UMD: Primordial Dry Ice Fuels Comet Jets

Find out the latest thinking about our universe.
Post Reply
User avatar
bystander
Apathetic Retiree
Posts: 21571
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

UMD: Primordial Dry Ice Fuels Comet Jets

Post by bystander » Thu Nov 11, 2010 3:14 pm

Primordial Dry Ice Fuels Comet Jets
University of Maryland | 10 Nov 2010
Initial science results on comet released from University of Maryland, much more to come UMD scientists say.
One of the biggest comet findings coming out of the amazing images and data taken by the University of Maryland-led EPOXI mission as it zipped past comet Hartley 2 last week is that dry ice is the 'jet' fuel for this comet and perhaps many others.

Images from the flyby show spectacular jets of gas and particles bursting from many distinct spots on the surface of the comet. This is the first time images of a comet have been sharp enough to allow scientists to link jets of dust and gas with specific surface features. Analysis of the spectral signatures of the materials coming from the jets shows primarily CO2 gas (carbon dioxide) and particles of dust and ice.

"Previously it was thought that water vapor from water ice was the propulsive force behind jets of material coming off of the body, or nucleus, of the comet," said University of Maryland Astronomy Professor Jessica Sunshine, who is deputy principal investigator for the EPOXI mission. "We now have unambiguous evidence that solar heating of subsurface frozen carbon dioxide (dry ice), directly to a gas, a process known as sublimation, is powering the many jets of material coming from the comet. This is a finding that only could have been made by traveling to a comet, because ground based telescopes can't detect CO2 and current space telescopes aren't tuned to look for this gas," Sunshine said.

Sunshine and other members of the EPOXI science team are meeting all this week at the University of Maryland to analyze the very large amount of data from the closest approach, and new data continues to come down at a rate of some 2000 images a day.

The Deep Impact spacecraft that flew past comet Hartley 2 has three instruments -- two telescopes with digital color cameras and an infrared spectrometer. The spectrometer measures the absorption, emission and reflection of light (spectroscopic signature) that is unique to each molecular compound. This allows Maryland scientists to determine the composition of the material on the comet's surface, in the jets, and in the coma, or cloud of particles around it. They have found that water and carbon dioxide dominate the infrared spectrum of comet Hartley 2's environment and that organics, including methanol, are present at lower levels.

This is no surprise to scientists. But what is surprising is that there is a lot more carbon dioxide escaping this comet than expected. "The distribution of carbon dioxide and dust around the nucleus is much different than the water distribution, and that tells us that the carbon dioxide rather than water takes dust grains with it into the coma as it leaves the nucleus, said Assistant Research Scientist Lori Feaga. "The dry ice that is producing the CO2 jets on this comet has probably been frozen inside it since the formation of the solar system."

http://www.nasa.gov/epoxi
http://epoxi.umd.edu/
Hartley 2: Primordial Dry Ice
Centauri Dreams | 11 Nov 2010
eep an eye on the EPOXI site at the University of Maryland. New images from the Hartley 2 comet encounter are coming in, some of them truly breathtaking, as is the one at left. The jets clearly visible in the image can be linked with distinct areas on the surface of the comet, the first time we’ve ever seen a comet with this degree of clarity. Image by image, the tiny comet is yielding its secrets. We now learn that spectral analysis of the material coming from the cometary jets shows it to be primarily carbon dioxide, along with dust and ice particles.
...
With new data arriving at the rate of 2000 images a day, we should have much more to look forward to from Hartley 2, but the amount of carbon dioxide escaping the comet has proven to be the biggest surprise so far. It’s fascinating to realize that the dry ice producing the jets we see in the images has most likely been inside the comet since the earliest days of the Solar System. The EPOXI findings are consistent with what Deep Impact found at Tempel 1 back in 2005, though mission scientist Tony Farnham (University of Maryland) explains why the Tempel 1 results were less conclusive:
...
Taking Deep Impact to a second comet, then, has paid big dividends in the Hartley 2 data, which now point to carbon dioxide rather than water as the driver for cometary surface activity here and likely on other comets. We’re learning about comets step by step — EPOXI’s mission marks only the fifth time we’ve had close-up imagery of one — but we’re finding things no ground-based telescope could show us. The montage below puts all five cometary investigations into perspective.

User avatar
owlice
Guardian of the Codes
Posts: 8406
Joined: Wed Aug 04, 2004 4:18 pm
Location: Washington, DC

Re: UMD: Primordial Dry Ice Fuels Comet Jets

Post by owlice » Thu Nov 11, 2010 3:35 pm

SO cool!!!!
A closed mouth gathers no foot.

User avatar
Ann
4725 Å
Posts: 13369
Joined: Sat May 29, 2010 5:33 am

Re: UMD: Primordial Dry Ice Fuels Comet Jets

Post by Ann » Thu Nov 11, 2010 4:08 pm

Fascinating stuff. That picture of the comet with all those jets coming out of it is amazing.

