The image top was taken by the EPOXI mission on Nov. 2, 2010 from a distance of 2.3 million kilometers (1.4 million miles). [Image credit: NASA/JPL-Caltech/UMD]
And Nasa have already reported some surprising observations
In recent years, international spacecraft have buzzed the cores of four comets: Halley, Tempel 1, Borrelly and Wild 2. Deep Impact even blew a hole in one of them (Tempel 1) to see what was beneath the surface. Those previous flybys, however, may not have prepared researchers for the comet at hand.
“Comet Hartley 2 is smaller yet much more active than the others,” explains A’Hearn. “Although its core is only 2 km wide—about a third the size of Tempel 1—it is spewing five times more gas and dust.”
The comet has already shocked the science team by producing a massive surge of CN, the cyanogen radical commonly known as “cyanide.” Cyanide itself wasn’t the surprise; CN is a common ingredient of comet cores. Rather, it was the size and purity of the outburst that has researchers puzzled.
There’s a short video here of multiple jets turning on and off while the spacecraft is 8 million kilometers (5 million miles) away from the comet.
And the Arecibo Planetary Radar has imaged the comet’s nucleus [Image Credit: NAIC-Arecibo/Harmon-Nolan].
And watching the event in the JPL mission control room will be Malcolm Hartley, who discovered the comet in 1986.
Adds Nasa JPL’s Ustream Live coverage
And The five close-approach images are online here.