... Tonight's Sky . ... Mars . ... solar system . ... NASA prepares its science fleet for Mars comet encounter . ... NASA s extensive fleet of science assets, particularly those orbiting and roving Mars, have front-row seats to image and study a once-in-a-lifetime comet flyby Sunday, October 19. ... The agency s Balloon Observation Platform for Planetary Science, a suborbital balloon-carried telescope, already has provided observations of the comet in the lead-up to the close encounter with Mars. ...