Saturday, September 10, 2005

What's The Weather Like On The Moon?

On Wednesday, September 7/2005, the sun unleashed one of the largest solar flares on record, according to CNET News.

The National Oceanic and Atmospheric Agency (NOAA) said the powerful flare that emerged from region 808 on the sun Wednesday afternoon rated the fourth-largest in the last 15 years. Intense radio emissions were associated with the flare.

Here on earth, our planet's thick atmosphere and magnetic field protects us from protons and other forms of solar radiation coming at us from the sun when larger solar flares occur.

The Moon is a different story.

"The Moon is totally exposed to solar flares," explains solar physicist David Hathaway of the Marshall Space Flight Center. "It has no atmosphere or magnetic field to deflect radiation." Protons rushing at the Moon simply hit the ground --- or whoever might be walking around outside.

If an astronaut were to be caught outside on the moon's surface when such a storm hits, at first he'd feel fine, but a few days later symptoms of radiation sickness would appear: vomiting, fatigue, low blood counts. These symptoms might persist for days.

One rem, short for Roentgen Equivalent Man, is the radiation dose that causes the same injury to human tissue as 1 roentgen of x-rays. A typical diagnostic CAT scan, the kind you might get to check for tumors, delivers about 1 rem [ref].

To die, you'd need to absorb, suddenly, 300 rem or more.

The key word is suddenly, according to NASA. You can get 300 rem spread out over a number of days or weeks with little effect. Spreading the dose gives the body time to repair and replace its own damaged cells. But if that 300 rem comes all at once ... "we estimate that 50% of people exposed would die within 60 days without medical care," says Francis Cucinotta, NASA's radiation health officer at the Johnson Space Center.

Such doses from a solar flare are possible. For example, the large solar storm of August 1972. A large sunspot appeared on August 2, 1972, and for the next 10 days it erupted again and again... Researchers have been studying it ever since.

Cucinotta estimates that a moonwalker caught in the August 1972 storm might have absorbed 400 rem.

An Apollo command module with its aluminum hull would have attenuated the 1972 storm from 400 rem to less than 35 rem at the astronaut's blood-forming organs. That's the difference between needing a bone marrow transplant ... or just a headache pill, according to Cucinotta.

Back in January 20th of 2005, a giant sunspot named "NOAA 720" exploded. The blast sparked an X-class solar flare, the most powerful kind, and hurled a billion-ton cloud of electrified gas (a "coronal mass ejection") into space. Solar protons accelerated to nearly light speed by the explosion reached the Earth-Moon system minutes after the flare --- the beginning of a days-long "proton storm."

A powerful solar flare on July 14/2000 triggered an ongoing radiation storm around our planet. The eruption also sent a fast-moving coronal mass ejection toward Earth.

As for last Wednesday's solar flare, what happened here on earth?

"This event created a complete blackout of high-frequency communications on the day-lit side of Earth, which included the entire U.S. and basically anywhere the sun was shining at this time," Larry Combs, solar forecaster at the NOAA Space Environment Center, said referring to Wednesday's solar flare in a prepared statement.

"Communications used by emergency services along the Gulf Coast may have experienced problems due to this flare. Low-frequency navigation systems may also have experienced a period of significant degradation," he added.

It rated an R-4, or severe, on NOAA's space weather scale for radio blackouts.

Who faces the most health risk when solar flares/storms occur? Both astronauts and high-altitude airline pilots/crew. Airline pilots that fly at great altitude, and especially near the poles, are exposed to more radiation from solar storms reaching our atmosphere. The same goes for astronauts. This results in a higher incidence of cancer among airline pilots and cabin crew. Astronauts have even reported seeing flashes of light because of high energy protons hitting their eyes.

Last Wednesday's solar flare is not the end for this year... more are expected. Click this link to see the current Space Weather Alerts directly from NOAA.

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