Posted on by Bob King

Mars-Bound Comet Siding Spring Sprouts Multiple Jets

Comet Siding Spring, on its way to a close brush with Mars on October 19, has been kicking up a storm lately. New images from Hubble Space Telescope taken on March 11, when the comet was just this side of Jupiter, reveal multiple jets of gas and dust. 

Illustration showing Comet Siding Spring's orbit and close pass of Mars as it swings around the sun this year. Credit: NASA
Illustration showing Comet Siding Spring’s orbit and close pass of Mars as it plies its way through the inner solar system this year. Credit: NASA

Discovered in January 2013 by Robert H. McNaught at Siding Spring Observatory in Australia, the comet is falling toward the sun along a roughly 1 million year orbit. It will gradually brighten through spring and summer until reaching binocular brightness this fall when it passes 130 million miles (209 million km) from Earth.

Views of the comet on three different dates. Top shows a series of unfiltered images while the bottom are filtered to better show the jets. Credit:
Views of the comet on three different dates. Top shows a series of unfiltered images while the bottom are filtered to better show the jets. Comet Siding Spring’s hazy coma measures about 12,000 miles across and it’s presently about 353 million miles (568 million km) from the sun. Credit: NASA, ESA, J.-Y. Li (Planetary Science Institute)

Astronomers were particularly interested in getting images when Earth crossed the comet’s orbital plane, the path the comet takes as it orbits the sun. The positioning of the two bodies allowed Hubble to make crucial observations of how fast dust particles streamed off the nucleus.

Comet C/2013 A1 Siding Spring photographed from Australia on March 4, 2014. Credit: Rolando Ligustri
Comet C/2013 A1 Siding Spring photographed from Australia on March 4, 2014. Credit: Rolando Ligustri

“This is critical information that we need to determine whether, and to what degree, dust grains in the coma of the comet will impact Mars and spacecraft in the vicinity of Mars,” said Jian-Yang Li of the Planetary Science Institute in Tucson, Arizona.

On October 19 this year, Comet Siding Spring will pass within 84,000 miles (135,000 km) of Mars or less than half the distance of our moon. There’s a distinct possibility that orbiting Mars probes like NASA’s Mars Reconnaissance Orbiter and the European Mars Express might be enveloped by the comet’s coma (hazy atmosphere) and pelted by dust.

Mars and Comet C/2013 A1 Siding Spring will overlap as seen from Earth on Oct. 19, 2014 when the comet might pass as close as 25,700 miles (41,300 km) from the planet’s center. View shows the sky at the end of evening twilight facing southwest. Stellarium
Mars and Comet C/2013 A1 Siding Spring will overlap as seen from Earth on Oct. 19, 2014 when the comet might pass as close as 25,700 miles (41,300 km) from the planet’s center. View shows the sky at the end of evening twilight facing southwest. Stellarium

While comet dust particles are only 1 to 1/10,000 of a centimeter wide, they’ll be moving at 124,000 mph (200,000 km/hr). At that speed even dust motes small can be destructive. Plans are being considered to alter the orbits of the spacecraft to evade the worst of the potential blast. On the bright side, the Red Planet may witness a spectacular meteor storm! Protected by the atmosphere, the Martian rovers aren’t expected to be affected.

I know where I’ll be on October 19 – in the front yard peering at Mars through my telescope. Even if the comet doesn’t affect the planet, seeing the two overlap in conjunction will be a sight not to miss.

One Reply to “Mars-Bound Comet Siding Spring Sprouts Multiple Jets”

  1. A million year orbit, eh? Lessee.. What was I doing a million years ago? Oh yeah, I was and so were you, lost somewhere in my ancestral gene pool. (Makes a monkey noise or two and thinks about Stanley Kubrick’s epic tome, 2001 A Space Odyssey)

    Thanks for the update Bob. This one looks like it may even surpass C. ISON’s apparition? THAT wouldn’t be hard to do. Cool beans at a Bar-B-Que! Maybe …
    Un-for-tuna-nettly, I am still experiencing an economic doldrums. As a result, I haven’t had the extra lucre to finish my 12 1/2″ Newt. – the mirror needs coating and a new secondary wouldn’t hurt. Still, I have my 4″ S/C, a 60mm refractor and 7X35 binoculars, but ACK! Dentist bills and the double hernia surgery I had earlier this year ate up most of my funds. Then my truck blow up… again. Sheesh….

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