Jul 12, 2019

50 years on, the Moon still rocks!


Fifty years ago, Cambridge mineralogist, Dr Stuart Agrell was given VIP treatment and a police escort after flying into Heathrow from the USA because he was carrying a bag full of very precious rock material. The samples were amongst the most expensive ever collected as they had been retrieved from the moon by two of the American Apollo 11 mission astronauts. The programme of their investigation was a remarkable and unprecedented example of international scientific collaboration, which still continues.

Stuart Agrell on the underground with a carpet bag of rocks from the Apollo 11 missionGuess what I’ve got in my bag? 50 years ago, Cambridge mineralogist, Stuart Agrell nonchalantly carried some of the most valuable rocks ever collected back to Cambridge in his holdall. (© Mirrorpix, reproduced with permission)

Category: 2019
Posted by: Sandra




Apollo 11
Launched from Cape Kennedy on July 16th 1969, the Apollo 11 mission opened a new era in the exploration of Earth’s moon. Four days later the lunar module Eagle landed with astronauts Neil Armstrong and Buzz Aldrin on board. An estimated 350 million people watched the televised images. One of their main aims was to sample as wide a range of rock and surface material as possible to help determine the moon’s composition and formation. They were also looking for any signs of past life or water on the moon.

On July 21, 1969, Armstrong and Aldrin spent some two hours collecting 50 rocks and surface dust from around the landing site. Although armed with a geological hammer, there was no available bedrock to sample. Eagle rejoined the orbiting command module Columbia, piloted by Michael Collins and they returned to Earth on July 24th. It was one of humankind’s most remarkable technological achievements.

Altogether the Apollo 11 mission recovered 21.5 kg of rock material from the Mare Tranquillitatis (Sea of Tranquillity). This vast region is in fact a very ancient impact basin between 3.5 and 3.8 billion years old and filled with basalt rock formed from molten lava. Its dust-covered surface is pockmarked by younger and smaller impact craters and rock debris, which created difficulties in landing Eagle.

Basalt lava sample photographs

Back on Earth, the samples had to be quarantined for 50 days to ensure that they contained no pathogens. Only then were they parcelled out to experts around the world for investigation. It is likely that no other set of rocks has been investigated so extensively or intensively.

A basalt lava collected by Apollo 11, seen in microscope thin section with polarized light. Numerous criss-crossing laths of feldspar, coloured white to black, intersect large pale brown pyroxene crystals. (© NASA/OU, imaged by Andy Tindle)







The moon comes to Cambridge
The Cambridge Department of Mineralogy and Petrology was one of the 150 recipient laboratories, thanks largely to the presence of mineralogist Stuart Agrell (1913-1996). He had spent much of the 1960s in America and became well known there for his precise chemical analyses of mineral samples and his work on meteorites. As a result Agrell along with Geoffrey Eglington (1927-2016), a Bristol University biogeochemist, were the only non-American geoscientists involved in planning the moon-sampling program, which required frequent trips to Houston.

There are various anecdotes, some of them contradictory, about Agrell’s seemingly nonchalant approach to this remarkable material. Apparently the security-conscious American team in Houston, were somewhat non-plussed by Stuart Agrell’s sole concession to the safe keeping of the samples. For the return trip to London, he just tucked them into his spare clothes in a large holdall. On arrival, the samples went on display for the press at the SRC (Science Research Council) headquarters in High Holborn before being collected by the principal investigators of the 15 UK research teams. Again, there was an emphasis on the need for sample security in transport and within laboratories along with an urgency in investigation. Initial results were to be reported within three months for publication in the international journal Science and at a conference in Houston.

Whilst many of the research teams had put in place all sorts of elaborate decoy plans to avoid hijacks of the priceless material, the Daily Mirror splashed a photo of Stuart on the London tube with the holdall on his knee. But by the time it was published Agrell and his samples were safely back in Cambridge. One puzzling aspect is that, according to the accompanying Daily Mirror caption, on 19th of September, 1969, Stuart was accompanied on the tube by Dr P. E. Clegg of Queen Mary College, London University. However, the lady sitting next to Agrell is definitely not the physicist Dr Peter Clegg. She may have been someone from the SRC.

Stuart Agrell on the underground with a carpet bag of rocks from the Apollo 11 mission
Press photo from September 19th, 1969 of Stuart Agrell on the London underground, having flown in from Houston that morning, clutching his holdall with moon rock samples. (© Mirrorpix, reproduced with permission)

Stuart Agrell and the Cambridge team
For over 30 years before the Apollo 11 mission, Agrell had been using optical microscopes and ‘wet chemical’ analysis to study fine-grained minerals. He was especially interested and knowledgeable about those minerals, which had undergone high temperature processing both industrially and naturally. Initially, this work was done during the decade from 1939, which he spent as a staff member at Manchester University. He continued this work when, in 1949, he moved back to Cambridge, where he had been both an undergraduate and Ph D student. Here, Agrell benefitted from the technological expertise of Jim Long who was working on a pioneering and ‘home made’ scanning X-ray micro-analyser in the Cavendish Laboratory. It had the advantage of being the first to provide in situ transmitted light viewing of polished and uncovered thin sections of the moon rocks. Agrell’s investigation of the Moon rocks was greatly aided by this newly emerging technology.
 
