Discovery: Could a Comet Hit Mars in 2014?

bystander · Post by **bystander** » Mon Feb 25, 2013 7:16 pm

Could a Comet Hit Mars in 2014?
Discovery News | Ian O'Neill | 2013 Feb 25

[i]Simulation of the close approach of C/2013 A1 to Mars in Celestia using the latest MPC elements.[/i] - [url=http://astroblogger.blogspot.com/2013/02/will-comet-c2013-a1-siding-spring-hit.html][b][i]Will Comet C/2013 A1 (Siding Spring) Hit Mars?[/i][/b][/url]
A recently discovered comet will make an uncomfortably-close planetary flyby next year — but this time it’s not Earth that’s in the cosmic crosshairs.

According to preliminary orbital prediction models, comet C/2013 A1 will buzz Mars on Oct. 19, 2014. The icy interloper is thought to originate from the Oort Cloud — a hypothetical region surrounding the solar system containing countless billions of cometary nuclei that were outcast from the primordial solar system billions of years ago.

We know that the planets have been hit by comets before (re: the massive Comet Shoemaker–Levy 9 that crashed into Jupiter in 1994) and Mars, in particular, will have been hit by comets in the past. It’s believed Earth’s oceans were created by water delivered by comets — cometary impacts are an inevitable part of living in this cosmic ecosystem.

C/2013 A1 was discovered by ace comet-hunter Robert McNaught at the Siding Spring Observatory in New South Wales, Australia, on Jan. 3. When the discovery was made, astronomers at the Catalina Sky Survey in Arizona looked back over their observations to find “prerecovery” images of the comet dating back to Dec. 8, 2012. These observations placed the orbital trajectory of comet C/2013 A1 through Mars orbit on Oct. 19, 2014.

Could the Red Planet be in for a potentially huge impact next year? Will Mars rovers Curiosity and Opportunity be in danger of becoming scrap metal?

It seems the likelihood of an awesome planetary impact is low — for now.

Click to play embedded YouTube video.
According to calculations by NASA’s Jet Propulsion Laboratory (JPL), close approach data suggests the comet is most likely to make a close pass of 0.0007 AU (that’s approximately 63,000 miles from the Martian surface). However, there’s one huge caveat.

Due to uncertainties in the observations — the comet has only been observed for 74 days (so far), so it’s difficult for astronomers to forecast the comet’s precise location in 20 months time — comet C/2013 A1 may fly past at a very safe distance of 0.008 AU (650,000 miles). But to the other extreme, its orbital pass could put Mars directly in its path. At time of Mars close approach (or impact), the comet will be barreling along at a breakneck speed of 35 miles per second (126,000 miles per hour).

Also, we don’t yet know how big comet C/2013 A1 is, but comets typically aren’t small. If it did hit, the impact could be a huge, global event. But the comet’s likely location in 2014 is also highly uncertain, so this is by no means a “sure thing” for Mars impact (Curiosity, you can relax, for now).

One thing is looking likely, however. Mars could be in for its own “cometary spectacular.”

A flyby of that distance will mean that should C3/2013 A1 erupt with a tail and coma around its nucleus (as it becomes heated by solar radiation), our Mars rovers and orbiting armada of planetary observation satellites will have a very intimate view of this historic moment. It has the potential to be a more impressive sight than Comet ISON’s inner-solar system trek later this year. But understanding the nature of comets is hard to predict; we won’t know if the sun’s heating will be sufficient enough for the comet nucleus to erupt and start out-gassing for some time to come.

bystander · Post by **bystander** » Tue Mar 05, 2013 11:48 pm

Click to play embedded YouTube video.

bystander · Post by **bystander** » Thu Mar 28, 2013 2:34 pm

Collision Course? A Comet Heads for Mars
NASA Science News | Dr. Tony Phillips | 2013 Mar 27

Click to play embedded YouTube video.
Over the years, the spacefaring nations of Earth have sent dozens of probes and rovers to explore Mars. Today there are three active satellites circling the red planet while two rovers, Opportunity and Curiosity, wheel across the red sands below. Mars is dry, barren, and apparently lifeless.

Soon, those assets could find themselves exploring a very different kind of world.

"There is a small but non-negligible chance that Comet 2013 A1 will strike Mars next year in October of 2014," says Don Yeomans of NASA's Near-Earth Object Program at JPL. "Current solutions put the odds of impact at 1 in 2000."

The nucleus of the comet is probably 1 to 3 km in diameter, and it is coming in fast, around 56 km/s (125,000 mph). "It if does hit Mars, it would deliver as much energy as 35 million megatons of TNT," estimates Yeomans.

