Today. 03.27 GMT
The US space agency (Nasa) has launched its latest mission to the Moon.
The unmanned LADEE probe lifted off from the Wallops rocket facility on the US east coast on schedule at 23:27 local time (03:27 GMT on Saturday).
Its $280m (£180m) mission is to investigate the very tenuous atmosphere that surrounds the lunar body.
It will also try to get some insights on the strange behaviour of moondust, which appears on occasions to levitate high above the surface.
In addition, LADEE will test a new laser communications system that Nasa hopes at some point to put on future planetary missions. Lasers have the capacity to transmit data at rates that dwarf conventional radio connections.
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The Moon's exosphere
Lunar atmosphere thought to be only 1/100,000th the density of Earth's atmosphere
Earth's atmosphere contains some 100 billion air molecules per cubic cm at sea level
May be only about 100,000 to 10 million molecules per cubic cm at the Moon's surface
Very little known about this atmosphere's precise atomic and molecular composition
LADEE stands for Lunar Atmosphere and Dust Environment Explorer.
Collisionless environment
Its programme scientist, Sarah Noble, says the mission is likely to surprise a lot of people who have been brought up to believe the Moon has no atmosphere.
It does; its just it's really, really thin, she told reporters.
Its so thin that the individual molecules are so few and far between that they dont interact with each other; they never collide.
Its something we call an exosphere. The Earth has an exosphere as well, but you have to get out past where the International Space Station orbits before you get to this condition that we can consider an exosphere. At the Moon, it happens right at the surface.
LADEE The Lunar Atmosphere and Dust Environment Explorer will operate for a total of about six months
Scientists are interested in understanding such wispy shrouds because they are actually the most common type of atmosphere in the Solar System. Mercury has one, as do a lot of the moons of the giant planets. Even some big asteroids are likely to have one, too.
The dust phenomenon has puzzled researchers for decades. Apollo astronauts reported seeing a diffuse glow above the lunar horizon just before sunrise. The speculation has been that this glow was caused by electrically charged dust particles being lifted from the Moon's surface by ultraviolet light from the Sun. LADEEs remote-sensing and sampling instrumentation will test this idea.
What it learns about the dust is also likely to inform engineers who are developing the systems to take humans back to the Moon and to other destinations where dust could be an issue, such as on asteroids.
This fine particulate material, which comprises remnant rock shattered through eons of meteorite impacts, is considered a major hazard.
Its not like terrestrial dust, observed Butler Hine, Nasas LADEE project manager.
Terrestrial dust is like talcum powder. On the Moon, its very rough. Its kinda evil. It follows electric field lines; it works its way into equipment. One of the questions about dust on the Moon is an engineering question: how do you design things so that they can survive the dust environment.
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Spacecraft is 2.4m high and 1.8m wide, and weighs 383kg fully fuelled
Based on a new low-cost modular chassis for use on other planetary missions
Mission will last six months in total with 100-day science observation phase
LADEE will be crashed into the lunar surface when its fuel supply has run out
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Apollo astronauts found the chaffing moondust would stick to everything. And there are concerns that if such material were breathed in, it could lead to respiratory problems.
Having been launched by its Minotaur V rocket, LADEE will be sent on a long spiral out to the Moon. This will take about a month. A further month will then be needed to commission the spacecraft before its altitude is taken down to as low as 20km above the surface for a 100-day phase of science observations.
LADEE will end its mission by crashing into the Moon.
As well as its three science instruments, LADEE carries a demonstration laser telecommunications payload.
This system promises a big jump in data transmission rates. Engineers are hoping the test terminal on LADEE will achieve download rates in the region of 600 megabits per second. A number of receiving stations on Earth will be used, including the European Space Agencys (Esa) optical ground station on Tenerife.
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