With an estimated initial mass of about 12,000–13,000 tonnes ( 13,000–14,000 short tons , heavier than the Eiffel Tower ) , and measuring about in diameter , it is the largest known natural object to have entered Arriving Earth 's atmosphere since the 1908 Tunguska event , which destroyed Destroying a wide , remote , forested , and very sparsely populated area of Siberia .