Interesting, too, that the comet is (or was? :wink: ) so full of carbon dioxide. It makes me think of Venus, which has a thick carbon dioxide atmosphere, and Mars, which has a thin carbon dioxide atmosphere. And now this comet is powered by carbon dioxide.

Well, look around on the Earth, and if you are like me you may not be able to refrain from humming "Where has all the carbon dioxide gone?".
Click to play embedded YouTube video.
I know, I know - the carbon dioxide of the Earth ended up in rocks. Well, we were lucky - again. Without all the carbon dioxide taken care of, there may not have been many flowers, girls, boys, soldiers or even graveyards to sing about.

Ann
Color Commentator

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18805
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: UMD: Primordial Dry Ice Fuels Comet Jets

Post by neufer » Thu Nov 11, 2010 5:08 pm

bystander wrote:Primordial Dry Ice Fuels Comet Jets
University of Maryland | 10 Nov 2010

"Previously it was thought that water vapor from water ice was the propulsive force behind jets of material coming off of the body, or nucleus, of the comet," said University of Maryland Astronomy Professor Jessica Sunshine, who is deputy principal investigator for the EPOXI mission. "We now have unambiguous evidence that solar heating of subsurface frozen carbon dioxide (dry ice), directly to a gas, a process known as sublimation, is powering the many jets of material coming from the comet. This is a finding that only could have been made by traveling to a comet, because ground based telescopes can't detect CO2 and current space telescopes aren't tuned to look for this gas," Sunshine said.
There weren't any dry ice in the house:
Click to play embedded YouTube video.
Art Neuendorffer

User avatar
Ann
4725 Å
Posts: 13369
Joined: Sat May 29, 2010 5:33 am

Re: UMD: Primordial Dry Ice Fuels Comet Jets

Post by Ann » Thu Nov 11, 2010 6:44 pm

Professor Jessica Sunshine
(even though sunshine isn't yellow)

I, too, thought it was a riot that an astronomer studying the effects of
Image


on
Image
is herself named
Image
...Sunshine!

Ann
Color Commentator

User avatar
bystander
Apathetic Retiree
Posts: 21571
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

UMD:Spacecraft Flew Through 'Snowstorm' on Encounter with Co

Post by bystander » Thu Nov 18, 2010 10:07 pm

Spacecraft Flew Through 'Snowstorm' on Encounter with Comet Hartley 2
University of Maryland | 18 Nov 2010
On its recent trip by comet Hartley 2, the Deep Impact spacecraft took the first pictures of, and flew through, a storm of fluffy particles of water ice being spewed out by carbon dioxide jets coming from the rough ends of the comet. The resulting images and data shed new light on the nature and composition of comets, according to the University of Maryland-led EPOXI science team, which today announced its latest findings and released the first images of this comet created snowstorm.
...
According to A'Hearn evidence of large chunks around comets including Hartley 2 has been found with the Arecibo Radio telescope, but Arecibo can't detect individual particles or determine what the chunks are made of. Around Hartley 2, the spacecraft clearly imaged clouds of large ice particles with the largest ranging from golf ball sized to the size of a basketball.
...
A'Hearn said that more detailed analysis will be needed to determine whether the difference in out gassing between the smooth and rough regions of the comet likely is the result of a mixing of dry-ice rich clumps with dry-ice poor clumps during the comet's formation some 4.5 billion years ago, or whether that difference is due to more recent evolutionary changes.

Images
NASA Spacecraft Sees Cosmic Snow Storm During Comet Encounter
NASA EPOXI Mission News | 18 Nov 2010
The EPOXI mission's recent encounter with comet Hartley 2 provided the first images clear enough for scientists to link jets of dust and gas with specific surface features. NASA and other scientists have begun to analyze the images.

The EPOXI mission spacecraft revealed a cometary snow storm created by carbon dioxide jets spewing out tons of golf-ball to basketball-sized fluffy ice particles from the peanut-shaped comet's rocky ends. At the same time, a different process was causing water vapor to escape from the comet's smooth mid-section. This information sheds new light on the nature of comets and even planets.

Scientists compared the new data to data from a comet the spacecraft previously visited that was somewhat different from Hartley 2. In 2005, the spacecraft successfully released an impactor into the path of comet Tempel 1, while observing it during a flyby.
Comet Snowstorm Engulfs Hartley 2
NASA Science News | 18 Nov 2010
NASA has just issued a travel advisory for spacecraft: Watch out for Comet Hartley 2, it is experiencing a significant winter snowstorm.

