No 6, December 1986, pp. Slow leak from interior of red planet. Comet reservoir gets more real. Hale-Bopp's tepid birthplace. Sky and Telescope, October 1997, p. 24.
New results suggest x-ray emission is a common property of comets.
By Charles Day, Physics Today , December 1997, pp. An explanation for cometary x-rays. Sky and Telescope , December 1997, p. 19.