Moon Archives

March 7, 2012December 23, 2015 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:

a11.1111231_dmh — 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!

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

March 6, 2012December 23, 2015 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.

AS11-40-5869 — 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 Boulder2 — 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.

March 5, 2012December 23, 2015 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.

a15_traverse2 — 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.

a15_tracks — 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

March 5, 2012January 24, 2021 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.

March 4, 2012December 23, 2015 by Tammy Plotner

Weekly SkyWatcher’s Forecast: March 5-11, 2012

Open Cluster Messier 50 - Credit: NOAO/AURA/NSF

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Greetings, fellow SkyWatchers! Our week begins with the dance of the planets and a gathering of asteroids. Keep watching as Mars makes its closest approach of the year – while Venus and Jupiter continue to get nearer. Celebrate the Full Worm Moon, interesting stars and beautful galaxies and clusters! Dust off those binoculars and telescopes and meet me in the backyard, because… Here’s what’s up!

Monday, March 5 – Today is the birthday of Gerardus Mercator, famed mapmaker, who started his life in 1512. Mercator’s time was a rough one for astronomy, but despite a prison sentence and the threat of torture and death for his “beliefs,” he went on to design a celestial globe in the year 1551.

Need a little celestial action of your own? Then be outside at twilight with a clear horizon to catch Mercury! joining the show with Venus and Jupiter. The swift inner planet will make a brief appearance on the western skyline just after the Sun dips below the horizon. To add to the fun, the planet Uranus is situated about 5 degrees to its southwest and asteroid Vesta is about 5 degrees south/southwest. More? Then know that asteroid Ceres is also here – just around 20 degrees to Mercury’s southeast. While the asteroids and Uranus really aren’t observable, it’s still fun to know they’re “hanging around” in the same small space!

Tonight we’ll ignore the Moon and use both Sirius and Beta Monocerotis as our guides to have a look at one fantastic galactic cluster for any optical aid – M50 (Right Ascension: 7 : 03.2 – Declination: -08 : 20). Hop about a fistwidth east-southeast of Beta, or northeast of Sirius…and be prepared!

Perhaps discovered as early as 1711 by G. D. Cassini, it was relocated by Messier in 1772 and confirmed by J. E. Bode in 1774. Containing perhaps as many as 200 members, this colorful old cluster resides almost 3000 light-years away. The light of the stars you are looking at tonight left this cluster at a time when iron was first being smelted and used in tools. The Mayan culture was just beginning to develop, while the Hebrews and Phoenicians were creating an alphabet. Do you wonder if it looked the same then as it does now? In binoculars you will see an almost heart-shaped collection of stars, while telescopes will begin to resolve out color and many fainter members – with a very notable red one in its midst. Enjoy this worthy cluster and make a note that you’ve captured another Messier object!

Now, point your telescope towards Mars! This universal date marks the closest approach of Mars and Earth (0.6737 AU = 100.78 million km). While it’s a far cry from being the much celebrated “size of the Moon”, Mars currently has an apparent diameter of 13.89″. This will make for some mighty fine observing, so be sure to check for a lot a great surface details!

Tuesday, March 6 – If you get a chance to see sunshine today, then celebrate the birthday of Joseph Fraunhofer, who was born in 1787. As a German scientist, Fraunhofer was truly a “trailblazer” in terms of modern astronomy. His field? Spectroscopy! After having served his apprenticeship as a lens and mirror maker, Fraunhofer went on to develop scientific instruments, specializing in applied optics. While designing the achromatic objective lens for the telescope, he was watching the spectrum of solar light passing through a thin slit and saw the dark lines which make up the “rainbow bar code.” Fraunhofer knew that some of these lines could be used as a wavelength standard so he began measuring. The most prominent of the lines he labeled with letters that are still in use. His skill in optics, mathematics and physics led Fraunhofer to design and build the very first diffraction grating which was capable of measuring the wavelengths of specific colors and dark lines in the solar spectrum. Did his telescope designs succeed? Of course! His work with the achromatic objective lens is the design still used in modern telescopes!