Deep Impact photographed the unexpected tempest when it flew past the comet's nucleus on Nov. 4th at a distance of only 700 km (435 miles). At first, researchers only noticed the comet's hyperactive jets. The icy nucleus is studded with them, flamboyantly spewing carbon dioxide from dozens of sites. A closer look revealed an even greater marvel, however. The space around the comet's core is glistening with chunks of ice and snow, some of them possibly as large as a basketball.
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18805
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: UMD: Primordial Dry Ice Fuels Comet Jets

Post by neufer » Thu Nov 18, 2010 11:04 pm

Click to play embedded YouTube video.
Click to play embedded YouTube video.
Click to play embedded YouTube video.
Click to play embedded YouTube video.
Art Neuendorffer

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18805
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: UMD: Primordial Dry Ice Fuels Comet Jets

Post by neufer » Fri Nov 19, 2010 5:33 pm

http://www.planetary.org/blog/article/00002781/ wrote:
[c]Deep Impact at Hartley 2: Two weeks after the flyby
The Planetary Society Blog By Emily Lakdawalla Nov. 18, 2010[/c]
<<Today the Deep Impact/EPOXI science team held a press briefing that followed up on their very successful flyby of two weeks ago, a status report on what they can say so far about the science that's coming out of the encounter. There's still years worth of work to be done with this data set, and actually the spacecraft hasn't even stopped taking Hartley 2 data yet; according to the timeline, it is still snapping photos every half an hour and will continue to do so until the last day of November.

Before I launch into detail, here were the major points from the briefing:
  • * Hartley 2's jets are spitting out big fluffy snowballs, some of which can be individually tracked in sequential images. (Cool.)

    * These snowballs did absolutely no damage to the spacecraft, although close examination of its telemetry revealed that it may have gotten hit by very low-mass particles nine times during the ten minutes around closest approach.

    * The comet has a split personality, with carbon dioxide-powered jets spitting ice and dust out of its ends, but behaving more like Tempel 1 at its waist.
Mike A'Hearn showed the first image from the High-Resolution Imager that has been revealed from the Hartley 2 encounter. Mike showed how the initially blurry images from that camera can be sharpened using "scene-dependent iterative deconvolution." Most of the best images from today were animations that show how you can track individual particles from one image to the next. Here's one that just floored the science team, according to Pete Schultz.

I'm mesmerized by how the jets have a visible 3D structure to them, but what Pete was looking at was the motions of individual "snowballs" visible against the sky. Go ahead, look at the animation, and see if you can track individual particles. Some of those apparent motions are optical illusions (the human brain likes to draw lines between two points) but there are particles whose motion can be tracked consistently across multiple frames, tracing out a 3D motion field of snowballs in space, reminding Pete of a snow globe:

This cloud of individually visible big snowbally particles were a complete surprise to the science team. They were not seen at Tempel 1 at all.

With all those snowballs flying around, was this actually a dangerous environment? Project manager Tim Larson said that one of the first things they looked at after close approach was spacecraft health, and that "we went past the comet, through the coma, with no discernible damage to the spacecraft" from any of the telemetry they received from Deep Impact's instruments or systems. So the next question is, were there any hits that resulted in no damage? Larson said that they examined whether they got hit by small particles by looking at torques that such hits may have exerted on the spacecraft. They performed a detailed examination of the spacecraft's attitude data, which was measured in two different ways (he didn't specify how), and that they corrected for any motions of the spacecraft that resulted from its autonomous navigation and even its switches of filters in the cameras and the tiny sweeping motion of the scanner in the infrared instrument. He said "we've identified nine events in the ten minutes around closest approach that could possibly have been dust hits." Making an assumption about where the particles hit -- assuming that they all hit at about a meter away from the spacecraft's center of mass -- they used the torques to determine the mass of the particles that may have struck the spacecraft to range from about 0.02 to about 0.2 milligrams. Snowflakes.

Jessica Sunshine presented the most detailed science story of the briefing, based on data from the High-Resolution Imager's infrared spectrometer. Seen in visible light, Hartley 2 is jetting from the two rough ends of the nucleus -- from the sunlit area on the right, and to a lesser extent, from the left side of the nucleus. But no jets arise from the smooth "waist." The story is similar when Hartley 2 is viewed at a wavelength at which carbon dioxide (CO2) emits light, and at other wavelengths where dust and ice particles are visible. However, the story is very different for water vapor, which seems to be emitted predominantly from the waist rather than the two ends.

So the comet is behaving one way on its ends -- spewing out carbon dioxide jets that have particles of dust and ice entrained in them -- but is behaving differently at its middle, where there's a calmer outgassing of water vapor. What on Earth does this mean? A'Hearn proposed an explanation, and provided a couple of cartoons to illustrate it.

The behavior that they observed in the "waist" area of Hartley 2 is actually the comet behavior that they're familiar with, and saw at Tempel 1. Subsurface water ice, mixed with dirt, is heated by the Sun and sublimates (turns from a solid to a gas) gradually through the comet's pore spaces into the coma.

But the ends of Hartley 2 are behaving very differently from this, probably because it is (for reasons no one understands yet) much richer in carbon dioxide than other comets we've visited. Subsurface carbon dioxide ice located deep inside the comet feels the warmth from the Sun and sublimates, breaking out of the nucleus as jets carrying bits of solid water ice with them. The jets appear above discrete surface features.>>
Art Neuendorffer

User avatar
Ann
4725 Å
Posts: 13369
Joined: Sat May 29, 2010 5:33 am

Re: UMD: Primordial Dry Ice Fuels Comet Jets

Post by Ann » Fri Nov 19, 2010 5:55 pm

Image

Mr. Hartley's snowball personality

Ann
Color Commentator


Post Reply