Scientists Discover Lunar Oasis; Shady Events On Jupiter Tonight

The Centaur rocket stage separates from the LCROSS craft on its way to impact with the moon last year. Credit: NASA

Before we wrap up our appreciation of the full moon, can I add one more way? Last October 9, the LCROSS spacecraft and its companion rocket stage were crashed into the floor of the lunar crater Cabeus near the moon’s south pole. Earlier, scientists had picked up hints of water ice in this and other craters in the polar regions. The lunar poles are literally areas “where the sun don’t shine.” They likely acquired their ice from long-ago comet hits, and it’s been preserved in the shadows ever since. Steady temperatures of 280 below zero Fahrenheit are common in a number of polar craters – low enough to prevent water ice from vaporizing for at least a billion years.

By observing the resulting impact plume, scientists initially confirmed the presence of water ice. Fast forward to this week when NASA scientists announced that much more ice and vapor were seen in the plume than expected. How about 41 gallons?

A temperature map of moon's south pole. The blues and purples indicate craters and areas that are -280 degrees or lower -- perfect spots where water ice or other icy compounds seen in comets could be trapped in a deep freeze. Credit: NASA

Mission chief scientist Anthony Colaprete of the NASA Ames Research Center calculates there could be 1 billion gallons of water in Cabeus. Talk about an oasis in a lunar desert! The water is in the form of ice grains bound up with the lunar soil, but could be separated and used by future astronauts as drinking water. That’s not all that LCROSS kicked up. Scientists found methane, ammonia, hydrogen gas, carbon dioxide and carbon monoxide as well as relatively large amounts of light metals such as sodium, mercury and possibly even silver. That nasty ammonia and methane can be processed to make rocket fuel. All of these compounds and ices in the lunar soil indicate that the moon has a “water cycle” of sorts, where icy vapors from comet strikes in the distant past may have migrated to the poles where they condensed into ice and interacted with other compounds. “The diversity and abundance of volatiles in the plume suggest a variety of sources, like comets and asteroids, and an active water cycle within the lunar shadows,” says Colaprete. Direct your gaze to the southern edge of the moon tonight and think about the unexpected treasures there. You’ll find more information HERE and some cool videos HERE.

Bright Capella, low in the northeastern sky, and the moon can help you find Algol. Around 7:30 p.m. Central time, the star will be nearly as bright as nearby Mirfak. By 11, Algol will more closely resemble Rho. Created with Stellarium

Although it looks like clouds for northern Minnesota this evening, if the weather’s fair by you, there are two interesting things going on tonight – one visible with the naked eye, the other in small telescopes. The Demon Star Algol in Perseus will undergo an eclipse by its larger, fainter companion. Mid-eclipse, when Algol is faintest, occurs at 11:10 p.m. Central time. This is ideal for watching Algol fade from near maximum brightness to minimum. If you’re out early, use the moon to help point you there. From nightfall until about 8:30 p.m. the star will appear its normal brightness. Look again around 10:30-11 p.m. and you’ll see it’s dimmed noticeably. For more information on Algol and its eclipses, check out this previous blog on the topic.

When shadows cast by Jupiter's moons move across the planet's face, they're called shadow transits. Catch the Europa-Ganymede "double feature" tonight between 8:40 and 10:04 CDT. The map shows the view in a typical telescope with south up. Created with Chris Marriott's SkyMap

I’m going to hate to miss this next one – a simultaneous shadow transit of the moons Europa and Ganymede across the face of Jupiter. Between 8:40 and 10:04 p.m. Central time, the shadows cast by the two moons will appear as inky black dots on Jupiter’s cloud tops. If you could somehow float in a balloon within the shadow, you’d see an eclipse of the sun.

Europa’s shadow is a little larger than a pinpoint, while Ganymede, the largest of the Jupiter’s moons,  looks more like a small dot. I’ve drawn the map for around 9:15 p.m when they’ll both be most easily visible at the same time. Ganymede itself is well removed to the left of Jupiter; Europa is in front of the planet until about 9:40, when it begins to move off and to the side of the planet. If you use high power, you can watch Europa – a tiny white speck – glide off the disk in real time. A wonderful sight!

6 Responses

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  2. Joni Gjermundson

    I wanted to let you know I read your blog @ the Dickinson Press website. Yours is very unique and astronomy is one of my hobbies. My daughter is 3 1/2 and can name all the planets and loves looking through the telescope. She has already discovered stars, the moon and the sun move across the sky and already asked me way they do. I was so proud!
    So we really like your blog. Even if she doesn’t understand it just yet.

    1. astrobob

      Wow Joni, that’s great your daughter can name every planet and is already asking questions about the sun’s movement. Thanks for writing – I appreciate your comments about the blog. Even if your daughter can’t quite understand what’s written, I hope she likes some of the pictures. It’s amazing what telescopes and spacecraft are doing these days.

  3. Jim Schaff

    Hi Bob,

    I got to see the double shadows on Jupiter last night. The weather was not that great; I was observing through cumulus clouds- sometimes very turbulent, sometimes pretty decent seeing. I always like how sharply defined the shadows are. It was also obvious that they were quite different in size.

    It is cooling off here a little. We have gotten down below 60F now- feels good.

    take care,

    1. astrobob

      Thanks Jim for letting us know what it was like. We were overcast here with a sharp east wind no former resident could ever forget.

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