Comet Siding Spring will soon pass close to Mars, and NASA is preparing observatories on and above the Red Planet for the display. The close encounter of the ancient, frozen body with Mars will take place on Oct. 19 at 2:27 p.m. EDT. The comet was discovered in 2013. During its rendezvous with the Red Planet, Siding Spring will pass just 87,000 miles from the world.
Astronomers studying the close encounter may learn more about the formation of the solar system in its earliest days. All comets studied so far by NASA formed between the orbits of Jupiter and the Kuiper Belt, a collection of debris orbiting beyond Neptune. Comet Siding Spring came to Earth after spending significant time in the Oort Cloud at the outskirts of the solar system.
"We can't get to an Oort Cloud comet with our current rockets. These orbits are very long and extended -- and at very great velocities ... It's a free flyby, if you will, and that's a very fantastic event for us to study," Carey Lisse, astrophysicist for the Johns Hopkins University Applied Physics Laboratory, stated during a NASA news conference on the flyby.
Siding Spring likely formed between the orbits of Jupiter and Neptune, before a gravitational nudge pushed the object outwards, toward the distant Oort Cloud. A passing star or a collision with another body then pushed Siding Spring back toward the inner solar system, toward close encounters with the sun, as well as the Red Planet.
The Mars Reconnaissance Orbiter, Mars Atmosphere and Volatile Evolution (Maven), and Mars Odyssey are each currently in orbit around the Red Planet. Mission controllers for NASA are forced to play a balancing game during the passage of the comet. Scientists want to carry out good science during the passage of the little-seen body from the Oort Cloud. However, dust from the comet could damage sensitive instruments aboard the orbiters.
"The hazard is not an impact of the comet nucleus itself, but the trail of debris coming from it. Using constraints provided by Earth-based observations, the modeling results indicate that the hazard is not as great as first anticipated. Mars will be right at the edge of the debris cloud, so it might encounter some of the particles -- or it might not," Rich Zurek, chief scientist for the Mars Exploration Program at NASA's Jet Propulsion Laboratory, said.
Curiosity and Opportunity, the two NASA rovers on the surface of the planet, will be protected from dust by the tenuous atmosphere of Mars. A myriad of telescopes in and around the Earth, including the Hubble Space Telescope, will also be watching the close encounter.