16 Feb. 2011

 

Stardust-NExT, mission accomplished!

 

Here are the first dramatic images of comet Tempel 1, just released by NASA, after the close flyby of the Stardust-NExT probe. These images were much anticipated as they provide, for the first time, the opportunity to see the changes in the cometary surface caused by a perihelion passage, and, above all, the effect of the impactor fired into the nucleus in 2005 by the Deep Impact probe.
The crater generated by Deep Impact has in fact been photographed, and is highlighted in the two central images with yellow circles. In the left image, a small hill can clearly be seen (not just due to the higher resolution), that in the right image appears almost absent due to the leveling effect of material ejected by the impact.
The inner of the two circles in the right hand image shows the crater itself, with a diameter of about 150 metres, while the outer circle indicates the region within which most of the ejecta fell. Although the depth of the crater is not yet known, it seems clear that it is not very deep.
Taken together, the dynamics of the 2005 impact and the scar now observed on the nucleus seem to indicate that Tempel 1 is rather fragile, something confirmed by Pete Schultz of Brown University, Providence, R.I.
Another interesting feature revealed by the Stardust-NExT images, 90% of which cover areas not imaged previously, is terracing on the surface (two leftmost images). This terraced terrain is characterised by stepped scarps 1-2 km wide, and is likely the result of the long history of collisions on the cometary nucleus.
Even more interesting are some of the erosion features highlighted with yellow lines in the images on the right. The lines trace a cliff (higher to the left) that has been eroded by as much as 20-30 metres, so that, in the lower of the two images, the lines are displaced to the left. Cometary activity has also removed other surface features, such as those indicated by the rectangles. We will know more when all the images from Stardust-NExT (some of which are available at www.nasa.gov/mission_pages/stardust/multimedia/gallery-index.html) have been analysed in detail. We await further news.

 

by Michele Ferrara & Marcel Clemens

credit: NASA/JPL-Caltech/University of Maryland/Cornell