C/2013 A1, also called Siding Spring, after the observatory from which it was first observed in January 2013 by Rob McNaught, an Australian astronomer.
This one, though, is special in that there is a slight chance that it may impact the surface of Mars. It’s also said to have an orbital cycle estimated at more than 1,000,000 years.
It’s too early to tell yet if Siding Spring will hit Mars, but scientists are currently working on measures to protect the satellites orbiting Mars as well as the probes exploring the surface in the event that impact is shown to be likely.
Even if there is no impact, there will be plenty of opportunity for observation and measurement, and we may even have a good view of it from Earth, as we are likely to with ISON later this year.
Will you be looking up when the time comes?