On November 4, NASA's mission EPOXI will make a flyby less than 450 miles from the comet Hartley 2. Here's what to know about this dirty snowball. 1. It's a frequent visitor.Malcolm Hartley discovered this namesake comet 24 years ago, and it's returned to swing around the sun a few times since.
Like the famous Halley's Comet, Comet Hartley 2 is a periodic comet that follows a years-long loop around the sun. It takes 6.46 years to complete one circuit, compared with Halley's 75.3 years. [Christian Science Monitor]
2. My God, it's full of cyanide. A deadly agent here on our planet, cyanide
is ubiquitous in comets. But NASA's recent observations of Hartley 2 show the gas acting strangely there, according to team member Mike A'Hearn.
"Our observations indicate that cyanide released by the comet increased by a factor of five over an 8-day period in September without any increase in dust emissions. We have never seen this kind of activity in a comet before, and it could affect the quality of observations made by astronomers on the ground." The new phenomenon is unlike typical cometary outbursts, which have sudden onsets and are usually accompanied by considerable dust. It also seems unrelated to the cyanide jets that are sometimes seen in comets. [Astronomy]
The NASA team members still don't know what those readings mean. They're ready to try to unravel the problem during their flyby. 3. New name, same game. EPOXI, the NASA mission visiting this comet, is a reuse of the old Deep Impact spacecraft
that visited and studied a comet called Tempel 1 in 2005. Since then, the Stardust mission has returned
with material it collected from the tail of comet Wild 2, and more missions are coming.
Over the next five years, new missions are likely to add even more complexity to the cometary picture. In February 2011, the Stardust mission — rebranded NExT — is scheduled to revisit Tempel 1 to see how it looks five years after inspection by Deep Impact. Three years later, Europe's Rosetta mission should reach comet Churyumov–Gerasimenko, and become the first spacecraft to orbit a comet nucleus and deposit a lander on its surface. [Nature]
4. You can see it yourself. Under clear night skies, Hartley 2 has been visible for the last several days. This Thursday, the 28th of October, it will be at its closest point to the sun. Check out Astronomy
for viewing details that day. Related Content: 80beats: Spacecraft-Collected Comet Dust Reveals Surprises From the Solar System’s Boondocks
DISCOVER: NASA Takes a Wild Comet Ride
Bad Astronomy: Deep Impact! Bang! Success!
Bad Astronomy: Ten Things You Don't Know About Comets
Image: Wikimedia Commons