In 1986, the first of eight consecutive days of flybys began as VEGA 1 and Giotto became the very first spacecraft to reach Halley’s Comet. Tonight let’s just fly by the Moon and have a look at Theta Aurigae. 2.7 magnitude Theta is a four star system ranging in magnitudes from 2.7 to 10.7. The brightest companion – Theta B – is magnitude 7.2 and is separated from the primary by slightly more than 3 arc seconds. Remember that this is what is known as a “disparate double” and look for the two fainter members well away from the primary.

Wednesday, March 7 – Today the only child of William Herschel (the discoverer of Uranus) was born in 1792 – John Herschel. He became the first astronomer to thoroughly survey the southern hemisphere’s sky, and he was discoverer of photographic fixer. Also born on this day, but in 1837, was Henry Draper – the man who made the first photograph of a stellar spectrum.

Tonight the great Grimaldi, found in the central region of the Moon near the terminator is the best lunar feature for binoculars. If you would like to see how well you have mastered your telescopic skills, then let’s start there. About one Grimaldi length south, you’ll see a narrow black ellipse with a bright rim. This is Rocca. Go the same distance again (and a bit east) to spot a small, shallow crater with a dark floor. This is Cruger, and its lava-filled interior is very similar to another study – Billy. Now look between them. Can you see a couple of tiny dark markings? Believe it or not, this is called Mare Aestatis. It’s not even large enough to be considered a medium-sized crater, but is a mare!

Take the time tonight to have a look at Delta Monocerotis with binoculars. Although it is not a difficult double star, it is faint enough to require some optical aid. If you are using a telescope, hop to Epsilon. It’s a lovely yellow and blue system that’s perfect for small apertures.

Thursday, March 8 – On this day in 1977, the NASA airborne occultation observatory made a unique discovery – Uranus had rings!

Tonight we’ll play ring around the Full Moon. In many cultures, it is known as the “Worm Moon.” As ground temperatures begin to warm and produce a thaw in the northern hemisphere, earthworms return and encourage the return of robins. For the Indians of the far north, this was also considered the “Crow Moon.” The return of the black bird signaled the end of winter. Sometimes it has been called the “Crust Moon” because warmer temperatures melt existing snow during the day, leaving it to freeze at night. Perhaps you may have also heard it referred to as the “Sap Moon.” This marks the time of tapping maple trees to make syrup. To early American settlers, it was called the “Lenten Moon” and was considered to be the last full Moon of winter. For those of us in northern climes, let’s hope so!

Friday, March 9 – Today is the anniversary of the Sputnik 9 launch in 1966 which carried a dog named Chernushka (Blackie). Also today we recognize the birth of David Fabricius. Born in 1564, Fabricus was the discoverer of the first variable star – Mira. Tonight let’s visit with an unusual variable star as we look at Beta Canis Majoris – better known as Murzim.

Located about three fingerwidths west-southwest of Sirius, Beta is a member of a group of stars known as quasi-Cepheids – stars which have very short term and small brightness changes. First noted in 1928, Beta changes no more than .03 in magnitude, and its spectral lines will widen in cycles longer than those of its pulsations.

When you’ve had a look at Beta, hop another fingerwidth west-southwest for open cluster NGC 2204 (Right Ascension: 6 : 15.7 – Declination: -18 : 39). Chances are, this small collection of stars was discovered by Caroline Herschel in 1783, but it was added to William’s list. This challenging object is a tough call for even large binoculars and small telescopes, since only around a handful of its dim members can be resolved. To the larger scope, a small round concentration can be seen, making this Herschel study one of the more challenging. While it might not seem like it’s worth the trouble, this is one of the oldest of galactic clusters residing in the halo and has been a study for “blue straggler” stars.

Saturday, March 10 – Since this is a weekend night and we’ve a short time before Moonrise, why not break out the big telescope and do a little galaxy hopping in the region south of Beta Canis Majoris?

Our first mark will be NGC 2207 – a 12.3 magnitude pair of interacting galaxies. Located some 114 million light-years away, this pair is locked in a gravitational tug of war. The larger of the pair is NGC 2207 (Right Ascension: 6 : 16.4 – Declination: -21 : 22), and it is estimated the encounter began with the Milky Way-sized IC 2163 about 40 million years ago. Like the M81 and M82 pair, NGC 2207 will cannibalize the smaller galaxy – yet the true space between the stars is so far apart that actual collisions may never occur. While our eyes may never see as grandly as a photograph, a mid-sized telescope will make out the signature of two galactic cores with intertwining material. Enjoy this great pair!

