A Planet called Lunar

The Queen of Night

Since time immemorial, people have gazed with wonder at the pale yellow orb that casts its soft radiance upon the Earth.  Throughout the ages, it has been clothed in a deep and glamorous mystery, a thing of legend and romance.  The coming of the spaceship has replaced many of the old superstitions by an even greater sense of wonder. There is hardly a person who was living at the time that will not remember the dramatic moment of touchdown by the lunar module of Apollo 11 on the Sea of Tranquillity.   World-wide television recorded the event as Neil Armstrong and 'Buzz' Aldrin landed on the Moon. It was the twenty-first of July 1969 and the hard and dedicated work of thousands of scientists and engineers had come to fruition.  Their one  lonely companion Michael Collins orbited the little world in the command module which was loaded with instruments carrying out geological and photographic surveys over the lunar surface.  Already several manned flights had gone round the Moon and unmanned spacecraft had already disturbed its ancient silence. 

From the scarred and battered surface of a planet called Lunar the first astronauts gazed into the black canopy of star spangled space and saw within that alien sky the large blue and white globe that was their home.  Shining with a radiance of sixty full moons it went through its phases and forever presented different aspects to the two silent figures who left the Lunar Module to tread upon the surface of the Moon and gaze upwards with awe at the planet from which they had come.

AS17-148-22727 (7 December 1972) --- This view of the Earth was seen by the Apollo 17 crew as they travelled toward the Moon on their NASA lunar landing mission. This outstanding trans-lunar coast photograph extends from the Mediterranean Sea area to the Antarctica south polar ice cap. This is the first time the Apollo trajectory made it possible to photograph the south polar ice cap. Note the heavy cloud cover in the Southern Hemisphere. Almost the entire coastline of Africa is clearly visible. The Arabian Peninsula can be seen at the northeastern edge of Africa. The large island off the coast of Africa is the Malagasy Republic. The Asian mainland is on the horizon toward the northeast. The Apollo 17 crew consisted of astronauts Eugene A. Cernan, mission commander; Ronald E. Evans, command module pilot; and Harrison H. Schmitt, lunar module pilot. While astronauts Cernan and Schmitt descended in the Lunar Module (LM) to explore the Moon, astronaut Evans remained with the Command and Service Modules NASA

 Photograph credit NASA

Missions to the Moon

Between 1969-1972, there were six successful manned missions to the Moon.   Since the first lunar landing there was only one dramatic failure.  Although it never reached the moon the three astronauts returned safely to Earth.    The dramatic rescue of the three astronauts is the subject of the famous film Apollo 13.

Large Scale Map of Moon showing Landing Sites Courtesy NASA

http://solarsystem.nasa.gov/multimedia/gallery/Moon_Landings.jpg   The direct hyperlink to this site is given in this web-site in the section at the end of this 'chapter'.  This web-site when accessed directly can be used to obtain magnified maps of the individual landing sites

Picture credit to NASA Apollo 16.

Locked in synchronous rotation, the Moon always presents its well-known near side to Earth. But from lunar orbit, the Apollo astronauts also grew to know the Moon's far side. This picture was taken from Apollo 16's mapping camera. It shows the eastern edge of the familiar near side (top) and the strange and heavily cratered far side of the Moon. Surprisingly, the rough and battered surface of the far side looks very different from the near side which is covered with smooth dark lunar maria.  The likely explanation is that the crust is thicker on the far side, making it harder for molten material from the interior to flow to the surface

The astronauts from each mission left a number of important instruments on the surface that continued to broadcast back to Earth the results of their findings for several years after they had been installed.  The name given to the collection of instruments was 'The Apollo Lunar Surface Experimental Package' or ALSEP

Some of the most important experiments involved the use of instruments to: -

Measure and analyse the Solar Wind.

Measure Seismic Activity - 'Moonquakes' (Seismometer)

Measure for Traces of Possible Lunar Atmosphere

Measure any Magnetic Field (Magnetometer)

Geological Surveys and other observations were also carried from orbit during the missions. In each mission, two of the astronauts landed on the surface and one member of the crew remained on board the space vehicle.

Probably the most important assignment during each mission for the astronauts was to carry out geological surveys around the landing sites and to collect rock specimens.  At the same time as his two companions explored the landing site, one lonely companion orbited the little world alone in the command module.

Altogether about 392 kilograms of rock samples were brought back to Earth by the six missions.  During the whole of the Apollo programme, rock samples were taken from many different types of sites - for example the Mare or 'sea areas' and the Mountainous Highlands.  

