Chapter 9:

Our Moon

Links from Chapter

Additional Links

Forthcoming Missions to the Moon
European Space Agency's SMART-1 (2002)
European Space Agency's Lunar-A (2003)
Japan's Space Agency's SELENE (2004)
LunarSat

Hawaii Moon Declaration on Future Investigation

No Ice at the Lunar Poles

ARECIBO, P.R. -- Despite evidence from two space probes in the 1990s, radar astronomers say they can find no signs of thick ice at the moon's poles. If there is water at the lunar poles, the researchers say, it is widely scattered and permanently frozen inside the dust layers, something akin to terrestrial permafrost.

Using the 70-centimeter (cm)-wavelength radar system at the National Science Foundation's (NSF) Arecibo Observatory, Puerto Rico, the research group sent signals deeper into the lunar polar surface -- more than five meters (about 5.5 yards) -- than ever before at this spatial resolution. "If there is ice at the poles, the only way left to test it is to go there directly and melt a small volume around the dust and look for water with a mass spectrometer," says Bruce Campbell of the Center for Earth and Planetary Studies at the Smithsonian Institution.

Campbell is the lead author of an article, "Long-Wavelength Radar Probing of the Lunar Poles," in the Nov. 13, 2003, issue of the journal Nature. His collaborators on the latest radar probe of the moon were Donald Campbell, professor of astronomy at Cornell University; J.F. Chandler of Smithsonian Astrophysical Observatory; and Alice Hine, Mike Nolan and Phil Perillat of the Arecibo Observatory, which is managed by the National Astronomy and Ionosphere Center at Cornell for the NSF.

Suggestions of lunar ice first came in 1996 when radio data from the Clementine spacecraft gave some indications of the presence of ice on the wall of a crater at the moon's south pole. Then, neutron spectrometer data from the Lunar Prospector spacecraft, launched in 1998, indicated the presence of hydrogen, and by inference, water, at a depth of about a meter at the lunar poles. But radar probes by the 12-cm-wavelength radar at Arecibo showed no evidence of thick ice at depths of up to a meter. "Lunar Prospector had found significant concentrations of hydrogen at the lunar poles equivalent to water ice at concentrations of a few percent of the lunar soil," says Donald Campbell. "There have been suggestions that it may be in the form of thick deposits of ice at some depth, but this new data from Arecibo makes that unlikely."

Says Bruce Campbell, "There are no places that we have looked at with any of these wavelengths where you see that kind of signature."

The Nature paper notes that if ice does exist at the lunar poles it would be considerably different from "the thick, coherent layers of ice observed in shadowed craters on Mercury," found in Arecibo radar imaging. "On Mercury what you see are quite thick deposits on the order of a meter or more buried by, at most, a shallow layer of dust. That's the scenario we were trying to nail down for the moon," says Bruce Campbell. The difference between Mercury and the moon, the researchers say, could be due to the lower average rate of comets striking the lunar surface, to recent comet impacts on Mercury or to a more rapid loss of ice on the moon.

What makes the lunar poles good cold traps for water is a temperature of minus 173 degrees Celsius (minus 280 degrees Fahrenheit). The limb of the sun rises only about two degrees above the horizon at the lunar poles so that sunlight never penetrates into deep craters, and a person standing on the crater floor would never see the sun. The Arecibo radar probed the floors of two craters in permanent shadow at the lunar south pole, Shoemaker and Faustini, and, at the north pole, the floors of Hermite and several small craters within the large crater Peary. In contrast, Clementine focused on the sloping walls of Shackleton crater, whose floor can't be "seen" from Earth. "There is a debate on how to interpret data from a rough, tilted surface," says Bruce Campbell.

The Arecibo radar probe is a particularly good detector of thick ice because it takes advantage of a phenomenon known as "coherent backscatter." Radar waves can travel long distances without being absorbed in ice at temperatures well below freezing. Reflections from irregularities inside the ice produce a very strong radar echo. In contrast, lunar soil is much more absorptive and does not give as strong a radar echo.

Related World Wide Web sites: The following sites provide additional information on this news release. Some might not be part of the Cornell University community, and Cornell has no control over their content or availability.

Arecibo Observatory: http://www.naic.edu

Center for Earth and Planetary Studies: http://www.nasm.si.edu/ceps/

Total Lunar Eclipse of November 8th

On Saturday night, November 8-9, 2003, the full Moon will pass through the Earth's shadow for skywatchers throughout the Americas, Europe, and Africa, and in parts of Asia. For the Americas, this will be the second lunar eclipse of 2003; the first took place the night of May 15-16.

