NASA Mission Discovers Mysterious Plumes of Particles Being Ejected From Asteroid’s Surface
2019-12-16 16:13

The space agency said they launched the mission to study the asteroid Bennu in 2016. Samples from the celestial body would not only shed light on how planets formed and life began, but also give a better understanding of how to protect our planet from an asteroid collision.


NASA's OSIRIS-REx mission made a surprising discovery when it spotted plumes of particles coming from the surface of the asteroid Bennu. The finding is not only rare, but is the first time that scientists observed particles being ejected from the surface of an asteroid up-close. It also proves that Bennu is an active asteroid.

美国国家航空航天局的 OSIRIS-REx 航天器探测到一个惊人发现,小行星贝努的表面喷出粒子羽流。这发现不仅罕见,也是科学家们首次观察到从近地小行星表面喷出的粒子。同时,还证明了贝努是一颗活跃的小行星。

"The discovery of plumes is one of the biggest surprises of my scientific career. This is a great opportunity to expand our knowledge of how asteroids behave", said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson.


OSIRIS-REx, which stands for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, “met” Bennu last year and the mission has been orbiting the asteroid ever since. The discovery itself was made in January this year, but scientists presented their observations in a study just days ago, on 6 December.

Osiris-Rex探测器,它的名称代表着(Origin)起源、(Spectral Interpretation)光谱释义、(Resource Identification)资源辨认、(Security-Regolith Explorer)安全风化层探测,自去年与贝努“相遇”后它便一直环绕着这颗小行星运行。羽流现象发生在今年1月,但科学家们在几天前,也就是12月6日,才在一项研究中公布他们的观察结果。

According to OSIRIS-REx's science team, the eruptions of particles occurred in different places on the asteroid. The first event was spotted in its southern hemisphere, while a second and a third originated near Bennu's equator. The particles were released from the surface, briefly orbited Bennu and then fell back or flew into space. They travelled at a speed of 3 metres per second and measured from smaller than an inch to 10 cm.

根据 OSIRIS-REx's 的科学团队观察,粒子喷发现象发生在小行星上的不同地方。首次喷出是在南半球,而第二与第三次则是发生在贝努的赤道附近。这些粒子从行星表面被释放出来,短暂地围绕着贝努,然后回落或飞向太空。它们以每秒3米的速度飞行,大小从不到1英寸(2.54厘米)到10厘米不等。

The team then examined mechanisms that could lead to these mysterious ejections. They concluded that it could be due to:


  • micrometeorites hitting Bennu's surface, shaking loose particles from the surface.
  • thermal fracturing as Bennu experiences temperatures fluctuations. It is extremely cold during the night and the temperature rises significantly during the afternoon. These huge temperature fluctuations can lead to cracks in the rock and subsequent release of the particles.
  • water release. Hydrated minerals are widespread on Bennu. When they are heated, water creates pressure that builds in cracks and pores in boulders and when water is released, the asteroid's surface becomes agitated and releases particles.




Scientists note that identifying the exact mechanism that leads to ejections of particles will be quite difficult.


"It could be that more than one of these possible mechanisms are at play. For example, thermal fracturing could be chopping the surface material into small pieces, making it far easier for meteoroid impacts to launch pebbles into space", said Steve Chesley, an author on the paper and Senior Research Scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.


Many of the particles are small enough for OSIRIX-REx to collect them and deliver to Earth and further study of these particles and samples from Bennu will help scientists better understand asteroids – their similarities and differences – as well as astronomers-to-help-space-agencies-save-earth-from-asteroids/">ways to deflect asteroids if they are set on a collision course with our planet. Bennu, which is categorised as a near-Earth object could pass our planet closer than the Moon in 2135, with even closer approaches possible in 2175 and 2195. Meanwhile, OSIRIS-REx will start collecting samples from Bennu in the summer of 2020 and is scheduled to return them to Earth in 2023.

许多颗粒的体积并不大, Osirix-Rex可以收集它们并传送至地球,对这些颗粒样品的进一步研究将有助于科学家更好地认识小行星---发现它们的异同---以及有助于天文学家帮助太空局寻找拯救地球免受行星撞击方法:一旦它们的前行路线将与地球碰撞,便使其偏离路线。贝努行星属于近地天体,2135年与地球间距离将比地月距离更短,在2175年和2195年甚至会离我们更近。与此同时,Osirix-Rex将于2020年夏季开始收集贝努行星的样本,并计划于2023年将样本送回地球。

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