Imagine getting buzzed by a flying mountain. This is exactly what will happen to the orbiters and rovers around and on Mars this Sunday. The comet known as Siding Spring will pass Mars at a distance of approximately 140,000 kilometers, which is less than half the distance between the Earth and its moon.

The comet flyby will also mark the closest a comet has passed by Earth in recorded history as it heads on by toward the sun. The comet will pass by the sun and travel onward to the edge of the solar system. Siding Spring is not expected to come by this way again for another million years.

NASA currently has five robotic craft deployed at Mars: three orbiters and two surface rovers. These instruments have been repurposed to observe the comet’s visit. Joining them will be spacecraft from Europe and India.

The orbiters will be used in an attempt to observe the approach of the comet and then hide behind Mars for protection from debris emitted from the comet’s tail. The rovers, Opportunity and Curiosity, will be protected by the Martian atmosphere. Barring a dust storm, the rovers will likely provide the best images of Siding Spring.

“We certainly have fingers crossed for the first images of a comet from the surface of another world,” said NASA program scientist Kelly Fast.

Particles in the comet’s tail even have the potential to damage computers on Earth and fry electronics, as well as interfere with transmissions to various spacecrafts.

NASA has been monitoring the comet from afar with the Hubble Space Telescope and from here on Earth with surface observatories and research balloons. The best amateur viewing, via binoculars or telescope, will be from the Southern Hemisphere. It will be difficult to see the Mars flyby from North America, Europe, and Asia.

Siding Spring, named for the Australian observatory used to detect it in January 2013, will approach Mars from below and shoot across its front on Sunday afternoon, Eastern Time. Its nucleus is roughly a half-mile in diameter and is assumed to have emitted from the Oort Cloud at the edge of the solar system where it formed some 4.6 billion years ago. It will be the first Oort Cloud comet to be studied from such short distances.