For those of you rooting for the wellbeing of Mars, here's some good news: the probability of a massive comet impact next year has decreased. For those of you who wanted to see some planetary carnage, however, this news will likely be a major bummer.
PHOTOS: Weirdest Mars Craters
Comet C/2013 A1 (Siding Spring) will still make a dazzling flyby of the red planet, but the odds of impact have increased from 1-in-8,000 to 1-in-120,000. Although the chances of impact were slim for an October 2014 impact anyway, refinements of the comet's trajectory will likely rule out any hope of a "planetary spectacular." But still, the refinements have determined that the "dirty snowball" will still make a very close approach.
"Based on data through April 7, 2013, the latest orbital plot places the comet's closest approach to Mars slightly closer than previous estimates, at about 68,000 miles (110,000 kilometers)," said a NASA update on Friday (April 12). "At the same time, the new data set now significantly reduces the probability the comet will impact the Red Planet, from about 1 in 8,000 to about 1 in 120,000."
Seeing a comet slam into the Martian atmosphere would have been terrifying, yet scientifically important. We've seen a planetary comet impact before, but witnessing a large comet hitting a neighboring rocky planet would be a historic event that may have invigorated a manned expedition to Mars.
ANALYSIS: Why a Mars Comet Impact Would be Awesome
The 1994 collision of Comet Shoemaker–Levy 9 with Jupiter's upper atmosphere was a stark reminder of the hazardous cosmic shooting gallery the planets of the solar system live in. During that event, Jupiter used its gravitational heft to shred and swallow Shoemaker–Levy 9′s debris. The gas giant is often credited with being the "protector" of the inner solar system, "vacuuming" up any marauding comets and asteroids. (Jupiter has also been pegged as being a little bit evil, but that's a whole other story.)
Depending on the size of Comet Siding Spring, a Mars impact would have likely been a global event. Astronomical observations of the atmospheric disruption and the surface damage would provide us with a clue as to how an impact of that size changes a planet. Also, as I've previously argued, comets are known to contain a cocktail of organic chemicals. The fresh impact of a comet into Mars would have invigorated robotic, and perhaps human, missions to examine the post-impact debris, perhaps understanding how the smorgasbord of organics interact with planetary chemistry.
And that's not even considering the large quantity of water that the comet would have delivered to the arid environment, potentially in quantities that could support a future manned base.
ANALYSIS: Could a Comet Hit Mars in 2014?
But it seems that this scenario is becoming less and less likely - we'll have to just hope that the comet produces a large, bright tail for our robotic Mars missions to see.
"The latest estimated time for close approach to Mars is about 11:51 a.m. PDT (18:51 UTC) on Oct. 19, 2014," added NASA. "At the time of closest approach, the comet will be on the sunward side of the planet."
Image credit: NASA, edit by Ian O'Neill