50th anniversary of the Moon landing

One gi­ant leap for greater knowl­edge

The first ‘flag’ on the Moon
The first ‘flag’ on the Moon
Image 1/3, Credit: NASA

The first ‘flag’ on the Moon

The first ‘flag’ on the Moon was not the US flag, but a sail made of alu­minum foil, with cap­tured so­lar wind par­ti­cles. The ex­per­i­ment was con­tribut­ed by Switzer­land.
Thin slice of a rock shattered by asteroid impacts
Thin slice of a rock shat­tered by as­ter­oid im­pacts
Image 2/3, Credit: Washington University, Brad Jolliff

Thin slice of a rock shattered by asteroid impacts

A 25 mi­crome­tre thin slice of a rock shat­tered by as­ter­oid im­pacts in po­larised light un­der a mi­cro­scope. Stud­ies of the 382 kilo­grams of rock col­lect­ed on the six lu­nar land­ings re­veal how the Moon and Earth evolved in their ear­ly days.
Experiments carried out during Apollo 17
Ex­per­i­ments car­ried out dur­ing Apol­lo 17
Image 3/3, Credit: NASA/JSC, Warren Harold

Experiments carried out during Apollo 17

The as­tro­nauts used their Has­sel­blad cam­eras to cap­ture dozens of frames us­ing Zeiss lens­es. The Panora­ma Mo­sa­ic shows the ex­per­i­ments car­ried out dur­ing Apol­lo 17 along a route that is more than 100 me­tres long

Houston: Tranquility Base here. The Eagle has landed! – Almost 50 years ago, on 20 July 1969 at 20:17 UTC, Neil Armstrong and Edwin ‘Buzz’ Aldrin landed on the Moon, achieving a goal that had become so important to the United States of America that for a decade they had prioritised it above almost everything else. Towards the end, the landing became quite difficult because there was only enough fuel for a few more seconds of flight and the landing approach almost had to be aborted. However, the two new national heroes – and not forgetting Michael Collins, the pilot of the Command and Service Module that remained in lunar orbit – mastered this situation with ice-cool professionalism. They ignored – after an “OK” from ground control – yet another (false) radar alarm. Admittedly, the first crewed Moon landing was largely a political demonstration. But regardless of how today’s historians judge the outcome of the ‘race to the Moon’ that culminated in Armstrong’s “That’s one small step for [a] man, one giant leap for mankind”, the Apollo project was much more than just 12 astronauts walking on the Moon. For technology, but even more so for scientific research, this was a giant step forward: the Apollo programme was the birth of planetary research.

The Apollo programme paved the way for insights into the Solar System

There it stood, the US flag, planted on the Moon, just metres from the Eagle Lunar Module. In fact, this was not the first flag to be placed in lunar soil. At the beginning of their two-and-a-half hours of extra-vehicular activities, Armstrong and Aldrin installed a ‘measuring device’: a piece of aluminium foil measuring 130 by 30 centimetres, suspended from a kind of flagpole. It was intended to catch solar wind particles, which do not reach Earth due to its magnetic field and could therefore be collected for the first time on the Moon. The experiment was devised by scientists at the University of Bern.

But two other scientifically relevant events took place before that: Neil Armstrong secured a sample of lunar dust in a fire-retardant sample return bag shortly after taking his first steps on the surface of the Moon and stowed it away in his space suit, so that he would have ‘a piece of Moon’ with him if they needed to make a speedy escape from the surface.

And as Buzz Aldrin looked closely at the first footprints made by his ‘Moon boots’, he thought “That’s interesting” – when realising that the edges of the impression did not slip away. “The lunar dust behaved like cement powder!” He then took a photograph of his footprint in the fine Moon dust, the regolith, never suspecting that it would become an iconic image of humankind’s history of discovery – and probably the most printed photograph of the Apollo era.

These events, which took place during the first half-hour of humans landing on another celestial body for the very first time, show how adventurous the Moon missions were and give some idea of the pressure those involved must have been under. The Apollo era began dramatically on 27 January 1967, with the posthumously named Apollo 1 mission, which claimed the lives of Gus Grissom, Roger Chaffee and Edward White while still on the ground – they burnt alive locked inside the command capsule, which was pressurised with pure oxygen. The Apollo 4, 5 and 6 missions follow – all without a crew. With Apollo 7, humans orbited Earth for the first time with the Command and Service Module, launched previously with a Saturn-1B; with Apollo 8 they circled the Moon at Christmas 1968 – the first time the fabolous Saturn-V rocket was used. During Apollo 9 and 10 – dress rehearsals for landing – the lunar module came to within 14 kilometres of the lunar surface. Then finally, the first Moon landing took place during Apollo 11. This was followed by another five successful lunar landings up until December 1972, including the dramatic rescue of the crew of Apollo 13, who were forced to loop round behind the Moon and continue back to Earth. These technical masterstrokes, the planning, construction, control and completion of which involved up to 400,000 people over time, have gone down in history.

