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Post Info TOPIC: Comet 9/P Tempel 1
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Observations by telescopes at Mauna Kea show a complex mix of silicates, water and organic compounds beneath the surface of the comet. These materials are similar to what is seen in another class of comets thought to reside in a distant swarm of pristine bodies called the Oort Cloud.
Oort Cloud comets are well preserved fossils in the frozen suburbs of the solar system that have changed little over the billions of years since their formation. When they are occasionally nudged gravitationally toward the Sun they warm up and release a profuse amount of gas and dust on a one-time visit to the inner solar system.

Periodic comets (returning comets) like Tempel 1 were believed to have formed in a colder nursery distinctly different from the birthplaces of their Oort Cloud cousins. The evidence for two distinct "family trees" lies in their vastly different orbits and apparent composition.

"Now we see that the difference may really be just superficial: only skin deep. Under the surface, these comets may not be so different after all" - Chick Woodward, University of Minnesota.

This similarity indicates that both types of comets might have shared a birthplace in a region of the forming solar system where temperatures were warm enough to produce the materials observed.

"It is now likely that these bodies formed between the orbits of Jupiter and Neptune in a common nursery. Another question that the Mauna Kea telescopes were able to address is the amount of mass ejected when the comet was impacted by the chunk of copper about the mass of a grand piano from the Deep Impact spacecraft" - Seiji Sugita, University of Tokyo and Subaru team member.

At the time of impact, the spacecraft was travelling at about 37,000 kilometres per hour.
Because the spacecraft was unable to study the size of the crater created after it was formed, the high-resolution Mauna Kea observations provided the necessary data to get a firm estimate of the mass ejection which was about 1000 tons.

"To release this amount of material, the comet must have a fairly soft consistency" - Seiji Sugita.

"The splash from NASA’s impact probe freed these materials and we were in the right place to capture them with the biggest telescopes on Earth. The close collaboration among Keck, Gemini and Subaru assured that the very best science was done by the best telescopes in the world, demonstrating that the whole is often greater than the sum of its parts" - Fred Chaffee, W.M. Keck Director.




Imaging and spectroscopy of four temporal epochs of comet 9P/Tempel 1 obtained before and after impact. For each epoch, the 10 µm spectrum (left column Fλ (W cm^ -2 µm ^-1)), and an 11.7 µm image (centre column) is shown. The thermal model (right column λFλ (W cm^ -2)) for each epoch is plotted on top of the observed spectra. For epochs T= 0:08; +1:0, and +1:8 hrs, the on-source integration time for each spectrum is 100.8 sec. For the T = +26:4 hrs epoch, the on-source integration time for the spectrum is 705.6 sec. The size of the extraction aperture for all spectra is a 0.6" x 1.0" rectangle (392,653 km) centred on the brightest part of the coma, and is indicated in red in each image. Plotted model components are: the total model SED (red line); asteriodal standard thermal model nucleus flux (orange line); amorphous olivine (blue line); amorphous pyroxene (cyan line); amorphous carbon (brown line); crystalline olivine (green line).

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Blobrana


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Scientists revealed that they detected green silicate crystals (olivine) in Tempel 1 similar to, but smaller than, Hawaiian green sand particles, according to articles by the researchers in the September 15, 2005 issue of the journal Science Express. They made their observations before, during and after the NASA Deep Impact spacecraft's 820-pound 'impactor' collided with the comet in early July 2005, as planned, so astronomers could determine what is in comets. The papers outline findings scientists made using infrared detectors on the Gemini and Subaru telescopes in Hawaii.


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"The silicate crystals are talcum powder-size, but they are made of the same materials as the green sand beaches in Hawaii" - Diane Wooden, co-author of both papers.
Diane Wooden is an astrophysicist at NASA Ames Research Centre, located in California's Silicon Valley. The principal author of the Gemini Telescope paper is David Harker, University of California, San Diego. Seiji Sugita of the University of Tokyo is the principal author of the second Subaru Telescope paper.

