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Before we get too excited about NASA’s asteroid deflection test, we should recognise that humanity is very bad at predicting impacts.
Since 1988 our planet has been hit by more than 1,200 asteroids larger than a metre in size. These weren’t big enough to completely destroy the planet or cause an extinction event (scientists are certain there won’t be anything like that for 100 years) but, they are certainly big enough to cause some damage.
But of those impacts, humanity only predicted five in advance – maybe six if we want to be generous and count the object known as A106fg, which may simply have been a close approach – but this accounts for less than 0.42% of all strikes on the planet. We cannot deflect asteroids we don’t know are there.
Even those five asteroids that were detected ahead of impacting Earth were discovered with just hours to spare. As they currently stand, our detection systems have never offered more than a day’s warning in advance – though scientists hope and expect them to improve.
That timeline between discovery and impact offers significantly less wriggle-room than the five years between the DART mission getting approval at NASA and its scheduled rendezvous with Dimorphos next year.
With so little notice we would not only be unable to deflect an asteroid off-course, we wouldn’t even be able to evacuate people expected to be affected by the impact.
Our ability to detect asteroids before they impact the planet is still in its infancy, in part because of limits set by the laws of physics.
Surveying asteroids in the dark of space in our solar system depends on them reflecting light towards us, and that depends on the direction of their approach relative to the sun and the phase of the moon.
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Source : skynews