A list of the manned space flights is given in the table below

Table 4.1. Apollo Missions to the Moon.

Each succeeding mission grew more ambitious.  The amount of rock samples collected was more on each occasion and the distance travelled by the astronauts and time spent on the Moon increased.   The final mission was Apollo 17.  Some idea of the nature of the mission can be seen from the photograph of  Commander Cernik in a 'moonmobile'

 Apollo 17 Site of Landing – The Taurus-Littrow Valley

Photographs, map and information courtesy Acknowledgement NASA/Apollo17

Acknowledgement NASA/Apollo17Astronaut Eugene A. Cernan, commander, makes a short checkout of the Lunar Roving Vehicle (LRV) during the early part of the first Apollo 17 Extravehicular Activity  at the Taurus-Littrow landing site. The Earth date was 11 December 1972. The photograph was taken by scientist-astronaut Harrison H. Schmitt, lunar module pilot. The mountain in the right background is the east end of South Massif. While astronaut's Cernan and Schmitt descended in the Lunar Module to explore the Moon, astronaut Ronald E. Evans, command module pilot, remained with the Command and Service Module.

Apollo 17 was the last of the Apollo series of moon landings.  It was also the most ambitious - the astronauts were on the Moon longer than any other Moon explorers and the greatest number of rock specimens were collected.  Harrison 'Jack' Schmitt was the only 'scientist ' to ever visit the Moon and was a civilian.  Schmitt was the only geologist in the astronaut corps.  Jack was born July 3, 1935 in Santa Rita, New Mexico, and grew up in the nearby town of Silver City. He received a B.S. from Caltech in 1957 and then spent a year studying geology at the University of Oslo in Norway. He received a Ph.D. in Geology from Harvard University in 1964. Before joining NASA as a member of the first group of scientist-astronauts in June 1965, he worked at the U.S. Geological Survey's Astrogeology Center at Flagstaff, developing geological field techniques that would be used by the Apollo crews. Following his selection, Schmitt played a key role in training Apollo crews to be geologic observers when they were in lunar orbit and competent geologic field workers when they were on the lunar surface. After each of the landing missions, he participated in the examination and evaluation of the returned lunar samples and helped the crews with the scientific aspects of their mission reports.

During their 75 hours on the Moon, the crew of Apollo 17 set up ten scientific experiments and collected a total of 120 kilograms of moon rock from 22 locations within the Taurus-Littrow Valley.  They spent 22 hours on the lunar surface and travelled a total of 36 kilometres.  They took a number of excellent photographs.  The map shows the landing area where these activities took place.

Map of Taurus-Littrow Valley.  Site of Apollo 17 Landing

Acknowledgement for map NASA /Apollo 17                              There were two main geological objectives undertaken in the area.  They were the collection of samples of ancient rocks from the lunar highlands and the investigation of young volcanic activity on the valley floor. The crew collected 741 individual rock and soil samples, with a total mass of 111 kilograms.   This include a deep drill core that obtained material from 3 meters below the lunar surface.

Rocks from the floor of the Taurus-Littrow Valley were found to be mostly mare basalts.  They consisted primarily of the minerals plagioclase and pyroxene and were formed from molten lava. They had developed from material that melted at depths of at least 130 to 220 kilometers below the surface.  They then rose to the surface before solidifying. Most of these Apollo 17 mare basalts formed between 3.7 and 3.8 billion years ago.   They were found to contain large amounts of the element titanium. The basalt layer is between 1.0 and 1.4 kilometers thick near the Apollo 17 landing site.  On quiet eruption the Mare basalts flowed easily across the Moon's surface.  Samples of an orange coloured glass were also obtained.  It is thought that the glass formed 3.64 billion years ago from material that melted about 400 kilometers below the surface.

