In less than two decades, perception of the threat posed to Earth from space rocks has changed from one of sci-fi to that of a real -- if remote -- peril on which serious money should be spent.Here are the main projects, either already underway, being planned or pitched, aimed at tackling the threat from near-Earth objects (NEOs), the term for asteroids and comets whose orbit brings them close to our planet.
- SPACEGUARD SURVEY: NASA initiative, set up in 1998, to identify 90 percent of all near-Earth asteroids larger than one kilometer (0.6 of a mile) across by the end of 2008. Uses US telescopes and support from amateurs, to be powerfully supplemented by two big American telescopes from 2008. (http://impact.arc.nasa.gov/index.html)
- DEEP IMPACT: US mission, culminating July 2005, in which a 370-kilopound) slug will be fired into a distant comet, Tempel 1, and the impact filmed from a flyby spacecraft. The goal is to understand more about the density and internal structure of comets, something that will be useful for determining whether it is safer to blow up, deflect or steer away any future head-on threat for Earth. (http://deepimpact.jpl.nasa.gov)
- ROSETTA: European spacecraft, launched in March 2004, which will send a robot lander on the Comet Churyumov-Gerasimenko in 2014 to examine its surface. En route, it will remote-scan two asteroids during a flyby: Steins, measuring several kilometers (a couple of miles) across, in 2008, and Lutetia, a 100-km (60-mile) leviathan, in 2010. (http://www.esa.int/export/SPECIALS/Rosetta/index.html).
- DON QUIJOTE: European Space Agency (ESA) scheme to send two probes to rendezvous with a distant asteroid. One would spend seven months filming and scanning the object and send down penetrators and seismometers to hook onto the rock's surface. It would then do a suicide plunge, smashing into the asteroid, while the instruments record the impact on the rock's structure. The data would be transmitted to the other probe. Project is top of ESA's asteroid wish-list but still needs approval and funding. Timeframe, if all goes well: 2010-2015. (http://www.esa.int/gsp/NEO/quijote/quijote.htm)
- ASTEROID TUGBOAT: Nickname for a proposed vehicle that would steer or tow a threatening asteroid towards a safer orbit around the Sun. Its backers are the B612 Foundation, a thinktank set up by former US astronauts Rusty Schweickart and Ed Lu. They are lobbying for a demonstration mission to take place within the next 10-12 years, using prototype nuclear propulsion, being explored by NASA under its Prometheus Program, to give the tugboat its thrust. (http://www.b612foundation.org/)