Apollo may have been conceived as a political vehicle during the US-Russian Cold War, but nonetheless the missions provided a spectacular hoard of science that continues to reward researchers today. The lunar rocks alone have become the foundation stones on which our modern understanding of planetary formation is built.

Despite being outside the lunar module for just two-and-a-half hours, the first moonwalkers, Armstrong and Aldrin, picked up 22kg of rocks.

They also deployed a number of experimental stations, including particle collectors, seismometers and mirrors to reflect laser beams from Earth. The later Apollo landings, when science became more important, augmented these.

The entire lunar surface covers an area just a little bigger than Africa. Between July 20, 1969, and December 14, 1972, six touchdowns took place across the nearside. The returned rocks all proved to be solidified lava; none had been built in rivers or oceans. This confirmed geologists’ belief that the Moon’s surface has never been touched by water, wind or rain.

How US was nearly pipped to first moon rock samples

Sir Bernard Lovell tells Erica Wagner how he listened from Jodrell Bank to the drama, with the original audio from 1969

BACKGROUND

• DIY on the Moon: how Buzz saved the launch back to Earth

• Moon rock of ages

• Apollo Gadgets: Can you guess what they were for?

• The Moon: Gods, myths and legends

Related Internet Links

• Moon landing 40th anniversary special supplement

• The 21 best space toys

Lunar rocks are valuable because they are much older than those on our planet. Earth’s moving continents and volcanoes constantly recycle our rocks, destroying the early geological record. As a result, no Earth rock has been subjected to the same level of scrutiny as the lunar samples. Two particularly valuable samples were the “Genesis Rock” and the less glamorously named Troctolite 76535. Both are more than four billion years old, dating them close to the formation of the Moon.

The composition of the moon rocks led astronomers to reject contemporary theories of lunar formation, namely that the Moon formed as a “sister world” to Earth, or formed elsewhere and was captured by Earth’s gravity. Instead, they plumped for a scenario in which Earth suffered a glancing blow from another planet-sized body late in its development. This threw up a cloud of debris, from which heavier chemicals fell to Earth, while lighter material stayed in orbit and became the Moon.

Apollo 12 landed in the debris blown out of the young looking crater Copernicus, more than 300km away. Dating those rocks gave the crater’s age as 800 million years. From this, planetary scientists could back calculate ages for the other craters on the Moon, finding that most were formed between 3.8 and 4.1 billion years ago. This era is now known as the “late bombardment” and is when much, if not all, of the water in Earth’s oceans was brought to the planet by colliding comets. This bombardment set the stage for life to emerge on our world.

In mid-June 1975, lunar seismometers alerted astronomers of a potential threat to Earth by recording a cluster of meteorite impacts. Astronomers went on to find a string of impacts with our world during the month of June, stretching back through history. They included the large 1908 impact in the Tunguska region of Siberia that devastated a region of forest as large as the M25 circle.

They also found indications that the Dark Ages began with similar impacts around AD 535. The evidence suggests that a shattered asteroid or comet has created a danger zone that Earth ploughs through every June, and helped to stimulate our modern quest to detect dangerous asteroids.

The lunar seismometers showed that the Moon is not as dead as most scientists assumed. Every 27 to 28 days, a deep moonquake rumbles through the rocks. Although weak, just 1 to 2 on the Richter scale, the regularity and the timing suggests that these are the lunar equivalent of the tides on Earth.

Although the automated science packages were turned off in 1977, one experiment continues to this day. It may turn out to be the most important of all. Started by Apollo 11, it is the lunar laser ranging experiment. Astronomers on Earth bounce laser beams off the mirrors left by Apollos 11, 14 and 15 to measure the orbit of the Moon. This orbit is described by Einstein’s theory of gravity, General Relativity.

Modern theories, such as string theory, all predict slightly different motions from General Relativity. Recent upgrades on Earth mean that the laser teams can measure the lunar orbit to within a few millimetres. Astronomers are preparing computer software to search these measurements for deviations from General Relativity. If they find any, Apollo may provide the breakthrough that leads to our understanding of string theory.

Not bad for a 40-year-old experiment.

Stuart Clark is the author of The Sun Kings

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