"Following the collision of the comet with the 'impactor,' there was a short-lived gas geyser associated with the impact site that carried the crystals from Tempel 1 into space. The Gemini and the Subaru telescopes are two of the biggest in the world, and we were able to focus in on the green dust particles in the jet and ejecta – something that most space-borne telescopes could not see in infrared light. The insides of comet Tempel 1 look very much like the outsides of comets that have not been 'cooked' by passages close to the sun " - Diane Wooden.

There might be green silicates on the surfaces of comets that swarm in the outer reaches of the solar system and are not exposed to intense sunshine.

Another comet, Hale-Bopp, was so active that it released green silicate crystals as it passed close to the sun in 1997.

"However, the Deep Impact spacecraft's 'impactor' had to blast the green silicate crystals from the interior of the comet Tempel 1 for us to see them with our ground-based instruments" - Diane Wooden.

Tempel 1 travels close to the sun during part of the comet's orbit, and strong sunlight hits the comet, causing its surface gases and other particles to fly off into space. These particles are what make up a comet's tail, which forms nearer the sun.

"In Tempel 1's case, it has passed near the sun so many times that it has lost much of its surface gases and particles. What's incredible to me is that the surface – or maybe the fluffiness of the body of Tempel 1 -- is protecting the primitive particles and gases just below the surface from being out-gassed. We discovered crystalline silicates in the dust that flew from the comet after its collision with the Deep Impact 'impactor.' We don't usually see these silicates in comets that have been 'cooked' by the sun" - Diane Wooden..


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Blobrana


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Newly analysed data from the Spitzer Space Telescope details the recipe for comets based on observations of Tempel 1.

"We are assembling a list of comet ingredients that will be used by other scientists for years to come" - Carey Lisse, Johns Hopkins University's Applied Physics Laboratory.

Spitzer used its infrared cameras to monitor material kicked up by the Deep Impact probe.
Lisse’s team found standard comet components, such as silicate. Though they were smaller than typical sand grains.
There were surprises, too, such as clay and carbonates. These were unexpected because they are thought to require liquid water to form.


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This graph shows the two spectra acquired by NASA's Spitzer Space Telescope before (middle) and after (bottom) it observed NASA's Deep Impact smash into comet Tempel 1. Above them is a past spectrum of comet Hale-Bopp, which illustrates the extra detail seen by Spitzer in Tempel 1.

"How did clay and carbonates form in frozen comets?"
We don't know, but their presence may imply that the primordial solar system was thoroughly mixed together, allowing material formed near the Sun where water is liquid, and frozen material from out by Uranus and Neptune, to be included in the same body" - Carey Lisse.

Scientists hope now to begin using this new recipe to make better computer models for how the solar system formed. Comet innards are thought to be pristine leftovers from the formation of the Sun and planets around 4.5 billion years ago.

"Now, we can stop guessing at what's inside comets. This information is invaluable for piecing together how our own planets as well as other distant worlds may have formed" - Mike A'Hearn, principal investigator for the Deep Impact mission and an astronomer at the University of Maryland.

Lisse presented the findings this week at the 37th annual meeting of the Division of Planetary Sciences in Cambridge, England.

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Blobrana


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The shape and surface features of the comet Tempel 1 are quite different from the two other comets whose cores have been studied, scientists said today.
The comet appears to be coated with fine powder rather than solid ice and rock. The powder is even finer than sand.
A thorough analysis confirms that and other preliminary conclusions about the 11-kilometer-long icy world, which appears to be rather fluffy.
The outer tens of meters of the comet is less strong than a snow bank, said Deep Impact principal investigator Michael A'Hearn, an astronomer at the University of Maryland.
The comets gravity holds it all together.

Dust emanates from the comet in frequent outbursts, likely a result of being warmed by the sun. The dust kicked up by the impact was not the same as surface dust, but it spread through space and dissipated in a manner similar to the natural outbursts.

While more analysis is needed, the interior is clearly different from the surface.
Inside, the comet harbours a relatively high concentration of organic compounds, the stuff from which life is made. The organics were more prevalent during and after the outburst than the water and carbon dioxide that routinely escape from the nucleus, or hard core of the comet.
The results were presented to reporters in a teleconference Monday and will be published later this week by the journal Science.

