Сборник пыли кометы Вильда 2: Миссия Stardust

Fourth mission of the Discovery program; sample return from the periodic Comet Wild 2

Stardust was a 385 kilogram robotic space probe launched by NASA on 7 February 1999. Its primary mission was to collect dust samples from the coma of comet Wild 2, as well as samples of cosmic dust, and return them to Earth for analysis. It was the first sample return mission of its kind. En route to Comet Wild 2, it also flew by and studied the asteroid 5535 Annefrank. The primary mission was successfully completed on 15 January 2006 when the sample return capsule returned to Earth. A mission extension, codenamed NExT, culminated in February 2011 with Stardust intercepting Comet Tempel 1, a small Solar System body previously visited by Deep Impact in 2005. Stardust ceased operations in March 2011. On 14 August 2014, scientists announced the identification of possible interstellar dust particles from the Stardust capsule returned to Earth in 2006.

Beginning in the 1980s, scientists began seeking a dedicated mission to study a comet. During the early 1990s, several missions to study Comet Halley became the first successful missions to return close up data. However, the US cometary mission, Comet Rendezvous Asteroid Flyby, was canceled for budgetary reasons. In the mid 1990s, further support was given to a cheaper, Discovery class mission that would study Comet Wild 2 in 2004. as particle impacts at over , even into aerogel, were believed to be terminal for any known microorganism.

On 19 March 2006, Stardust scientists announced that they were considering the possibility of redirecting the spacecraft on a secondary mission to image Comet Tempel 1. The comet was previously the target of the Deep Impact mission in 2005, sending an impactor into the surface. The possibility of this extension could be vital for gathering images of the impact crater which Deep Impact was unsuccessful in capturing due to dust from the impact obscuring the surface. On 3 July 2007 the mission extension was approved and renamed New Exploration of Tempel 1 (NExT). This investigation would provide the first look at the changes to a comet nucleus produced after a close approach to the Sun. NExT also would extend the mapping of Tempel 1, making it the most mapped comet nucleus to date. This mapping would help address the major questions of comet nucleus geology. The flyby mission was expected to consume almost all of the remaining fuel, signaling the end of the operability of the spacecraft.

At 04:39:10 UTC on 15 February 2011, Stardust NExT encountered Tempel 1 from a distance of The impact site from Deep Impact was also observed, though it was barely visible due to material settling back into the crater.

On 24 March 2011 at approximately 23:00 UTC, Stardust conducted a burn to consume its remaining fuel. with a velocity of , the fastest reentry speed into Earth's atmosphere ever achieved by a human made object. The capsule followed a drastic reentry profile, going from a velocity of Mach 36 to subsonic speed within 110 seconds. Peak deceleration was 34 g, encountered 40 seconds into the reentry at an altitude of 55 km over Spring Creek, Nevada. The capsule then parachuted to the ground, finally landing at 10:12 UTC at the Utah Test and Training Range, near the U. S. Army Dugway Proving Ground. The capsule was then transported by military aircraft from Utah to Ellington Air Force Base in Houston, Texas, then transferred by road in an unannounced convoy to the Planetary Materials Curatorial facility at Johnson Space Center in Houston to begin analysis.

The sample container was taken to a clean room with a cleanliness factor 100 times that of a hospital operating room to ensure the interstellar and comet dust was not contaminated. Preliminary estimations suggested at least a million microscopic specks of dust were embedded in the aerogel collector. Ten particles were found to be at least 100 micrometers (0.1 mm) and the largest approximately 1,000 micrometers (1 mm). An estimated 45 interstellar dust impacts were also found on the sample collector, which resided on the back side of the cometary dust collector. Dust grains are being observed and analyzed by a volunteer team through the citizen science project, Stardust@Home. The combined mass of the harvested sample was approximately 1 mg. In December 2006, seven papers were published in the scientific journal Science, discussing initial details of the sample analysis. Among the findings are: a wide range of organic compounds, including two that contain biologically usable nitrogen; indigenous aliphatic hydrocarbons with longer chain lengths than those observed in the diffuse interstellar medium; abundant amorphous silicates in addition to crystalline silicates such as olivine and pyroxene, proving consistency with the mixing of Solar System and interstellar matter, previously deduced spectroscopically from ground observations; hydrous silicates and carbonate minerals were found to be absent, suggesting a lack of aqueous processing of the cometary dust; limited pure carbon (CHON) was also found in the samples returned; methylamine and ethylamine was found in the aerogel but was not associated with specific particles. In 2010, Dr. Andrew Westphal announced that Stardust@home volunteer Bruce Hudson found a track (labeled "I1043,1,30") among the many images of the aerogel that may contain an interstellar dust grain. The program allows for any volunteer discoveries to be recognized and named by the volunteer. Hudson named his discovery "Orion". In April 2011, scientists from the University of Arizona discovered evidence for the presence of liquid water in Comet Wild 2. They have found iron and copper sulfide minerals that must have formed in the presence of water. The discovery shatters the existing paradigm that comets never get warm enough to melt their icy bulk. In the spring of 2014, the recovery of particles of interstellar dust from the Discovery program's Stardust mission was announced. The Stardust samples are currently available for everyone to identify after completing the training at Berkeley webpage.

The return capsule is currently located at the National Air and Space Museum in Washington, D. C. It began exhibition there on 1 October 2008, the 50th anniversary of the establishment of NASA. The return capsule is displayed in sample collection mode, alongside a sample of the aerogel used to collect samples.