This weekend, Comet Siding Spring will make a historically close approach to Mars.
Satellites and rovers, like NASA's Maven spacecraft will get a great view of this comet as it passes less than 140,000 km above the red planet.
Possible side effects of the flyby include a Martian meteor shower and auroras.
If you have mid-sized telescope and a bit of astronomy experience you might be able to spot Comet Siding Spring for yourself in the nights ahead. Just look for it near Mars.