On Friday, the space agency announced plans to redirect the course of a small asteroid approaching Earth, as part of the Double Asteroid Redirection Test (DART), according to a NASA press release.

　　根据美国宇航局NASA的新闻稿，上周五(6月30日)美国航天局宣布计划改变一个飞往地球的小行星的飞行方向，这是双小行星重定向测试(DART)的一部分。

　　The release notes that asteroids hit Earth nearly every day, but most are small enough to burn up in the atmosphere.

　　该新闻稿强调：几乎每一天都会有小行星撞向地球，但是绝大多数体积都太小以至于在大气层中燃尽。

　　But the DART project -- a joint effort between NASA and the John Hopkins Applied Physics Laboratory in Maryland -- is for the asteroids that are too big to break up -- those that could have severe consequences for the Earth if they hit.

　　但是DART计划，这个由NASA和马里兰州的约翰·霍普金斯应用物理实验室共同支持的项目针对的是那些体积较大而不能在大气层中燃尽的小行星。它们一旦撞击地球将会造成严重的后果。

　　DART would be NASA’s first mission to demonstrate what’s known as the kinetic impactor technique -- striking the asteroid to shift its orbit -- to defend against a potential future asteroid impact. This approval step advances the project toward an historic test with a non-threatening small asteroid.

　　DART将会是NASA首个采用动力学撞击器技术的任务，通过撞击小行星来改变它的运行轨道，进而防止未来潜在的小行星撞击。这项被批准的步骤应用一颗无威胁小行星促使这个计划成为了一个具有历史意义的测试。

　　The target of the test is an asteroid system called Didymos, the release said. Didymos -- Greek for "twin" -- is a binary asteroid system, made up of one asteroid, Didymos A, and a smaller one, Didymos B, which orbits its larger neighbor.

　　这项测试的目标是一个被称为Didymos的小行星系统。Didymos是希腊语”双胞胎”的意思，这是一个二元的小行星系统，由小行星A和另外一个较小的小行星B组成，B围绕着A转。

　　refrigerator-sized spacecraft towards the asteroids, aimed at Didymos B, the release said. When the DART spacecraft and the asteroid collide, the spacecraft will be traveling at a staggering 3.7 miles per second.

　　预计在2022年10月，随着Didymos靠近地球，NASA将会朝这些小行星发射一个冰箱大小的航天器，瞄准小行星B。当DART航天器与小行星发生碰撞，航天器将会以惊人的每秒3.7英里(约6km/s)的速度飞行。

　　The kinetic impact technique works by changing the speed of a threatening asteroid by a small fraction of its total velocity, the release says, "but by doing it well before the predicted impact so that this small nudge will add up over time to a big shift of the asteroid’s path away from Earth."

　　这个动力学撞击的原理是通过改变小行星总速度的一小部分分量来改变小行星的飞行速度。但是如果在预测的撞击之前很好的利用此技术，那么这一个小小的推进将会随着时间的推移而对小行星的运行轨道造成巨大的改变从而使其远离地球。

　　Back home, scientists will study the impact and the effect it has on Didymos B’s orbit around Didymos A, to determine whether this technique is a feasible method for saving the planet from asteroids that could otherwise have devastating impacts.

　　回到家中，科学家们还会研究这个撞击以及它对A行星外围轨道上的B行星造成的影响，从而确定这项技术是否可以将地球从一场毁灭性的撞击中挽救出来。

　　DART is a critical step in demonstrating we can protect our planet from a future asteroid impact, said Andy Cheng, one of the leaders of the Johns Hopkins team. "With DART, we can show how to protect Earth from an asteroid strike with a kinetic impactor by knocking the hazardous object into a different flight path that would not threaten the planet."

　　“DART”是展示我们在未来保护地球以免遭到小行星撞击的一个重要步骤，约翰·霍普金斯团队的领导者之一Andy Cheng说道。”通过DART，我们将通过一个动力学撞击器撞击危险目标并将其推入不同的对地球无威胁飞行轨道中来展示如何保护地球免受小行星撞击。

　　The announcement coincided with International Asteroid Day, which commemorates the largest recorded asteroid impact in Earth’s history, when in 1908 a meteorite hit Russia’s Podkamennaya Tunguska River in a remote forest, leveling trees and knocking over people in a town 40 miles away.

　　这项声明的发布日期正式国际小行星日(6月30日)，这是为了纪念历史上有记载以来最大的一次小行星撞击地球事件，发生于1908年一颗陨石撞击在俄罗斯通古斯卡河一片偏远的森林里，大片森林被夷为平地，40英里(约64公里)外的居民也受到了震动。