For comparison, the asteroid strike that ended the dinosaurs on Earth 65 million years ago was about three times as powerful, 100 million megatons. Another point of comparison is the meteor that exploded over Chelyabinsk, Russia, in February of 2013, damaging buildings and knocking people down. The Mars comet is packing 80 million times more energy than that relatively puny asteroid.

An impact wouldn't necessarily mean the end of NASA's Mars program. But it would transform the program-- along with Mars itself.

"I think of it as a giant climate experiment," says Michael Meyer, lead scientist for the Mars Exploration Program at NASA headquarters. "An impact would loft a lot of stuff into the Martian atmosphere--dust, sand, water and other debris. The result could be a warmer, wetter Mars than we're accustomed to today."

Meyer worries that solar-powered Opportunity might have a hard time surviving if the atmosphere became opaque. Nuclear-powered Curiosity, though, would carry on just fine. He also notes that Mars orbiters might have trouble seeing the surface, for a while at least, until the debris begins to clear.

A direct impact remains unlikely. Paul Chodas of NASA's Near-Earth Object Program stresses that a 1 in 2000 chance of impact means there's a 1999 in 2000 chance of no impact. "A near-miss is far more likely," he points out.

Even a near miss is a potentially big event. The latest orbit solutions put the comet somewhere within 300,000 km of the red planet at closest approach. That means Mars could find itself inside the comet's gassy, dusty atmosphere or "coma." Visually, the comet would reach 0th magnitude, that is, a few times brighter than a 1st magnitude star, as seen from the Red Planet.

"Cameras on ALL of NASA's spacecraft currently operating at Mars should be able to take photographs of Comet 2013 A1," says Jim Bell, a planetary scientist and Mars imaging specialist at Arizona State University. "The issue with Mars Odyssey and the Mars Reconnaissance Orbiter will be the ability to point them in the right direction; they are used to looking down, not up. Mission designers will have to figure out if that is possible."

"The issue with the Opportunity and Curiosity rovers will be power for imaging at night," he continues. "Opportunity is solar powered and so would need to dip into reserve battery power to operate the cameras at night. Whether or not we will be able to do this will depend on how much power the rover is getting from dusty solar panels in the daytime. On the other hand, Curiosity is nuclear powered, so it could have better odds at night-time imaging."

Researchers will be keenly interested to see how the comet's atmosphere interacts with the atmosphere of Mars. For one thing, there could be a meteor shower. "Analyzing the spectrum of disintegrating meteors could tell us something interesting about the chemistry of the upper atmosphere," notes Meyer.

Another possibility is Martian auroras. Unlike Earth, which has a global magnetic field that wraps around our entire planet, Mars is only magnetized in patches. Here and there, magnetic umbrellas sprout out of the ground, creating a crazy-quilt of magnetic poles concentrated mainly in the southern hemisphere. Ionized gases hitting the top of the Martian atmosphere could spark auroras in the canopies of the magnetic umbrellas.

Even before the comet flyby was known, NASA had already decided to send a spacecraft to Mars to study the dynamics of the Martian atmosphere. If the probe, named MAVEN (short for "Mars Atmosphere and Volatile Evolution"), is launched on time in November 2013, it would reach Mars just a few weeks before the comet in 2014.

However, notes MAVEN's principal investigator Bruce Jakosky of the University of Colorado, the spacecraft won't be ready to observe the comet when it reaches Mars. "It takes a while to get into our science mapping orbit, deploy the booms, turn on and test the science instruments--and so on," he explains. "MAVEN won't be fully operational until perhaps two weeks after the comet passes. There are some effects that I would expect to linger for a relatively long period--especially if the comet hits Mars--and we will be able to observe those changes."

Astronomers around the world are monitoring 2013 A1. Every day, new data arrive to refine the comet's orbit. As the error bars shrink, Yeomans expects a direct hit to be ruled out. "The odds favor a flyby, not a collision," he says.

Either way, this is going to be good. Stay tuned for updates as the comet approaches.

Interactive 3D orbit of Comet 2013 A1 (Siding Spring)

Why a Mars Comet Impact Would be Awesome
Discovery News | Ian O'Neill | 2013 Mar 28

Starship Asterisk*

Discovery: Could a Comet Hit Mars in 2014?

Discovery: Could a Comet Hit Mars in 2014?

Re: Discovery: Could a Comet Hit Mars in 2014?

Science@NASA: Collision Course? A Comet Heads for Mars