It's a once-in-a-million years event. Siding Spring comet is due to fly past Mars on Sunday evening, and Slooh telescope will broadcast the dramatic space event.
Astronomers say the Siding Spring comet has travelled billions of miles to reach Mars, originating from the Oort Cloud, a vast expanse of residual material from the formation of the solar system.
The comet is expected to miss Mars by about 87,000 miles, a distance four times closer to the planet than the moon is to Earth. It will be flying at a speed of 126,000 miles per hour.
This close-encounter has forced Nasa to protect its Mars orbiters Mars Reconnaissance, Mars Odyssey and MAVEN from comet dust
Nasa is now taking steps to protect its Mars Reconnaissance Orbiter, Mars Odyssey and MAVEN orbiters from any comet dust produced by the close fly-by, as well as preserving any opportunities to gather valuable data from the event.
The organisation says Comet Ison in October 2013 gave teams on Mars observatories a good chance to practice looking at an object hurtling past the planet.
David Humm, of the Johns Hopkins University Applied Physics Laboratory described the event as "unique, unexpected, and lucky for us".
The best viewing on Earth, with binoculars or a telescope, will be from the Southern Hemisphere.
The Slooh Community Observatory will broadcast the comet passing Mars, which you can watch here.Reuse content