Now shift further southeast for NGC 2223 (Right Ascension: 6 : 24.6 – Declination: -22 : 50). Slightly fainter and smaller than the previous pair, this round, low surface brightness galaxy shows a slightly brighter nucleus area and a small star caught on its southern edge. While it seems a bit more boring, it did have a supernova event as recently as 1993!

Sunday, March 11 – Tonight let’s return to Canis Major with binoculars and have a look at Omicron 1, the western-most star in the central Omicron pair. While this bright, colorful gathering of stars is not a true cluster, it is certainly an interesting group.

For larger binoculars and telescopes, hop on to Tau northeast of Delta and the open cluster NGC 2362 (Right Ascension: 7: 18.8 – Declination: -24 : 5). At a distance of about 4600 light-years, this rich little cluster contains about 40 members and is one of the youngest of all known star clusters. Many of the stars you can resolve have not even reached main sequence yet! Still gathering themselves together, it is estimated this stellar collection is less than a million years old. Its central star, Tau, is believed to be a true cluster member and one of the most luminous stars known. Put as much magnification on this one as skies will allow – it’s a beauty!

Until next week? Dreams really do come true when you keep on reaching for the stars!

If you enjoy this weekly observing column, then you’d love the fully illustrated The Night Sky Companion 2012. It’s available in both Kindle and soft cover formats!

March 2, 2012April 26, 2016 by Irene Antonenko

A ‘Melted’ Moon Makes for Bad Future Landing Sites

Very rough melts show up as red in the mini-RF data (left), but still appear smooth in the corresponding LRO wide angle camera image (right). These impact melts are located just outside Tycho crater, whose rim is visible at the top left. Image Credit Left: Carter et al. Image Credit Right: NASA/GSFC/ASU

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The miniature radio frequency (min-RF) radar instrument aboard the Lunar Reconnaissance Orbiter (LRO) is revealing some interesting things about how impact melts form around craters on the Moon. Impacts produce a crater, ejecta (pulverized rock that is thrown around the crater), and melt. A lot is known about craters and ejecta, because they form such spectacular features on the planetary surfaces. But melt is a fairly minor component of the impact process, and so is not as easily observed. Relatively little is therefore known about impact melts. Now, new data from the mini-RF radar instrument is helping to fill this knowledge gap and also offering insight into future landing spots on the Moon.

Radar is an active remote sensing system, meaning it transmits a signal and then records what bounces back, providing information about the surfaces that were encountered. If the transmitted signal hits a smooth surface, then the returned signal will have a polarization direction that is opposite to what was transmitted. But, if the surface is rough, the signal may bounce more than once, switching polarization each time, so the returned polarization will be the same as the transmitted signals. By controlling the polarization of the transmitted signal and monitoring the polarization of the returned signals, researchers can calculate the ratio of same-sense to opposite sense circular polarization, a parameter called CPR. Smooth surfaces will have a low CPR, while rough surfaces will have a high CPR.

Tycho Melt close up view with LROC data — Pressure ridges can be seen in the rough part of this melt, where the underlying fluid pushed the chilled crust and bunched it up like a table cloth. But even the smooth parts of this melt contain numerous bits of rock, which can't be seen at the scale of this LRO narrow angle camera image.
Image credit: NASA/GSFC/Arizona State University.
Click on the image to explore the LROC data from this area in greater detail.

The mini-RF transmits in the radar S band, at wavelengths of 12.6 cm, and so tells us about surface roughness at the 12.6 cm scale. For example, a sandy beach covered with sand grains that are about 1-2 mm in size (much smaller than the transmitted wavelength) will appear smooth to the Mini-RF (have low CPR values). But, a beach covered with hand-sized pebbles (about the size of the transmitted wavelength) will appear rough (have high CPR values). It is important to note that this kind of information is not currently available from our existing image data, which even at its best can only resolve things on the 50 cm scale. Furthermore, the mini-RF radar can penetrate up to 1 m below the surface, providing information about buried surfaces as well.

