Recently my Catalina Sky Survey teammate Richard Kowalski discovered a 0.4 mile diameter asteroid with the Catalina Sky Survey Schmidt telescope on Mt. Bigelow, AZ. Two hours and 11 minutes later it came into a set images I obtained with the 60 inch telescope on Mt. Lemmon, AZ. After I reported it, the new object was tracked by telescopes in Arizona, New Zealand, Slovenia, Kansas, Australia, Hungary, France, and Brazil. The Minor Planet Center used these data to calculate it's 1,353 day long orbit around the Sun, estimate it's size, and give it the name 2017 MB1. Fortunately it will not impact the Earth in the foreseeable future. An object the size of 2017 MB1 strikes the Earth every 200,000 years or so releasing the energy of about 300 large hydrogen bombs. It's impact onto a land area could produce a crater 6 miles in diameter, a fire storm that would ignite vegetation, clouds of toxic dust, acid rain, and produce other ill effects. If 2017 MB1 landed in the middle of the ocean it would make a splash that would send up billions of tons of water into the atmosphere and create waves 1,200 feet high which would quickly dissipate and would be no threat to land many miles away.