA/GSFC/Arizona State University/J. Major)

Some interesting boulder trails in there!

See this image on Arizona State University’s LROC news page here, and zoom into the full NAC scan here.

Posted on by Nancy Atkinson

Look, It’s a Moon Buggy! LRO’s Best Look Ever at the Apollo 15 Landing Site

Apollo 15 landing site imaged from an altitude of 25 km, allowing the highest resolution view from orbit. The Lunar Roving Vehicle (LRV) is parked to the far right, and the Lunar Module descent stage is in the center, LRV tracks indicated with arrows. Credit: NASA/GSFC/Arizona State University.

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A new image from the Lunar Reconnaissance Orbiter’s Narrow Angle Camera provides the most detailed orbital look ever at the Apollo 15 landing site on the Moon. The image of the Hadley plains shows the hardware left behind by astronauts Dave Scott and Jim Irwin and the tracks from the lunar rover.

“We like to look at the Apollo landing site images because it’s fun,” said LRO principal investigator Mark Robinson said at a briefing last year on LRO images. And these latest images are really fun, as look how clearly the lunar lander and the ‘Moon buggy’ show up! (Click images for larger views.) Additionally, we can basically follow all the movements of the rover and the astronauts during their 67-hour stay on the Moon’s surface in August of 1971.

See below for a traverse map of their rover travels.

Apollo 15 traverse routes sketched on an image from LRO. Visible is Hadley Rille. Credit: NASA/GSFC/Arizona State University.

Apollo 15 was the first mission to have the Lunar Rover, which allowed the astronauts to traverse far from the Lunar Module and explore much more local geology than the astronauts on the previous missions (Apollo 11, 12, 14).

“Not only did the LRV allow the astronauts to move from place-to-place at a lively rate of eight to sixteen kilometers per hour (five to ten miles per hour), but the LRV also allowed brief periods of rest that in turn helped to conserve oxygen,” said Robinson on the LROC website.

The goals of Apollo 15 were to sample the basalts in the region, search for ancient crustal rocks and explore a lunar rille for the first time – the long, narrow depressions in the lunar surface that resemble channels. Additionally, Scott and Irwin deployed the third Apollo Lunar Surface Experiments Package (ALSEP), which consisted of several experiments that were powered by a Radioisotope Thermoelectric Generator (RTG) and sent back valuable scientific data to the Earth for over six years after the astronauts left.

Details showing Apollo 15 LRV tracks, see traverse map above for locations. Credit: NASA/GSFC/Arizona State University.

Robinson and his team can figure out the details of what pieces of equipment are in each location by comparing what they see in orbital images to images taken from the surface by the astronauts.

One of the most commonly asked questions is if the flags left on the Moon are still visible.

“All we can really see is the spots where the flag was planted because the astronauts tramped down the regolith,” Robinson said last year. “I’m not sure if the flags still exist, given the extreme heat and cold cycle and the harsh UV environment. The flags were made of nylon, and personally I would be surprised if anything was left of them since it has been over 40 years since they were left on the Moon and the flags we have here on Earth fade after they are left outside for one summer. If the flags are still there they are probably in pretty rough shape.”

For two one-month periods last year (2011), the LRO orbit was lowered such that overflights of the Apollo sites were only 25 to 30 kilometers, rather than the usual 50 kilometers. These low passes resulted in NAC pixel scales near 25 centimeters, Robinson said. “LRO has a ground speed of a bit over 1600 meters (5249 feet) per second, and the shortest NAC exposure time is 0.34 millseconds, so images taken from this low altitude are smeared down track a bit. However, the smear is hardly noticeable and features at the Apollo sites definitely come into sharper focus. In this new low-altitude NAC image of the LRV, tracks are visible about half of the time, usually when the tracks are at an angle to the Sun direction, rather than parallel,” he said.

You can see the close-up images of the Apollo 12, 14 and 17 at a previous article on Universe Today.

Source: LROC website

Posted on by Jason Major

Pick Up Some Good Librations With This Stunning Moon Video

A waning gibbous moon. Rises after sunset, high in the sky after midnight, visible to the southwest after sunrise. (NASA/GSFC)


As the Moon orbits Earth, it rotates at such a rate as to keep the same face aiming our way… but not exactly the same face, as shown in this excellent video from NASA’s Goddard Space Flight Center (lovingly annotated by the Bad Astronomer himself, Dr. Phil Plait.)

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The Moon has a slight wobble to its axial rotation, and over the course of a month its orientation shifts slightly — an effect called libration. Think of it like a top or gyroscope spinning on a table; it doesn’t spin perfectly vertically, but rather sways a bit while it spins. Libration is that sway.

In addition to that movement, the Moon also moves closer to and further from the Earth over the course of a year due to its elliptical orbit. This makes it appear to change size slightly.

Except for the Moon’s phases, such effects aren’t immediately obvious from one night to the next. But when assembled into a high-resolution video using images and laser altimetry data maps from the Lunar Reconnaissance Orbiter, the monthly motions of the Moon become incredibly clear!

This video shows all the views of the Moon for the entire year of 2012.

Thanks to Phil Plait of Discover Magazine’s Bad Astronomy blog for adding the music and descriptions to the GSFC’s amazing video. What a marvelous night for a Moon dance!

See the current Moon phase and the original video on the Goddard Space Flight Center’s “Dial-A-Moon” page here.

Video: NASA/Goddard Space Flight Center Visualization Studio. Notations by Phil Plait. Music by Kevin MacLeod/incomptech.com.