Why a Mars Comet Impact Would be Awesome

When Jupiter's tides ripped Comet Shoemaker–Levy 9 to shreds, only for the icy chunks to succumb to the intense Jovian gravity, ultimately slamming into the gas giant's atmosphere, mankind was treated to a rare cosmic spectacle (in human timescales at least). That was the first time in modern history that we saw a comet do battle with a planet... and lose.

But next year, astronomers think there's a chance - albeit a small one - of a neighboring planet getting punched by an icy interplanetary interloper. However, this planet doesn't have a generously thick atmosphere to soften the blow. Rather than causing bruises in a dense, molecular hydrogen atmosphere, this comet will pass through the atmosphere like it wasn't even there and hit the planetary surface like a cosmic pile-driver, ripping into the crust.

What's more, we'd have robotic eyes on the ground and in orbit should the worst happen.

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I am, of course, talking about Mars. And the comet? C/2013 A1 - a fresh lump of dusty ice that was spotted by the Australian Siding Spring Observatory on Jan. 3 making its dive from the outermost regions of the solar system.

Presently, astronomers only have a short period of observations to forecast the comet's path through the inner solar system and they know the probability of Mars "taking one for the celestial team" on Oct. 19, 2014, is small - in all likelihood the comet will fly by, creating a wonderful astronomical event for Earth and Mars-based observers alike. But...

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

The odds may be low, but they're certainly not "winning the lottery" small, or "getting hit by lightning" small; in scientific terms the odds are "non-negligible," meaning there's a fascinating possibility - a non-zero chance of a planetary collision.

PHOTOS: Weirdest Mars Craters

According to NASA, the comet is likely 1-3 kilometers (0.6-1.9 miles) wide and traveling at 56 kilometers per second (125,000 mph). "It if does hit Mars, it would deliver as much energy as 35 million megatons of TNT," added Yeomans. That would be a violent impact with global effects "I think of it as a giant climate experiment," said 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."

We currently have three satellites orbiting Mars - NASA's Mars Reconnaissance Orbiter and Odyssey, plus Europe's Mars Express - and two operational rovers - NASA's Opportunity and Curiosity. Should Mars be the scene of a cometary smash-up, wouldn't that be bad news for the rovers?

Barring a direct hit over Gale Crater or Endeavour Crater (Curiosity and Opportunity's homes, respectively), both rovers should survive the impact, with varying results.

An amazing climate experiment it may be, but Opportunity, a solar powered robot, would suffer if the atmosphere became thick with light-obscuring dust after impact. Mars' newest arrival, Curiosity, however, should carry on just fine as the larger robot is nuclear powered, drawing its power from a radioisotope thermoelectric generator (RTG).

So we'd not only have eyes in orbit, we'd also have two tenacious observers on the ground capable of carrying out "event science" right at time of impact.

ANALYSIS: Mars Gets Hit By Cosmic Buckshot

But this wouldn't only satisfy our macabre fascination with seeing a real doomsday scenario play out on our cosmic doorstep, it might also motivate manned exploration of Mars.

For decades, NASA has been aiming to get the first human on Mars, but the lack of political will and the inevitable funding restraints has stymied our Martian dreams, resigning us to watching robots do the exploring and hope the private sector may one day build a viable business model around joyrides to Mars.

A massive impact event, however, could be the motivation for us to finally take the interplanetary plunge and send a manned expedition.

The motivation to send a mission to the site of a recent cometary impact would be several-fold.

As Meyer points out, this would present a fascinating opportunity to witness climatic changes to a rocky world after impact. Furthermore, if we could send a manned expedition to a geologically-recent deep impact excavation site, the upper layers of fresh Martian crust will be laid bare for geologists to explore. This wouldn't be a million, or billion year-old crater eroded and sanitized by the sun's radiation, fresh deposits would be accessible just below the surface inside the comet's impact basin.

Was there ever life on Mars? The pristine basin may hold the best clues yet. Is there life on Mars? All Mars astronauts would need to do is chisel into the crater sides to definitively answer that question.

ANALYSIS: Could a Comet Hit Mars in 2014?

Although much of the comet's water and other volatiles would have been blown far and wide, evaporating and sublimating in the immense energies of impact, some will inevitably remain, perhaps coating the upper layers of the crater with a supply of accessible water. A drop of water in an arid desert it may be, but some comet ice may remain locked underground or remain as chunks surrounding the impact basin. Water will be to Mars explorers what gold was to Californian prospectors in the mid-19th Century.

From a practical standpoint, Mars is a rough place for human biology. The carbon dioxide-dominated atmosphere is ridiculously cold and tenuous - 100 times thinner than Earth's atmosphere. Combine this with the fact that the small planet doesn't possess a global magnetic field, humans on Mars would experience prolonged exposure to solar radiation and high-energy cosmic rays. If the comet did have an impact on climate - perhaps warming the atmosphere, or suspending radiation blocking dust for years in the upper atmosphere - the more the better; we'd need all the help we can get.

And then there's the rich astrobiology that could be done. Complex chemicals, known precursors to the amino acids that form the building blocks of known biology, can be found in comets. Where better to mine for the forensic evidence of a recently crashed ancient "dirty snowball" strewn across a planetary landscape?

