Comet Hartley 2

Comet Hartley 2 was studied by the Deep Impact spacecraft as part of its EPOXI mission on November 4, 2010. This comet is small, measuring approximately 2.3 km (1.4 miles) in length and 0.9 km (0.6 mile) wide. Its nucleus appears to be composed of two bodies joined together, with the smaller body being significantly more active than the larger one. This activity is thought to be driven by carbon dioxide sublimation, which was an unexpected finding for a short-period comet. The comet also exhibits complex rotation, a phenomenon not previously observed in comets. Observations by the Herschel space telescope also studied Comet Hartley 2, revealing that its water has the same isotopic signature as Earth's oceans, suggesting a potential cometary origin for Earth's water.123