本帖最后由 人与自然 于 2012-11-28 10:26 编辑
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资料来源：http://www.dailymail.co.uk/sciencetech/article-2239233/Nasa-spacecraft-finds-thermal-image-Pac-Man-Saturns-moons.html
标题：It's Pac-Moon 2! Nasa spacecraft finds thermal image of 1980s iconic video game character in another of Saturn's moons
By Charles Walford
PUBLISHED: 14:45 GMT, 27 November 2012 | UPDATED: 17:28 GMT, 27 November 2012
（以下蓝色字体为翻译内容）
This must be what happens when Pac-Man meets Space Invaders.
Astronomers have discovered how one of Saturn's moons bears a striking resemblance to the dot-munching 1980s video game icon.
Scientists with NASA's Cassini mission spotted a thermal phenomenon shaped like the character on the moon Tethys.
A similar pattern was spotted in 2010 on Mimas, another Saturnian moon.
Pac-Man the sequel: NASA has recently spotted a thermal pattern on Tethys similar to that seen on Mimas two yeas ago
The original: Pac-Man from the 80s video game
The pattern appears in thermal data obtained by Cassini's composite infrared spectrometer, with warmer areas making up the distinctive shape.
The probe measures temperature differences across the object's surface and scientists believe the variations are probably related to the diversity of textures in surface materials.
Lighter areas of the moon which appear in the image may retain the heat better than others, scientists explain.
Scientists who examined the data from Mimas believe it is caused by high-energy electrons bombarding the side of the moon that faces forward as it orbits around Saturn.
The bombardment turns that part of the surface into hard-packed ice.
As a result, the altered surface does not heat as rapidly in the sunshine or cool down as quickly at night.
The 'Pac-Man' on Tethys confirms that high-energy electrons can dramatically alter the surface of an icy moon.
'Finding a second Pac-Man in the Saturn system tells us that the processes creating these Pac-Men are more widespread than previously thought,' said Carly Howett, the lead author of a paper recently released online in the journal Icarus.
'The Saturn system - and even the Jupiter system - could turn out to be a veritable arcade of these characters.'
Thermal images of both moons were obtained by the Cassini-Huygens mission, launched in 1997 to study the Saturn system in detail.
Phenomenon: Tethys appears to have a smoother surface than Mimas, but the effect is the same
'Studies at infrared wavelengths give us a tremendous amount of information about the processes that shape planets and moons,' said Mike Flasar, the spectrometer's principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Md. 'A result like this underscores just how powerful these observations are.'
Scientists saw the new Pac-Man on Tethys in data obtained on Sept. 14, 2011, where daytime temperatures inside the mouth of Pac-Man were seen to be cooler than their surroundings by 29F
The warmest temperature recorded was a chilly -300F, which is actually slightly cooler than the warmest temperature at Mimas (about -290F).
The Cassini project is a joint venture between the Nasa, the European Space Agency and the Italian Space Agency.
Its mission was recently extended until 2017.
A panoramic image of Saturn was created by combining a total of 165 images taken by the Cassini wide-angle camera over nearly three hours on September 15, 2006
Saturn has 62 moons with confirmed orbits. The largest is Titan, which is larger than the planet Mercury.
Mimas is only around 250 miles across. It has a distinctive scar called the Herschel Crater, which has led to many comparisons with the 'Death Star' from the Star Wars movies.
The Cassini team says the creation of the crater itself may have played a key role in the changing conditions across vast swathes of the moon's surface.
At Tethys, unlike Mimas, the Pac-Man pattern can also be seen subtly in visible-light images of the surface, as a dark lens-shaped region. This brightness variation was first noticed by NASA's Voyager spacecraft in 1980.
'Finding a new Pac-Man demonstrates the diversity of processes at work in the Saturn system,' said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
'Future Cassini observations may reveal other new phenomena that will surprise us and help us better understand the evolution of moons in the Saturn system and beyond.'
Space invaders: Two years ago the thermal image of Mimas taken by the Cassini spacecraft revealed the outline of Pac-Man on the moon surface | 
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