Featured Research

from universities, journals, and other organizations

Rediscovered Apollo data gives first measure of how fast moon dust piles up

Date:
November 20, 2013
Source:
American Geophysical Union
Summary:
Scientists used rediscovered Apollo data to make the first determination of how fast lunar dust accumulates. It builds up unbelievably slowly by the standards of any Earth-bound housekeeper -- just fast enough to form a layer about a millimeter (0.04 inches) thick every 1,000 years. Yet, that rate is 10 times previous estimates. It's also speedy enough to pose a serious problem for the solar cells that serve as critical power sources for space exploration missions.

The Lunar Dust Detector, attached to the leftmost corner of this experiment package left by the Apollo 12 astronauts, made the first measurement of lunar dust accumulation. As the matchbox-sized device’s three solar panels became covered by dust, the voltage they produced dropped.
Credit: NASA

When Neil Armstrong took humanity's first otherworldly steps in 1969, he didn't know what a nuisance the lunar soil beneath his feet would prove to be. The scratchy dust clung to everything it touched, causing scientific instruments to overheat and, for Apollo 17 astronaut Harrison Schmitt, a sort of lunar dust hay fever. The annoying particles even prompted a scientific experiment to figure out how fast they collect, but NASA's data got lost.

Or, so NASA thought. Now, more than 40 years later, scientists have used the rediscovered data to make the first determination of how fast lunar dust accumulates. It builds up unbelievably slowly by the standards of any Earth-bound housekeeper, their calculations show -- just fast enough to form a layer about a millimeter (0.04 inches) thick every 1,000 years. Yet, that rate is 10 times previous estimates. It's also more than speedy enough to pose a serious problem for the solar cells that serve as critical power sources for space exploration missions.

"You wouldn't see it; it's very thin indeed," said University of Western Australia Professor Brian O'Brien, a physicist who developed the experiment while working on the Apollo missions in the 1960s and now has led the new analysis. "But, as the Apollo astronauts learned, you can have a devil of a time overcoming even a small amount of dust."

That faster-than-expected pile-up also implies that lunar dust could have more ways to move around than previously thought, O'Brien added.

In his experiment, dust collected on small solar cells attached to a matchbox-sized case over the course of six years, throughout three Apollo missions. As the granules blocked light from coming in, the voltage the solar cells produced dropped. The electrical measurements indicated that each year 100 micrograms of lunar dust collected per square centimeter. At that rate, a basketball court on the Moon would collect roughly 450 grams (1 pound) of lunar dust annually.

Comparing the effects on cells from dust and from damaging high-energy radiation from the sun, O'Brien found that long-term dust accretion could diminish the output from shielded power supplies of a lunar outpost more than even the most intense solar outbursts.

Because the threat posed by radiation damage was recognized early on, solar-cell makers fortified their devices against that sort of harm. Yet, "while solar cells have become hardier to radiation, nothing really has been done to make them more resistant to dust," said O'Brien's colleague on the project Monique Hollick, who is also a researcher at the University of Western Australia, in Crawley. "That's going to be a problem for future lunar missions."

The work is detailed this week in Space Weather, a publication of the American Geophysical Union.

Answers from Apollo

Before Apollo 11 blasted off to the Moon in 1969, NASA scientists realized the Lunar Module would likely kick up a large amount of lunar soil on takeoff, potentially coating nearby science experiments with dust. Detachable covers would require either a small explosive or a physical mechanism to remove after the astronauts left, creating more engineering challenges and room for failure.

"Then I asked what I thought was a pretty common sense question," recalled O'Brien. "If we've got to guard ourselves against damage from the lunar module taking off, who's measuring whether any damage actually took place; who's measuring the dust?"

O'Brien proceeded to quickly invent the Lunar Dust Detector experiment as a small add-on device to the larger experiments. Requiring little power and weighing only 270 grams (0.6 pounds), the dust detector reported back to Earth alongside the non-scientific housekeeping data.

"It really got a free ride," O'Brien said.

The detectors flown on Apollo 12, 14 and 15 operated until NASA shut them off in September 1977 due to budgetary concerns. While the detectors worked properly, NASA did not preserve the archival tapes of the data they collected. For three decades NASA assumed the dust detector data had been lost forever, until 2006 when O'Brien heard about NASA's mistake and told them he still had a set of backup copies.

