This close-up view of comet Hartley 2 was taken by NASA's EPOXI mission during its flyby of the comet on Nov. 4, 2010. It was captured by the spacecraft's Medium-Resolution Instrument.
CREDIT: NASA/JPL-Caltech/UMD Enlarge

Comet Hartley 2, officially known as 103P/Hartley, visits the inner solar system about every 6.5 years. The comet was discovered by an amateur astronomer in 1986 and received a visit from a NASA mission, Epoxi, in 2010. It is expected to return in April 2017.

Although the comet is a frequent visitor to the sun, it's still a very active small body. NASA has called Hartley 2 a "weird little comet", and one NASA astronomer characterized Hartley 2 as "a hyperactive little comet, spewing out more water than most other comets its size."

Scientists studying the small comet have raised the possibility that more comets behave the same way, especially if they carry plenty of carbon dioxide or monoxide in their composition.

Hartley 2's visit by Epoxi also revealed some strange scientific discoveries, such as "glittering blocks" on either end of the comet.

Caught by quality control

Hartley 2 is named after its discoverer, Malcolm Hartley, an amateur astronomer working for the Siding Spring Observatory in New South Wales, Australia. He has held several roles at the facility over the years, but in March 1986 he was a quality controller examining the accuracy of images taken by a Schmidt telescope on site.

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