Timeline for What is "Planetary Defense", and what are the threats one can potentially defend against?
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Aug 27, 2020 at 21:28 | comment | added | David Hammen | @Heopps - It's impossible to evacuate a continent, or even a country (tiny countries the size of a city excluded). The type of mitigation I wrote about can only occur for impactors that aren't huge and for which the trajectory and predicted impact point are fairly precise. | |
| Aug 27, 2020 at 8:58 | comment | added | Heopps | I'm agree with the answer, but for the example with Cheliabinsk meteorite - there are many transitional stages in precision of trajectory knowledge between "the asteroid will probably hit Earth in day X" and "it will hit Cheliabinsk city area". The mid-stages are like: "the asteroid will fall in day X somethere in North Eurasia", "the asteriod will hit Siberia somethere in ground track 3000 km long and 50 km wide, including several big cities". With such uncertainties it's impossible to manage evacuation. But probably radar ranging can narrow them down when the asteroid comes close enough. | |
| Aug 27, 2020 at 7:26 | comment | added | David Hammen | The primary reason that planetary protection focuses on asteroids is numbers. The number of potentially hazardous asteroids is estimated to be orders of magnitude larger than is the number of potentially hazardous comets. | |
| Aug 27, 2020 at 7:23 | comment | added | David Hammen | Melt??? You should reconsider. Think of Comet Shoemaker–Levy 9, which Jupiter's large gravity field tore apart. The biggest chunk tore a hole in Jupiter's atmosphere the diameter of the Earth. Imagine a comet and an asteroid of the same mass impacting the Earth. The comet would be an order of magnitude more destructive due to its much larger relative velocity. A dark comet (one that has vented most of its volatiles on previous perihelion passes) forms the basis of a nightmare scenario. A comet that still contains lots of volatiles would be just as deadly, but perhaps easier to see in advance. | |
| Aug 27, 2020 at 6:23 | comment | added | uhoh | Thanks! "Mitigation" is the word I needed when writing this comment. I understand that comets can be NEO's, but would they be significant threats, or just melt and release some gravel before impact? I'm imagining the literal dirty snowballs I used to make when I was young, maybe that's not a good model for a comet. :-) | |
| Aug 27, 2020 at 6:17 | history | answered | David Hammen | CC BY-SA 4.0 |