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Colorful Lunar Eclipse

On Wednesday morning, Oct. 8th, not long before sunrise, the bright full Moon over North America will turn a lovely shade of celestial red.  It’s a lunar eclipse—visible from all parts of the USA.

“It promises to be a stunning sight, even from the most light polluted cities,” says NASA’s longtime eclipse expert Fred Espenak. “I encourage everyone, especially families with curious children, to go out and enjoy the event.”

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A new ScienceCast video examines the red and turquoise colors sky watchers can expect to see during the Oct. 8, 2014, total lunar eclipse. Play it

From the east coast of North America, totality begins at 6:25 am EDT.  The Moon will be hanging low over the western horizon, probably swollen by the famous Moon illusion into a seemingly-giant red orb, briefly visible before daybreak. West-coast observers are even better positioned. The Moon will be high in the sky as totality slowly plays out between 3:25 am and 4:24 am PDT.

During a lunar eclipse, the Moon passes deep inside the shadow of our planet, a location that bathes the the face of the Moon in a coppery light.

A quick trip to the Moon explains the color: Imagine yourself standing on a dusty lunar plain looking up at the sky. Overhead hangs Earth, nightside down, completely hiding the sun behind it. The eclipse is underway.

You might expect Earth seen in this way to be utterly dark, but it’s not. The rim of the planet is on fire! As you scan your eye around Earth’s circumference, you’re seeing every sunrise and every sunset in the world, all of them, all at once. This incredible light beams into the heart of Earth’s shadow, filling it with a coppery glow and transforming the Moon into a great red orb.

However, red is not the only color.  Many observers of lunar eclipses also report seeing a band of turquoise.

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Click to see a worldwide eclipse visibility map

The source of the turquoise is ozone. Atmospheric scientist Richard Keen of the University of Colorado explains: “During a lunar eclipse, most of the light illuminating the moon passes through the stratosphere where it is reddened by scattering. However, light passing through the upper stratosphere penetrates the ozone layer, which absorbs red light and actually makes the passing light ray bluer.” This can be seen, he says, as a soft blue fringe around the red core of Earth’s shadow.

To catch the turquoise on Oct. 8th, he advises, “look during the first and last minutes of totality. The turquoise rim is best seen in binoculars or a small telescope.”

The depth and hue of lunar eclipse colors depends a lot on the dustiness of the stratosphere.  When volcanoes erupt and chock the stratosphere with aerosols, lunar eclipses can turn such a deep red that the Moon looks almost black.  That’s not the case this time, however:

“Despite some recent eruptions that look spectacular from the ground, there have been no large injections of volcanic gases into the stratosphere,” says Keen. “In the absence of volcanic effects, I expect a rather normal reddish-orange lunar eclipse similar in appearance to last April’s eclipse.”

In other words, this is going to be good.

Espenak notes that “the total lunar eclipse of Oct. 8 is the second of four consecutive total lunar eclipses. Such a set of total eclipses is known as a tetrad.” The next eclipse in the tetrad is six months from now, in April 2015.

“Don’t wait,” he urges. Mark your calendar for October 8th, wake up early, and enjoy the show.

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First test to predict Alzheimer’s years in advance

The death of nerve cells makes the brains of people with Alzheimer's disease (left) smaller than those of people showing no signs of dementia (right) <i>(Image: Pasieka/Science Photo Library)</i>

The death of nerve cells makes the brains of people with Alzheimer’s disease (left) smaller than those of people showing no signs of dementia (right) 

The world’s first blood test to predict Alzheimer’s disease before symptoms occur has been developed. The test identifies 10 chemicals in the blood associated with the disease two to three years before symptoms start, but it might be able to predict Alzheimer’s decades earlier.

Globally, 35 million people are living with Alzheimer’s. It is characterised by a toxic build up of amyloid and tau proteins in the brain, which destroys the neurons. Several blood tests can diagnose the disease, but until now, none has had the sensitivity to predict its onset.

Howard Federoff at Georgetown University in Washington DC and his colleagues studied 525 people aged 70 and over for five years. The group showed no signs of mental impairment at the start of the study. Each year, the team performed a detailed cognitive examination and took blood samples from all the participants. During this time, 28 people developed Alzheimer’s or mild cognitive impairment, thought to be the earliest noticeable sign of dementia, including Alzheimer’s disease.

An analysis of the participants’ blood highlighted 10 metabolites that were depleted in those with mild cognitive impairment who went on to get Alzheimer’s compared with those who didn’t. In subsequent trials, the team showed these chemicals could predict who would go on to get Alzheimer’s within the next three years with up to 96 per cent accuracy.

Decades of warning?

The 10 metabolites play a key role in supporting cell membranes, maintaining neurons or sustaining energy processes. “We think the decrease in these chemicals reflects the breakdown of neural populations in the brain,” says team member Mark Mapstone at the University of Rochester Medical Center in New York.

Once verified in a larger group, the test should provide a cheap and quick way of predicting Alzheimer’s. Mapstone says that it may even be able to predict the disease much earlier, because the brain changes associated with Alzheimer’s begin many years before symptoms occur. “These metabolic changes might occur 10 or 20 years earlier – that would give us a real head start on predicting the disease,” he says.

The team is hoping to investigate this by looking back at other dementia studies in which blood has been taken over decades and seeing whether the chemical changes can be detected that early, says Federoff.

The group also analysed the full genome sequence of all of the participants in the study. That work has yet to be published, but Federoff says the changes in genes over the five years of the study are even more powerful than the metabolites at predicting who will develop dementia. “The gene changes are linked to the metabolite changes, so we’re hoping to put all this together to provide a more complete description of the underlying pathology of the disease,” he says. “What’s most exciting is that we know the function of all the affected genes so if we can intercept these changes, they might make good candidates for new drugs.”

Knowledge is power

But with no treatments available, would anyone want to take these tests?

Mapstone says yes. “In my experience, the majority of people are very interested to know whether they will get Alzheimer’s. They believe that knowledge is power – particularly when it comes to your own health. We may not have any therapy yet but there are things we can do – we can get our financial and legal affairs in order, plan for future care, and inform family members.”

If the test could predict the disease 20 years before symptoms appear, the implications are huge, he says. “Imagine what you would do in your early 40s to slow the onset of the disease. You could eat the right foodsavoid head trauma or do more exercise.”

“In the short term, I think some people would want to know and some wouldn’t,” says Tracy Young-Pearse, a neurologist at Harvard Medical School. However, if treatments are developed that are only effective before neurons have started dying in large numbers, then it will be an easy decision to choose to take the blood test, she says.

Meanwhile, the new test will be valuable for drug discovery efforts, she says. Years of failed drugs trials have shown that you have to catch the disease early to have any influence.

Three studies starting this year hope to do just that. One will test anti-amyloid drugs on healthy people with a rare mutation that gives them early onset Alzheimer’s by age 45 (see “Testing a drug for the memory curse“).

The second will take advantage of a chemical developed last year that can be injected into the body and which accumulates in tau tangles. It will allow researchers to track the progression of tau in the living brain.

A third trial will investigate whether anti-amyloid drugs can prevent Alzheimer’s in older people who don’t yet have memory problems but do have amyloid building up in their brain.

“If an even earlier pre-clinical population could be identified with this blood test, it could be game changing,” says Young-Pearse.

Journal reference: Nature Medicine, DOI: 10.1038/nm.3466