From Michael Paine
The Torino Scale, which attempts to quantify the risk of potential impacts, was developed by Rick Binzel at MIT (25 June, p 34). He has put great effort into public awareness of the level of threat from comets and asteroids.
You also fail to point out that it might be possible to exploit detection of the “keyholes” through which an asteroid must pass if it is going to hit us next time round. Ex-astronaut Rusty Schweickart has pointed out that when 2004 MN4 flies by us in 2029, the keyhole will be only 600 metres across. This means that deflecting the asteroid by only a few hundred metres could ensure that it missed us in 2036 or beyond, were it found to be on a collision course.
Finally, Jay Melosh of the University of Arizona has pointed out to me that painting an asteroid white, or wrapping it in aluminium foil, produces thrust from sunlight in the least helpful direction. The best deflection direction is along the orbital path.
From Ed Lyden
Advertisement
It seems to me that MN4 is the greatest gift mankind could ever get. A 300-metre hunk of metal comes within 26,000 kilometres. Does that ring the dinner bell? You have 25 years to get space tugs ready to pull it into a near-Earth orbit or to the L5 Lagrange position. Then you have trillions of dollars’ worth of metal ready to be transformed into a floating city. If humans can’t see this as a once-in-a-millennium opportunity then we don’t deserve to have a future.
Katy, Texas, US
Beacon Hill, New South Wales, Australia