Sedgwick Club group photographStuart Agrell in 1952, seen in a Sedgwick Club photo, three years after his appointment in the Department of Mineralogy and Petrology. Agrell is third from left on the front row.

















What are the moon rocks?
The Apollo 11 lunar rock material ranged from fragments of igneous rock and microbreccia to the lunar surface dust. Agrell worked with other members of the Department, the mineralogist I.D. Muir, the ‘wet chemist’ J.H Scoon and the crystallographers P. Gay and M.G. Bown on the analysis of the larger dust fragments. This revealed the presence of basaltic igneous rocks derived from the underlying bedrock lavas. But there are also fragments of other moon rocks, especially a feldspar –rich igneous rock called anorthosite from the lunar highlands. In addition, the mixture of crystalline and glassy fragments in the dust records successive episodes of impact and melting. Agrell’s expertise and striking personality led to him being in constant demand for television interviews during the Apollo programmes.

Laboratory notebook, handwritten notes
A laboratory notebook showing the results of a wet chemical analysis of some lunar samples that was made within days of arriving in Cambridge, probably by J.H. Scoon who was a chemist who worked with Stuart Agrell in the Department of Mineralogy and Petrology. (image Sedgwick Museum archives, reference AGRL DDF 880a)

The Soviets join in
Just four months later in November 1969 Apollo 12 also made the trip and recovered another 34 kg of samples, mostly ancient basaltic rocks from the moon’s Oceanus Procellarum (Ocean of Storms)’ region. Dated to between 3.1 and 3.3 billion years old, these basalts are some 500 million years younger than the Apollo 11 basalts. And then in September the following year (1970), the Russians finally succeeded in landing an unmanned robotic Russian Luna 16 probe on the moon. They drilled 35 cm into the surface deposits and recovered a 101 gm core sample from the Mare Fecunditatis.

The next four years saw successive Apollo and Luna missions recovering a total of several hundred kilos of moon rocks and dust. Some of this material found its way to Cambridge and other British laboratories. Overall, the geological samples provided many new insights into the processes that formed the moon and its surface but did not resolve the problems of its origin. No signs of life were found nor initially any indication of water. However, subsequent lunar probes have detected patches of crystalline water-ice at the moon’s poles.

The Cambridge team expands and contracts
In 1976, Agrell invited Colin Pillinger, who was a member of a Bristol University lunar research team working on the carbon chemistry of the lunar samples, to join him in Cambridge. Pillinger brought the ‘carbon’ team with him and so there were two independent lunar research teams in the Cambridge Department of Earth Sciences. Then, in 1985, Colin Pillinger and the ‘carbon’ team moved to the Open University at Milton Keynes. There, Pillinger formed the Planetary and Space Sciences Research Institute and later conceived and the 2003 Beagle 2 spacecraft which landed on Mars in 2003.

Group picknicking 1982

Moon rock researchers picknicking in the Pillinger’s garden. From left to right: Jean and Stuart Agrell and Colin Pillinger along with Peter Swart and others.
Credit: with thanks to Judith Pillinger

 

 









Stuart Agrell retired from formal academic duties in 1980 and was elected President of the Mineralogical Society of Great Britain in 1983. He continued publishing his research work into the 1990s.

The Moon still rocks: An ongoing story
Research continues on the lunar samples including the basalts. Eleanor Jennings’ Cambridge PhD looked at large-scale eruptions of basalts and the relation to their source in the underlying mantle. Currently a lecturer at Birkbeck, University of London she is extending this work to the very ancient and primitive lunar basalts collected in the Apollo 12 mission (See Fig X) to see what they can tell us about their mantle source rocks. She is collaborating with Iris Buisman in the Cambridge Department of Earth Sciences where the microprobe technology allows them to measure trace elements at high precision in individual crystals. This provides clues as to the original temperature of crystallization of the basalts.

Basalt sample photographs
An Apollo 12 basalt sample (on loan from NASA), is being investigated using a Quanta 650-F Scanning Electron Microscope (SEM) at the University of Cambridge, Earth Sciences Department.  As the rock crystallised from a primitive lunar magma, it gets us a close as possible to the lunar mantle from which it was derived.
Upper: Called a phase map, this image shows olivine crystals (pale green) with a variety of forms – skeletal, dendritic and equant. The resulting texture probably reflects fast cooling of a low viscosity ‘fluid’ magma. The phase map shows the magma’s high iron content (see lower hand image) which is derived from the lunar interior.
Lower: An Fe-map shows iron concentrations in the olivine crystals, with the dendritic forms being the most Fe-rich whilst the equant olivines show increasing Fe from core to rim. (image NASA, courtesy Dr. I. Buisman)

Douglas Palmer
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