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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Deep Impact (spacecraft) | 3/5 | https://en.wikipedia.org/wiki/Deep_Impact_(spacecraft) | reference | science, encyclopedia | 2026-05-05T12:46:37.709114+00:00 | kb-cron |
Impact phase began nominally on June 29, 2005, five days before impact. The Impactor successfully separated from the Flyby spacecraft on July 3 at 6:00 UTC (6:07 UTC ERT). The first images from the instrumented Impactor were seen two hours after separation. The Flyby spacecraft performed one of two divert maneuvers to avoid damage. A 14-minute burn was executed which slowed down the spacecraft. It was also reported that the communication link between the Flyby and the Impactor was functioning as expected. The Impactor executed three correction maneuvers in the final two hours before impact. The Impactor was maneuvered to plant itself in front of the comet, so that Tempel 1 would collide with it. Impact occurred at 05:45 UTC (05:52 UTC ERT, +/− up to three minutes, one-way light time = 7m 26s) on the morning of July 4, 2005. The impactor returned images as late as three seconds before impact. Most of the data captured was stored on board the Flyby spacecraft, which radioed approximately 4,500 images from the HRI, MRI, and ITS cameras to Earth over the next few days. The energy from the collision was similar in size to exploding five tons of dynamite and the comet shone six times brighter than normal.
== Results ==
Mission control did not become aware of the Impactor's success until five minutes later at 05:57 UTC. Don Yeomans confirmed the results for the press, "We hit it just exactly where we wanted to" and JPL Director Charles Elachi stated "The success exceeded our expectations." In the post-impact briefing on July 4, 2005, at 08:00 UTC, the first processed images revealed existing craters on the comet. NASA scientists stated they could not see the new crater that had formed from the Impactor, but it was later discovered to be about 100 meters wide and up to 30 meters (98 ft) deep. Lucy McFadden, one of the co-investigators of the impact, stated "We didn't expect the success of one part of the mission [bright dust cloud] to affect a second part [seeing the resultant crater]. But that is part of the fun of science, to meet with the unexpected." Analysis of data from the Swift X-ray telescope showed that the comet continued outgassing from the impact for 13 days, with a peak five days after impact. A total of 5 million kg (11 million lb) of water and between 10 and 25 million kg (22 and 55 million lb) of dust were lost from the impact. Initial results were surprising as the material excavated by the impact contained more dust and less ice than had been expected. The only models of cometary structure astronomers could positively rule out were the very porous ones which had comets as loose aggregates of material. In addition, the material was finer than expected; scientists compared it to talcum powder rather than sand. Other materials found while studying the impact included clays, carbonates, sodium, and crystalline silicates which were found by studying the spectroscopy of the impact. Clays and carbonates usually require liquid water to form and sodium is rare in space. Observations also revealed that the comet was about 75% empty space, and one astronomer compared the outer layers of the comet to the same makeup of a snow bank. Astronomers have expressed interest in more missions to different comets to determine if they share similar compositions or if there are different materials found deeper within comets that were produced at the time of the Solar System's formation.
Astronomers hypothesized, based on its interior chemistry, that the comet formed in the Uranus and Neptune Oort cloud region of the Solar System. A comet which forms farther from the Sun is expected to have greater amounts of ices with low freezing temperatures, such as ethane, which was present in Tempel 1. Astronomers believe that other comets with compositions similar to Tempel 1 are likely to have formed in the same region.
=== Crater === Because the quality of the images of the crater formed during the Deep Impact collision was not satisfactory, on July 3, 2007, NASA approved the New Exploration of Tempel 1 (or NExT) mission. The mission utilized the already existing Stardust spacecraft, which had studied Comet Wild 2 in 2004. Stardust was placed into a new orbit so that it passed by Tempel 1 at a distance of approximately 200 km (120 mi) on February 15, 2011, at 04:42 UTC. This was the first time that a comet was visited by two probes on separate occasions (1P/Halley had been visited by several probes within a few weeks in 1986), and it provided an opportunity to better observe the crater that was created by Deep Impact as well as observing the changes caused by the comet's latest close approach to the Sun. On February 15, NASA scientists identified the crater formed by Deep Impact in images from Stardust. The crater is estimated to be 150 meters (490 ft) in diameter, and has a bright mound in the center likely created when material from the impact fell back into the crater.
== Public interest == The mission coincidentally shared its name with the 1998 film, Deep Impact, in which a comet strikes the Earth.
=== Media coverage ===