[meteorite-list] Exploding Lunar Eclipse

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Tue, 28 Aug 2007 22:40:15 -0500
Message-ID: <047a01c7e9ee$509b1ee0$2850e146_at_ATARIENGINE>

Dear Jerry, List,

> Excuse a dumb question but wouldn't such "blasts" be visible
> on the lunar surface on the darkened side of the terminator?

    Excuse a dumb answer, but my guess is that
it requires a very sensitive detector to capture the
tiny flash of a meteoroid impact on the darkened
lunar surface and the very nearby presence of any
illuminated portion of the Moon would swamp it
with so much stray light as to make that impossible.

    You don't know where a hit will happen so you
want to watch as much of the entire darkened lunar
surface as possible which you can't really do with
any part of it illuminated.

    Secondly, only at the moment of a total lunar
eclipse does the Earth, as seen from the Moon, not
have some portion of an illuminated crescent of its
own, which will illuminate the face of the Moon with
Earthshine. At the New Moon, when so much of the
surface of the Moon is dark and at the perfect New
Moon moment, the Moon is too close to the Sun
to be observed.

    The eclipse occurs when the Moon is Full and
the Earth acts as a convenient sunshield. Even then,
there's the illumination of the "red ring" around the
Earth. Perhaps they have a detector with low red
sensitivity? Or some other trick...

    No doubt you could see a sufficiently big impact
on the dark side of the terminator but that would be
a rarer event. If you recall the impact of the SMART-1
probe on the Moon, it took a monster scope with a
whopping huge detector array to capture it, and only
because we knew where and when the hapless probe
would smash down were we lucky enough to catch it
at all.

    And we do see the rarer, bigger (and hence flasher)
impacts, such as on May 2, 2006:
http://www.nasa.gov/vision/universe/solarsystem/13jun_lunarsporadic.html
and December 22, 2005:
http://science.nasa.gov/headlines/y2005/22dec_lunartaurid.htm
and November, 1999:
http://www.space.com/scienceastronomy/solarsystem/leonids_crash_000621.html



Sterling K. Webb
-----------------------------------------------------------------------------
----- Original Message -----
From: "Jerry" <grf2 at verizon.net>
To: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>; "Meteorite Mailing List"
<meteorite-list at meteoritecentral.com>
Sent: Tuesday, August 28, 2007 8:51 PM
Subject: Re: [meteorite-list] Exploding Lunar Eclipse


Excuse a dumb question but wouldn't such "blasts" be visible on the lunar
surface on the darkened side of the terminator?
Jerry Flaherty
----- Original Message -----
From: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>
To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
Sent: Monday, August 27, 2007 7:50 PM
Subject: [meteorite-list] Exploding Lunar Eclipse



http://science.nasa.gov/headlines/y2007/27aug_explodingeclipse.htm

Exploding Lunar Eclipse
NASA Science News
August 27, 2007

August 27, 2007: Most people appreciate lunar eclipses for their silent
midnight beauty. NASA astronomer Bill Cooke is different: he loves the
explosions.

On Tuesday morning, Aug. 28th, Earth's shadow will settle across the
Moon for a 90-minute total eclipse: full story
<http://science.nasa.gov/headlines/y2007/03aug_dreamyeclipse.htm>. In
the midst of the lunar darkness, Cooke hopes to record some flashes of
light--explosions caused by meteoroids crashing into the Moon and
blasting themselves to smithereens.

"The eclipse is a great time to look," says Cooke, who heads up NASA's
Meteoroid Environment Office (MEO) at the Marshall Space Flight Center.
The entire face of the Moon will be in shadow for more than two hours,
offering more than 7 million sq. miles of dark terrain as target for
incoming meteoroids.

Lunar explosions are nothing new. Cooke's team has been monitoring the
Moon since late 2005 and they've recorded 62 impacts so far. "Meteoroids
that hit Earth disintegrate in the atmosphere, producing a harmless
streak of light. But the Moon has no atmosphere, so 'lunar meteors'
plunge into the ground," he says. Typical strikes release as much energy
as 100 kg of TNT, gouging craters several meters wide and producing
bursts of light bright enough to be seen 240,000 miles away on Earth
through ordinary backyard telescopes.

"About half of the impacts we see come from regular meteor showers like
the Perseids and Leonids," says MEO team-member Danielle Moser. "The
other half are 'sporadic' meteors associated with no particular asteroid
or comet."

The MEO observatory is located on the grounds of the Marshall Space
Flight Center in Huntsville, Alabama, and consists of two 14-inch
telescopes equipped with sensitive low-light video cameras. Moser and
colleague Victoria Coffey will be on duty Tuesday morning.

During the eclipse, they hope to catch an elusive variety of meteor
called Helions.

"Helion meteoroids come from the direction of the sun," Cooke says, "and
that makes them very difficult to observe." They streak across the sky
most often around local noon when the sun's glare is too intense for
meteor watching.

Wait a minute. Meteors from the sun? "The sun itself is not the source,"
he explains. "We believe Helion meteoroids come from ancient sungrazing
comets that laid down trails of dusty debris in the vicinity of the sun."

No one can be certain, however, because Helion meteoroids are so devilishly
difficult to study. Astronomers see them only in small numbers briefly
before dawn or after sunset. Attempts to study Helions via radar during
the day have been foiled, to a degree, by terrestrial radio interference
and natural radio bursts from the sun - both of which can drown out
meteoroid "pings."

Enter the eclipse.

During the eclipse, the Man in the Moon (the face we see from Earth)
will be turned squarely toward the sun??""perfect geometry for
intercepting Helion meteoroids," says Moser. "And with Earth's shadow
providing some darkness, we should be able to see any explosions quite
clearly."

"Watching Helion meteoroids hit the Moon and studying the flashes will
tell us more about their size, velocity and penetration," she adds.
That, in turn, will further the MEO's goal of estimating meteoroid
hazards to spacecraft and future Moon-walking astronauts.

No one has ever seen a lunar impact during an eclipse, "but there's a
first time for everything," Cooke says. Stay tuned to Science at NASA for
results.

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Received on Tue 28 Aug 2007 11:40:15 PM PDT