Lunar levitation

Each detector in the experiment had three solar cells, each covered with a different amount of shielding against incoming radiation. By comparing damage to the unshielded and shielded solar cells, O'Brien made his determination that dust, rather than radiation, caused the most degradation to the protected cells.

Previous model-based estimates of lunar dust accumulation assumed the dust came entirely from meteor impacts and falling cosmic dust. "But that's not enough to account for what we measured," O'Brien said.

With no atmosphere for wind, the Moon's soil should be stagnant. However, O'Brien said a popular idea of a "dust atmosphere" on the Moon could explain the difference. The concept goes that, during each lunar day, solar radiation is strong enough to knock a few electrons out of atoms in dust particles, building up a slight positive charge. On the nighttime side of the Moon, electrons from the flow of energetic particles, called the solar wind, which comes off the Sun strike dust particles and give them a small negative charge. Where the illuminated and dark regions of the moon meet, electric forces could levitate this charged dust, potentially lofting grains high into the lunar sky.

"Something similar was reported by Apollo astronauts orbiting the Moon who looked out and saw dust glowing on the horizon," said Hollick.

The idea of levitating lunar dust could soon be confirmed by NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE), launched in September. The spacecraft orbits 250 kilometers (155 miles) above the surface of the Moon, searching for dust in the lunar atmosphere.

While LADEE scours the Moon's atmosphere, O'Brien looks back on a decades-long science experiment that finally has a result.

"It's been a long haul," said O'Brien. "I invented [the detector] in 1966, long before Monique was even born. At the age of 79, I'm working with a 23-year old working on 46-year-old data and we discovered something exciting -- it's delightful."


Story Source:

The above story is based on materials provided by American Geophysical Union. Note: Materials may be edited for content and length.


Journal Reference:

  1. Monique Hollick, Brian J. O'Brien. Lunar weather measurements at three Apollo sites 1969-1976. Space Weather, 2013; DOI: 10.1002/2013SW000978

Cite This Page:

American Geophysical Union. "Rediscovered Apollo data gives first measure of how fast moon dust piles up." ScienceDaily. ScienceDaily, 20 November 2013. <www.sciencedaily.com/releases/2013/11/131120143804.htm>.
American Geophysical Union. (2013, November 20). Rediscovered Apollo data gives first measure of how fast moon dust piles up. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2013/11/131120143804.htm
American Geophysical Union. "Rediscovered Apollo data gives first measure of how fast moon dust piles up." ScienceDaily. www.sciencedaily.com/releases/2013/11/131120143804.htm (accessed July 25, 2014).

Share This




More Space & Time News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: ISS Cargo Ship Launches in Kazakhstan

Raw: ISS Cargo Ship Launches in Kazakhstan

AP (July 23, 2014) The Progress 56 cargo ship launched from the Baikonur Cosmodrome in Kazakhstan Wednesday. NASA says it will deliver cargo and crew supplies to the International Space Station. (July 23) Video provided by AP
Powered by NewsLook.com
Raw: Cargo Craft Undocks from Space Station

Raw: Cargo Craft Undocks from Space Station

AP (July 22, 2014) A Russian Soyuz cargo-carrying spacecraft undocked from the International Space Station on Monday. The craft is due to undergo about ten days of engineering tests before it burns up in the Earth's atmosphere. (July 22) Video provided by AP
Powered by NewsLook.com
NASA Ceremony Honors Moon Walker Neil Armstrong

NASA Ceremony Honors Moon Walker Neil Armstrong

AP (July 21, 2014) NASA honored one of its most famous astronauts Monday by renaming a historic building at the Kennedy Space Center in Florida. It now bears the name of Neil Armstrong, the first man to walk on the moon. (July 21) Video provided by AP
Powered by NewsLook.com
Neil Armstrong's Post-Apollo 11 Life

Neil Armstrong's Post-Apollo 11 Life

Newsy (July 19, 2014) Neil Armstrong gained international fame after becoming the first man to walk on the moon in 1969. But what was his life like after the historic trip? Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

      Environment News

        Technology News



          Save/Print:
          Share:

          Free Subscriptions


          Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

          Get Social & Mobile


          Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

          Have Feedback?


          Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
          Mobile: iPhone Android Web
          Follow: Facebook Twitter Google+
          Subscribe: RSS Feeds Email Newsletters
          Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins