Recently, scientist have also discovered comets in the main asteroid belt -these main-belt comets might be a key source of water for the inner terrestrial planets.
最近,科学家在主小行星带中也发现了一些彗星——这些主带彗星可能是类地内行星上水的关键来源。
2
What's the main goal of the Belt and Road Forum for the countries?
“一带一路”高峰论坛对各国的主要目标是什么?
3
Rock Farm: Most asteroids lie in the mainbelt [white] between Mars and Jupiter and pose no threat.