Adler Planetarium

Comet ISON to Sweep Closely Past Mars on October 1

Artist's concept of Comet ISON as it flies by Mars. Image Credit: NASA

Artist's concept of Comet ISON as it flies by Mars.

Image Credit: NASA

This year's most anticipated comet, Comet ISON, will pass within 0.07 AU from Mars tomorrow. That’s around six times closer than the comet will come to Earth.  Comet ISON is on its way to to its encounter with the Sun which will take place on Thanksgiving Day. Hopefully there will be a good showing in Earth’s night sky. As of now, amateur astronomers are the main ones capturing images of the comet with the assistance of their telescopes and photographic equipment.

NASA and ESA are preparing an armada of spacecraft in Mars orbit or on Mars’ surface which will attempt to record the comet’s passage near Mars. NASA will have 16 spacecrafts and the astronauts aboard the International Space Station observing the comet.

Mars rovers and satellites may get a close-up view depending on the comet’s current brightness. ISON is fainter than anticipated but recent photos show a greenish color to the comet, a sign that the comet has crossed the “frost line,” a place outside Mars’ orbit where solar heating is enough to start vaporizing ices on ISON’s surfaces.

Scientists hope to learn how large Comet ISON’s nucleus is. Astronomer Carey Lisse explained that if ISON’s nucleus is much bigger than 0.5 km, it will probably survive its Thanksgiving Day brush with the sun. If the nucleus is intact, it could mean the comet will be bright and visible from Earth in early December.

Read the full story on the EarthSky website

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