Lunar Highland Rocks

A variety of very old rocks were collected from the mountains to the north and south of the landing site. Some of these rocks had been melted by the heat of a large impact and are referred to as impact melts.   Studies of such rocks indicate that the impact that formed the Serenitatis basin (the basin of which the Taurus-Littrow is part) occurred 3.89 billion years ago. Other rocks obtained included norites, troctolites, and dunites which were formed even earlier in the Moon's history. Norite consists primarily of the minerals plagioclase and pyroxene. Troctolite consists primarily of plagioclase and olivine, but small amounts of pyroxene are also present. Dunite is nearly pure olivine. Many of these rocks originally formed in the lower half of the Moon's crust and were later brought to the Moon's surface by large meteorite impacts. They formed between 4.2 and 4.5 billion years ago (the solar system formed about 4.56 billion years ago).   The impact that produced the sea of serenity occurred during ther time of the late heavy bombardments

The Soviet Lunar Programme

The Soviet Union also undertook an elaborate lunar programme.   It was a very long-running undertaking, with the first mission flying in 1959 and the last flying in 1976. The Luna missions were designed to collect information about the Moon and its environment, not only for scientific purposes but also to be used in the planning of future lunar missions including manned landings. The series included flyby, lunar-orbiting, and soft-landing missions. It also included three missions that removed samples of rock that were then returned to Earth.   They were obtained from areas not covered by the Apollo landings.  Selected Luna missions are noted in the list in the table..Although the Luna program experienced many ups and downs and failed to lead to a manned mission to the Moon, it achieved many “firsts.” Among them were the first flyby of the Moon, the first impact on the Moon, the first photographs of the farside, the first analysis of lunar soil, the first soft landing, the first lunar rover deployment and the first return of a sample of moon rock to Earth.

Table 4.2 Russian Luna Programme

The Lunar Surface

Although the Moon has not suffered erosion by water or by wind the surface of the Moon has changed considerably over geological time.  The changes have been brought about by the action of impact processes, volcanic activity and tectonic activity in the very distant past .  By far the most important are those that have been caused by bombardment from meteorites and by the incessant and prolonged action of the Solar Wind and cosmic radiation on the lunar surface.

The age of lunar rocks is split into a number of periods named after certain large craters.  The periods recommended by D.E.Wilhelms of the U.S, Geological Survey are: -

            Copernican Period         1,200 million years age to present day

            Eratosthenian Period      3,300 million years ago to 1,200 million years ago

            Imbrian Period              3,850 million years ago to 3,200 million years ago

            Nectarian Period           3,920 million years ago to 3,850 million years ago

Pre-Nectarian Period     Before 3,920 million years ago

One of the most recently formed lunar craters is the Crater of Copernicus which is 96 kilometres in diameter and is believed to have originated about 900 million years ago.  The Copernican Period covers from 1,200 million years ago up to the present day

The Eratosthenes Crater is considerably older than Copernicus and the period covers from approximately 3,200 million up to 1,200 million years ago.

The formation of the Imbrian Basin was caused by a huge impact.  It was a major event in lunar history.   It has given its name to a period lasting from about 3,850 million up to 3,200 years ago.  Much of the volcanic activity, caused by the Moon's own internal action, occurred during this period.

Acknowledgements of photograph NASA/Apollo 11

As a result of the changes that have occurred over these vast periods of geological time,a blanket of loose material covers the surface of the Moon.  It is referred to as the'REGOLITH'.  It consists of rock fragments, fine stones and dust. The word 'soil' isused for any material under one centimetre in diameter. The regolith is of variabledepth.  It covers the bedrock to a depth of 4 to 5 metres in the Mare Areas and 10 metresor more in the Highland Regions.  The regolith is loose and the footprints of hemoonboots of the astronauts and the tracks of the moonmobiles can clearly beseen in photographs taken during the missions. The illustration shows a photograph of an astronaut’s boot-print in the regolith taken on the Apollo 11 Mission.

Later Missions to the Moon

Since the Apollo Landings there have been no further attempts to land people on the Moon.  With the robot landings on Venus, Mars and Titan and the astounding progress obtained by the Galileo and Cassini missions and many more, some of the glamour of the moon landings has perhaps faded a little.  However the time will soon arrive in the next decade when men and women will return to the moon and set up permanent bases similar to the space station and to the Antarctic bases on our own planet.

The moon is however not being neglected.  Three important missions have been launched recently

Clementine Mission

Thanks are due to NASA for supplying the information of the Clementine Mission.

On January 25, 1994, the Deep Space Program Science Experiment (DSPSE) (better known as Clementine) was launched from Vandenberg Air Force Base, California, on a mission designed to test lightweight miniature sensors and advanced spacecraft components by exposing them, over a long period of time, to the difficult environment of outer space. In addition to testing the various sensors, Clementine was given the complex task of mapping the moon. The mission results were spectacular.

