美国宇航局的小行星偏转任务可能引发一场人造流星雨

美国宇航局的小行星偏转任务可能引发一场人造流星雨

A proof-of-concept demonstration by NASA to determine whether we could save Earth from a doomsday asteroid by literally knocking it off course may end up causing the first human-generated meteor shower.

美国国家航空和宇宙航行局(NASA)进行了一次概念验证性的演示，以确定我们是否能够通过将小行星撞出轨道来拯救地球，从而在世界末日来临之际引发首个由人类产生的流星雨。

NASA's DART mission will attempt to deflect a small asteroid off-course as a proof-of-concept demonstration for defending Earth against much larger threats. (Photo: NASA)

Called the Double Asteroid Redirection Test (DART), the unprecedented mission will begin with the launch of an 1,100-pound NASA probe aboard a SpaceX Falcon 9 in 2021. It will then travel roughly 6.6 million miles for a dramatic rendezvous with a binary asteroid system called Didymos in late September 2022. Instead of targeting Didymos, which measures nearly 2,600 feet across, DART will set its sights instead on a smaller, 500-foot-wide orbiting object nicknamed "Didymoon." Traveling at a speed of 13,500 mph, DART's collision with Didymoon is expected to generate enough force to change the small rock's orbit.

这一前所未有的任务被称为“双小行星重定向测试”(DART)，将于2021年由SpaceX公司的猎鹰9号搭载一枚重达1100磅的NASA探测器开始。在2022年9月下旬，它将旅行大约660万英里，与一个名为Didymos的双星小行星系统进行一次戏剧性的会合。DART的目标不是直径近2600英尺的Didymos，而是一个更小的、直径500英尺的轨道物体，昵称为“Didymoon”。DART以每小时13500英里的速度运行，与Didymoon的碰撞预计将产生足够的力量来改变小岩石的轨道。

A new manmade meteoroid stream

一个新的人造流星体

An illustration of the DART spacecraft just before its collision with Didymoon. (Photo: NASA/Johns Hopkins University Applied Physics Laboratory)

When DART collides with Didymoon, the resulting explosion is expected to create a 30-foot-wide crater in the asteroid and, according to The New York Times, eject anywhere from 22,000 to 220,000 pounds of centimeter-sized debris. While the vast majority of these tiny meteoroids will envelope the Didymos system like a cloud, an unknown number will be ejected into space. Due to the asteroid's orbit passing by Earth only a few days after the collision, it's likely that some will burn up in the atmosphere as part of the first meteor shower caused by human activities in space.

据《纽约时报》报道，当DART与Didymoon相撞时，由此产生的爆炸预计会在小行星上形成一个30英尺宽的陨石坑，并喷射出2.2万到22万磅厘米大小的碎片。虽然这些微小的流星体中的绝大多数会像云一样包裹着Didymos系统，但仍有未知的数量会被喷射到太空中。由于小行星的轨道在撞击地球后仅仅几天就经过地球，很可能其中一些会在大气层中燃烧，这是人类在太空活动引起的第一次流星雨的一部分。

According to Paul Wiegert, an astronomy professor at the University of Western Ontario, this precedent is as much a warning as an opportunity. In a new paper published in The Planetary Science Journal he writes that while the vast majority of the ejecta created by DART won't cross paths with Earth for potentially thousands of years, the experiment still proves that we need to be careful –– particularly in regards to spacecraft safety –– and understand the repercussions of violent actions in space.

根据西安大略大学天文学教授Paul Wiegert的说法，这个先例既是一个警告也是一个机会。他在行星科学杂志最新发表的一篇论文中写道,尽管DART产生的绝大多数喷出物在未来数千年内都不会与地球相遇，但该实验仍然证明，我们需要保持谨慎——尤其是在航天器安全方面——并了解太空中暴力行为的后果。

"Though one is tempted to dismiss the problem as negligible at this time, it is reminiscent of the problem of space debris in low Earth orbit," he writes. "Neglected initially, we are now reaching a point where we may be denied the full use of valuable portions of near-Earth space because of orbital debris build-up. Much future expense and risk could be averted if the same story does not unfold with asteroidal debris production."

他写道:“虽然现在人们倾向于忽视这个问题，但它让人想起近地轨道的太空碎片问题。最初被忽视的是，我们现在可能会因为轨道碎片堆积而无法充分利用近地空间的宝贵部分。如果同样的情况不发生在小行星残骸的生产上，未来的很多费用和风险都可以避免。”

An illustration of the probe's collision with the asteroid. (Photo: European Space Agency)

Wiegert adds in the paper that future instruments, such as the mirrors on the upcoming James Webb Space Telescope, could be critically damaged by artificially-generated meteoroid streams. He urges researchers to monitor not only the results of the collision, but also the path of the debris field. Setting such a precedent could help protect future missions from increased human activity elsewhere in our solar system.

维格特在论文中补充说，未来的仪器，比如即将发射的詹姆斯·韦伯太空望远镜的镜片，可能会被人为产生的流星体严重损坏。他敦促研究人员不仅要监测碰撞的结果，还要监测碎片区域的路径。设立这样一个先例可以帮助保护未来的任务不受太阳系其他地方人类活动增加的影响。

"Though it is unlikely to occur in the case of the DART impact, future human asteroid operations such as planetary defense tests or asteroid mining, could conceivably produce debris streams whose meteoroid particle content rivals or exceeds naturally occurring meteoroid streams," he warns.

他警告说:“虽然DART撞击的情况不太可能发生，但未来的人类小行星操作，如行星防御测试或小行星采矿，可以令人信服地产生陨石碎片流，其陨石颗粒含量可与自然形成的陨石颗粒流相媲美或超过它。”