Study: Mars is rocked by asteroids, comets each day
Alyssa Samson | Thursday, May 16, 2013
Recent images from NASA’s Mars Reconnaissance Orbiter suggest that Mars is bombarded with hundreds of cosmic impacts a year, forming craters that measure up at an average size of 12.8 feet.
Using images from the University of Arizona-led HiRISE imaging instrument aboard the Orbiter, the device has found at least 248 new impact craters that have been created on the surfaces of Mars within the past decade.
However, scientists have estimated roughly 200 impacts a year based on the number identified in a systematic survey conducted on a portion of the Red Planet. HiRISE collected images of sites that had been already taken by the Context Camera (CTX) or by other cameras, providing a before-and-after comparison of the impacts. With these images, researchers were able to make direct measurements of the impact rate on Mars. The new craters are noticeable because the impact disturbs the dust from the previous craters ...
http://www.sciencerecorder.com/news/study-mars-is-rocked-by-asteroids-comets-each-day/
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high in the atmosphere ... The moon, however, has no atmosphere, so meteoroids have nothing to stop them from striking the surface. The slowest of these rocks travels at 20 km/sec (45,000 mph); the fastest travels at over 72 km/sec (160,000 mph). At such speeds even a small meteoroid has incredible energy -- one with a mass of only 5 kg (10 lbs) can excavate a crater over 9 meters (30 ft) across ....
... Current meteoroid models indicate that the moon is struck by a meteoroid with a mass greater than 1 kg (2 lbs) over 260 times per year. This number is very uncertain, however, as observations for objects in this mass range are embarrassingly few -- a single fireball survey conducted by Canadian researchers from 1971 to 1985 ...
... U.S. Space Exploration Policy eventually calls for extended astronaut stays on the lunar surface ... Spacecraft, vehicles, habitats, and EVA suits must all be designed to withstand the stresses posed by the harsh lunar environment ...
... A second part, produced by meteor showers, is also present to varying degrees at certain times of the year. It is well known that the Earth experiences meteor showers when it encounters the debris left behind by comets; so too does the moon, though perhaps at not exactly the same time. On Earth these showers are capable of producing spectacular celestial fireworks displays, delighting the public. On the airless moon, however, these showers are swarms of high energy projectiles, producing fireworks only when they strike the surface with tremendous force. During such times, the rate of shower meteoroids can greatly exceed that of the sporadic background rate ...
http://www.nasa.gov/centers/marshall/news/lunar/program_overview.html