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| source: internet images |
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 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 debris for one moon, there was enough for two.
The small second moon become stuck in a gravitational tug of war between the Earth and its much larger sibling.
After millions of years in this position the new moon was drawn into a collision at a speed of less than three kilometers per second.
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A previous collision with a smaller companion could explain whythe Moon's two sides look so different. Martin Jutzi and Erik Asphaug |
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.
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 metres.
The researchers hope that Nasa observational missions might prove this new theory within a year.
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| source: internet images |
Earth had always been an oddball in the solar system as the only planet with a single moon. While Venus and Mercury have no moons, Mars has two, while Saturn and Jupiter have more than 60 each. Even tiny Pluto, which was demoted to dwarf status, has four moons.
Vocabulary:
build up (verb): enlarge, develop, or increase by degrees or in stages; bolster or strengthen
highland: relating to mountains and hills
struck (verb): (the past tense and past participle of strike) to strike: to hit; to crash
smash (noun): violent collision
debris (noun) /dÉ™’bri/: the broken pieces that are left when something large has been destroyed, especially by an explosion, fire, or accident.
stuck (verb): (the past tense and past participle of stick) to stick: if something sticks in, into, or through something else, its end remains pushed into or through it.
gravitational tug of war: pull in opposite directions by the force of gravity
sibling (noun): brother or sister
draw into (verb): to pull someone or something into something; to attract someone or something in.
slow paced: moving at low speed
far side: face of the Moon that can't be seen from the Earth
oddball: (things) strange; bizarre; (people) someone whose behavior is strange or unusual
demote (verb): to give something a less important position
dwarf: (SCIENCE) a very small star that does not shine brightly.
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| Journalist and Barone English's press agent |