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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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