... ESO is building what will be the World's largest optical telescope array, The Very Large Telescope (VLT). The VLT Project organisation is responsible for the design and construction of the Unit Telescopes, including enclosures, optics, adapter-rotators and coating unit. ... Unit Telescopes Overview - This page is outdated, an update is in process. ... Secondary mirror (M2 Unit) - This page is outdated, an update is in process. ... Coating Unit - This page is outdated, an update is in process. ...

... The craters were caused by the impacts of comets and asteroids. ... In fact, up to a diameter of about 10 meters (33 feet), most stony meteoroids are destroyed in the atmosphere in a terminal explosion. ... The famous meteor crater in northern Arizona, some 1.2 kilometers (4,000 feet) in diameter and 183 meters (600 feet) deep, was created 50,000 years ago by a nickel-iron meteorite perhaps 60 meters (197 feet) in diameter. ... These range in diameter from a few meters to about 8 km. ...

... Before the Galileo encounters with Ganymede it was thought that Ganymede and Callisto were composed of a rocky core surrounded by a large mantle of water or water ice with an ice surface (and that Titan and Triton were similar). ... Ganymede's surface is a roughly equal mix of two types of terrain: very old , highly cratered dark regions (left), and somewhat younger (but still ancient) lighter regions marked with an extensive array of grooves and ridges (right). ... Callisto .. ...

... B efore the Galileo encounters with Ganymede it was thought that Ganymede and Callisto were composed of a rocky core surrounded by a large mantle of water or water ice with an ice surface (and that Titan and Triton were similar). ... G anymede's surface is a roughly equal mix of two types of terrain: very old , highly cratered dark regions (left), and somewhat younger (but still ancient) lighter regions marked with an extensive array of grooves and ridges (right). ... Callisto .. ...

Astronomy Picture of the Day . Asteroid 253 Mathilde's Large Craters . ... Credit: NEAR Spacecraft Team , JHUAPL , NASA Explanation: You're zipping through the Solar System when you pass ... asteroid 253 Mathilde. ... Mathilde has more large craters than asteroids 243 Ida and 951 Gaspra , which were photographed by the Galileo spacecraft now orbiting Jupiter . ... NASA Official: Jay Norris. ... Publications with keywords: Mathilde - asteroid . Publications with words: Mathilde - asteroid . ...

... Tonight's Sky . ... Sky this Month . ... The Sky This Week: April 1 - 10 . ... Sky this Week . ... Sky Events . ... Tour the Deep Sky . ... Observing springtime deep-sky objects with a large telescope . ... How large a body would it take to make a crater as wide as the Gulf of Mexico? ... The Gulf of Mexico is the result of plate tectonics, or "continental drift," in which the plates comprising the Earth's crust change position over time. ... Get instant access to subscriber content on Astronomy.com...

Ganymede is the largest moon in our solar system, larger even than the planets Pluto and Mercury. ... Ganymede's surface consists of two main types of terrain: old, dark polygonal units, and young, bright valleys and ridges (see figure 11 ). ... In a similar way, hitting a large block of ice with a hammer makes white marks. ... Ganymede as seen by Voyager 2. ... Because Voyager couldn't spot any large impact craters, scientists have concluded that the moon's surface is young. ... Moon . ... Europa . ...

... A team of Japanese scientists including Armagh astronomer Dr David Asher have announced the