1. There is an asteroid on a collision course with the Earth.
2. The largest asteroid is Ceres, which is about a quarter the size of the moon.
3. A spacecraft returning from an asteroid is not limited to carrying water.
4. The importance of Spacewatch and other asteroid search programs becomes more evident as we learn more about the impact hazard.
5. Hundreds of asteroid spectra have been compared with laboratory reflection spectra of meteorites and pure mineral samples.
6. Were this asteroid to hit an ocean, it would create massive tidal waves that would roar far inland on all continents.
7. Unfortunately, determining the physical properties of an asteroid be-fore its impact is quite challenging.
8. The spectral classes established by asteroid observers are based on the colors and total reflectivity of their targets.
9. But some, including Eros, wander out of the asteroid belt and into the inner solar system during each orbit.
10. Therefore a carbonaceous asteroid, although unlikely, can not be ruled out as an explanation of the Tunguska event.
11. The asteroid flew within 10000 miles of Earth, which astronomers considered a near miss.
12. The pictures were taken during the spacecraft's 25-minute flyby of the asteroid.
13. Ninety-nine out of a hundred wildcatters went broke or crazy or both and abandoned their last asteroid with the equipment in situ.
14. Finally the day arrived when they were ready to begin loading the asteroid for the trip.
15. Much water has been lost for ever from Mars, blasted into space by comet and asteroid impacts.