Between February 26 and April 22, 1994, Clementine was able to deliver more than 1.8 million digital images of the moon back to the Clementine ground network, including the NRL satellite ground-tracking station located in Maryland. These images were quickly accessible to the general public via the Internet and World Wide Web. When scientists reviewed the data from Clementine, they made a major scientific discovery: the possible existence of ice within some of the moon's craters.

The Pentagon announced on December 3, 1996, that radar data acquired by the Clementine spacecraft indicated ice in the bottom of a crater on the South Pole of the Moon.

In 1994, President Clinton cited Clementine as one of the major national achievements in aeronautics in space. He stated "The relatively inexpensive, rapidly built spacecraft constituted a major revolution in spacecraft management and design; it also contributed significantly to lunar studies by photographing 1.8 million images of the surface of the Moon"

The Lunar Prospector
Thanks are due to NASA for information on the Lunar Prospector. 

Beginning on January 15, 1998, Lunar Prospector spent one year mapping the entire surface of the Moon from a distance of about 100 kilometers (60 miles). The data collected during this phase of the mission greatly improved on the quality of data collected previously. Among the early returns from the instruments were those from the Neutron Spectrometer indicating significant amounts of water ice at the lunar poles.

Lunar Prospector's Flight Path to the Moon Credit NASA The Lunar Prospector crashed, as planned, and several teams of researchers tried to detect that cloud, but without success. Either there was no water, or there was not enough water to be detected by Earth-based telescopes, or the telescopes were not looking in precisely the right place. In any event, no water was found from Prospector's impact. In 2008, NASA plans to send a new spacecraft to the Moon: the Lunar Reconnaissance Orbiter (LRO), bristling with advanced sensors that can sense water in at least four different ways. Scientists are hopeful that LRO can decide the question of Moon water once and for all. Our interest is not just scientific. If we are indeed to build a base on the Moon, the presence of water already there would offer a tremendous advantage in building and running it.

Smart - 1

The European Space Agency sent a very novel kind of spacecraft to the Moon called SMART-1  Those people who were fortunate enough to attend the recent 2007 European Astrofest Conference at Kensington Town Hall in London were entertained by a most interesting lecture on SMART- I given by Dr Dave Heather from ESTEC the European Space Agency Center  at Noordwijk in the Netherlands. 

Telescopic view of the whole Moon seen from Earth Credit ESA SMART-1 Mission.

Caption SMART-1 is Europe's first mission to the Moon. The scientists taking part have a 21st-Century view of our companion in space, which makes our connection with it more intimate than ever. The Moon is no longer seen merely as a satellite, but as the Earth's daughter, forming in a double planet.

Thanks and credits are due to ESA for the descriptions and details given in their web-site .  A hyperlink is given to the ESA website in the section of this web-site devoted to outside webs. 

Over 30 years after the last Apollo mission visited the Moon in 1972, there is still much that we do not know about our satellite. How was it created? What role did it play in the formation and evolution of Earth? SMART-1 may help to answer these questions.

The main purpose of the SMART-1 mission is to flight-test the new solar-electric propulsion technology – a kind of solar-powered thruster that is ten times more efficient than the usual chemical systems employed when travelling in space. If all goes well, such a system could be providing the propulsion system for future ESA missions into deep space, such as BepiColombo.

SMART-1 will be leading the way in the latest imaging techniques. Images taken from many different angles and X-ray and infrared detection work will allow scientists to draw up new three-dimensional models of the Moon’s surface.

SMART-1 will be looking at the darker parts of the Moon's south pole for the first time. It will be mapping the so-called Peak of Eternal Light, an eerie mountaintop that is permanently bathed in sunlight, while all around are dark craters never touched by the Sun. These craters are believed to harbour water-ice in the lunar soil. SMART-1 will also help scientists to confirm if ice is present at the lunar poles, where the temperature never rises above –170°C. Any water on the lunar surface would be very helpful in the creation of permanent bases on the Moon.

SMART-1  is heading for the Moon using revolutionary propulsion techniques and carry a battery of miniaturised instruments.

As well as testing new technology, SMART-1 will make the first comprehensive inventory of key chemical elements in the lunar surface. It will also investigate the theory that the Moon was formed following the violent collision of a smaller planet with Earth, four and a half thousand million years ago.