Comets are leftovers from the formation of the solar system. They're frozen vaults of primordial material, stuff that escaped the planet-formation process and therefore holds clues to what the raw materials of Earth and other worlds was like.
Before Deep Impact, scientists had gotten close-up looks at the nuclei of only two comets, Borrelly and Wild 2. Tempel 1 is much different from either of those.
In recent years, our impression of comets has shifted from dirty snowballs to snowy dirtballs. That latter description holds true with comet Tempel 1.
There is more dust than ice, but the ratio is less than 10-to-1. More significant to the new data is the revelation that there's not much there.

"The comet is mostly empty" - Michael A'Hearn.

It is probably more than 75 percent porous with perhaps no solid core. Instead, it's likely made of ice grains loosely packed through and through.
That conclusion would not alter how comets might have delivered water and organic material to early Earth. One leading theory for the formation of life on our planet holds that the raw material was delivered by comets.
Scientists are still analyzing the chemicals that came out of the Tempel 1, from ammonia and acetylene to hydrogen cyanide. The molecules don't seem to be different from what previous ground-based observations had revealed, however.
Tempel 1 is also dotted with round depressions that the scientists think are impact craters, which have not been seen before on comets.



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Blobrana


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Astronomers using the Palomar Observatory's 200-inch Hale Telescope have been amazed by comet Tempel 1's behaviour during and after its collision with the Deep Impact space probe.

In the minutes just after the impact the comet was seen to increase its near-infrared brightness nearly fivefold. As the event progressed astronomers at Palomar were able to distinguish jets of material venting from the comet's nucleus that have persisted for days.

Early results from the data, in images taken just minutes after impact, showed a possible plume of dust and gas extending outward some 320 km (200 miles) from the comet's centre, roughly coinciding with the site of the probe's final demise.

This apparent dust plume has persisted for several nights, allowing astronomers to watch the comet's slow rotation. The night after impact the plume was on the far side of the comet, but was visible again the next evening as the comet's rotation brought it back into view. Two days after impact, the plume was seen again, this time extending about 200 km (124 miles) from the comet's centre.
According to Bidushi Bhattacharya of the California Institute of Technology's (Caltech) Spitzer Science Centre, "This could be indicative of an outburst of gas and dust still taking place near the region of the impact."

"We are very excited by these results. It is a fabulous time to be studying comets," says James Bauer of the Jet Propulsion Laboratory (JPL). "It will be interesting to see how long the effects of the impact persist," he adds.

The images of the comet, obtained by Bauer and Bhattacharya, were sharper than those from most ground-based telescopes because they used a technique known as adaptive optics. Adaptive optics allows astronomers to correct for the blurring of images caused by Earth's turbulent atmosphere, giving them a view that often surpasses those of smaller telescopes based in space.

Using the adaptive-optics technique to improve an astronomer's view is generally only possible when a bright star is located near the object they want to study. On the night of impact there was no bright star close enough to the comet to use. Mitchell Troy, the adaptive-optics group lead and Palomar adaptive-optics task manager at JPL, worked with his team to make adaptive optics corrections anyway. "Through the dedicated efforts of the JPL and Caltech teams we were able to deploy a new sensor that was 25 times more sensitive then our normal sensor. This new sensor allowed us to correct for some of the atmosphere's distortions and significantly improve the view of the comet," says Troy. This improved view allowed astronomers to see the dust and ejected material moving out from the comet's surface immediately following the impact event and again days later.

Earth-based observations from telescopes like the 200-inch at Palomar give astronomers an important perspective on how the comet is reacting to the impact, a perspective that cannot be achieved from the front-row seat of a fly-by spacecraft. Astronomers on the ground have the luxury of long-term observations that may continue to show changes in the comet for weeks to come.

Collaborators on the observations include Paul Weissman (JPL), and the Palomar 200-inch crew. The Caltech-adaptive optics team is made up of Richard Dekany (team leader), Antonin Bouchez, Matthew Britton, Khanh Bui, Alan Morrissett, Hal Petrie, Viswa Velur and Bob Weber.
The JPL Palomar adaptive-optics team includes Mitchell Troy (team leader), John Angione, Sidd Bikkannavar, Gary Brack, Steve Guiwits, Dean Palmer, Ben Platt, Jennifer Roberts, Chris Shelton, Fang Shi, Thang Trinh, Tuan Truong and Kent Wallace.