Fifty years ago, the focus was not on lunar research, but it was precisely this that made the success of the Apollo missions possible and undoubtedly led to the lasting triumphs of this project – the exploration of the Moon.

A new science

Ensuring a successful first Moon landing – comprising the approach to the Moon, a safe landing and exit from the landing probe and, above all, the return of the astronauts to Earth alive and well – required knowledge of the characteristics of this somewhat unfamiliar celestial body. It was important to know more about its surface and conditions, such as its load capacity, topography, radiation environment, temperatures and much more. Despite high-precision observations with terrestrial telescopes, much remained unclear. The Earth’s atmosphere set unassailable physical limits on Moon observations: even the most powerful telescopes only enabled the identification of features one kilometre across on the Moon – about 380,000 kilometres away. That was not precise enough for landing.

Only space travel made close-up observations possible. In 1959 – two years after Sputnik 1 –the Soviet Union photographed the far side of the Moon for the first time with the Lunik 3 probe. From the mid1960s onwards, the US began researching the Moon intensively using probes and robotic tools in the run-up to the Apollo missions. The kamikaze Ranger series of probes delivered the first high-resolution images of the lunar surface during their deadly nosedive flight. Five probes of the Lunar Orbiter series mapped the entire surface of the Moon from their orbit, making it possible to carry out large-scale geological and geodetic studies and determine landing sites. Finally, the slender yet robust Surveyor lander probes demonstrated that the Moon had a firm surface and that a lunar module would not sink into the lunar dust. However, as large footpads had already been constructed and attached to the spider-shaped landing struts of the Lunar Module, they were not removed due to safety reasons and time constraints.

The scientists who studied the Moon, selected the landing sites and made the preparations for the activities on the lunar surface were geologists, geodesists, geographers, geophysicists, geochemists and mineralogists. In addition to the physicists and astronomers, there were mainly geoscientists. Of course, ‘geo’ refers to Gaia, or Earth, but when it comes to the Moon we are talking about something definitely extraterrestrial. So how should these researchers be referred to? At NASA and the United States Geological Survey (USGS), they were categorised as astrogeologists – geologists of the stars. But this was far from accurate for the pioneers of this collection of disciplines – the Don Davises, the Ron Greeleys and the James Heads, not to mention the tireless Eugene Shoemaker (who would have loved to become an astronaut and, as a geologist, wanted to carry out research on the Moon). They made a huge contribution towards the Apollo moon landings. They described the Moon and the landing sites, devised an all-encompassing concept for the accompanying scientific programme and prepared the astronauts, who were – with the exception of geologist Harrison ‘Jack’ Schmidt on Apollo 17 – US Air Force and Marines fighter pilots, training them to achieve the objectives of their missions through field exercises and seminars.

‘Gene’ Shoemaker said, “It only takes a couple of minutes to plant a flag, so what do you do for the rest of your time on the Moon?” NASA saw the wisdom of this and made the comprehensive study of the Moon an integral part of all its Apollo missions. This was especially true of the three last missions – Apollo 15, 16 and 17 – which benefited from electromobility – how progressive at that time… – in the form of a rustic mobile device called the Lunar Roving Vehicle. Astrogeologists soon became lunar geologists, as the methods and tools used were the same as those used on Earth.

After Apollo, the profession of planetary researcher continued to develop, not least because together with the long sought-after landing of humans on the Moon, Venus and Mars also began to attract the attention of the two space nations, the US and the USSR. Earth’s two neighbouring planets began to be explored up close by numerous robotic probes at the same time as the Apollo project.

Of course, the Moon is not a planet, but – and this was one of the first great discoveries made by Apollo – its development and many of its characteristics make the Moon a planetary body. This is due to its solid surface and mineral composition, with a high proportion of silicon and aluminium, and deeper inside, in its mantle, a high quantity of heavy minerals, rich in iron and magnesium, and even a small iron core, like Mercury, Venus, Earth and Mars. Above all, the crust of the Moon is far older than Earth’s dynamic crust, which is constantly changing because of plate tectonics. As such, the Moon offers scientists a window into the past of planetary evolution.

382 kilograms of Moon - the 'Holy Grail'

On 14 December 1972 Eugene Cernan, Commander of Apollo 17, was the last visitor from Earth to lift off from the Taurus Littrow valley, returning to Earth in the Challenger Lunar Module. No one has set foot on the Moon since then, and there has been a hiatus of almost three decades during which no robotic probes have visited the Moon on scientific missions. There are good reasons for this. In political terms, the Moon had served its purpose, following six triumphant, accident-free landings – in other words, mission accomplished. In addition, scientists then had enormous quantities of data, measurements, images, and above all, Moon samples to analyse. In total, the 12 moonwalkers brought 382 kilograms of lunar samples back to Earth – the Holy Grail of planetary research! Previously, there were no samples of precisely known extraterrestrial origin on Earth. Examining them under a microscope and using geochemical analysis methods opened up a wide portal to fundamental findings for planetary research.

