A massive asteroid equal to Eiffel Tower's size is heading towards Earth. The asteroid titled 387746 (2003 MH4), which is 335 metres in width and 1,100 feet high, will zip by Earth on May 24. Its proximity and magnitude make it a Potentially Hazardous Asteroid (PHA). PHAs are objects bigger than 140 metres and approach Earth within 7.5 million kilometres.