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Deep Impact: The Independence Day Impactor!

Deep Impact mission' impact sequence, July 4th, 2005 EDT. picture site 'Amateur Astronomy' based on pictures NASA/JPL-Caltech/UMD

click to a larger view of the impact at comet Tempel 1, July 4th, 2005, 1:52 a.m. EDT. picture courtesy NASA/JPL-Caltech/UMD

Operations. The Deep Impact's impactor successfully hit comet Tempel 1, just in time, at 1:52 a.m. EDT on July 4th, 2005. The mother ship, meanwhile, successfully flew by, imaging the impact. It appears that the impact first released a small, rapidly expanding flash as a pause followed before a bright, narrow plume of debris quickly extended. This is pointing to that the impactor struck deep, with gases heating and explosively getting out of the impact location. A large crater was created. Such an impact sequence is leading to that the upper surface is likely fluffy -or highly porous, and rich in volatile substances
The pictures taken by the impactor as it was heading to its crash with the comet, on the other hand, are showing various relief features like impact craters, ridges, scalloped edges, or bright features. A thoroughful study by the science team will provide more about such features. Comet Tempel 1 is a matte black comet, approximately 8.7 by 2.5 miles (14 by 4 kilometers), that is about one-half the size of Manhattan. last updated July 21st, 2005

->Another Life for Deep Impact
Deep Impact will perform a Trajectory Correction Maneuver (TCM) in July to place it on a trajectory to fly past Earth on Dec. 31 2007. This maneuver preserves options for future use of the craft. NASA invited all interested investigators in the use of the craft as is to submit proposals

->More Science From the Mission
Last studies about Deep Impact results are showing that a comet is geologically active body, as water ice has been found at the surface of a comet for the first time. Such surface ice has been reported into three pockets of thin ice, covering 300,000 square feet or the 1.2 billion square feet the surface of the comet is representing. Only 6 percent of the pockets' area consists of pure water ice, as the remaining is dust only. The mechanism why the ice surfaced is that it became exposed over time. A comet's surface changes over time. That's because large organic components and water are found at comets that they are believed to have been one of the life-bringing agent to the primitive Earth. The origin of comet Tempel 1 has been found to lie at the current orbit of Uranus and Neptune. The impact allowed the Spitzer Space Telescope finding that cometary material in our own solar system resembles that around nearby stars

->Impact's First Teachings

click the thumbnails to views of comet Tempel 1. 1, 2, 3. pictures NASA/JPL-Caltech-UMD

Gygabytes of data have been beamed back Earth, as 4,500 pictures were taken. The science team is beginning to investigate them. The first remarks concern the fact that the comet's surface was likely very finely powdery due to the impact's plume being opaque and giving off a lot of light. The dust excavated from the comet is thought to look like talcum powder. The impactor hit at an approximately 25 degree oblique angle to the surface, as it created a crater which is thought to be at the large end of the expectations, that is a diameter of 165 to 820 ft (50-250 m). Views above were taken by the impactor as it was rushing to the comet. The rightmost picture was taken 20 seconds before the impact only. Comet Tempel 1 is a matte black comet, approximately 8.7 by 2.5 miles (14 by 4 kilometers), that is about one-half the size of Manhattan. The fewer craters seen at Tempel, along with the varied surfaces and tectonic lines seen are hinting to a likely young comet on one hand and to a possible differentiation process on the other hand. A differentation process is the process by which a celestial body, at a moment of its formation, is differentiating into some layers of material, bringing for example the rocky planets to form a core, a mantle, and a crust
LATEST: Tempel 1, from further data analysed from the impact and flyby, was found having a very fluffy surface, weaker than a bank of powder snow as two impact craters seem to hint that some parts of the surface are strong enough to allow such features. . The surface has been found very porous too, which means that it heats up and cools down very rapidly in response to sunlight. This should mean too that heat is not easily conducted into the interior of the nucleus. The impact plume was seen holding a lot of carbon-containing molecules, that is that the comet contains a substantial amount of organic material. This matches the idea that comets were likely life-building blocks bringers to the young planets

->From the Approach to the Impact

comet Tempel 1 as taken by Deep Impact. From left to right: Apr. 25, 2005, Jun. 13, Jun. 20, June 21. Both rightmost pictures (from left to right) were taken from 7.7 and 7.2 million miles (12.5 and 11.5 million km) respectively. pictures courtesy NASA/JPL/UMD (first left) and NASA/JPL-Caltech/UMD (others)

Deep Impact's impactor after its release, as seen by Deep Impact's mother ship on July 3rd, 2005. picture courtesy NASA/JPL