In short, the aftermath of a cometary collision would be a scientific smorgasbord. If we ever needed to be "pushed" to send a manned mission to the surface of Mars, I can think of no better time than in the years after a massive comet strike.

A 1 in 2000 chance it may be, but it's hard not to think how awesome a Mars comet impact would be.

Image credit: NASA (edit by Ian O'Neill)

The Martian surface is peppered with impact craters of all shapes, sizes and ages. However, many of the craters are just plain weird.

But just how 'weird' is weird?

Curious, Discovery News asked the High-Resolution Imaging Science Experiment (HiRISE) team which craters they considered to be the strangest. HiRISE is the most advanced camera to be put into Mars orbit. It is attached to NASA's Mars Reconnaissance Orbiter (MRO) and currently snapping features on the Red Planet's surface -- it has seen a ton of strange objects (sadly, it hasn't found a top secret military base yet, despite what you may have heard to the contrary). So, let's take a tour of some of the weirdest craters Mars has on offer...

Special thanks to Ari Espinoza of the HiRISE team for helping to compile this list (originally published Dec. 30, 2011. Updated May 7, 2013)

Crater, Horst and Graben: Is that a piece of modern art? Actually, it's an impact crater that has been bent and twisted by tectonic processes. Along the fault line that crosses this crater, blocks of rock are forced upward (called "horst") and downward (called "graben"). This is interesting to planetary scientists as it shows that tectonic activity was occurring after the crater was formed.

Rolling Stones Logo? If you squint and use a little imagination, you may see the Rolling Stones' logo. Well, that's what the HiRISE team told us anyway. (I'm still squinting...) In reality, it's an impact crater on a sloping surface. Presumably, the "tongue" of material is slipping down the slope.

Bulls-Eye Impact? Did a small meteorite have the incredible fortune to slam into the center of a larger impact crater? Probably not.

This is one of several examples of "terraced" craters where alternating layers of hard and soft material in the surface layers of the Martian surface have been hit by a single meteorite. The result is a concentric nesting of ridges inside the same crater. Pretty!

What the...? What's the weirdest kind of impact crater? The kind that may not be an impact crater at all (but looks like one). On the slopes of Pavonis Mons, one of Mars' shield volcanoes, this crater has a hole in the middle. The hole is a "skylight," or the collapsed roof of a subterranean lava tube. The loose material above the collapsed roof appears to have slumped into the skylight, creating a crater lookalike. But what caused the roof of the lava tube to collapse? Could a meteorite be to blame? No idea, but HiRISE will be taking some more photos of this little oddity to find out.

Two-for-One Crater Special: What could be worse than a meteorite hitting you? Two meteorites hitting you... at the same time! Yes, that's exactly what happened here. It seems highly likely that one object tumbled through the Martian atmosphere and split in two. In doing so, the two halves impacted in the same location. As can be seen from this example, both halves were likely the same size, producing a rather satisfying imprint.

Another Double-Whammy: Looks like double-impacts are becoming a trend! This time, in addition to the two co-joined impact craters, HiRISE has picked out the rays that are produced when space rocks slam into the Martian surface.

Hit Me Baby Three More Times? It may seem hard to believe, but Mars also has triple-impact craters! It stands to reason that after countless impacts, you might get the occasional meteorite that splits into three when blasting through the atmosphere. So here you have it, a triple-impact crater.

A Triple Ricochet Crater: Another three (likely simultaneous) impacts, only this time their craters are elongated. This suggests the meteorites hit the surface at an oblique angle.

A Simple Blemish: In an apparently featureless plain in the north polar region, a single, small crater appears as the only blemish. Looking closely, the crater seems to be filled with ice.

Bubbly Landscape: This cluster of impact craters in the northern plains of Utopia Planitia contain strange uplift features likely caused by ground ice upheaval.

Crater of Mud: The strange concentric rings inside this crater near the Martian volcano Elysium Mons are thought to be the ancient remnants of a mud flow. Therefore, it is believed this crater wasn't caused by an impact from space, but by material flowing away from under the surface. The crater was then formed as the material above slumped.

Cracked Cookie Crater? There's an odd pair of craters in Hrad Vallis that the HiRISE website describe as a "pair of odd craters." Why so... odd? Well, to me, the larger crater looks like a cracked cookie, probably crevasses and faults carved across its diameter.

The Crater with a Robot Visitor: What makes this crater weird? Well, it's not the crater, it's the little man-made robot that's parked on the crater's western rim that makes this scene weirdly awesome. It's even weirder to think that a robot in Mars orbit has taken a photo of another robot on the Martian surface a couple of hundred miles below. Robots looking out for robots on alien worlds...

This is of course NASA's tenacious Mars Exploration Rover Opportunity that keeps exploring the Martian surface since exceeding its primary mission duration of 3 months back in 2004. Opportunity now has company on the Martian surface -- on Aug. 5, 2012, the nuclear-powered Curiosity landed inside Gale Crater to look for clues behind the habitability of the red planet.

In March 2013, HiRISE spotted a series of non-impact craters in Acidalia Planitia. These may not be impact craters, but they are unlike any other crater discovered on Mars to date! So the process behind their formation will remain a mystery... for now.