What the samples have taught us

How did the Moon form? Almost all of the knowledge we have acquired up until now from the lunar samples indicates that a Marssized body grazed Earth 4.52 billion years ago, when Earth was just 20 to 30 million years old and in bulk still molten-hot. The impact affected parts of Earth’s first crust, the early mantle and core, which then mixed. So much material was thrown off and evaporated from Earth’s mantle that a satellite – the Moon – emerged as the ejected materials cooled and condensed. How did this planetary duo develop? Under heat, not cold! There was a great deal of controversy over whether the Earth had assembled as a cold mass after being formed out of small bodies – planetesimals – or whether it had undergone an extremely hot stage of development due to the heat released in the collisions and the high temperatures generated by the decay of radioactive elements.

Today we know that the latter is the case: in the beginning, the young Earth and the Moon were both covered in a glowing ocean of magma hundreds – and in the case of Earth, thousands – of kilometres deep, with lighter minerals rising up and cooling on the surface, while heavier minerals sank into the depths, forming a thick mantle and an iron and nickel core. This process was typical of all planets in the inner Solar System (and the Moon). It also occurred on some larger bodies at a greater distance from the Sun and is referred to as differentiation by geologists. The scientists learned all this and more from the lunar samples. Even so, the matter of the Moon’s formation has yet to be completely determined. The answers could lie in samples from a huge impact crater on the far side of the Moon, where material from great depths can be found.

Six Moon landings with Apollo landing capsules have impressively demonstrated that humans – namely astronauts – play an invaluable role in exploring our immediate cosmic neighbourhood. This was even truer decades ago, when automation and robotics were not as advanced as they are today. The immense yield of data and research findings provided by remote-controlled lander probes and rovers on Mars is utterly awe-inspiring. Yet the achievements of the astronauts on the Moon remain unsurpassed: people can apply their intuition to solving tasks to a degree that is thus far unmatched by any robot, and humans can also make decisions without the need for ground control and information. A Mars rover requires many days or indeed weeks of pre-programmed steps, steered from Earth, to complete a task that could be accomplished by an astronaut in a matter of seconds, minutes or hours.

Back to the Moon? Yes, back to the Moon!

What does this snapshot mean for the future of lunar research? Many questions relating to the origin of the Moon and the early history of the Earth-Moon system remain unanswered. Finding solutions is hugely important, not least to resolve the mystery of when and how life developed on our planet. Earth’s development over its first 4.5 billion years is not yet fully understood, and the Moon, and indeed Mars, can provide answers. At the top of the lunar research wish list is the (preferred robotic) extraction of more samples, especially from the depressions in the South Pole-Aitken impact basin at the far side of the Moon, which could reveal rocks from the Moon’s mantle. These could show us what happened during the early days of the inner Solar System. The far side of the Moon, which is never visible from Earth due to the fact that it rotates once around its own axis every 28 days, and once around the Earth in that same amount of time, would also provide a remarkable observation platform for radio astronomy. Here, radio signals from Earth would not interfere with the search for the echo of the Big Bang – and the perfect vacuum on the Moon would provide materials scientists with an ideal laboratory.

Humans – whether astronauts, cosmonauts, taikonauts or ‘euronauts’ – are also set to return to the Moon in the medium term, whether in pursuit of a temporary or even permanent settlement on another celestial body, or to use the Moon, where the gravitational pull is six times lower, as a springboard for missions to Mars. The Moon’s poles are pockmarked with craters that inside never see the Sun and, due to the lack of atmosphere, never warm up. There is ice in these permanently dark places, observed by spacecraft, and it could be used for hydrogen and oxygen rocket fuel. The steep crater rims are always lit by the Sun and are in constant direct visual and radio contact with Earth.

It is precisely at one of these shaded craters that the research community has paid tribute to the man who, at the beginning of the Apollo missions, insisted that landing on Earth’s satellite also be put at the service of science. On 31 July 1997, the Lunar Prospector space probe was deliberately crashed into the floor of a crater that would be named after him. At the end of its two-year mission, it brought part of the ashes of lunar geologist Eugene Shoemaker, who died in 1997, to the site of his longing.

This article was published in DLRmagazine 160.

  • Elke Heinemann
    Ger­man Aerospace Cen­ter (DLR)

    Com­mu­ni­ca­tions and Me­dia Re­la­tions
    Telephone: +49 2203 601-2867
    Linder Höhe
    51147 Cologne
  • Prof.Dr. Ralf Jaumann
    Freie Uni­ver­sität Berlin
    In­sti­tute of Ge­o­log­i­cal Sci­ences
    Plan­e­tary Sci­ences and Re­mote Sens­ing
    Telephone: +49-172-2355864
    Malteserstr. 74-100
    12249 Berlin
  • Ulrich Köhler
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Plan­e­tary Re­search
    Rutherfordstraße 2
    12489 Berlin
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