Mars breathes sigh of relief as comet collision odds drop

Comet C/2013 A1 will pass only 68,000 miles from Mars on October 19, 2014. At the time, the comet should be bright enough to see from Earth with binoculars. Credit: NASA/JPL-Caltech

Martians can finally breathe easier. No, we haven’t terraformed the planet yet, but the chances of Comet C/2013 A1 (Siding Spring) hitting the Mars have just dropped from 1 in 8,000 to about 1 in 20,000 after new observations further refined the comet’s orbit. Interestingly, the closest approach has tightened a bit to 68,000 miles. No matter what the view from the planet’s surface should be spectacular.

Comet C/2013 A1 will shine around 8th magnitude from Earth and be visible right alongside Mars low in the southwestern sky on the BIG DAY. Created with Chris Marriott’s SkyMap software

If only you and I could be there. Closest approach happens at 1:51 p.m. Central Time October 19, 2014 on Mars’ sunward side. Since a comet’s coma (temporary atmosphere formed from ice and dust vaporized by the sun) can measure many thousands of miles across, there’s a slight possibility it could graze Mars’ atmosphere. Dust might then flare as meteors when heated by friction with the air.

The fantastic coma and pale blue tail of 17P/Comet Holmes on Nov. 4, 2007. Credit: Ivan Eder

One of the largest comas belonged to Comet Holmes. Astronomers don’t know for sure whether Holmes experienced an explosive event from within or was struck by a meteoroid, but it suddenly brightened by half a million times in October 2007. Within a week, the comet had released so much gas and dust, its coma ballooned to 869,900 miles or about 5,000 miles larger than the sun!

Our current comet celebrity is C/2011 L4 PANSTARRS making appearances in both evening and morning (shown here) skies. Image made on April 14, 2014 in the northeastern sky at the start of dawn. Photo: Bob King

We’re not saying C/2013 A1 will even approach those dimensions, but it’s possible that dust from its coma might eventually drift toward Mars to create a meteor shower. My wish would be for NASA and the European Space Agency to point the rover and orbiting satellite cameras at the comet sometime during the flyby. Comet usually start to develop tails about the time they cross the orbit of Mars. The thought of seeing one arcing above a Mars landscape gives me the chills.

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

3 thoughts on “Mars breathes sigh of relief as comet collision odds drop

  1. Hi bob – It would be very cool to witness a comet flying only 68,000 miles away. If you were on mars would the comet zip across the sky being so close to it? It wouldn’t be like a traditional watching of a comet from earth were you can’t notice it’s movement through it’s orbit. At 68,000 miles that thing has to be almost slashing across the Martian sky at closest approach, now that would really be something to see.

    • Robert,
      It will be moving at 35 miles per second at the time, so it would march slowly across the sky to the naked eye kind of like a near-Earth asteroid. Rough guess – you’d be able to detect motion, again with the naked eye, in something like 30 minutes.

  2. What will we see here? About an 8th magnitude comet near Mars I believe. Comet Panstaars will be out there for our viewing too I believe. That is not the same Panstaars we are now seeing at about magnitude 6.2. In a week or 2, Lemmon should be easier to see which now is about magnitude 5.6.

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