A recently discovered comet has given scientists a unique chance to study an object from the farthest reaches of our Solar System. The comet, named ‘siding spring’, was discovered on the 3rd January 2013 and is believed to have originated from the region of the solar system known as the Oort cloud. The Oort cloud is a spherical cloud of predominantly icy objects which surrounds the solar system, this spherical region of space on the outer edge of the solar system is responsible for the introduction of Comets into the inner solar system.
On the 19th October, Siding Spring made its closest approach to Mars. The comet was seen to race past Mars at 56km per second at a distance of 139,500km away from the planet. The comet is believes to have formed more than 4.5 billion years and has changed little since then. Carey Lisse, from the Johns Hopkins University Applied Physics Laboratory, stated that, “Siding Spring was knocked into the inner Solar System by the passage of a star near the Oort Cloud, and has been travelling into the solar system since the dawn of man but is now just coming in.” Carey Lisse then went on to explain that the reason that the comet can be observed in such detail is due to the man-made satellites and rovers which have been placed on Mars.
The passing of Siding Spring was observed by NASA’s five robotic explorers, three orbiters and two rovers, as well as one ESA spacecraft and India’s spacecraft, which only arrived at the red planet at the end of September.
NASA’s Mars Reconnaissance Orbiter was tasked with photographing and resolving the comets shape, something that has never been observed with an Oort cloud visitor. Other orbiting satellites studied the interaction between the comet’s coma and the Martian atmosphere. The two rovers Curiosity and Opportunity also studied the comets interaction with the Martian ‘air’ from the surface.
Siding Spring is thought to only complete a pass through the solar system every 1 to 2 million years. A team member from NASA’s Curiosity and Opportunity rovers said “It is very much a once-in-a-lifetime event for us and our rovers”.