Mystery of Comets : Comets remain one of the most elusive bodies within our Solar System. Though scientists have speculated about their evolution and composition, there has been little conclusive data to definitively suggest or support any particular theories. Recently, scientists have begun to aggressively investigate comets, resulting in several NASA missions aimed at collecting data from various comets orbiting within our Solar System. By continuing the investigation of comets and other small bodies, we can explore the mystery of life and the wonders of the universe.
Deep Impact Mission :
Deep Impact is a NASA space probe launched on January 12, 2005. It was designed to study the composition of the comet interior of 9P/Tempel, by releasing an impactor into the comet. At 5:52 UTC on July 4, 2005, the impactor successfully collided with the comet's nucleus. The impact excavated debris from the interior of the nucleus, allowing photographs of the impact crater. The photographs showed the comet to be more dusty and less icy than had been expected. The impact generated a large and bright dust cloud, which unexpectedly obscured the view of the impact crater.
Previous space missions to comets, such as Giotto and Stardust, were fly-by missions. These missions were only able to photograph and examine the surfaces of cometary nuclei from a distance. The Deep Impact mission was the first to eject material from a comet's surface, and the mission garnered large publicity from the media, international scientists, and amateur astronomers.
Upon the completion of its primary mission, proposals were made to further utilize the spacecraft. Consequently, Deep Impact flew by Earth on December 31, 2007 on its way to an extended mission, designated EPOXI, with a dual purpose to study extrasolar planets and comet Hartley 2.
Stardust is a 300-kilogram robotic space probe launched by NASA on February 7, 1999 to study the asteroid 5535 Annefrank and collect samples from the coma of comet Wild 2. The primary mission was completed January 15, 2006, when the sample return capsule returned to earth.
Operating for 12 years and 8 days, Stardust is currently on an extended mission to intercept and study asteroid Tempel 1 on February 15, 2011. Tempel 1 was previously visited by Deep Impact on July 4, 2005. It is the first sample return mission to collect cosmic dust and return the sample to Earth.
Comet Tempel 1:
Tempel 1 (official designation: 9P/Tempel), is a periodic comet discovered by Wilhelm Tempel in 1867. It currently completes an orbit of the Sun every 5.5 years. Tempel 1 was the target of the Deep Impact space mission, which photographed a deliberate high-speed impact upon the comet. It was re-visited by the Stardust spacecraft on February 15, 2011.
Comet Wild 2 :
Comet 81P/Wild, also known as Wild 2, is a comet named after Swiss astronomer Paul Wild, who discovered it in 1978 using a 40-cm Schmidt telescope at Zimmerwald.
For most of its 4.5 billion-year lifetime, Wild 2 probably had a more distant and circular orbit. In September 1974, it passed within less than one million kilometers of the planet Jupiter, whose strong gravitational pull perturbed the comet's orbit and brought it into the inner Solar System.Its orbital period changed from 43 years to about 6 years, and its perihelion is now about 1.59 AU (astronomical unit).