NASA has been studying all aspects of Mars using various spacecraft and rovers on the planet surface for a number of years. One of the most important scientific instruments orbiting Mars is NASA's Mars Reconnaissance Orbiter. Recently, NASA has been using the MRO to observe how many asteroid impacts and how many little bits of comets hit the surface of Mars each year that form craters of a certain size.
NASA's specifically looking for impacts that form craters that are at least 12.8 feet across. The investigation has led researchers to identify 248 new impact sites on different portions of the surface of Mars in the past decade. NASA scientists used images from the MRO to determine when the craters appeared.
NASA arrived at the conclusion that more than 200 small asteroids or little pieces of comets impact the surface of Mars each year by calculating a number based on the actual number of craters found in a systematic survey of a smaller portion of the red planet. NASA used the MRO's Hi Resolution Science Experiment camera to take pictures of fresh craters at sites where before and after images by other cameras were available.
NASA says that Mars is struck with a significantly higher number of asteroid and comet fragments than Earth because Mars has a much thinner atmosphere, therefore these smaller fragments don't burn up during entry. The asteroid or comet fragments that hit the planet are usually in the area of 3 to 6 feet in diameter according to NASA scientists.
NASA also notes that the meteor that created such a sensation when it entered the Earth's atmosphere over Chelyabinsk, Russia in February was about 10 times bigger than the chunks of asteroid and comet fragments causing these craters on the surface of Mars. NASA says that its new estimates on the rate at which new craters appear on the surface of the planet will be used to estimate the ages of exposed landscape features on Mars and other planets. Mars gets an average of one new crater each year on each portion of its surface measuring approximately the size of the state of Texas.