At first, astronomers thought it might be a so-called "main belt comet" — a rare case of a comet orbiting in the asteroid belt.

起先，天文学家们认为这种景象不过是所谓的“主带彗星”——即较为少见的轨道在小行星主带内的彗星。

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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。

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The inner belt orbits at a distance of about 3 astronomical units from its star — or about the same position as the asteroid belt in our own solar system.

内侧行星带距离它的恒星为3个天文单位——或者相当于太阳系中的行星带与太阳的距离。

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The American space agency's Dawn spacecraft began circling Vesta, a member of the asteroid belt that orbits the sun.

VOA: special.2011.07.27

"We will use the tremendous capabilities of this ion propulsion system to climb out of orbit around Vesta, travel for almost another three years through the asteroid belt to dwarf planet Ceres and then go into orbit around Ceres and undertake the same kind of measurements there that we'll be doing at Vesta.

VOA: special.2011.07.27

T. and an expert on the Main Asteroid Belt, points out, the belt could have never hosted a planet large enough to claim Mars as a satellite.

FORBES: Main Asteroid Belt No Remnant Of Exploded Planet

Abell says the best estimates now are that the Russian object was initially a rocky silicate asteroid that almost certainly originated from the main asteroid belt.

FORBES: NASA Eager To Analyze Russian Meteor Fragments

Early on, Moskovitz says the entire solar system probably resembled one giant asteroid belt.

FORBES: Main Asteroid Belt No Remnant Of Exploded Planet