A cast-off crumb from the solar system鈥檚 early days has wound its way back towards the sun. The unusual, tiny-tailed comet C/2014 S3 seems to be a leftover piece of the stuff that clumped together into rocky planets like Earth.
The odd-looking C/2014 S3 was spotted 18 months ago through the Pan-STARRS telescope. Most comets are bright with brilliant tails of evaporating ice, and started life in the Oort cloud on the solar system鈥檚 edges. But C/2014 S3 looks as dark and rocky as an asteroid, and has a stubby tail made mostly of dust.
鈥淚 had never heard of such a thing. We wondered, what are we going to call this?鈥� says of the University of Hawaii. 鈥溾�楶otentially dead comet鈥� is too much of a mouthful.鈥�
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Her research team dubbed it a 鈥淢anx comet鈥� after the tailless cat, representing a new class of solar system objects.
Why does it look so different? Meech and her colleagues suggest that its strange dimness means it didn鈥檛 form in the Oort cloud at all. It looks more like an asteroid, but its mineral contents suggest it hasn鈥檛 been spending time in the warmer asteroid belt, either. Instead, it could be left over from the beginning of the solar system.
鈥淢aybe it has been in cold storage all this time,鈥� Meech says. That would mean the Manx comet can teach astronomers about how the Earth came to be.
鈥淲e no longer have samples of the material that built Earth. That鈥檚 just gone,鈥� she says. 鈥淭his might be one of the closest things we can find.鈥�
Giant planets jostling
Small, primitive objects like C/2014 S3 鈥� which measures between one-third and two-thirds of a kilometre in diameter 鈥� witnessed the solar system鈥檚 violent beginnings. The chemical fingerprints of planet formation are embedded in them, and we can use those fingerprints to figure out where the objects scattered during the solar system鈥檚 turbulent youth.
This will help pin down the influence of the giant planets, whose jostling would have knocked the smaller bits around and caused them to settle far from their places of birth.
鈥淲e are searching for evidence about exactly what happened in the early solar system, and we do believe it was a very chaotic environment,鈥� says at the Carnegie Institution for Science in Washington DC. 鈥淭here have been suggestions that some inner solar system material got tossed into the outer solar system and could be sitting out there, but how much is a big unknown. That鈥檚 what this paper is starting to address.鈥�
We鈥檒l need to find a lot more objects like this one before we can determine how many pre-planet pieces are left over. But all-sky survey telescopes like Pan-STARRS, and the future Large Synoptic Survey Telescope, will be able to find them. 鈥淥ur ability to find these things is going to increase dramatically in the next few years,鈥� Sheppard says.
Meech hopes to find up to 100 more Manx objects. But her team have to act fast. C/2014 S3 was discovered in September 2014, but by the time Meech鈥檚 team waited until after the full moon and observed it with several large telescopes, it was almost too faint to see. Shortly after their observations, the sun blocked it from view. Now it is lost for another 860 years.
Journal reference: Science Advances, DOI: 10.1126/sciadv.1600038