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February
12, 2007: Picture this: The year is 2025 and you're
on the moon. "Home" is 100 meters away—an outpost
on the rim of Shackleton Crater. NASA started building it
five years earlier, and it is growing fast. You're one of
the construction workers.
As
always in these polar regions, the sun hangs low, barely above
the craggy lunar horizon. You adjust your visor. It amazes
you how bright a low sun can be when there's no atmosphere
to dim it.
 Suddenly,
the lights go out.
Up
in the sky, a big black disk covers the sun. A red "ring
of fire" appears where the sun was only moments before,
and its glow turns the ground red beneath your feet.
You've
been waiting for this. It's an eclipse.
Right:
On the moon, the ground turns red during a lunar eclipse.
This photo was taken by Doug Murray of Palm Beach Gardens,
Florida, during the total lunar eclipse of Oct. 27, 2004.
[More]
Astronauts
on the moon are going to experience eclipses typically once
or twice a year: Earth glides in front of the sun turning
lunar day into a strange kind of ruddy night. It'll be one
of the highlights of any lunar tour.
The
charm of the eclipse comes from Earth. Our planet is big enough
by a factor of three to block the entire sun but, curiously,
this doesn't cause complete darkness. Rays of sunlight bend
around the edge of Earth, filtering through the atmosphere.
As seen from the moon, the edge of Earth lights up like a
sunset-red ring of fire—one of the most beautiful sights in
the solar system. (A simplified, 1.2 MB animation of the process
may be seen here.
Credit: Graphic artist Larry Koehn.)
Can't
wait until 2025? The next eclipse is right around the corner:
Saturday, March 3, 2007. Stuck on Earth, we can't see the
ring of fire, but we can see the red glow it produces on the
moon. The phenomenon will be visible from parts of all seven
continents including the eastern half of North America.
Above:
A visibility map of the March 3, 2007, total lunar eclipse.
Credit: Fred Espenak, NASA/GSFC. [More]
In
the USA, the eclipse will already be underway when the moon
rises on Saturday evening. Observing tip: Find a place with
a clear view of the eastern horizon and station yourself there
at sunset. As the sun goes down behind you, a red moon will
rise before your eyes.
Rising
moons are often reddened by clouds or pollution, but this
moon will be the deep, extraordinary red only seen during
a lunar eclipse. As you watch it ascend into the night, imagine
what it would be like to stand by Shackleton Crater watching
from the opposite direction.
It's
not so far-fetched. NASA plans to return astronauts to the
moon no later than 2020. From their polar base camp, humans
will explore the countryside hunting for resources they can
use to "live off the land." They'll study the moon's
geology, learning more about the unique potential of the moon
to reveal ancient
secrets of Earth and the solar system. They'll also evaluate
technologies needed for future missions to Mars.
And
occasionally when the ground turns red, they'll pause and
look up at a glowing ring in the sky.
March
3rd is a good night to imagine that.
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Author: Dr.
Tony Phillips | Editor:
Dr. Tony Phillips | Credit: Science@NASA
| More
to the story... |
| NASA's
eclipse home page
-- more information about the March 3, 2007, total lunar
eclipse.
Nomenclature:
Solar vs. lunar eclipses. What's the correct
name for the astronomical event described in this story?
Here on Earth we call it a "lunar eclipse,"
because the moon is darkened as it passes through Earth's
red shadow. But on the moon, it is the sun that is darkened
by the intervening body of the Earth. Future astronauts
will probably call this a "solar eclipse."
It all depends on your point of view.
Eclipse
Frequency: How often will astronauts on the moon
see Earth eclipse the sun? According
to expert Fred Espenak of NASA/GSFC, "during the
five millennium period from 2000BC through 3000 AD, there
are 7,718 eclipses of the Moon (including both partial
and total). There are anywhere from 0 to 3 lunar eclipses
(including partial and total) each year. The last time
that three total lunar eclipses occurred in one calendar
year was in 1982. Partial eclipses slightly outnumber
total eclipses by 7 to 6." [More]
In
short, one or two total eclipses per year is typical;
three is possible on rare occasions.
Why
the Moon? -- answers from NASA
NASA's
Future: The
Vision for Space Exploration |
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