Working with the mini-RF data, Dr. Lynn Carter and a team of researchers from NASA Goddard Space Flight Centre, Johns Hopkins University, and the Lunar and Planetary Institute have taken a look at impact melts around a variety of craters. They found that impact melt ponds and flows tend to have CPR values that are greater than surrounding non-melt regions. This means that mini-RF data can be used to help find and identify melt materials, including buried ones! From their limited survey, Dr. Carter and her team have found that impact melt ponds and flows are more common on the Moon than was previously known. With more work, they will be able to better catalogue the number and size of melt ponds and flows around lunar craters, improving our understanding of how much melt is produced by impacts and how it travels.

Dr. Carter and her team also found that, within individual melt ponds or flows, roughness values can vary. Rough surfaces may represent bunching up of a partially cooled crust as it is pushed by the still fluid melt underneath. Such pressure ridges are seen in terrestrial lava flows. Smooth surfaces may represent melts that cooled quickly, or the last melts to arrive at a pond (and so not subject to pushing from more inflowing melt). But, even the “smooth” melts, which appear quite flat in visual imagery, tend to have very high CPR values, indicating that they are, in fact, very rough. There is probably a lot of solid rock and ejecta debris (something we can’t see in the currently available imagery) entrained in the melt material to make them so rough at this scale. To understand what this kind of surface might look like, we can consider terrestrial a’a flows (which are actually slightly less rough than lunar melts).

This work has important implications for future lunar exploration. Imagine how difficult landing on a surface as rugged at an a’a flow would be. This is why site selection scientists work very hard at identifying smooth areas for spacecraft to land. However, if surfaces that look extremely smooth in visual imagery are actually rough like an a’a flow, this can present a problem. Mini-RF data could be helpful in identifying such rough regions and eliminating them from consideration.

1-ameltedmoonm — Even "smooth" impact melt flows are rougher than this a'a flow, produced by the Kamoamoa fissure eruption in Hawaii. Image Credit: U.S. Department of Interior, U.S. Geological Survey.

Source: Initial observations of lunar impact melts and ejecta flows with the Mini-RF radar, Carter et al., Journal of Geophysical Research V117, 2012, doi:10.1029/2011JE003911.

March 2, 2012December 23, 2015 by Jason Major

Is There Life on Earth?

An Earthshine-lit moon sets over ESO's Paranal Observatory in Chile.

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It may seem like a silly question — of course there’s life on Earth — but what if we didn’t know that? What if we were looking at Earth from another vantage point, from another planet in another star system, perhaps? Would we be able to discern then if Earth were in fact teeming with life? All we’d have to go on would be the tiniest bit of light reflected off Earth, nearly lost in the intense glare of the Sun.

Researchers have found that the secret is knowing what kind of light to look for. And they discovered this with a little help from the Moon.

eso1210c — How Earthshine works. (ESO/L. Calçada)

By using Earthshine — sunlight light reflected off Earth onto the Moon — astronomers with the European Southern Observatory have been able to discern variations that correlate with identifying factors of our planet as being a happy home for life.

In observations made with ESO’s Very Large Telescope (VLT), the presence of oceans, clouds, atmospheric gases and even plants could be detected in the reflected Earthshine.

The breakthrough method was the use of spectropolarimetry, which measures polarized light reflected from Earth. Like polarized sunglasses are able to filter out reflected glare to allow you to see clearer, spectropolarimetry can focus on light reflected off a planet, allowing scientists to more clearly identify important biological signatures.

“The light from a distant exoplanet is overwhelmed by the glare of the host star, so it’s very difficult to analyze — a bit like trying to study a grain of dust beside a powerful light bulb,” said Stefano Bagnulo of the Armagh Observatory, Northern Ireland, and co-author of the study. “But the light reflected by a planet is polarized, while the light from the host star is not. So polarimetric techniques help us to pick out the faint reflected light of an exoplanet from the dazzling starlight.”

Since we have fairly reliable proof that life does in fact exist on Earth, this provides astronomers with a process and a benchmark for locating evidence of life on other distant worlds — life as we know it, anyway.