The Palomar adaptive-optics instrument was built and continues to be supported by the Jet Propulsion Laboratory as part of a Caltech-JPL collaboration.

Support for the adaptive-optics research at Caltech's Palomar
Observatory comes from the Oschin Family Foundation, the Gordon and
Betty Moore Foundation and the National Science Foundation Centre for Adaptive Optics.

Images are available at:
http://www.astro.caltech.edu/palomarnew/deepimpact.html

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Ten days after part of the Deep Impact spacecraft plunged onto Comet Tempel 1 with the aim to create a crater and expose pristine material from beneath the surface, astronomers are back in the ESO Offices in Santiago, after more than a week of observing at the ESO La Silla Paranal Observatory.

In this unprecedented observing campaign - among the most ambitious ever conducted by a single observatory - the astronomers have collected a large amount of invaluable data on this comet.
The astronomers have now started the lengthy process of data reduction and analysis. Being all together in a single place, and in close contacts with the space mission' scientific team, they will try to assemble a clear picture of the comet and of the impact.

The ESO observations were part of a worldwide campaign to observe this unique experiment. During the campaign, ESO was connected by phone, email, and videoconference with colleagues in all major observatories worldwide, and data were freely exchanged between the different groups.
This unique collaborative spirit provides astronomers with data taken almost around the clock during several days and this, with the largest variety of instruments, making the Deep Impact observing campaign one of the most successful of its kind, and thereby, ensuring the greatest scientific outcome.
From the current analysis, it appears most likely that the impactor did not create a large new zone of activity and may have failed to liberate a large quantity of pristine material from beneath the surface.


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Images obtained at the VLT show that after the impact, the morphology of Comet Tempel 1 had changed, with the appearance of a new plume-like structure, produced by matter being ejected with a speed of about 700 to 1000 km/h.
This structure, however, diffused away in the following days, being more and more diluted and less visible, the comet taking again the appearance it had before the impact. Further images obtained with, among others, the adaptive optics NACO instrument on the Very Large Telescope, showed the same jets that were visible prior to impact, demonstrating that the comet activity survived widely unaffected by the spacecraft crash.

The study of the gas in Comet Tempel 1, made with UVES on Kueyen (UT2 of the VLT), reveals a small flux increase the first night following the impact. At that time, more than 17 hours after the impact, the ejected matter was fading away but still measurable thanks to the large light collecting power of the VLT.
The data accumulated during 10 nights around the impact have provided the astronomers with the best ever time series of optical spectra of a Jupiter Family comet, with a total of more than 40 hours of exposure time. This unique data set has already allowed the astronomers to characterize the normal gas activity of the comet and also to detect, to their own surprise, an active region.

This active region is not related to the impact as it was also detected in data collected in June. It shows up about every 41 hours, the rotation period of the comet nucleus determined by the Deep Impact spacecraft.
Exciting measurements of the detailed chemical composition (such as the isotopic ratios) of the material released by the impact as well as the one coming from that source will be performed by the astronomers in the next weeks and months.

Further spectropolarimetric observations with FORS1 have confirmed the surface of the comet to be rather evolved - as expected - but more importantly, that the dust is not coming from beneath the surface. These data constitute another unique high-quality data set on comets.
Comet Tempel 1 may thus be back to sleep but work only starts for the astronomers.

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Blobrana


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The plume of debris that spilled from a comet after it collided with a space probe is as fine as talcum powder, suggesting the comet formed gradually.
Scientists continued to pore over data gathered when a copper probe from NASA's Deep Impact spacecraft blasted a crater in comet Tempel 1 on July 4 to expose its primordial core.
Comets are believed to be the frozen leftover building blocks of the solar system, formed when a huge cloud of gas and dust collapsed about 4.5 billion years ago. Studying them could provide clues to the birth of the solar system.
Soon after the 820-pound probe hit Tempel 1, scientists detected evidence of water, carbon dioxide and organic substances spewing from the comet. The high-speed collision produced two flashes of light and hurled a plume of fine, powdery dust from the comet thousands of miles into space.

