Continuing our top 10 ranges, today we will write about top 10 largest cities in the world by land area.
NASA’s Dawn spacecraft has revealed unexpected details on the surface of the giant asteroid Vesta.
The new photos of Vesta from NASA’s Dawn spacecraft highlight odd, shiny spots that are nearly twice as bright as other parts of the asteroid, suggesting it is original material left over from the space rock’s birth 4 billion years ago, NASA officials said on March 21. With a width of about 330 miles (530 km), asteroid Vesta is one of the largest and brightest objects in the main asteroid belt between the orbits of Mars and Jupiter. NASA’s Dawn probe has been orbiting Vesta since 2011 to study the space rock in unprecedented detail. As said Jian-Yang Li, a Dawn participating scientist at the University of Maryland, College Park, their analysis finds this bright material originates from Vesta and has undergone little change since the formation of Vesta over 4 billion years ago. They are eager to learn more about what minerals make up this material and how the present Vesta surface came to be. Bright areas appear everywhere on Vesta but are most predominant in and around craters. The areas vary from several hundred feet to around 10 miles (16 kilometers) across. Rocks crashing into the surface of Vesta seem to have exposed and spread this bright material. This impact process may have mixed the bright material with darker surface material.While scientists had seen some brightness variations in previous images of Vesta from NASA’s Hubble Space Telescope, Dawn scientists also did not expect such a wide variety of distinct dark deposits across its surface. The dark materials on Vesta can appear dark gray, brown and red. They sometimes appear as small, well-defined deposits around impact craters. They also can appear as larger regional deposits, like those surrounding the impact craters scientists have nicknamed the “snowman.” The dark materials seem to be related to impacts and their aftermath. Scientists theorize carbon-rich asteroids could have hit Vesta at speeds low enough to produce some of the smaller deposits without blasting away the surface. Higher-speed asteroids also could have hit Vesta’s surface and melted the volcanic basaltic crust, darkening existing surface material. That melted conglomeration appears in the walls and floors of impact craters, on hills and ridges, and underneath brighter, more recent material called ejecta, which is material thrown out from a space rock impact.Vesta’s dark materials suggest the giant asteroid may preserve ancient materials from the asteroid belt and beyond, possibly from the birth of the solar system.