Total Lunar Eclipse 08-28-07. Credit: Conrad Jung

December 10, 2011 marks your last chance to see a total lunar eclipse—one of the most breathtaking celestial events that you can witness with your unaided eye–until 2014. For us on the West Coast, the drama of the Moon's occlusion will play out in the early morning hours of Saturday—weather permitting, as always.

A total lunar eclipse occurs when the Moon passes through the long shadow the Earth casts into space. We see a partial lunar eclipse when only part of the Moon grazes the Earth's shadow and a total eclipse when it is completely engulfed in darkness.

The overall eclipse begins at about 3:33 AM on the morning of December 10, when the Moon first touches Earth's penumbra, or "half shadow" (the region of space where only some of the Sun's light is blocked by the Earth). At the beginning, you might be challenged to notice anything different about the Full Moon, unless you're looking for something—in which case you might start to notice a slight darkening at one edge of the Moon's disk.

By 4:46 AM, the real show begins: the Moon will begin to enter the umbra, the Earth's full shadow, in which no direct sunlight shines. Now, a very noticeable "bite" will be taken out of the Full Moon—as if some great celestial creature is nibbling it at the edge. (To the Chinese, this animal was thought of as a dog or a dragon; to the Maya, often a jaguar; and if you mix your myths well, you might imagine those creatures eating green cheese….)

Finally, at 6:06 AM, with the Moon low near the western horizon, it will become completely engulfed in the umbra and will likely turn a dim, coppery, orange, or possibly even reddish color—like a shiny copper penny, or a molding orange. I hope that image doesn't spoil the experience for you….

This is totality, when the entire disk of the Moon is within the umbra. From Earth, the Full Moon goes very dark during totality. From the Moon, if you were so lucky to be there during totality, the Earth (in its "New" phase as seen from Luna) would be a black disk surrounded by a ring of red or orange light—from the Moon's perspective, a total solar eclipse.

Why is the Moon lit at all during totality if it's supposed to be in the umbra where no direct sunlight shines? And why orange and red tones?

The answer is in Earth's atmosphere, which simultaneously bends, or "scatters," the sunlight that grazes by the edges, and filters the colors of the sunlight to favor the redder wavelengths passing through. If you've seen sunlight shining around the edges of a cloud, making that "silver lining" and shedding light into the cloud's shadow, then you may have an idea how the sunlight is scattered around the edge of the Earth into the otherwise dark umbral shadow.

And, if you've seen the colors of a sunrise or a sunset—orange and red, more or less depending on atmospheric conditions—then you can understand why the light is reddish. Earth's atmosphere acts like a piece of red glass: white light, containing all the colors of the rainbow, enters the glass, but the bluer colors are absorbed, and only the orange and red tones pass through and shine onward. (What does Earth's atmosphere do with that stolen blue light? Take a look at a clear daytime sky and you'll see!)

So, for the 41 minutes of totality, you'll witness one of the most spectacular partnerships of the Earth and Moon, when the Earth "touches" the Moon with the tip of its shadow and the russet tones of all its sunrises and sunsets acting in concert.

Totality will end at 6:47 AM when the Moon's leading edge begins to depart the umbral shadow—and at 7:17 the show will be over for us when the Moon sets. Then, it's another three years until we can see such a sight again, so be sure to catch this one! Weather permitting, we'll have the Observatory Deck open at Chabot Space & Science Center from 4:00 to 7:00 AM, in case you'd like to watch the event in good company….

Total Lunar Eclipse Dec 20/21 2010

One of the most striking and beautiful examples of the Earth-Moon relationship takes place during a total lunar eclipse, when the Moon passes through the Earth's shadow, transforming in a couple of hours from the stark brilliance of the Full Moon to the dark ruby-hued wonder of "umbral occlusion"—or totality.

Monday evening, December 20th, starting at about 9:30 PM, the Moon will begin to enter the Earth's partial, or "penumbral," shadow. Around 10:30, it begins to enter the umbra (full shadow), and by 11:40 will be completely engulfed: "totality." Totality will last until 12:53 AM Tuesday morning, when the Moon begins to leave the umbra.

