[ti:NASA Spacecraft, Dawn, Close to Reaching a 'Dwarf Planet'] [ar:Marsha James] [al:Technology Report] [by:www.51voa.com] [00:00.00]An American spacecraft is moving closer [00:03.55]to a dwarf planet called Ceres. [00:07.20]The American space agency's Dawn spacecraft [00:11.80]is set to reach the planet-like object in March. [00:16.42]Space agency scientists will then place Dawn [00:20.75]in an orbit around the dwarf planet. [00:24.14]Agency scientists want to know more about ice on Ceres. [00:30.28]The spacecraft will gather clues about whether Ceres [00:34.89]may have once had conditions to support life as we know it. [00:39.91]Dawn left Earth more than seven years ago on a trip [00:45.39]to explore Ceres and another dwarf planet, called Vesta. [00:50.53]Both dwarf planets are in the main belt of asteroids, [00:55.72]a group of large objects, between the planets Mars and Jupiter. [01:01.74]Marc Rayman is the chief engineer and director of the Dawn mission. [01:07.95]"This is the first time in more than 57 years [01:11.16]of space exploration that we have a spacecraft [01:13.79]targeted to orbit any two extraterrestrial destinations." [01:17.08]Scientists call Vesta and Ceres "protoplanets." [01:22.69]Mr. Rayman says they were in the process [01:27.24]of becoming full-size planets when, [01:30.42]in his words, "their growth was terminated." [01:34.60]Scientists believe Ceres is made of rock, and covered with ice. [01:40.81]The Dawn mission is based in Los Angeles, California. [01:45.94]Scientists there send second-by-second commands to the spacecraft. [01:52.85]They direct its every move, [01:55.74]including telling it what pictures to take. [01:59.02]Dawn will make a map of the dwarf planet. [02:03.01]It will also try to discover how Ceres' surface has changed. [02:09.30]Carol Raymond is the deputy principal investigator of the project. [02:15.26]"One of the interests in bodies like Ceres and other icy bodies [02:20.07]in the outer solar system [02:22.15]is that when objects like that impacted the terrestrial planets, [02:25.99]they brought a lot of water with them. [02:28.03]So there's a very vigorous debate at the current time [02:34.45]as to whether wet asteroids like Ceres -- [02:38.23]and we know there are other wet asteroids [02:41.73]in the outer edge of the main belt -- [02:43.60]whether they were the dominant source of water in the Earth's ocean." [02:48.19]Carol Raymond says Dawn made an unexpected discovery while orbiting Vesta. [02:55.74]"Instead of being bone dry, [02:57.77]which we expected, [02:59.28]there were patches on the surface of Vesta [03:02.52]that showed significant amounts of water [03:05.49]bound in the rocks and possibly even free water [03:11.08]that could have flowed on the surface in the past." [03:13.84]She says that if Earth's water came from wet worlds [03:19.00]like Vesta and Ceres, then life could have developed there, too. [03:24.69]If Dawn finds that the environment of Ceres [03:29.43]could have supported life, [03:31.26]scientists may seek to explore the dwarf planet [03:35.22]with other scientific instruments. [03:38.04]Dawn will gather information about Ceres [03:41.28]until the middle of 2016. [03:44.58]It will then continue to orbit the small planet. [03:49.20]I'm Marsha James. [03:51.58]¸ü¶àÌýÁ¦Çë·ÃÎÊ51voa.com