美國宇航局的小行星偏轉(zhuǎn)任務(wù)可能引發(fā)一場人造流星雨

美國宇航局的小行星偏轉(zhuǎn)任務(wù)可能引發(fā)一場人造流星雨

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.

美國國家航空和宇宙航行局(NASA)進行了一次概念驗證性的演示，以確定我們是否能夠通過將小行星撞出軌道來拯救地球，從而在世界末日來臨之際引發(fā)首個由人類產(chǎn)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.

這一前所未有的任務(wù)被稱為“雙小行星重定向測試”(DART)，將于2021年由SpaceX公司的獵鷹9號搭載一枚重達1100磅的NASA探測器開始。在2022年9月下旬，它將旅行大約660萬英里，與一個名為Didymos的雙星小行星系統(tǒng)進行一次戲劇性的會合。DART的目標不是直徑近2600英尺的Didymos，而是一個更小的、直徑500英尺的軌道物體，昵稱為“Didymoon”。DART以每小時13500英里的速度運行，與Didymoon的碰撞預(yù)計將產(chǎn)生足夠的力量來改變小巖石的軌道。

A new manmade meteoroid stream

一個新的人造流星體

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.

據(jù)《紐約時報》報道，當DART與Didymoon相撞時，由此產(chǎn)生的爆炸預(yù)計會在小行星上形成一個30英尺寬的隕石坑，并噴射出2.2萬到22萬磅厘米大小的碎片。雖然這些微小的流星體中的絕大多數(shù)會像云一樣包裹著Didymos系統(tǒng)，但仍有未知的數(shù)量會被噴射到太空中。由于小行星的軌道在撞擊地球后僅僅幾天就經(jīng)過地球，很可能其中一些會在大氣層中燃燒，這是人類在太空活動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.

根據(jù)西安大略大學(xué)天文學(xué)教授Paul Wiegert的說法，這個先例既是一個警告也是一個機會。他在行星科學(xué)雜志最新發(fā)表的一篇論文中寫道,盡管DART產(chǎn)生的絕大多數(shù)噴出物在未來數(shù)千年內(nèi)都不會與地球相遇，但該實驗仍然證明，我們需要保持謹慎——尤其是在航天器安全方面——并了解太空中暴力行為的后果。

"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."

他寫道:“雖然現(xiàn)在人們傾向于忽視這個問題，但它讓人想起近地軌道的太空碎片問題。最初被忽視的是，我們現(xiàn)在可能會因為軌道碎片堆積而無法充分利用近地空間的寶貴部分。如果同樣的情況不發(fā)生在小行星殘骸的生產(chǎn)上，未來的很多費用和風險都可以避免。”

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.

維格特在論文中補充說，未來的儀器，比如即將發(fā)射的詹姆斯·韋伯太空望遠鏡的鏡片，可能會被人為產(chǎn)生的流星體嚴重損壞。他敦促研究人員不僅要監(jiān)測碰撞的結(jié)果，還要監(jiān)測碎片區(qū)域的路徑。設(shè)立這樣一個先例可以幫助保護未來的任務(wù)不受太陽系其他地方人類活動增加的影響。

"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.

他警告說:“雖然DART撞擊的情況不太可能發(fā)生，但未來的人類小行星操作，如行星防御測試或小行星采礦，可以令人信服地產(chǎn)生隕石碎片流，其隕石顆粒含量可與自然形成的隕石顆粒流相媲美或超過它。”