While the extended weather forecast at the moment doesn't look favorable for the SF Bay Area, there are always freak changes in weather to hope for. Also, we'll be having a Lunar Eclipse celebration at Chabot Space & Science Center, rain or moonshine, which will be a lot of fun: Lunar Labs, planetarium shows, sci-fi movie reels, and every Moon-related song we could find—hope to see you there!

Though a total lunar eclipse is a rare event to see, this one is rarer still–not the least reason being that for the Western US it will be one of the highest lunar eclipses you can see, with the Moon reaching its apex for the night over 75 degrees from the horizon (practically overhead) close to mid-totality. For our latitudes in the Bay Area, the Moon can't get much higher than that. So, we get High Moon when the eclipse is at its best (weather permitting).

What makes this eclipse rare among the rare is the fact that the Moon is crossing several important features in the sky simultaneously. First, it's crossing the Ecliptic, the path of the Sun's apparent motion over the course of a year, cutting through the 12 constellations of the Zodiac. In essence, the Ecliptic is the projection of Earth's orbital plane onto the sky. Is it a coincidence that the Moon will be crossing the Ecliptic during this eclipse? Actually…not at all. By virtue of the geometry of a lunar eclipse, the Moon must be on the Ecliptic in order to pass through Earth's shadow, since the Earth's shadow, cast by the Sun's light, always runs along Earth's orbital plane, and so too the Ecliptic.

Another line is crossed during this eclipse because it happens on Winter Solstice. On this day, the Sun is located in Sagittarius, and so the Earth's shadow is cast toward the opposite point on the sky, in Taurus. Halfway around the circle of the Ecliptic from the Winter Solstice point you find the other solstice point, the spot on the Ecliptic where the Sun is located at Summer Solstice.

The Moon will also be crossing the Galactic Equator: the line representing the plane of the Milky Way Galaxy. This alignment is a bit more tangible than those with the Ecliptic and the Solstice point since the Milky Way is a visible sky feature—at least in areas not impacted by urban light pollution. If you live in a place where you can normally see the Milky Way on a dark night, you have an extra wonder to marvel at during this eclipse: when the bright Full Moon enters totality and goes dark, the subtle light of our galaxy will be revealed, with the Moon set like a darkling gem in a diamond bracelet….

Well, we can only hope for clear skies—but in either event, come up to Chabot and celebrate with us this midnight delight….

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Artist's rendering of the LCROSS spacecraft and its upper stage Centaur rocket. Image courtesy of NASA.

Reported for KQEDnews.org.

Last year, NASA scientists in Mountain View made international headlines when they crashed a rocket into a permanently shadowed crater on the moon's south pole and announced they had found water there.

On Thursday, they unveiled new findings about the amount of water on the moon and a "treasure trove" of gases and metals buried within the lunar soil, which along with the water, could be extracted to make rocket fuel on the moon. The research appears in the October 22nd edition of the journal Science.

"If you took the 10 kilometer region around the LCROSS site, that is said to have 5 percent concentration of water, that would be equivalent to a billion gallons of water," said Tony Colaprete, the principal investigator on the Lunar Crater Observation and Sensing Satellite mission to search for water on the moon. A billion gallons is enough to fill 1500 Olympic-sized swimming pools. The lunar scientists now suspect that there is 50 percent more water than they had previously estimated.

Colaprete also said that given the large number of craters on the moon, which function as "cold traps" that accumulate molecules of water over billions of years, "potentially, you could have 10 to 100 times that total amount of water."

"We found some of the coldest places in the solar system and they’re on our moon. These places have temperatures that are so cold that they can preserve water ice in a vacuum for billions of years," said Michael Wargo, a chief lunar scientist at NASA headquarters in Washington, D.C.

The lunar water is thought to exist in "oases," or deposits, instead of being uniformly distributed across the moon. It also exists mainly in the form of water ice crystals.

"That's good news because water ice is very much a friendly resource to work with. It's easy to extract and turn it into a resource, you don’t have to warm it very much, you can pull it out of the dirt really easy," said Colaprete, who described a process of extraction whereby the ice-bearing lunar soil could be heated to 100 degrees Celsius to collect the water vapor.

During the live NASA teleconference, the scientists said that the amount of other materials they detected on the moon – including mercury, ammonia, methane, carbon dioxide, sodium and silver – may make up as much as 20 percent of the lunar dust plume kicked up by the impact of the LCROSS rocket.

