The afternoon panel on Monday is on how big the problem is, and what we can do about it.
[Update, it’s starting]
David Morrison is speaking first. He treats asteroids as enemies, while John Lewis treats them as friends. Going through arguments, and explaining what’s been happening in last few years.
Asteroid hazard is one that we can not only mitigate, but eliminate through space technology. First real awareness of hazard goes back to the Alvarez discovery that the dinosaurs were wiped out, and it was a surprise that an event that had no effect on the orbit, magnetic field, or earth itself could wipe out an ecosystem. Referring to a 1991 statement by the Congress that said we should study it internationally, and that while the risk is very small the consequences are very large, and it is a perfect charge: look at the risk, assess the threat, and figure out what to do about it.
Comes in big chunks, can go thousands of years without killing anyone, and then be catastrophic. Showing terrestrial impact frequence graph on log-log scale of megatons of energy on the X axis and frequency on the Y axis (it’s a linear relationship). Upper left is Hiroshima-size event, which occurs almost annually. Tonguska was much worse, and occurs once every few hundred years. Explosions are produced so high in the atmosphere that they don’t reach the ground, and we didn’t realize how often they occur until they got data from Air Force satellites that could see them happening. Those data were invaluable in quantifying the threat. The Air Force had stopped releasing the data a few months ago, but have started to do so again in the last week, though not to the degree of precision that they have themselves, but it’s good enough.
[Update]
D’oh!
I accidentally erased the John Lewis and part of the Morrion talk, and have no obvious way to get it back. Sorry.
I sure wish people thought of asteroids as a solution, rather than a problem.
Sounds like Spaceguard is moving toward the most probable outcome: no NEOs are going to be civilization killers in the near future. This would neuter NEO deflection as a driver for a space program. (There are still longer period comets to consider, however.)
I sure wish people thought of asteroids as a solution, rather than a problem.
John Lewis does, but unfortunately I just lost my notes from his talk. He didn’t have anything new, however.
This would neuter NEO deflection as a driver for a space program.
I think that you can justify it even if it’s only a city killer.
I think that you can justify it even if it’s only a city killer.
The most likely (read: cheapest) way to deal with a very small asteroid of that kind (Tunguska-scale) would be to nuke it into safe fragments. It’s not clear why you need anyone in space for that.
Not just safe fragments, Paul, but safe trajectories too. That requires a complete catalog and ephemeris so that the highest risk objects are identified and prioritized.
Ultimately though, whether the asteroid threat can be dealt with remotely, doesn’t address whatever benefits might be realized by going to them.
I wish John Lewis would either update Mining the Sky, or release it as a wiki. I’ve tried to get in touch with him several times; while his (lost) talk might not contain anything new, that book is sorely out of date.
The low delta-v of a hera-like missions as well as the increasing near earth asteroid detection rate may well herald a sane set of stepping stones to the solar system, but lacking some key software, it’s hard to prove this adequately. There’s a lot of potentially useful mass in the sub 1km asteroids.
With respect to the alleged Jupiter impact, what I want to know is asteroid or comet?
It seems that the dust grains coming off comets account for the known meteor showers (for a proper meteor shower this also means that the places where the comet orbit punctures the plane of the ecliptic also has to be near the orbit or the Earth around the sun — this means that meteor shower comets are a minority of comets).
On the other hand, it is said that all of the recorded “falls”, where the particles were big enough to get to Earth, are all Main Belt asteroids. People keep saying stuff like Tunguska had to be a comet, but people keep coming back to an asteroid source.
Reason this matters is that sooner or later there will be a comprehensive inventory of Main Belt asteroids at risk of hitting the Earth, but there is no way to get such an inventory of comets, so comets seem more dangerous.
But for the lack of cometary meteorites, the last big smoosh on Jupiter was a comet, and the jury is not back on the new impact.
Maybe comet impacts are more rare, but they seem to be a more dangerous wild card.
There’s a lot of potentially useful mass in the sub 1km asteroids.
Motion for this to be understatement of the century.
@ken:
Oh, I expect so. It’s going to take some coding to prove out the trade routes, however.