Arramon wrote:If an asteroid miles upon miles wide hit the Moon... oi! Possibly shattering it or breaking large chunks off. Light side, dark side, no matter. This entire region of space would be awash in the afterglow. But how large would the object need to be to cause such an event? And can scientists tell what the largest object may have been so far from the size of the craters upon the Moon's surface?
http://www.solarviews.com/eng/tercrate.htm
It seems to be a general rule of thumb that:
15 x Diameter of meteor ~ Diameter of crater
So the biggest "craters" observed today are caused
by (~4 billion year old) ~150km sized meteors:
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http://en.wikipedia.org/wiki/South_Pole-Aitken_basin
<<The South Pole-Aitken basin is an impact crater on Earth's Moon. Roughly 2500 kilometers in diameter and 13 kilometers deep, it is the largest known impact crater not only on the Moon, but also in the entire solar system. >>
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http://en.wikipedia.org/wiki/Hellas_Planitia
<<With a diameter of about 2,300 km (1,400 mi), [Hellas Planitia] is the largest impact structure on Mars. The altitude difference between the rim and the bottom is ~9 km (30,000 ft). If all the material excavated from it were spread evenly on the continental United States, there would be a 3.5 km (12,000 ft) thick layer of debris. The basin is thought to have been formed during the Late Heavy Bombardment period of the Solar System, over 3.9 billion years ago, when a large asteroid hit the surface.>>
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http://tinyurl.com/3exxpy
<<This image shows details of [Mercury's] Caloris basin, one of the largest impact basins in the solar system. MESSENGER's images indicate that the basin rim, shown as a blue dotted line in the image, is [about] 1550 kilometers in diameter.>>
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