Rumblings on the moon could be problematic for lunar base

Apr 07, 2006
Earth\'s Moon

As NASA envisions it, astronauts will return to the moon within the next decade or so. Unlike in the earlier, quick, Apollo visits, these astronauts will build a permanent base and prepare for an historic undertaking that will send explorers to Mars. As Clive Neal, associate professor of civil engineering and geological sciences at the University of Notre Dame, envisions it, these same astronauts may be in for a shocking — and rocking — surprise.

Neal and a team of 15 other planetary geologists have reexamined data from seismometers placed by Apollo astronauts at lunar landing sites from 1969 to 1972. They found that instruments from Apollo missions 12, 14, 15 and 16 consistently radioed back seismic data to Earth until they were turned off in 1977 in a NASA cost-cutting measure.

Neal and his colleagues discovered a surprising number of relatively large “moonquakes,” including some that lasted a remarkably long time.

“The moon is seismically active,” Neal said. “When a quake occurs, the moon rings like a bell.”

There are four different types of moonquakes. Deep moonquakes, occurring at roughly 700 kilometers below the surface, were most likely caused by lunar forces triggered by the effect of Earth’s gravity. Other quakes were caused by vibrations from the impact of meteorites, and “thermal quakes” were caused when the frigid crust of the moon expanded when struck by the morning sun after two weeks of deep-freeze lunar night. The first three classes of moonquakes were generally mild.

However, shallow quakes, which occurred only 20 or 30 kilometers below the surface, were another story. They were powerful and long-lasting.

“Between 1972 and 1977, the Apollo seismic data detected 28 shallow quakes,” Neal said. “A few of the shallow quakes registered up to 5.5 on the Richter scale. A magnitude 5 quake on Earth can move heavy furniture and crack plaster.”

Neal points out that vibrations from most earthquakes cease in less than a minute. The biggest earthquakes stop shaking in less than two minutes. The shallow quakes on the moon produced movement that continued for more than 10 minutes.

Neal and other scientists aren’t exactly sure what causes the shallow moonquakes, although they suspect that the rims of large and relatively young moon craters may slump and cause them.

They also aren’t sure precisely where the quakes are occurring.

“The Apollo seismometers were all in one relatively small region on the front side of the moon, so we can’t pinpoint the exact location of these shallow quakes,” Neal said.

Although he isn’t sure of the precise location of the shallow quakes, Neal is convinced that NASA needs additional analysis and data before proceeding with construction of a permanent lunar base. In the corner of his office is a floor-to-ceiling bookshelf containing binders of data from the Apollo missions, which he continues to analyze and which, he feels, will offer important guidance for the planned return to the moon.

He notes that we know relatively little about the lunar poles, which is critical given that one suggested location for a lunar base is a region on the rim of Shackleton Crater at the south pole of the moon that is permanently sunlit.

NASA planners also will need to develop building materials that are flexible enough to withstand the stress of shaking and bending from these long-lived shallow moonquakes.

Neal also believes that the moon can offer critical data that will potentially impact the planned missions to Mars.

“The moon is a technology test bed for establishing such networks on Mars and beyond,” he said.

Source: University of Notre Dame, by William G. Gilroy

Explore further: Mysteries of space dust revealed

add to favorites email to friend print save as pdf

Related Stories

LADEE mission ends with planned lunar impact

Apr 18, 2014

(Phys.org) —Ground controllers at NASA's Ames Research Center in Moffett Field, Calif., have confirmed that NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft impacted the surface ...

Venus visible in the daytime sky

Dec 05, 2013

Here's a feat of visual athletics to amaze your friends with this week. During your daily routine, you may have noticed the daytime Moon hanging against the azure blue sky. But did you know that, with careful ...

Engineers building hard-working mining robot

Jan 29, 2013

(Phys.org)—After decades of designing and operating robots full of scientific gear to study other worlds, NASA is working on a prototype that leaves the delicate instruments at home in exchange for a sturdy ...

Recommended for you

Mysteries of space dust revealed

Aug 29, 2014

The first analysis of space dust collected by a special collector onboard NASA's Stardust mission and sent back to Earth for study in 2006 suggests the tiny specks open a door to studying the origins of the ...

A guide to the 2014 Neptune opposition season

Aug 29, 2014

Never seen Neptune? Now is a good time to try, as the outermost ice giant world reaches opposition this weekend at 14:00 Universal Time (UT) or 10:00 AM EDT on Friday, August 29th. This means that the distant ...

How can we find tiny particles in exoplanet atmospheres?

Aug 29, 2014

It may seem like magic, but astronomers have worked out a scheme that will allow them to detect and measure particles ten times smaller than the width of a human hair, even at many light-years distance.  ...

Spitzer telescope witnesses asteroid smashup

Aug 28, 2014

(Phys.org) —NASA's Spitzer Space Telescope has spotted an eruption of dust around a young star, possibly the result of a smashup between large asteroids. This type of collision can eventually lead to the ...

User comments : 0