But the total phase of November's eclipse will be unusually brief, lasting only 25 minutes as the Moon skims barely inside the southern edge of our planet's dark shadow.

Skywatchers in eastern North America will see the entire eclipse during dark evening hours. Those living in the western half of North America will find the eclipse already in progress as the Moon rises around sunset.

All of Europe and most of Africa will see the eclipse in its entirety much later Saturday night. Observers in eastern and southern Africa, the Middle East, and southern Asia will see the eclipsed Moon set around sunrise on Sunday morning.

A total lunar eclipse occurs when the Sun, Earth, and Moon form a nearly straight line in space, so that the full Moon passes through Earth's shadow. Unlike a solar eclipse, which requires special equipment to observe safely, you can watch a lunar eclipse with your unaided eyes. Binoculars or a small telescope will enhance the view dramatically.

As the Moon moves into the outer fringe, or penumbra, of Earth's shadow, it will fade very slightly -- imperceptibly at first. Only when the leading edge of the Moon is at least halfway into the penumbra is any shading visible at all.

The real show starts when the Moon's leading edge first enters the shadow's dark core, or umbra, and the partial eclipse begins. For the next hour and 34 minutes, more and more of the Moon will slide into dark shadow.

The total eclipse begins when the Moon is fully within the umbra. But it likely won't be blacked out. The totally eclipsed Moon should linger as an eerie dark gray or coppery red disk in the sky, as sunlight scattered around the edge of our atmosphere paints the lunar surface with a warm glow. This is light from all the sunrises and sunsets that are in progress around Earth at the time.

Each total lunar eclipse is different. Sometimes the Moon looks like an orange glowing coal, while at other times it virtually disappears from view. Its brightness depends on the amount of dust in the Earth's upper atmosphere at the time, which influences the amount of sunlight that filters around the Earth's edges.

Because the Moon passes just inside the umbra, totality will be very short and the Moon's southern edge, in particular, should remain fairly bright. After only 25 minutes the leading edge of the Moon will emerge back into sunlight, and the eclipse is again partial. In another hour and 33 minutes the last of the Moon emerges out of the umbra.

Details about this event, and the solar eclipse visible from Antarctica, Australia, and New Zealand on November 23-24, appear in the November 2003 issue of SKY & TELESCOPE magazine.

The next total eclipse of the Moon falls on May 4-5, 2004, and is visible from central and south Asia, the Middle East, and the eastern two-thirds of Africa. North Americans will see their next lunar eclipse on October 27-28, 2004.

http://SkyandTelescope.com/aboutsky/pressreleases/article_1087_1.asp

European Space Agency's SMART-1 En Route to the Moon

http://sci.esa.int/jump.cfm?oid=34105

The European Space Agency Launches SMART-1 to the Moon

SMART stands for Small Missions for Advanced Research and Technology. SMART-1 is testing electric propulsion, miniaturization, and other technologies. Among other things, it will search for ice in lunar craters at the South Pole from the spacecraft's eventual elliptical polar orbit, ranging from a perihelion of 300 km to an aphelion of 10,000 above the lunar surface. The ion propulsion engine is slow but steady, and it will take 16 months (compared with Apollo's 4 dfays) to get from the Earth to the Moon.

No Cheese on the Moon, Chandra Results Say

Observations of the bright side of the Moon with NASA's Chandra X-ray Observatory have detected oxygen, magnesium, aluminum and silicon over a large area of the lunar surface. The abundance and distribution of those elements will help to determine how the Moon was formed.

"We see X-rays from these elements directly, independent of assumptions about the mineralogy and other complications," said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass, at a press conference at the "Four Years with Chandra" symposium in Huntsville, Alabama.

"We have Moon samples from the six widely-space Apollo landing sites, but remote sensing with Chandra can cover a much wider area," continued Drake. "It's the next best thing to being there, and it's very fast and cost-effective.

The lunar X-rays are caused by fluorescence, a process similar to the way that light is produced in fluorescent lamps. Solar X-rays bombard the surface of the Moon, knock electrons out of the inner parts of the atoms, putting them in a highly unstable state. Almost immediately, other electrons rush to fill the gaps, and in the process convert their energy into the fluorescent X-rays seen by Chandra.

According to the currently popular "giant impact" theory for the formation of the Moon, a body about the size of Mars collided with the Earth about 4.5 billion years ago. This impact flung molten debris from the mantle of both the Earth and the impactor into orbit around the Earth. Over the course of tens of millions of years, the debris stuck together to form the Moon. By measuring the amounts of aluminum and other elements over a wide area of the Moon and comparing them to the Earth's mantle, Drake and his colleagues plan to help test the giant impact hypothesis.

