KOUROU, French Guiana (27 September 2003) â€” More than 30 years after the Apollo astronauts walked on the Moon's surface, a European space probe has been launched to investigate its far side in a mission that could finally answer questions about the origin of Earth's closest neighbor.
Smart 1, launched on board an Ariane 5 rocket from the Kourou spaceport in French Guiana on Saturday night (27 September), will map the far side of the Lunar surface, searching for signs of water ice in craters near its poles and gathering data on the chemical composition of its rocks.
The information will be used to test the "giant impact theory", which suggests that the Moon was created in a collision between Earth and another object not long after our solar system formed.
"We think we know what the Moon is made of because the Apollo astronauts went there and brought back half a ton of rock samples. But they went to the Earth side, on the equator and on the flat bits," said Professor Manuel Grande of the European Space Agency, who developed Smart 1 with the Swedish Space Corporation and contributions from 11 European countries.
"Those areas aren't typical and, importantly, they're not the ancient ones. What we need to do is a global survey of what the Moon is made of, and Smart 1 with our X-ray spectrometer will do that," he said.
The giant impact theory suggests that an object roughly the size of Mars crashed into Earth 4.5 billion years ago, throwing up vast amounts of debris that then aggregated into the Moon.
The theory has been supported by the similar composition of Earth and Moon rocks, but the probe should find that the Moon contains less iron than Earth, compared with lighter elements such as magnesium and aluminum.
This theory, that the Moon's core is less massive than the Earth's, has also been used to explain the Moon's orbit around the Earth, which is inclined by around 10 degrees relative to the equator. Most other planetary satellites in the solar system have orbital inclinations less than 1 or 2 degrees. By measuring the absolute amounts of these chemical elements comprehensively for the first time, Smart 1 might finally prove or disprove the theory.
The probe, which is about the size of a toaster, and cost just â‚¬110-million to develop, is being heralded as a test run for future, high-budget, European space missions.
It will map the Moon using a special x-ray camera developed in Oxfordshire. The photographs will be sent back to mission control where they can be compared to maps of the Earth's mineral make-up.
As well as using new miniaturized instruments, the probe will test a novel, solar-electric propulsion system that uses a stream of charged ions to create thrust rather than conventional chemical engines.
Although considerably less powerful and slower than a chemical rocket, the ion propulsion system, whose energy comes from solar panels of the probe's wings, is far more fuel-efficient, allowing the 370kg probe to cover the 385,000 kilometers to the Moon on just 60 liters of fuel.
Once the propulsion system is switched on for the first time tomorrow, it will take the probe 15 months to enter orbit above the Moon.
The Ariane 5 rocket also carried two research satellites from India and France.
The launch comes at a time of heightened public awareness of space exploration after the recent, damning report into safety lapses at NASA that contributed to the Columbia space shuttle crash that killed seven astronauts in February.
China has announced that it plans to launch its first manned mission to space within the next three months, although officials stress it will not be landing on the Moon.
China also confirmed recently that it had struck a deal to invest â‚¬230-million in the EU's Galileo satellite tracking system. The network of 30 satellites is being developed at a total cost of â‚¬1.1-billion to provide an alternative to America's global positioning system, which is favored by the Pentagon.