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  Dust cloud will eventually erase Apollo bootprints

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Author Topic:   Dust cloud will eventually erase Apollo bootprints
Robert Pearlman
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Posts: 43576
From: Houston, TX
Registered: Nov 1999

posted 06-17-2015 05:57 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The moon is engulfed in a permanent but lopsided dust cloud that increases in density when annual events like the Geminids spew shooting stars, according to a new study led by University of Colorado Boulder.

"Eventually this will erase the footprints of the astronauts," Mihaly Horanyi, who led the team that found the dust cloud, told USA Today.

University of Colorado, Boulder release

Moon engulfed in permanent, lopsided dust cloud

The moon is engulfed in a permanent but lopsided dust cloud that increases in density when annual events like the Geminids spew shooting stars, according to a new study led by University of Colorado Boulder.

The cloud is made up primarily of tiny dust grains kicked up from the moon's surface by the impact of high-speed, interplanetary dust particles, said CU-Boulder physics Professor Mihaly Horanyi. A single dust particle from a comet striking the moon's surface lofts thousands of smaller dust specks into the airless environment, and the lunar cloud is maintained by regular impacts from such particles, said Horanyi, also a research associate at CU-Boulder's Laboratory for Atmospheric and Space Physics.

The cloud was discovered using data from NASA's Lunar Atmosphere and Dust Environment Explorer, or LADEE, which launched in September 2013 and orbited the moon for about six months. A detector on board called the Lunar Dust Experiment (LDEX) designed and built by CU-Boulder charted more than 140,000 impacts during the six-month mission.

"Identifying this permanent dust cloud engulfing the moon was a nice gift from this mission," said Horanyi, the principal investigator on LDEX and lead study author. "We can carry these findings over to studies of other airless planetary objects like the moons of other planets and asteroids."

A paper on the subject appears in the June 17 issue of Nature. Co-authors include Jamey Szalay, Sascha Kempf, Eberhard Grun and Zoltan Sternovsky from CU-Boulder, Juergen Schmidt from the University Oulu in Finland and Ralf Srama from the University of Stuttgart in Germany.

Horanyi said the first hints of a cloud of dust around the moon came in the late 1960s when NASA cameras aboard unmanned moon landers captured a bright glow during lunar sunsets. Several years later, Apollo astronauts orbiting the moon reported a significant glow above the lunar surface when approaching sunrise, a phenomenon which was brighter than what the sun alone should have been able to generate at that location.

Since the new findings don't square with the Apollo reports of a thicker, higher dust cloud, conditions back then may have been somewhat different, said Horanyi. The dust on the moon — which is dark and sticky and regularly dirtied the suits of moonwalking astronauts — was created over several billion years as interplanetary dust particles incessantly pounded the rocky lunar surface.

Knowledge of the dusty environments in space has practical applications, said Horanyi. Knowing where the dust is and where it is headed in the solar system, for example, could help mitigate hazards for future human exploration, including dust particles damaging spacecraft or harming astronauts.

Many of the cometary dust particles impacting the lunar surface are traveling at thousands of miles per hour in a retrograde, or counterclockwise orbit around the sun -- the opposite orbital direction of the solar system's planets. This causes high-speed, near head-on collisions with the dust particles and the moon's leading surface as the Earth-moon system travel together around the sun, said Horanyi.

The Geminid meteor showers occur each December when Earth plows through a cloud of debris from an oddball object called Phaethon, which some astronomers describe as a cross between an asteroid and a comet. "When these 'beams' we see from meteors at night hit the moon at the right time and place, we see the cloud density above the moon skyrocket for a few days," said Horanyi.

Horanyi also is the principal investigator on a CU-Boulder student dust-counting instrument on board NASA's New Horizons spacecraft that will whip by Pluto on July 14 after a journey of more than nine years.

p51
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From: Olympia, WA
Registered: Sep 2011

posted 06-17-2015 06:17 PM     Click Here to See the Profile for p51   Click Here to Email p51     Edit/Delete Message   Reply w/Quote
I never heard of this, but it's a given due to impacts that at least one of the landing sites (if not more than one) has already been changed by something hitting the area.

Someday, there'll only be smashed debris at most - if not all- of the Apollo landing sites...

Headshot
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From: Vancouver, WA, USA
Registered: Feb 2012

posted 06-18-2015 07:07 AM     Click Here to See the Profile for Headshot   Click Here to Email Headshot     Edit/Delete Message   Reply w/Quote
It is interesting that these researchers did not give any rough estimates about how long the astronauts' boot prints might last. A few years after the last lunar landing mission I read an estimate of 20 million years (not accounting for any nearby, large random impacts). With this new information, it sounds like natural erosion/settling dust debris might make it significantly sooner.

dom
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posted 06-18-2015 07:54 AM     Click Here to See the Profile for dom   Click Here to Email dom     Edit/Delete Message   Reply w/Quote
I think the sites are more in danger from future Moon tourists!

moorouge
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From: U.K.
Registered: Jul 2009

posted 06-18-2015 09:12 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
Just out of curiousity - how can a dust cloud be lopsided?

Robert Pearlman
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From: Houston, TX
Registered: Nov 1999

posted 06-18-2015 09:23 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The cloud is thicker near the terminator, the boundary between the moon's dayside and nightside.

Blackarrow
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Posts: 3160
From: Belfast, United Kingdom
Registered: Feb 2002

posted 06-18-2015 06:30 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Headshot:
A few years after the last lunar landing mission I read an estimate of 20 million years...
I can remember news reports at the time of Apollo 11 suggesting that the footprints would last half a million years, but nobody ever explained how they calculated this. I agree with Dom - tourists will be the deciding factor.

Jonnyed
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Posts: 408
From: Dumfries, VA, USA
Registered: Aug 2014

posted 06-20-2015 12:26 PM     Click Here to See the Profile for Jonnyed   Click Here to Email Jonnyed     Edit/Delete Message   Reply w/Quote
Beyond the footprints, what possible wear from the dustcloud might happen to the LEM bases, equipment, flags (cloth material?) and rovers left behind? Probably very minimal over thousands and thousands of years but some wear, nonetheless.

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