Water on Moon?
The Apollo lunar landings were a gift to science that keeps on giving. Since the lunar surface is not subject to weather or plate tectonics, it gives us a much longer geologic history. The "Genesis Rock" found on the Moon is 4.5 billion years old, nearly as old as the Solar System. In the 1980's, similiarities between lunar ejecta and Earth samples from 65 million years ago led to the theory that an asteroid ended the age of disnoaurs. year 40-50 researchers receive Moon samples for continued experiments.
Prior to Apollo, scientists had no clue what the Moon was made of or where it came from. Today most researchers believe that the Moon was born when a Mars-size object struck Earth and blew off the outer layers. The surviving fragments were big enough to attract each other gravitationally until a single satellite remained. The early Moon was a ball of hot magma, with a lighter crust that became the lunar highlands. The lunar "seas" are seen as erupted materiel from the interior. The Moon formed much closer to Earth, and has been drifting away due to tidal forces.
In a study published this week in NATURE, geologist Alberto Saal found evidence of water in Apollo samples. It took 3 years getting the funding to study old rocks, an example of how long good research can take. Using the newer technique of secondary ion mass spectrometry, Saal found traces of volatiles including water. Data showed that hydrogen had been concentrated in the centres of samples, indicating that it dated from the Moon's infancy. Water may even have arrived on the fragments blown from Earth, indicating that our planet had water 4 billion years ago.
As a practical matter, water would make settling the Moon much simpler. It would mean drinks for humans and fuel for Spacecraft. Future Space missions could be resupplied in Earth orbit with hydrogen from the Moon. The Lunar Prospector mission from 1999 found tantalising hints of water ice in the poles. Scientists at ICES last week were itching for the chance to prospect on the lunar South Pole.
Less than a month ago evidence for water was found in The Sands of Mars. Not long ago Earth was thought to be the only watery world. Today there is evidence of H2O in worlds as far-flung as Enceladus and Europa. The dwarf planet (asteroid) Ceres may contain more water that Earth! Water, and possibly other ingredients for life, may turn out to be common in the Solar System.
Human exploration of the Moon has been a huge benefit to science. As mentioned before, the Moon has been slowly drifting away. The Lunar Laser Ranging Experiment from 1969 measures the recession rate as 3.82 cm/yr. Geology and paleontology disagree, measuring recession as about 2.9 +/- 0.6 cm/yr. How can two such precise measurements disagree? If the speed of light is slowing, that will increase the time for light signals to return each year, making the Moon appear to recede faster as seen by LLRE. Starting with GM = tc^3, the prediction is 0.935 cm/yr, precisely accounting for the discrepancy. For measuring small changes in c, it helps to have a long baseline.