Video above: The launch of Deep Impact in 2006. Courtesy of hackreik via YouTube.
This week sees the fly by of the Deep Impact space craft with comet Hartley 2. In preparation the comet has been given the once over by both the mighty Arecibo radio telescope and the Hubble space telescope.
Hartley 2 is the smallest comet ever visited by a space craft at roughly a mile across, and observations from Arecibo radio telescope show it to be almost peanut shaped.
Image right: The Deep Impact space craft in its clean room. Image courtesy of Ball Aerospace.
Deep impact (re-christened EPOXI for this new mission) will map its tightly curved surface and study the make up of gasses emitted by it.The mission has already thrown up at least one surprise: The comets emission of the gas cyanogen was seen to wax and then wane by five times its initial value, without any signs of a new pocket of gas being violently released. Outbursts, particularly of cyanogen, like these are usually accompanied with and increase in the amount of dust emitted by a comet, by this has not been seen. And Hartley 2, despite its small size, is throwing out as much water vapour as the much larger Tempel 1, suggesting it surface is a cauldron of activity.
The various differences between comets, and the plethora of surprises they keep flashing at science makes the exact origins of these wanderers form the deep dark of the outer solar system a tantalising mystery. The current best model is that these are icy stragglers left behind by the great protoplanetary disk that birthed our solar system. But the many and varied behaviors they show suggests that they may not all have the same origins.
Punters can follow the mission on its blog, or if you prefer there will be a u-stream lecture given by the comets discoverer tomorrow. Deep impacts first target was the comet Tempel 1 which was analysed in a unique fashion by blowing a hole in it with a huge copper projectile. Since then the probe has been moonlighting by studying extrasolar planets, and now is set to fly past Hartley 2 at a distance of 700km on November the 4th. Hopefully the fly by will give us back here on Earth a better understanding of where this little wandered came from, how old it is and what is is made of. Emily Lakdewalla over at the Planetary Society has a good write up on this, and their website includes a timeline of what the long serving spacecraft will be doing and when!
Image above: The bizarre surface of comet Tempel 1, Deep Impacts first voyage of exploration. Courtesy of NASA.
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