Both discoveries could be instrumental in one day making it easier to set up a lunar colony, the researchers said, because of the high cost of transporting materials to the moon, which can exceed thousands of dollars per pound.

Last year, NASA shot a Centaur rocket carrying the LCROSS and Lunar Reconnaissance Orbiter from Cape Canaveral, Florida, and in October, they deliberately crashed the rocket at 6,000 mph into Cabeus, a cold, dark crater on the moon’s south pole that hasn’t seen sunlight in billions of years.

The impact sent up a plume of lunar soil and debris several miles over the crater’s rim, exposing it to sunlight. Meanwhile, the spacecraft collected data for four crucial minutes, allowing scientists to analyze the chemical makeup of the ejected lunar soil, before it too crashed into the crater. Since then, the LCROSS team has been sifting through the information to glean clues about earth’s 4.5 billion year-old neighbor.

So how did the water get there? According to Colaprete, it’s likely a combination of sources. One way it could have arrived is from solar wind depositing hydrogen into the lunar granules which contain oxygen atoms. Another way is from impacts by icy comets slamming into the moon, a theory supported by the observation of these other chemicals and hydrocarbons that also exist in comets.

The last manned lunar mission was Apollo 17 in 1972. In recent years, the U.S., along with Japan, China and India have launched various unmanned lunar mission. NASA is scheduled to launch two other lunar exploratory missions, GRAIL and LADEE in 2011 and 2012, respectively, to map the moon’s interior structure and further analyze the moon’s dust.

Sometime in the next several decades, a new generation of astronauts may return to set up a lunar outpost, setting the stage for future missions to Mars.

“In the next 20 years, next 10 years, you’re going to see the moon continue to expand in its diversity, and its complexity and its interest, among the communities of both laypeople and professionals and that’s going to pull us there,” said Colaprete.

Instruments currently orbiting the moon are allowing the scientists to map in much greater detail hydrogen-rich, lunar "permafrost" regions that may contain deposits of water ice and other compounds that could help support a future lunar colony.

But before that lunar colony can be set up, there has to be a more sophisticated understanding of where exactly the water is and how easy or difficult it will be to mine when it's found.

"The next step is to look at smaller and smaller scales at the lunar surface of the distribution of water as a resource," said Colaprete.

"If I were an astronaut walking along, how far do I have to walk before I find some water and how extensive are these pockets of water?"

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Artist's rendering of the LCROSS spacecraft and its upper stage Centaur rocket. Image courtesy of NASA.

Originally reported for KQED News.

Last year, NASA scientists in Mountain View made international headlines when they crashed a rocket into the moon and announced they had found water there.

On Tuesday, they revealed that the water – which exists as ice and vapor – isn’t spread out in vast oceans, but rather is concentrated in oases, and that the lunar surface appears to contain a wealth of other materials, from mercury to magnesium.

Both discoveries could be instrumental in one day making it easier to set up a lunar colony, the researchers said, because of the high cost of transporting materials to the moon, which can exceed thousands of dollars per pound.

“It’s water and much more,” said Anthony Colaprete, an astrophysicist at NASA Ames Research Center in Mountain View. “The others, from a scientific standpoint and a resource standpoint may prove to be as important or more important.”

Colaprete is the principal investigator on the mission to find water on the moon, which is known as LCROSS or the Lunar Crater Observation and Sensing Satellite. Last year, the scientists shot an unmanned spacecraft from Cape Canaveral, Florida, and in October, they deliberately crashed its rocket at 6,000 mph into Cabeus, a cold, dark crater on the moon’s south pole that hasn’t seen sunlight in billions of years.

The impact sent up a plume of lunar soil and debris several miles over the crater’s rim, exposing it to sunlight. Meanwhile, the spacecraft collected data for four crucial minutes, allowing scientists to analyze the chemical makeup of the ejected lunar soil, before it too crashed into the crater. In the nine months since then, the LCROSS team has been sifting through the information to glean clues about earth’s 4.5 billion year-old neighbor.

How wet is the moon?

“As wet as the Sahara, perhaps wetter in some places”, said Colaprete.