Deep Impact took several images of comet Tempel 1 as it was approaching the comet. At the moment of the release, on July 3, at 2:07 a.m. EDT, the Deep Impact mission was eventually 547,000 mi (880,000 km) away from comet Tempel 1. The mother ship had performed an ultimate Trajectory Correction Maneuver (TCM) in order that the impactor be placed as close as possible to the right path towards the comet, as the impactor was prepared. Its batteries were activated at 1:12 a.m. Sunday EDT. Separation pyros were eventually fired with an uncoiling spring separating the two spacecraft at a speed of about 0.78 mph (35 cm/s). The Deep Impact mother ship performed its own divert burn soon after to move out of the path of the comet and to reach its flyby trajectory. The mission controllers confirmed that the impactor's S-band antenna was talking to the flyby spacecraft. The impact and imaging sequences unfolded like planned, with the impactor turning into autonomous navigation mode two hours before the impact and correctly performing, in time, its 3 targeting maneuvers at 90, 35 and 12.5 minutes before the impact, as the flyby craft imaged and monitored during 14 minutes before entering in shield mode at 2:05 a.m. EDT as it was flying at its closest through the comet's inner coma. The link with the craft was re-established by the engineers 27 mn later!

->Comet Tempel 1 Was Outgasing Before the Impact!

As Deep Impact was nearing the comet lately, comet Tempel 1 was seen enduring several outbursts of dust, gas, ice and other particles. Such an activity is linked to the fact that comet Tempel 1 is now near its perihelion -that is its nearest Sun- and that distorting pressures are likely exerting unto the nucleus, having some parts of the surface and sub-surface blasted out. Such outbursts, in such conditions, are likely common at most comets. The outbursts were seen inducing a dramatic increase in brightness of comet Tempel 1, with an increase in size of the comet's coma and a modification of the compounds therein. The ejected material eventually dissipated within a half day. A total of 4 outbursts was observed during the last three weeks, as the last occurred just last July 2nd! Let's hope that no any one more will occur during the approach of the impactor or the flyby of the mother ship ;-) picture NASA/JPL

Detailed Schedule of the Encounter back

note that an updated timeline is available at the Deep Impact site

click to a view of the mission's journey to the comet and of the impact and flyby's configuration. diagrams site 'Amateur Astronomy'

Mission

Deep Impact is a swift mission! It launched on January 12th, 2005 from the Cape Canaveral Air Force Station (CCAFS), launch pad 17-B for an encounter at its target in July 2005. Deep Impact's aim is to fire a 39-by-39-inch (1-by-1-meter) impactor unto comet 9P/Tempel 1, as the craft will observe what ensues from a mere 310 miles (500 km) away. Such an impactor will create a crater at the comet helping to determine whether a comet's nucleus is a conglomerate of unprocessed

What are Comets? Comets are icy and rock balls which vaporize when they come in the inner solar system, developing a gas tail. It becomes to be established now that comets come from the "Kuiper Belt", an annular zone of leftovers from the time when the Sun and the planets formed, or, further, from the Oort Cloud. Less than 10 percent of the comets recorded are visible naked-eye only. more about comets

material only or whether there was some differentiation leading to a more consistent surface. Comet Tempel 1 is the size of the island of Manhattan. The impact, by creating a crater at the comet's surface, is expected to uncover the underlying layers of materials, providing further a glimpse at a material dating back to the origins of the solar sysem. Mission is officially ending in August 2005, as scientists will continue data analysis during 8 months, ending in March 2006

The impact at the comet is scheduled on July, 4th 2005 -the Independence Day in the USA- as the impactor will separate 24 hr before the impact. The craft will follow up, flybying the comet by 300 miles (500 km) to collect data using its medium and high resolution imagers and infrared spectrometer. The impact will occur as the craft and the comet will be then 83 million miles (133.6 million km) away from Earth. The operation will in no way affect the comet's trajectory due to the huge difference of size between the impactor and the comet. It's as if a mosquito was hitting a 767 airliner. Some questions were raised however about whether the impact might lead the comet to eventually shatter. It's only in the case if the comet would have had a much smaller nucleus that the impact might possibly have shattered it.The rotation period of comet Tempel 1 is 41.85 hrs. The project is managed by the Jet Propulsion Laboratory (JPL), as the spacecraft was built by Ball Aerospace & Technologies Corporation, Boulder, Colo.

Space and ground telescopes, and amateurs as well, will be able to watch the impact. Comet's pre-impact magnitude will be about 10, which means it will be observable in a small telescope. A network of at least 30 telescopes around the world, including Spitzer, Hubble and the Chandra X-ray Observatory, will be watching the dramatic impact. By analyzing the material blown out of the interior of the comet, this global network of telescopes will assemble a list of the raw ingredients that went into making the planets in our solar system. The impact might increase the comet's brightness by a few magnitudes but whether or not the brightening will be sufficient to render the comet a naked eye object remains unsure. Both the impactor and the craft will beam images in near real time during one month. observers may find here a JPL HORIZONS system ephemeris providing orbital data about comet Tempel 1!

for more, see at Deep Impact site