New evidence that asteroid, not comet, struck Jupiter in 2009

Jan 26, 2011
These infrared images obtained from NASA's Infrared Telescope Facility in Mauna Kea, Hawaii, show particle debris in Jupiter's atmosphere after an object hurtled into the atmosphere on July 19, 2009. Image credit: NASA/IRTF/JPL-Caltech/University of Oxford

(PhysOrg.com) -- Infrared images of the aftermath of an impact on Jupiter in 2009 have been combined with other observations to conclude that an asteroid, not a comet, slammed into the planet.

A hurtling asteroid about the size of the Titanic caused the scar that appeared in Jupiter's atmosphere on July 19, 2009, according to two papers published recently in the journal Icarus.

Data from three infrared telescopes enabled scientists to observe the warm atmospheric temperatures and unique chemical conditions associated with the impact debris. By piecing together signatures of the gases and dark debris produced by the impact shockwaves, an international team of scientists was able to deduce that the object was more likely a rocky asteroid than an icy comet. Among the teams were those led by Glenn Orton, an astronomer at NASA's Jet Propulsion Laboratory, Pasadena, Calif., and Leigh Fletcher, researcher at Oxford University, U.K., who started the work while he was a postdoctoral fellow at JPL.

"Both the fact that the impact itself happened at all and the implication that it may well have been an asteroid rather than a comet shows us that the outer solar system is a complex, violent and dynamic place, and that many surprises may be out there waiting for us," said Orton. "There is still a lot to sort out in the ."

The new conclusion is also consistent with evidence from results from NASA's indicating the impact debris in 2009 was heavier or denser than debris from , the last known object to hurl itself into Jupiter's atmosphere in 1994.

Before this collision, scientists had thought that the only objects that hit Jupiter were icy comets whose unstable orbits took them close enough to Jupiter to be sucked in by the giant planet's . Those comets are known as Jupiter-family comets. Scientists thought Jupiter had already cleared most other objects, such as asteroids, from its sphere of influence. Besides Shoemaker-Levy, scientists know of only two other impacts in the summer of 2010, which lit up Jupiter's atmosphere.

The July 19, 2009 object likely hit Jupiter between 9 a.m. and 11 a.m. UTC. Amateur astronomer Anthony Wesley from Australia was the first to notice the scar on Jupiter, which appeared as a dark spot in visible wavelengths. The scar appeared at mid-southern latitudes. Wesley tipped off Orton and colleagues, who immediately used existing observing time at NASA's Infrared Telescope Facility in Mauna Kea, Hawaii, the following night and proposed observing time on a host of other ground-based observatories, including the Gemini North Observatory in Hawaii, the Gemini South Telescope in Chile, and the European Southern Observatory's Very Large Telescope in Chile. Data were acquired at regular intervals during the week following the 2009 collision.

The data showed that the impact had warmed Jupiter's lower stratosphere by as much as 3 to 4 Kelvin at about 42 kilometers above its cloudtops. Although 3 to 4 Kelvin does not sound like a lot, it is a significant deposition of energy because it is spread over such an enormous area.

This infrared image, showing thermal radiation at a wavelength of 9.7 microns, was obtained by the Gemini North Telescope in Hawaii. Image credit: Gemini Observatory/AURA/UC Berkeley/SSI/ JPL-Caltech

Plunging through Jupiter's atmosphere, the object created a channel of super-heated atmospheric gases and debris. An explosion deep below the clouds – probably releasing at least around 200 trillion trillion ergs of energy, or more than 5 gigatons of TNT -- then launched debris material back along the channel, above the cloud tops, to splash back down into the atmosphere, creating the aerosol particulates and warm temperatures observed in the infrared. The blowback dredged up ammonia gas and other gases from a lower part of the atmosphere known as the troposphere into a higher part of the atmosphere known as the stratosphere.

"Comparisons between the 2009 images and the Shoemaker-Levy 9 results are beginning to show intriguing differences between the kinds of objects that hit Jupiter," Fletcher said. "The dark debris, the heated atmosphere and upwelling of ammonia were similar for this impact and Shoemaker-Levy, but the debris plume in this case didn't reach such high altitudes, didn't heat the high stratosphere, and contained signatures for hydrocarbons, silicates and silicas that weren't seen before. The presence of hydrocarbons, and the absence of carbon monoxide, provide strong evidence for a water-depleted impactor in 2009."

The detection of silica in this mixture of Jovian atmospheric gases, processed bits from the impactor and byproducts of high-energy chemical reactions was significant because abundant silica could only be produced in the impact itself, by a strong rocky body capable of penetrating very deeply into the Jovian atmosphere before exploding, but not by a much weaker comet nucleus. Assuming that the impactor had a rock-like density of around 2.5 grams per cubic centimeter (160 pounds per cubic foot), scientists calculated a likely diameter of 200 to 500 meters (700 to 1,600 feet).

Scientists computed the set of possible orbits that would bring an object into Jupiter in the right range of times and at the right locations. Then they searched the catalog of known asteroids and comets to find the kinds of objects in these orbits. An object named 2005 TS100 – which is probably an asteroid but could be an extinct comet – was one of the closest matches. Although this object was not the actual impactor, it has a very chaotic orbit and made several very close approaches to Jupiter in computer models, demonstrating that an asteroid could have hurtled into Jupiter.

"We weren't expecting to find that an asteroid was the likely culprit in this impact, but we've now learned Jupiter is getting hit by a diversity of objects," said Paul Chodas, a scientist at NASA's Near-Earth Object Program Office at JPL. " Asteroid impacts on Jupiter were thought to be quite rare compared to impacts from the so-called 'Jupiter-family comets,' but now it seems there may be a significant population of asteroids in this category."