Face-to-Face With Some Shattered Lunar Boulders

The remains of crumbled boulders in Schiller crater (NASA/GSFC/Arizona State University)

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Breaking up may be hard to do, but these two lunar boulders seem to have succeeded extremely well! Imaged by the Lunar Reconnaissance Orbiter Camera (LROC) in October of 2009, this crumbled couple was recently identified by Moon Zoo team member Dr. Anthony Cook and brought to the attention of the project’s forum moderator.

The tracks left in the regolith — lunar soil — behind the boulders tell of their past rolling journeys down the slope of the elongated Schiller crater, in which they reside. Rolling boulders have been spotted before on the Moon, but what made these two split apart? And…why does that one on the lower right look so much like half a face?

Several things can cause lunar boulders to come loose and take the nearest downhill course. Meteorite impacts can shake the ground locally, giving the rocks enough of a nudge to set them on a roll. And moonquakes — the lunar version of earthquakes, as the name implies (although not due to tectonic plate shifts but rather to more mysterious internal lunar forces) — can also dislodge large boulders.

The low gravity on the Moon can make large rocks take a bounding path, evidenced by the dotted-line appearance of some of the trails.

Could all that bounding and bouncing have made the two boulders above shatter apart? Or was something else the cause of their crumbling?

Dr. Cook suggested that the boulders could have fractured before they began rolling, and then the added stress of their trip down the crater’s slope (uphill is to the right) made them break apart at the end of their trip… possibly due to further weathering and the extreme temperature variations of lunar days and nights.

Although a sound idea, Dr. Cook added, “I’m a bit puzzled though why the one on the top left has rock debris so far away from the centre. The boulder that looks like a skull rock on the bottom right has debris a lot closer to it, that could simply be explained by bits falling off as one would expect from the explanation above.”

Face-shaped Boulder — This is one rock that's not happy about its breakup!

Another idea is that the boulders were struck by meteorites, but it seems extremely improbable that two would have been hit right next to each other. Still, not impossible, especially given the geologic time spans in play.

And as far as the “skull rock” boulder is concerned… that’s a little something called pareidolia, the tendency for our brains to interpret random shapes as something particularly significant. In this case it’s a human face, one of the most popular forms of pareidolia (perhaps best known by the famous “Face on Mars”, which, as we all now know, has been since shown to be just another Martian mesa.)

It does look like a face though, and not a particularly happy one!

Find out more about rolling boulders and Schiller crater on the LROC site hosted by Arizona State University here, and take a look at the full image scan of the region yourself… you may find more of these broken-up rolling rocks!

ILIADS-LOLA-WAC-Schiller-raw-580x800 — LROC WAC global 100-meter mosaic image of the 180-km long, 70-km wide Schiller crater. Overlaid onto a laser altimetry elevation model. (NASA/GSFC/Arizona State University)

February 26, 2012December 24, 2015 by Jason Major

A Weekend Sky Show: Moon, Venus and Jupiter

Moon and Venus on Feb. 25, 2012. © Jason Major

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As promised by Nancy in a previous article on Universe Today, Venus was visible during the daylight hours this Saturday, very close to the crescent Moon. If you had clear weather you may have been able to catch a glimpse of the scene above, photographed from my location in north Texas at 6:35 p.m. local time.

Dim but visible, Venus is the “star” at lower left.

Later that same evening the show really went into full force as the Moon was illuminated by Earthshine in the western sky, with Venus ablaze and Jupiter making a bright appearance as well!

Nancy wrote on Feb. 24: If you don’t see Venus during the day, try to see Venus immediately at sunset; and right now, the Moon, Venus and Jupiter are lining up for triple conjunction at dusk, and with clear skies, it will be a great view that is almost impossible to miss!

A great view indeed! I grabbed a quick shot with my iPhone camera of the conjunction, and took the opportunity to point out the view to some neighbors as well.

396340_10150709194212498_203773717497_11239629_1124307257_n — Conjunction of the Moon, Venus and Jupiter on Feb. 25, 2012. (Jason Major)

One of the more dramatic planetary conjunctions I’ve seen, especially with the light from a fading sunset illuminating the stage.

Sometimes the best astronomy is the type you can see with your own eyes… and be able to easily share with others!

