TEXTO:
Earth may once have had two moons
A new theory suggests the Earth once had a small
second moon that disappeared after a collision with its
big sister. Researchers say in an article in the journal
Nature that the slow speed of the collision may explain
[5] the build up of highlands on the rarely seen part of the
Moon.
This new theory builds on the idea that around four
billion years ago the Earth was struck by a Mars-like
planet, but instead of the smash producing enough
[10] debris for one moon, this scientific essay argues there
was enough for two.
This small second moon became stuck in a
gravitational tug of war between the Earth and its much
larger sister. After millions of years in this position the
[15] new moon was drawn into a collision at a speed of less
than three kilometers per second.
The scientists say this slow paced crash may have
caused a build up of material and the formation of
highlands on the Moon’s far side, the face of the Moon
[20] that can’t be seen from the Earth. For decades scientists
have been trying to understand why the visible near side
of the Moon is covered in craters while the far side has
mountain ranges higher than 3,000 meters. The
researchers hope that NASA observational missions
[25] might prove this new theory within a year.
McGRATH, Matt. Earth may once have had two moons. Disponível em:<www.bbc.co.uk/worldservice/learningenglish/language/ wordsinthrnews/2011/08/110805witnmoonspage.shtml>. Acesso em: 12 out. 2011.
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