Michael McCollum 
Thunderstrike! [EPUB ebook] 

The new comet found near Jupiter was an incredible treasure trove of water-ice and rock. Immediately, the water-starved Luna Republic and Sierra Corporation, a leader in asteroid mining, were squabbling over rights to the new resource. But all thoughts of profit and fame were abandoned when a scientific expedition discovered that the comet’s trajectory placed it on a collision course with Earth!As scientists struggled to find a way to alter the comet’s course, world leaders tried desperately to restrain mass panic, and two lovers quarreled over the direction the comet was to take, all Earth waited to see if humanity had any future at all…