Planetary Defense!

Some wild news items have popped up recently about near-Earth asteroids and how to deal with them if they become a “problem” and seem to be on a collision course with the Earth.  Turns out that just in the first week of 2022, an asteroid was discovered that for a while was thought to be something we needed to keep our eyes on.  The object in question, Asteroid 2022 AE1, was detected first from Arizona’s Mt. Lemmon Observatory on January 6.  It appears to be about 70 m in diameter, or roughly the size of the dramatic Chelyabinsk meteor that fell over Russia back in 2013.  The early determination of its orbital motion caused JPL scientists to put it initially on a level 1 of the Torino scale of categorizing the hazard associated with an asteroid impact.  Doing so was just a matter of raising the level of concern about this object, and the definition of the scale is “A routine discovery in which a pass near Earth is predicted, that poses no unusual level of danger. Current calculations show the chance of collision is extremely unlikely with no cause for public attention or public concern. New telescopic observations very likely will lead to reassignment to Level 0.”  Notably, no other known asteroid is anything but Level 0.  Further observations improved the orbital calculation and happily caused 2022 AE1 to be downgraded to Level 0.  Then some further calculations showed the object’s orbit could be disturbed when it next passes near the Earth in early July 2023 and its hazard level was raised back up to Level 1.  Happily, yet more data has caused it to be downgraded the threat again back to Level 0, i.e. none.  Whew!  Here’s a link to a good summary about 2022 AE1 on the EarthSky site, and I’m surprised I hadn’t heard about this saga before today.

Interestingly, 2022 AE1 was not spotted earlier because it was coming towards us from the direction of the Sun, which is a particularly hard place to look for faint objects.  Indeed, such objects are arguably the scariest because there’d be little time to react if its approach is relatively masked.  The issue of how to deal with such incoming impactors is a matter of planetary defense, and is actually taken seriously by many.  For instance, just this week a UC Santa Barbara researcher presented an idea for which he has obtained some NASA funding to develop.  The idea, called the “PI-Terminal Defense for Humanity” project (where PI stands for “pulverize it"), is a scheme to intercept an incoming asteroid with an array of rods, some of which have explosives, to break it up into smaller bits that can more easily disintegrate in our atmosphere, e.g., ones 15 m in diameter or less.  (Note: using nuclear weapons would be a particularly bad idea here, as then you’d have radioactive debris burning up through the atmosphere.)  These rods could be deployed from an station orbting the Earth or even from a lunar base, which would could speed up our reaction time to a short-notice, incoming threat.  Allegedly, only five hours of lead time would be needed to take out something about the size of 2022 AE1.  About 10 days’ notice, however, could eliminate a larger asteroid like Apophis, which is 370 m in diameter and perhaps the most threatening of asteroids known so far.  Hmm… Personally, I’d hope those rod arrays would be always pointed away from the Earth.  That said, I think a defense moonbase would be awesome, especially if it were just as cool as the one on that old TV show, UFO that is. Meanwhile, if you’d like more information here’s a link to the press statement about the decidedly “well-outside-the-box” concept.