ADDED 2/26: Sunday evening brought some great views as well! Here’s a photo from around 6:45 pm on Feb. 26th:

Moon Venus and Jupiter 2-26-12 — Jupiter, the Moon and Venus on Feb. 26, 2012. © Jason Major

February 22, 2012December 24, 2015 by Irene Antonenko

If the Moon Currently has Liquid Magma, Why isn’t it Erupting?

A new look at old data has given scientists more insight into the Moon's core. Credit: Science

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Last year, scientists took another look at the seismic data collected by Apollo era experiments and discovered that the lower mantle of the Moon, the part near the core-mantle boundary, is partially molten (e.g., Apollo Data Retooled to Provide Precise Readings on Moon’s Core, Universe Today, Jan. 6, 2011). Their findings suggest that the lowest 150 km of the mantle contains anywhere from 5 to 30% liquid melt. On the Earth, this would be enough melt for it to separate from the solid, rise up, and erupt at the surface. We know that the Moon had volcanism in the past. So, why is this lunar melt not erupting at the surface today? New experimental studies on simulated lunar samples may provide the answers.

It is suspected that the current lunar magmas are too dense, in comparison to their surrounding rocks, to rise to the surface. Just like oil on water, less dense magmas are buoyant and will percolate up above the solid rock. But, if the magma is too dense, it will stay where it is, or even sink.

Motivated by this possibility, an international team of scientists, led by Mirjam van Kan Parker from the VU University Amsterdam, has been studying the character of lunar magmas. Their findings, which were recently published in the Journal Nature Geoscience, show that lunar magmas have a range of densities that are dependent on their composition.

Ms van Kan Parker and her team squeezed and heated molten samples of magma and then used X-ray absorption techniques to determine the material’s density at a range of pressures and temperatures. Their studies used simulated lunar materials, since lunar samples are considered too valuable for such destructive analysis. Their simulants modelled the composition of Apollo 15 green volcanic glasses (which have a titanium content of 0.23 weight %) and Apollo 14 black volcanic glasses (which have a titanium content of 16.4 weight %).

Samples of these simulants were subjected to pressures up to 1.7 GPa (atmospheric pressure, at the surface of the Earth, is 101 kPa, or 20,000 times less than what was achieved in these experiments). However, pressures in the lunar interior are even greater, exceeding 4.5 GPa. So, computer calculations were conducted to extrapolate from the experimental results.

Apollo 15 green glass beads. Credit: NASA

The combined work shows that, at the temperatures and pressures typically found in the lower lunar mantle, magmas with low titanium contents (Apollo 15 green glasses) have densities that are less than the surrounding solid material. This means they are buoyant, should rise to the surface, and erupt. On the other hand, magmas with high titanium contents (Apollo 14 black glasses) were found to have densities that are about equal to or greater than their surrounding solid material. These would not be expected to rise and erupt.

Since the Moon has no active volcanic activity, the melt currently located at the bottom of the lunar mantle must have a high density. And, Ms van Kan Parker’s results suggest that this melt should be made of high titanium magmas, like those that formed the Apollo 14 black glasses.

This finding is significant, because high titanium magmas are thought to have formed from titanium-rich source rocks. These rocks represent the dregs that were left at the base of the lunar crust, after all the buoyant plagioclase minerals (which make up the crust) had been squeezed upwards in a global magma ocean. Being dense, these titanium-rich rocks would have quickly sunk to the core-mantle boundary in an overturn event. Such an overturn even had been postulated over 15 years ago. Now, these exciting new results provide experimental support for this model.

These dense, titanium-rich rocks are also expected to have a lot of radioactive elements, which tend to get left behind when other elements are preferentially taken up by mineral crystals. The resulting radiogenic heat from the decay of these elements could explain why parts of the lower lunar mantle are still hot enough to be molten. Ms van Kan Parker and her team further speculate that this radiogenic heat could also be helping to keep the lunar core partially melted even today!

Sources:
X-Rays Illuminate the Interior of the Moon, Science Daily, Feb. 19, 2012.
Neutral buoyancy of titanium-rich melts in the deep lunar interior, van Kan Parker et al. Nature Geoscience, Feb. 19, 2012, doi:10.1038/NGEO1402.