Abstract
The images of comet Halley's nucleus returned during three spacecraft encounters in March 19861,2 are challenging the theory of the release of particles from a comet's nucleus. Instead of a spherically symmetric outflow, each spacecraft observed strong jets flowing from the sunward side of the nucleus. Here we present ground based 2-23 μm photometry and 10.3 μm imaging of Halley taken within hours of the Giotto spacecraft encounter. The photometry shows a colour temperature of 360 K and silicate emission features at 10 and 20 μm, and the image shows jet activity similar to that observed by Giotto, but on a scale of thousands of km. The expected 10 μm surface brightness, based on the particle mass distribution measured by Giotto and assuming solid, spherical grains, is a factor of six lower than the observed value. We suggest that fluffy particles could remove this discrepancy.
Original language | English (US) |
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Pages (from-to) | 55-57 |
Number of pages | 3 |
Journal | Nature |
Volume | 326 |
Issue number | 6108 |
DOIs | |
State | Published - 1987 |