1.   But planetary astronomers believe that the comet may have been pulled into thousands of small chunks besides the big ones.

2.   But the earliest date that life could have started has been pushed forward by planetary astronomers.

3.   Dr. Clark Chapman, a planetary astronomer at the Southwest Research Institute in Boulder, Colo., said a first priority should be to organize astronomers for cooperative response.

4.   Planetary astronomers are hoping for more information next year, when the Galileo spacecraft reaches Jupiter and releases a probe that will descend into the Jovian atmosphere.

5.   Planetary astronomers have so often guessed wrong in their attempts to predict the brightness of comets that they have come to couch all their forecasts in caveats.

6.   Soon she began working with planetary astronomer David Jewitt.