Scientists are still working to figure out what that frequency at is, but asteroids of this size hit Earth about once every 100,000 years. The next steps in this investigation will be to use detailed simulations of the impact to refine the size and properties of the impactor, and to continue to use imaging at infrared, as well as visible wavelengths, to search for debris from future impacts of this size or smaller.

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Quantum_Conundrum
4.5 / 5 (4) Jan 26, 2011
Glad it happened there an not here. That explosion is 25 times the size of the biggest explosion of the Krakatoa eruption. It is the equivalent of a VEI 8 eruption.

The worst thing about this is that once again absolutely nobody detected this object until several hours after impact, and worse, they couldn't even retroactively model exactly where it came from...

Next, even if it had been detected, we would have had no response at all had it been determined to be on a collision course with earth...

To put this in perspective, the low estimate mass of this object, if assumed spherical, was greater than Apophis, and the high estimate mass would be more than 8 times Apophis...

and it was never detected at all until it was too late to have mattered...
Quantum_Conundrum
5 / 5 (2) Jan 26, 2011
Another way of looking at this, is this explosion is 100 times as large as the largest nuclear device ever detonated by humans...

If Tsar Bomba's shockwave circled earth 3 times, and Krakatoa circled earth 7 times, I wonder how many this woudl do?

I wonder what the radius of 1000mph winds would be? what about 300mph winds radius?

If this hit a city, the entire city would be vaporized and ionized to a depth of several hundred feet of soil, and maybe even experience nuclear fusion.

For example:
If this hit Tokyo, almost every living thing in Japan would die instantly, and most of east Asia would be destroyed by the earthquakes, shockwave and winds...The tsunamis would annihilate Hawaii, Chile, and the entire west coast of N and S america, not to mention indonesia and parts of Australia...
Quantum_Conundrum
5 / 5 (1) Jan 26, 2011
Purdue Impact calculator gives some truly ridiculous results for the low end mass of this object, at a position 1000km distant from the point of impact...

According to their impact calculator, it would be a ~6 gigaton explosion, but would somehow many to have minimal seismic effects, no fireball, and only about 5mph wind at a 1000km radius, and 60 decibel sound at 1000km radius...

Krakatoa exceeded that at just 200megatons, as did the Tunguska event, whic was also felt and seen around most of the world.

So it's extremely inconsistent with known impactors and explosive phenomenon.
Quantum_Conundrum
5 / 5 (2) Jan 26, 2011
yeah, something is broken with that stupid calculator.

Mt. St. Helens is only a VEI 5 eruption on the order of 20 megatons or so, and the real world effects of Mt. St. Helens were almost as bad as the stupid impact calculator says a 6 gigaton explosion/impact would be...

This things broken as they come...

It does say 738mph winds at 30km radius, w/ magnitude 9 or 10 earthquake and half meter to meter sized ejecta....so everything within 30km will die, we can be sure...

5cm ejecta (velocity 540m/s,) and 258mph wind at 60km distance.

Mmm...5cm ejecta at that velocity has kinetic energy of a cannon ball. Everyone dead here too...

At 120km:

Ejecta is still bullet sized, and moving at greater than rifle muzzle velocity.

Wind is 85mph.

So most stuff at 120km will still be killed instantly, or mortally wounded and likely die shortly thereafter...
LKD
5 / 5 (1) Jan 27, 2011
"and it was never detected at all until it was too late to have mattered"

Considering the distance between us and Jupiter, and that we are not terribly worried if an asteroid targets Jupiter for impact, it is expected we will not see it coming. We do not have the technology to map all the solar system's objects and track them, to assume we do or have or can, is silly.

If this was coming near earth, due to its size, all sorts of alarms would sound out about a year before it gets here. And I'm sure we could do something, the question is who's paying for it.
LKD
not rated yet Jan 27, 2011
Quantum_Conundrum,

Are you considering the shockwave blast that will be far more deadly then getting hit by debris?

What about the deformation on the opposite side of the planet as the force runs through the core and causes the crust to surge out? Forgive me for forgetting the technical name...
Bog_Mire
not rated yet Jan 27, 2011
visa
71STARS
2.3 / 5 (3) Jan 27, 2011
This makes such good sense that it was an asteroid and not a comet because I am of the belief that Jupiter's gravitational pull on the only Moon from Mars resulted in the Asteroid Belt around Mars. To pull a comet apart would inflict "icy" particles of material that would have melted in the ensuing speed to the surface of Jupiter. This did not happen, meaning that the particles were more dense; an asteroid.

Sometimes it takes time to make sense out of what has happened. Very good.
Quantum_Conundrum
not rated yet Jan 27, 2011
LKD:

An object with a typical asteroid velocity of 17km/s could travel from Jupiter to Earth in as little as 400 days.

An asteroid could get to earth from the first peak in the main belt in about 145 days.

How many months warning does NASA need to launch a machine they've had for 3 decades? Nevermind some last second "save the planet" plan...
LKD
not rated yet Jan 27, 2011
In a year, with the threat of the world hanging in the balance? I believe humankind will do very nicely in assuring it continues. But that is worst case that some asteroid slingshot's around Jupiter while we are the absolute closest possible point.

This has been talked about and planned for for years, without any serious building sadly. I am not too worried of it happening. If we could securely contain antimatter in any amount? I would not worry at all.
TheQuietMan
not rated yet Jan 30, 2011
Hmmm, would you rather be hit with a large caliber bullet or a shotgun blast. Explosions don't destroy objects, they disperse them.