2025年5月1日
MESSENGER’s Last Day on Mercury
Image Credit: NASA, Johns Hopkins Univ. APL, Arizona State Univ., CIW
Explanation: The first to orbit inner planet Mercury, the MESSENGER spacecraft came to rest on this region of Mercury’s surface on April 30, 2015. Constructed from MESSENGER image and laser altimeter data, the projected scene looks north over the northeastern rim of the broad, lava filled Shakespeare basin. The large, 48 kilometer (30 mile) wide crater Janacek is near the upper left edge. Terrain height is color coded with red regions about 3 kilometers above blue ones. MESSENGER’S final orbit was predicted to end near the center, with the spacecraft impacting the surface at nearly 4 kilometers per second (over 8,700 miles per hour) and creating a new crater about 16 meters (52 feet) in diameter. The impact on the far side of Mercury was not observed by telescopes, but confirmed when no signal was detected from the spacecraft given time to emerge from behind the planet. Launched in 2004, the MErcury Surface, Space ENvironment, GEochemisty and Ranging spacecraft completed over 4,000 orbits after reaching the Solar System’s innermost planet in 2011.
Tomorrow’s picture: burning hydrogen
信使号在水星的最后一天
影像提供: NASA, Johns Hopkins Univ. APL, Arizona State Univ., CIW
说明: 人类历史上第一艘绕行水星的信使号航天器，在2015年4月30日堕毁在水星表面的这个区域。这幅由信使号的影像数据和雷射高度仪数据所建构而成的影像，北眺宽广、底部灌满岩浆的莎士比亚盆地之东北沿。而影像左上角，则可见到宽为48公里的Janacek大撞击坑。影像以色泽来表现表面的高度，红色区比蓝区约高3公里。信使号的最后轨道预测终止于影像中心附近，它以将近每秒4公里的速度（时速超过14,000公里）撞击表面，预期会形成一个宽16公尺的撞击坑。这个发生在水星反面的撞击事件，地面望远镜不得见，不过在航天器应该从行星背后复现并传回讯号的时刻，并未收到任何讯号，故可确定发生了撞击。这艘发射于2004年、英文全名为MErcury Surface, Space ENvironment, GEochemisty and Ranging spacecraft （MESSENGER；水星表面、太空环境、地质化学与测距航天器）的探测器，于2011年抵达太阳最内围的水星之后，共绕行了4,000多圈。
明日的图片: burning hydrogen