On Tuesday, at the third annual Lunar Science Forum at NASA Ames, researchers discussed everything from the physics of the LCROSS impact to the complex chemistry of the moon. Among their findings:

- The distribution of water on the moon is not uniform, but “chunky”, occurring in deposits in dark craters like the one LCROSS struck.
- The range of chemicals found on the moon is wider than once thought and includes mercury, magnesium, sulfur dioxide and possibly, formaldehyde, along with sodium, hydrogen sulfide, carbon dioxide and methane.
- The total amount of water in the target site and the plume observed by LCROSS: 26 gallons

So how did the water get there? According to Colaprete, it’s likely a combination of sources. One way it could have arrived is from solar wind depositing hydrogen into the lunar granules which contain oxygen atoms. Another way is from impacts by icy comets slamming into the moon, a theory supported by the observation of these other chemicals and hydrocarbons that also exist in comets.

The last manned lunar mission was Apollo 17 in 1972. In recent years, the U.S., along with Japan, China and India have launched various unmanned lunar mission. NASA is scheduled to launch two other lunar exploratory missions, GRAIL and LADEE in 2011 and 2012, respectively, to map the moon’s interior structure and further analyze the moon’s dust.

Sometime in the next several decades, a new generation of astronauts may return to set up a lunar outpost, setting the stage for future missions to Mars.

“In the next 20 years, next 10 years, you’re going to see the moon continue to expand in its diversity, and its complexity and its interest, among the communities of both laypeople and professionals and that’s going to pull us there,” said Colaprete. “There’s a lot you can do with the moon. It’s fundamental to understanding our place in the solar system and we’ve always appreciated that and recent studies have accentuated it.”

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Artwork from Jules Verne’s 1865 novel, From the Earth to the Moon

Sounds like something out of a Jules Verne novel… but that's exactly what NASA's up to this year with the upcoming LCROSS (Lunar Crater Observation and Sensing Satellite) mission, scheduled for launch on June 2nd and impact sometime in October– exact date TBA.

And it's not unprecedented, either: the Lunar Prospector spacecraft back in 1998/1999, whose instruments detected possible signs of water ice in craters around the Moon's poles, was crashed into the Moon's South Pole at the end of its mission. The aim was to blast up a cloud of material from the lunar surface and spectroscopically analyze the plume in search of water vapor. None was detected then, but that's where LCROSS comes in.

LCROSS will seek to verify the presence or absence of water ice and related hydrated materials buried at the bottom of a permanently shadowed crater floor on the Moon's South Pole. Water ice cannot persist on any part of the Moon's surface that is subjected to sunlight, but because of the Moon's low axial tilt with respect to the ecliptic (the Sun's apparent annual path in the sky)– only about 1.5 degrees– there are craters at the Moon's poles whose floors never see the light of day, all month long and year round. Water ice could persist near the surface in these places.

LCROSS consists of two pieces: a "Shepherding Spacecraft" that will guide the whole affair to the proper location on the Moon's South Pole, and the Centaur rocket stage that propelled the spacecraft to the Moon. The pair will separate, and the Centaur rocket will become the primary impactor, striking ground and producing a crater and plume of ejected material. Viewing the event from above, the Shepherding Spacecraft will use cameras and other instruments to analyze the plume from a distance, and will then follow the same course as the Centaur, descending four minutes after impact through the ejected plume and analyzing material samples as it falls.

Then, the Shepherding Spacecraft, too, will impact the Moon– and the plume it kicks up may well be visible through modest sized telescopes on Earth. We're planning to watch the explosion live through our telescopes at Chabot, weather permitting. Keep an eye on our website for details.

Now, back to Jules Verne for a moment. The launching of a projectile with the intent of striking the Moon was indeed the subject of one of his novels, From the Earth to the Moon, published in 1865. Fired from an enormous cannon, the goal of that post Civil War mission was to catch the attention of anyone living on the Moon, to open up a line of communication with their civilization.

My wife asked me if crashing a probe into the Moon would have any harmful effects, particularly if in fact there is any form of life (subsurface microbes or such) living there. Well, certainly, if you happen to be a lifeform living at ground zero of the impact… but the fact is the Moon is frequently struck by meteorites much larger than the LCROSS impactor anyway. To paraphrase Douglas Adams, "that kind of thing goes on all the time."

One last fun tidbit about the Jules Verne novel: the launch site for his cannon-fired projectile was a place in Florida, 50 miles south of Tampa Bay, and only about 135 miles from the Kennedy Space Center, from which LCROSS will be launched…

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