"This probably means the material in the comet came together very gently. If it melted and resolidified, it would have the strength of solid ice" - Michael A'Hearn, an astronomer at the University of Maryland and the mission's principal investigator.

Scientists are waiting for the dust from the larger-than-expected debris cloud to settle before they can get their first glimpse at the inside of the comet and determine the size and depth of the crater. They said the crater was larger than a house and possibly as big as a football stadium.

Comets are believed to be abundant in water, and astronomers were surprised to find a lack of water vapour after the collision. Preliminary findings by a science instrument aboard a NASA satellite in Earth orbit showed Tempel 1 released about 550 pounds of water per second, similar to the amount before the impact, suggesting the comet contains more dust than ice.

"It's pretty clear that this event did not produce a gusher" - Gary Melnick of the Harvard-Smithsonian Centre for Astrophysics.

The findings appear to contradict results by the European Space Agency's XMM-Newton Observatory, which this week found evidence of increased water in the comet's emissions after the impact.
The impactor probe was equipped with a camera and beamed back close-up pictures of the comet before slamming into the surface at a 25-degree angle.
The last picture was taken three seconds before the probe was obliterated, revealing crater-like features on the comet's surface.



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Blobrana


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The Tempel 1 comet impacted by a projectile from the Deep Impact probe was covered with powder on its surface, explaining the huge cloud of matter created afterward..

"Data from Deep Impact's instruments indicate an immense cloud of fine powdery material was released when the probe slammed into the nucleus of comet Tempel 1 at about 10 kilometres per second" - statement from Nasa's Jet Propulsion Laboratory (JPL) at Pasadena, near Los Angeles.

"The major surprise was the opacity of the plume the impactor created and the light it gave off. The cloud indicated the comet is covered in the powdery stuff. The Deep Impact science team continues to wade through gigabytes of data collected during the July 4 encounter with the comet measuring five kilometres wide by 11km long" - Michael A'Hearn, Deep Impact chief investigator, University of Maryland.

The information also includes 4500 images taken when the impact occurred.

Within minutes of the crash, scientists were able to pore over a wealth of high-resolution images showing a bright flash of light as the projectile collided with the potato-shaped comet that was discovered in 1867.


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This false-colour image shows comet Tempel 1 as seen by the Chandra X-ray Observatory on June 30, 2005.


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The comet was bright and condensed.
The Chandra data indicate that the X-rays observed from Tempel 1 are primarily due to the interaction between highly charged oxygen ions in the solar wind and neutral gases from the comet.
Chandra observed the comet during the collision of NASA's Deep Impact impactor probe with Tempel 1 on July 4, and it will continue to monitor the comet in the upcoming weeks. These observations could provide information about the expansion of the ejected material away from the comet.

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Blobrana


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The Gemini North telescope on Mauna Kea successfully captured the collision of NASA's Deep Impact probe with Comet 9P/Tempel 1.
Preliminary analysis of the data from the mid-infrared spectroscopic observations indicates that there was strong evidence for silicates or rocky material exposed by the impact.


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Gemini North Michelle mid-infrared (11.6 micron) false-colour images of 9P/Temple 10 minutes before impact (left), 3 hours after (centre) and 24 hours after impact (right). Scale and orientation are the same for all images. Note: the middle image represents a physical expanse about that of the Big Island of Hawaii.

"The properties of the mid-infrared light were completely transformed after impact; In addition to brightening by a factor of about 4, the characteristics of the mid-infrared light was like a chameleon and within five minutes of the collision it looked like an entirely new object" - David Harker, University of San Diego, co-investigator for the research team.

The Gemini observations were made using Michelle, the facility mid-infrared imager/spectrograph built at the Royal Observatory of Edinburgh (ROE) in the UK. The instrument has unique capabilities in the mid-infrared especially at Gemini which uses protected silver coatings on main mirrors to provide exceptional performance in the `thermal` or mid-infrared part of the spectrum.

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