"One early result," quipped Drake, "is that there is no evidence for large amounts of calcium, so cheese is not a major constituent of the Moon."

The same Chandra data have also solved a long-running mystery about X-rays from the dark side of the Moon, as reported by Brad Wargelin also of CfA. Wargelin discussed how data from the German Roentgen satellite (ROSAT) obtained in 1990 showed a clear X-ray signal from the dark side. These puzzling "dark-Moon X-rays" were tentatively ascribed to energetic electrons streaming away from the Sun and striking the lunar surface.

However, Chandra's observations of the energies of individual X-rays, combined with simultaneous measurements of the number of particles flowing away from the Sun in the solar wind, indicate that the X-rays only appear to come from the Moon. In reality they come from much closer to home.

"Our results strongly indicate that the so-called dark Moon X-rays do not come from the dark side of the Moon," said Wargelin. "The observed X-ray spectrum, the intensity of the X-rays, and the variation of the X-ray intensity with time, can all be explained by emission from Earth's extended outer atmosphere, through which Chandra is moving."

In the model cited by Wargelin and colleagues, collisions of heavy ions of carbon, oxygen and neon in the solar wind with atmospheric hydrogen atoms located tens of thousands of miles above the surface of Earth give rise to these X-rays. In the collisions, the solar ions capture electrons from hydrogen atoms. The solar ions then kick out X-rays as the captured electrons drop to lower energy states.

Private Moon Exploration Venture

In 2003, both the Japanese Lunar-A spacecraft and the European Space Agency's "Small Missions for Advanced Research in Technology 1" (SMART-1) have long been scheduled for launch. Lunar A will not only map the moon but also drop two probes that will penetrate the lunar surface, carrying seismometers and equipment to measure heat flow.

To that pair of missions, and to a potential Chinese mission, a private American company called TransOrbital has received a license from NOAA and the US Departments of Defense and State to launch a spacecraft to the moon. ("How does a United States body like NOAA get the right to issue a license for anything to do with the Moon anyway" is an interesting question.)

TransOrbital's TrailBlazer spacecraft's main aim is to get public attention. Further, it will carry an HDTV camera to take high-resolution images with a resolution as high as 1 meter on the lunar surface. It is to be launched from the Baikonur Cosmodrome in Kazakhstan and is planned for 90 days of orbiting the moon. It is then to be crashed into the moon, carrying a time capsule as well as things people have paid to have crashed into the moon in that way.

Trailblazer: http://www.transorbital.net
SMART-1: http://sci.esa.int/home/smart-1/index.cfm
Lunar-A: http://www.estec.esa.nl/ilewg/lunara.htm
http://www.isas.ac.jp/e/enterp/missions/lunar-a/index.html

Measuring the Distance to the Moon to a Millimeter

Tom Murphy plans to spend much of the next five years using the Apache Point telescope in New Mexico as a tape measure 239,000 miles long - give or take a millimeter.

He'll employ the telescope, a laser beam and reflectors left by several lunar missions in a technique known as laser ranging to provide the most exacting measure yet of the Earth's distance from the moon.

Scientists have long known the center of the moon is about 238,700 miles from the center of Earth. In the early 1970s, the distance was known to within about 25 centimeters (10 inches) but technological advances since the mid-1980s have sharply reduced that margin to about 2 centimeters (less than an inch).

Now Murphy, a University of Washington postdoctoral researcher in physics and astronomy, hopes to reduce that uncertainty to a millimeter - about the thickness of a paper clip. He will lead a team that includes Christopher Stubbs, a UW astronomy professor; Eric Adelberger, a UW physics professor; and Jana Strasburg, a physics graduate student.

In making such a precise measurement, the team will perform the most sensitive tests ever done on several features of gravity. One involves Einstein's equivalence principal, which essentially states that bodies of different compositions accelerate at the same rate in a gravitational field. Another deals with variability of the strength of the gravitational interaction - testing to determine whether there are signs that the force of gravity is diluted as the universe expands.

"We don't know enough about gravity, so we have to probe gravity with every tool we have available," Murphy said.

He will use the 3.5-meter telescope at Apache Point, near Sunspot, N.M., owned and operated by the Astrophysical Research Consortium of which the UW is a member. He will attach a laser that generates an average power of 2 watts, but that will jump to a peak power of a gigawatt (1 billion watts) long enough to generate a 1-inch "bullet" of light aimed through the telescope at the lunar surface. The distance is calculated by measuring the light pulse's round-trip travel time and multiplying that figure by the speed of light.

