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Planetary Defence: The Energy-Flux Density Factor

Printable version / Version imprimable

by Benjamin Laurence Deniston

Mankind is battling an array of natural disasters which continually pose a threat to life on this planet. Thanks to advancements in satellites and weather monitoring systems, our ability to forecast major storms and other extreme weather events is improving. Progress is being made in developing earthquake forecasting systems, designed to detect precursors signals which can provide early warnings before seismic events.1 Even our Sun is being watched and analyzed more closely than ever, in attempt to forecast “space weather” events and their effects here on the Earth. However there is another class of events that can not only be foreseen, but can the stopped from ever occurring. Asteroid and comet impacts represent a unique challenge, as we can take the necessary actions to see them coming, but also to ensure the Earth is never again struck in a catastrophic event. While it is likely that we will be able to control storms and certain extreme weather events in the not-too-distant future (if appropriate scientific/economic programs are pursued), for now asteroid defense can hold the title of the only currently preventable natural disaster.

But what are the factors determining our ability to defend the planet, and how can these limits be expanded? In defending the Earth from impacts, there are many possible scenarios we could face: a relatively small near-Earth asteroid on a short-term collision course, giving us little time to act; a large asteroid threatening a possible impact in a few decades, proving more time to act, but proving a larger foe; a worst case scenario of a large long-period comet only months away; and any number of possible variations in between.

The first line of defense is clear: early detection. No matter how large the threat is, the more warning time we have, the better off we will be. While asteroid and comet detection systems have been discussed in other locations,2 the subject here is our ability to act on this knowledge. This takes us beyond just asteroid or comets per se, to a general consideration of our power for action within the universe.

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