This is a writeup of a shallow investigation, a brief look at an area that we use to decide how to prioritize further research.
In a nutshell
What is the problem?
Asteroids occasionally hit Earth, and a sufficiently large asteroid could cause enormous humanitarian damage. NASA reports that all of the near-earth asteroids as large as the one believed to have killed the dinosaurs have been detected, and substantial progress has been made in detecting other dangerously large asteroids. A 2010 National Research Council report, the most authoritative we’re aware of, estimated remaining actuarial risk due to asteroid strikes equivalent to less than 100 fatalities a year.
What are possible interventions?
To substantially reduce residual risk from asteroid strikes, we would need better detection technology – a new telescope – followed, in the unlikely event of detecting a hazard, by action to divert it or minimize humanitarian damage. The B612 Foundation is currently raising funds to attempt to design and launch such a space-based telescope, which would be the first ever deep-space satellite launched by a private group. Philanthropic funds could also potentially also be used to lobby a government to fund such a satellite, instead of funding it directly.
Who else is working on it?
Although the most recent asteroid tracking goal set by the U.S. Congress is not expected to be met, the issue appears to remain on the agenda of NASA and Congress to some extent.
1. Why did we look into this area?
- Asteroid impact is a possible global catastrophic risk (i.e. it could conceivably endanger the survival of humanity). The potential catastrophe from such an impact is so great that an investment in asteroid detection could conceptually have high returns.
- Unlike other GCRs (e.g., nuclear war), asteroid risk is extremely quantifiable: scientists have estimated the number and size of near-earth asteroids and are able to track how many have been discovered.
- Multiple asteroid deflection mechanisms have been designed and, according to advocates, could be carried out with components of existing technology,1 suggesting that a focus on asteroid detection is appropriate. Early detection could also help minimize damage from an impact that couldn’t be avoided by giving sufficient warning for people to be evacuated from a given area.
2. What is the problem?
The risk of asteroid impacts is quite well-understood relative to other long-term risks to humanity like climate change or nuclear war, though the humanitarian impact of asteroid strikes is more difficult to assess: there has only been one asteroid impact in recorded history that caused serious damage, so there are not many past examples to study,2 and the effects of impact depend on many characteristics of the asteroid and the way it collides with Earth.3 Our understanding is that the risk from asteroids is believed to be much larger than the risk from comets, which are harder to detect, so we focus here on asteroids.4
NASA reports that all near-earth asteroids larger than 10 kilometers in diameter—the size of impact thought to have caused the extinction of the dinosaurs—have already been identified.5 As of September 2011, roughly 93% of asteroids larger than 1km in diameter—large enough to have potentially global effects—had also been tracked, according to NASA.6 This eliminates much of the estimated risk due to asteroids, since extremely harmful low-probability impacts dominate expected-value calculations of asteroid risk.7 We have not vetted these claims, but our rough understanding is that the NASA study indicating that 93% of asteroids larger than 1 km in diameter have been found is likely to be robust.8
Taking the frequency of impacts by asteroids of different sizes, the proportion of asteroids of different sizes that have been successfully tracked, and the expected humanitarian effects of such impacts, it is possible to estimate the expected number of deaths due to asteroids each year. Scientists have conducted these calculations several times as near-earth asteroid tracking has progressed.
In a 2003 report, NASA estimated that the expected value of asteroid risk would be roughly 150 global deaths per year in 2008.9 In an update published in 2010 by the National Research Council, the most authoritative report on this issue that we’re aware of, the estimated remaining actuarial risk due to asteroid strikes declined to 91 fatalities a year.10 (A 2012 presention by the scientist cited in the National Research Council report suggested an even lower current value—64 expected fatalities per year, on track to decline to 33 by 2030—though we have not seen a published estimate to that effect.11)
3. What are possible interventions?
The B612 Foundation is a non-profit organization that is currently raising funds to launch a satellite to detect potentially hazardous near-earth asteroids.12 They estimate that their mission will cost $450 million and be able to catalog 90% of asteroids large enough to create a crater on earth (140 meters).13 No deep-space satellite has ever before been launched by a private body,14 and the B612 Foundation’s satellite would need to be custom-built for the mission.15
Instead of directly financing a telescope, as the B612 Foundation is attempting to do, a philanthropist could also attempt to lobby a one or more governments to fund a new telescope. We do not have a sense of how expensive such a lobbying effort might need to be or how it might compare in likelihood of success to directly funding a telescope.
4. Who else is working on this?
In 1998, the U.S. Congress set a goal of finding and tracking 90% of near-earth asteroids larger than 1 kilometer in diameter by 2008. Although it was not completed by 2008, NASA reports that that goal has since been met.16
In 2005, Congress set an additional goal: identifying 90% of asteroids larger than 140 meters in diameter by 2020.17 The National Research Council estimates that $50 million per year would be required to reach the new 90% goal a decade late, by 2030, but current funding is only approximately $20 million per year, and the goal is not expected to be met.18
Despite the lack of funding to date, it seems to us that this issue continues to be on NASA and Congress’ agenda to some extent. For instance, in February 2013, two Democrats on the House subcommittee on space wrote an op-ed in the Washington Post calling for more spending on asteroid risk mitigation, and the committee chairman, a Republican, announced a hearing to discuss the risk.19 (Both were triggered by the coincidence of a meteor strike that caused many injuries—but no deaths—in Russia and a near-miss of Earth by a 45 meter-wide asteroid on February 15.) In addition, over the past decade, NASA has conducted multiple cost-effectiveness analyses of further work to detect near-earth asteroids.20
5. Questions for further investigation
Our research in this area has been relatively limited, and many important questions remain unanswered by our investigation.
Amongst other topics, our further research on this cause might address:
- How quickly will the remaining 7% of near-earth asteroids larger than one kilometer in diameter be found at current rates?21 How reliable are the underlying estimates of the likely numbers of different sizes of near-earth asteroids?
- How precise and reliable are extant estimates of humanitarian damages for different sizes of asteroids? How much is known about the likely humanitarian damages and what are the chances that scientists are mistaken?
- At current levels of funding, how long would it take NASA to find the remaining undiscovered near-earth asteroids larger than 140 meters in diameter?
- What might be the cost and likelihood of success of efforts to lobby a government to fund further detection capacity?
Chapman, Clark R. – Source (PDF)
Morrison, David, et al. 2002. Asteroids III, ed. William Bottke, Alberto Cellino, Paolo Paolicchi, and Richard P. Binzel. Tucson: University of Arizona Press – Source (PDF)
NASA Near-Earth Object Science Definition Team. 2003 – Source (PDF)
NASA. 2006 – Source (PDF)
National Research Council. 2009 – Source (PDF)
National Research Council. 2010 – Source (PDF)