Clark Chapman (SwRI) Piet Hut (IAS) Ed Lu (NASA) Rusty Schweickart Clark Chapman (SwRI) Piet Hut (IAS) Ed Lu (NASA) Rusty Schweickart [Venue; Date] Project B612 Goal: To significantly alter the orbit of an asteroid in a controlled manner by 2015

Note: This is a draft presentation. It is incomplete. Things need to be checked. The last several slides were not constructed for this presentation but could be used as a basis for more in-depth treatment of certain issues. The Southwest Research Institute logo needs to be removed…I just haven’t done it yet (because I don’t know how, off the top of my head). Clark Chapman, October 21, 2002

What is the Danger from Asteroids? During your lifetime, there is a 1-in-3000 [ck] chance that an undiscovered asteroid (or comet) more than one kilometer wide will strike the Earth, threatening civilization. During your lifetime, there is a few-percent chance that a 100-meter (or larger) asteroid will strike the Earth with the energy of 100 Megatons (5000 Hiroshima bombs) The impact hazard is an extreme example of a natural disaster (a small chance of happening, but with huge consequences) that challenges a rational response by citizens and policy-makers.

The Asteroid Belt, the Trojans, and the Near-Earth Asteroids

The Range of Asteroid Impacts... Meteorites hit regularly Devastating events in our lifetime Civilization destroyers Dinosaur killers (mass extinctions)

The 20th Century’s Biggest Impact was Very Destructive This Siberian forest (the size of a major city) was felled in 1908 by a 15-Megaton asteroid explosion, “Tunguska”

What are we Doing About the Threat? The only thing we are doing right now is to search for asteroids (larger than 1 kilometer) that might strike There are suggestions that we should be searching for smaller asteroids We are only beginning to think about what we might do if an asteroid were found to be heading toward Earth Project B612 has a more concrete suggestion!

We Have a Goal: Why is development of a deflection program important? Why is development of a deflection program important? An insurance policy. Why do we need to test? Why do we need to test? We want to know that the technology will work before we have to use it for real. Why by 2015? Why by 2015? Because we can, and we should not wait. What kind of an asteroid will we move? What kind of an asteroid will we move? A small, repre- sentative one (whose orbit does not threaten Earth). What is “a controlled manner”? What is “a controlled manner”? It is deflected far enough so that it would miss the Earth (had it been headed toward Earth) and it doesn’t break up into dangerous pieces. Significantly alter the orbit of an asteroid in a controlled manner by 2015

How Much Warning will we Have? Asteroids found by Spaceguard: Nearly all will be certified as “not going to hit” If one is found headed to Earth, we’ll likely have decades of warning. Extremely rarely, we might have short warning but time to evacuate Asteroids NOT found before they hit: Would hit with near-zero warning.

How Can we Deflect an Asteroid? Blowing it up is NOT a good option Uncontrolled shattering into spray of dangerous fragments Not as effective as you might think, especially for a “rubble pile” How would we PUSH it away from collision course, and hold it together? Yarkovsky effect: “paint it white” Solar sail: use “light pressure” Mass driver: throw rocks off the surface Ablation: evaporate a spot on the surface Attach a rocket

Criteria for Evaluating Deflection Options Should miss the Earth given a decade of warning: a few cm/sec change in velocity Must move asteroids at least 100 meters in size, preferably many hundreds of meters Must transport the device from Earth’s surface to speeding asteroid using available launch vehicle Should work for a wide variety of asteroids (weak, metallic, icy, etc.)

Eros is NOT Like the Moon! The Moon has craters. Eros has rocks.

Some Salient Facts about the Impact Hazard not It is not a “Deep Impact” or “Armageddon” shoot-em- down just before they hit scenario For asteroids, orbiting in the inner solar system, it is a case of finding them decades in advance of an impact…with long lead-times for mitigation: For every asteroid with <1 year warning time, there are 50 with 5 decades of lead-time (but comets are another matter) It is one of the few big hazards for which it is technologically feasible, with some confidence, to stop the catastrophe from happening (by deflection)

Conclusions 1… The impact hazard is REAL but it is VERY UNLIKELY to happen during our lifetimes Its potential consequences are horrific… exceeding any other natural hazard and equalling all-out nuclear war We could avert a threatened impact In a post-September 11th world, it is difficult (for me) to predict how people might react to near- misses, huge-but-low-probability disasters, bombs in space, and other impact hazard issues

Tsunami Stratospheric Dust Risk vs. Scale of Impact Annual fatalities peak for events near the “threshold size”, about 2 km Orange/yellow zone illustrates our range of uncertainties for agricultural disaster due to stratospheric dust

Chances from Dying from Selected Causes (for U.S.A.) By terrorism (mostly due to Sept. 11th attacks)

The Torino Scale Events Having No Likely Consequences Events Meriting Careful Monitoring Events Meriting Concern Threatening Events Certain Collisions

How the Torino Scale is Calculated: From the Probability of Impact and Size

Why are the big/rare ones so much more important than Tunguskas? Only asteroids larger than ~1 mile across can be globally destructive and threaten civilization For every devastating 15-MT Tunguska blast, there are ~100 earthquakes, floods, and typhoons that are equally destructive Cost-effectiveness drops sharply with size: the average annual fatalities drop while the costs of finding the objects and responding to them rises But, there are contrary viewpoints and interests: On a politician’s “watch”, why would he/she care about what might happen decades from now? “Star Warriors” in the DOE and DOD who would like to test their inventions and try shooting down small asteroids. And astronomers who would love to have more and bigger telescopes.