Scientists demand more from space missions travelling to other worlds and beyond than ever before an, traditional rocket technologies are beginning to show shortcomings. In response to this need, ESA are developing a new type of engine, known as solar-electric propulsion, or an 'ion' engine, which could mark a whole new era of space exploration. Solar-electric propulsion does not burn fuel as chemical rockets do; instead the technique converts sunlight into electricity via solar panels and uses it to electrically charge heavy gas atoms, which accelerate away from the spacecraft at high speed. This drives the spacecraft forwards. In a chemical rocket, the burning fuel creates gases which are expelled relatively slowly compared to ion thrusters. However, in an ion engine, the gas is ejected at high velocity, which makes it much more efficient and requires less fuel.

Ion engines are very important because their high efficiency makes previously impossible missions achievable. Since they do not need to carry so much fuel, ion engines release room for more scientific instruments. As technology continues to get smaller, the size of instruments decreases and the overall size and mass of the spacecraft decreases, further increasing efficiency.

Further away from the Sun, where the light is weaker, a new power source, such as a nuclear reactor, would be needed. This type of engine could take spacecraft to the Kuiper belt and even farther away. The Kuiper belt extends beyond the planet Pluto. It is a dream destination for many scientists because it contains comets that have been undisturbed since the formation of the Solar System. Beyond Pluto is a mysterious realm of magnetic fields and rarefied gases known as interstellar space. Solar-electric propulsion would make such a mission possible because an ion engine can run almost constantly, so that eventually it outperforms any chemical rocket on such long flights.
 
 
Journey
 
SMART-1 was launched from Kourou, French Guiana, on 27 September 2003. After launch, SMART-1 uses its ion drive to spiral out from the Earth until the Moon's gravity catches it and pulls it towards the Moon. The final operational orbit is a polar elliptical orbit, ranging from 300 to 10 000 kilometres above the Moon's surface.
 
 Partnerships
 
The SMART-1 project is being driven by a team at ESTEC in Noordwijk in the Netherlands. The industrial prime contractor is the Swedish Space Corporation (SSC) through its Science Systems Division. Some 15 subcontractors and suppliers from six European countries are involved in building the spacecraft. For the science and technology payload, co-investigators come from nine European countries, from ESA and from the United States.

The solar-electric primary propulsion that has been selected is a Stationary Plasma Hall-effect thruster, the PPS-1350 developed by SNECMA, France.

 Illustration Credit ESA

The European Space Agency's Science Programme encompasses, in addition to the ambitious 'Cornerstone' and medium-sized missions, recently dubbed 'flexi-missions', small relatively low-cost missions. These have been given the generic name SMART - 'Small Missions for Advanced Research in Technology'. Their purpose is to test new technologies that will eventually be used on bigger projects.

SMART-1 is the first in this programme. Its primary objective is to flight test Solar Electric Primary Propulsion as the key technology for future Cornerstones in a mission representative of a deep-space one. ESA's projected BepiColombo mission to explore the planet Mercury could be the first to benefit from SMART-1's demonstration of electric propulsion. Another objective is to test new technologies for spacecraft and instruments.

The planetary objective selected for the SMART-1 mission is to orbit the Moon for a nominal period of six months. It is the first time that Europe sends a spacecraft to the Moon. The project aims to have the spacecraft ready early in 2003 for launch as an Ariane-5 auxiliary payload. In addition to the use of solar electric primary propulsion to reach Earth's natural satellite, the spacecraft will carry out a complete programme of scientific observations in lunar orbit.

The Shape of Things to Come

The European Space Agency's SMART-1 craft, currently orbiting the Moon, is expected to shed additional light on lunar topography. NASA has plans for a robotic reconnaissance effort in 2008 that would provide more information on polar illumination. Meanwhile, India's first mission to the Moon, planned for 2007, would pack a U.S.-made radar instrument designed to pin down the locations of water ice.

References

In the recent February 2007 edition of Astronomy Now there is an interesting article by William Harwood based on an interview with NASA Administrator Mike Griffin on the future of the exploration of the Moon entitled 'Fly me to the Moon'.  It is well worth reading.

Although it was published sixteen years there is a very comprehensive book entitled 'Lunar Sourcebook - A user's guide to the Moon'.  It was edited by Grant. H.Heinken, David.T.Vaniman and Bevan.M.French.   There is a foreword by Harrison.H.Schmitt.

It was published in by the Cambridge University Press in 1991 (ISBN Number 0-521-33444-6).  There are over 700 pages of scientific details of work done on the Moon and on moon rocks.  It will be of particular interest to geologists and geochemists.

Solar System

Lunar Chemistry, Mineralogy and Petrology are dealt with in another section of the web-site hyperlinked to this one

Moon Chemistry