Each laser bullet will be aimed at one of five retroreflectors, banks of 100 to 300 special prisms that reflect a beam of light back to its point of origin. The retroreflectors, each about the size of a suitcase, were left behind by three Apollo missions (including Apollo 11, the first manned mission to land on the moon) and two unmanned Soviet missions.

"You pick which retroreflector you want to aim at, then you focus the beam as tightly as you can. But even then, the atmosphere distorts the beam so that when it hits the moon it's 2 kilometers in diameter," Murphy said.

"Only one in 30 million of the photons that you launch to the moon will actually find the retroreflector. It's like winning the lottery - very tall odds," he said. "And then for a photon to make it back to the telescope, the odds again are about one in 30 million." That's because once the light makes it back to Earth, it has expanded to about 15 kilometers - or 9.3 miles - in diameter.

The number of photons detected depends a lot on the technology and the size of the telescope. Current laser-ranging experiments detect just a single photon from every 100 laser pulses sent. But this will be the first time advanced measuring technology has been used in conjunction with a telescope as large as that at Apache Point, so Murphy hopes to detect five to 10 photons for each laser pulse.

"We're going to shoot 20 pulses per second, so at any given time we'll have 50 pulses in the air coming and going from the lunar surface," he said.

For each 30-minute session, Murphy plans to use all five retroreflectors, which will remove any ambiguous measurements related to the moon's orientation to the Earth. He expects to complete preparations and begin taking measurements in about a year, and says the work is likely to last five years. The project, paid for by the National Aeronautics and Space Administration, is actually a feasibility study for performing laser-ranging experiments from space.

When he's done, Murphy also expects to add to the understanding of how the sun's gravitational field exerts a pull on the Earth's gravitational field.

"This is essentially measuring the weight of gravity, and this is the only type of project that can currently do that," he said.

Released Kennedy Tapes Show Moon-Landing Motivation

Confirming earlier reports that the Apollo Program largely resulted from political desires, tapes released by the John F. Kennedy Library in August 20001 show: converation with James Webb, NASA Administrator, Nov. 21, 1962, about a month after the Cuban Missile crisis: "This is important for political reasons, international political reasons, and this is, whether we like it or not, in a sense a race.... Second to the moon is nice, but it's like being second any time. If we're second by six months, and didn't give it the kind of priority, then of course that would be very serious.

If we weren't first to the Moon, "Otherwise we shouldn't be spending this kind of money because I'm not that interested in space.... But we're talking about fantastic expenditures. We've wrecked our budget, and all these other domestic programs, and the only justification for it, in my opinion, is to do it in the time element I'm asking."

Improved Model of the Formation of the Moon

Roban Canup of the Southwest Research Institute in Boulder, Colardo, and Eric Asphaug of UC Santa Cruz have been able to calculate computer models of lunar formation with more effects and particles included. In Nature Magazine, vol. 412, pp. 708-712, 16 August 2001, they conclude that a planet the size of Mars hit the Earth when it was almost fully formed. Prior models had needed for the impacting object to hit the Earth before it had cooled as much. An analysis by Jay Melosh of the University of Arizona's Lunar and Planetary Laboratory on pp. 694-5 of that issue discusses the importance of the new work. Figure 1, p. 709, of the Canup and Asphaug article shows a sequence of 11 stages over about one day plus a side view of the result.

The Moon On Line at High Resolution

http://www.lpi.usra.edu/research/lunar_orbiter/index.html

The Lunar and Planetary Institute (LPI) has created a digital version of the "Lunar Orbiter Photographic Atlas of the Moon," published in 1971 and considered "the definitive reference manual to the global photographic coverage of the Moon." The site includes all 675 plates contained in the original work, digitally enhanced to increase photo quality. Visitors can view images by feature name, listed alphabetically or by descending latitude and longitude, or they can search by feature name, photo number, or coordinate range. Returns include a large thumbnail image, photo number, feature name, latitude and longitude, size, sun angle, spacecraft altitude, and medium photo center latitude and longitude. Students and general users may wish to consult the even easier to use Consolidated Lunar Atlas, which allows browsing by a long list of plates, thumbnails, or even better, an interactive image map.

"One small step" anagram

"That's one small step for a man, one giant leap for mankind."
- Neil Armstrong

The Anagram:
"Thin man ran; makes a large stride, left planet, pins flag on moon! On to Mars!"

IceBreaker mission

In the absence of a NASA plan for a future lunar spacecraft, the private company LunaCorp and the Robotics Institute of Carnegie Mellon University are planning to send the "IceBreaker" mission to the moon in 2002. A rover is to land near the crater Peary, looking for ice both with a radar and a drill.

URL's:
LunaCorp: www.lunacorp.com/
Robitics Institute of CMU: www.ri.cmu.edu/