Clark R. Chapman and Daniel D. Durda

Office of Space Studies

Southwest Research Institute

Boulder, CO 80302


Robert E. Gold

Space Engineering and Technology Branch

Johns Hopkins University Applied Physics Laboratory

Laurel, MD 20723

24 February 2001


The threat of impact on Earth of an asteroid or comet, while of very low
probability, has the potential to create public panic and — should an
impact happen — be sufficiently destructive (perhaps on a global scale)
that an integrated approach to the science, technology, and public policy
aspects of the impact hazard is warranted. This report outlines the
breadth of the issues that need to be addressed, in an integrated way,
in order for society to deal with the impact hazard responsibly. At the
present time, the hazard is often treated — if treated at all — in a
haphazard and unbalanced way.

Most analysis so far has emphasized telescopic searches for large (>1
km diameter) near-Earth asteroids and space-operations approaches to
deflecting any such body that threatens to impact. Comparatively little
attention has been given to other essential elements of addressing and
mitigating this hazard. For example, no formal linkages exist between
the astronomers who would announce discovery of a threatening asteroid
and the several national (civilian or military) agencies that might
undertake deflection. Beyond that, comparatively little attention has
been devoted to finding or dealing with other potential impactors,
including asteroids smaller than 1 km or long-period comets. And
essentially no analysis has been done of how to mitigate other
repercussions from predictions of impacts (civil panic), how to plan
for other kinds of mitigation besides deflection (e.g. evacuation of
ground zero, storing up food in the case of a worldwide breakdown of
agriculture, etc.), or how to coordinate responses to impact predictions
among agencies within a single nation or among nations.

We outline the nature of the impact hazard and the existing ways that
a predicted impact would be handled at the present time. We describe
potential solutions to existing gaps in the required approaches and
structures (both technical and governmental) for dealing with impacts,
including the kinds of communications links that need to be established
and responsibilities assigned.

We recommend crafting, adoption, and implementation of improved procedures
for informing the broader society about the impact hazard, notifying the
public and relevant officials/agencies about an impact prediction, and
putting in place (in advance of such predictions) procedures for
coordination among relevant agencies and countries. We recommend that
pro-active steps be taken, perhaps through a high-visibility international
conference and other types of communication, to educate the broader
technical community and public policy makers about the impact hazard and
the special aspects of mitigating this atypical hazard. For example,
the most likely international disaster that would result from an impact
is an unprecedentedly large tsunami; yet those entities and individuals
responsible for warning, or heeding warnings, about tsunamis are
generally unaware of impact-induced tsunamis. We also recommend that
additional attention be given to certain technical features of the hazard
that have not received priority so far, including the need to discover
and plan mitigation for asteroids smaller than 1 km and for comets, study
of the potential use of space-based technologies for detection of some
kinds of Near-Earth Objects, study of chemical rockets as an approach to
deflection that is intermediate between bombs and low-thrust propulsion,
and further evaluation of the risks of disruption (rather than intended
deflection) of an oncoming object.

Finally, we believe that international human society (and elements of it,
like the U.S. government) needs to make an informed, formal judgement
about the seriousness of the impact hazard and the degree to which
resources should be spent toward taking steps to address, and plan for
mitigation of, potential cosmic impacts. The existing unbalanced,
haphazard responses to the impact hazard represent an implicit judgement;
but that judgement does not responsibly address the extraordinary and
unusual consequences to nations, or even civilization, that could result
from leaving this hazard unaddressed in such an arbitrary, off-hand way.
For example, we believe it is appropriate, in the United States, that
the National Research Council develop a technical assessment of the
impact hazard that could serve as a basis for developing a broader
consensus among the public, policy officials, and governmental agencies
about how to proceed. The dinosaurs could not evaluate and mitigate
the natural forces that exterminated them, but human beings have the
intelligence to do so.

[NOTE: Full text of the SwRI White Paper is available at:]