Workshop on Scientific Requirements for Mitigation of Hazardous Comets and Asteroids

September 3-September 7, 2002

Hyatt in Arlington, Virginia

(Workshop Sponsored by NASA; co-sponsored by Ball Aerospace and Science Applications International Corporation)

Background Rationale and Goals for the Workshop

One hundred years is approximately the time scale for a 10% probability of an Earth impact by a 100-meter sized near-Earth asteroid, one capable of causing substantial regional disruption or destruction of societal infrastructure.

This is also the estimated time (~ 70 years) necessary to assure the development of an appropriate mitigation technology and learn how to apply it to an Earth threatening object (Belton et al, 2001).

These timescales are similar to the typical lifetime of a family from birth through the death of grandchildren, and can be expected to be of particular interest to contemporary society.

This confluence of timescales gives present urgency and special interest to consideration of the scientific foundations on which near-Earth object (NEO) collision avoidance and impact mitigation technologies must be based.

Programs for the detection of possible impactors are well in hand, and ideas abound on how to apply the energy required to either disrupt or deflect an incoming impactor (Hazards due to Comets & Asteroids, T. Gehrels, Ed., 1994). Yet little published work exists to address the detailed scientific and technical requirements for avoidance and mitigation technologies, and whether an adequate knowledge base exists.

The need for space exploration of NEOs is widely recognized (e.g. in the Spaceguard Survey report, Morrison, 1992; Space Surveillance, Asteroids and Comets, and Space Debris, USAF Science Advisory Board report, 1997). More recently, a UK Task Force on NEOs (Atkinson, 2001) recommends that an international approach be considered that employs a coordinated set of rendezvous missions based on inexpensive micro-satellite technology.

Even with the publication of such recommendations it is not clear, from what has been published, that they are offered on a secure scientific and technical basis. For example, micro-satellite spacecraft do have an important role to play in the future scientific exploration of NEOs. Yet for impact mitigation or collision avoidance technologies to succeed, a high priority must be placed on scientific investigations intimately associated with the deep interior structure and special material properties of these objects.

Beyond revealing fundamental clues to the origins of planets, knowledge of the deep interior structure of asteroids and comets is a requirement if one means to apply whole-body forces to them and achieve predictable results.

To measure and characterize the needed properties encompassing mass, mass distribution, material strengths, internal structure, shape, and spin state (Huebner and Greenberg, 2002), novel kinds of spacecraft investigations will be required. Locally, drilling and digging from the surface can provide some of these data, but will probably be restricted to a limited depth. Globally, radio and seismic wave experiments with active sources analogous to those used in terrestrial exploration may be necessary. This will require the development of whole new encounter technologies, and may lead to new mitigation strategies as well.

This workshop will review what is known about the physics and chemistry of the interiors of small cometary nuclei and asteroids with the purpose of attaining a geophysical understanding of asteroids and comets in near-Earth space. In addition, the workshop will work towards the following specific goals:

  1. Determination of the scientific requirements for those collision avoidance and impact mitigation technologies that are considered viable. This includes identification of measurements that are needed and the accuracy that should be attained.
  2. Determination of what mission models and instrumentation developments are needed to make these measurements.
  3. Construction of a mission and research roadmap for achieving an adequate level of knowledge on which to base the future development of practical and reliable collision avoidance and impact mitigation systems.


Atkinson, H. 2001. UK Task Force on Near-Earth Objects. This report is best acquired through its web page:

Belton, M.J.S., E. Asphaug, W. Huebner, and D. Yeomans 2001. Scientific requirements for NEO Impact Mitigation. Presented at Asteroids 2001 meeting, Palermo, Sicily.

Hazards due to Comets and Asteroids 1994. Edited by Tom Gehrels, University of Arizona Press.

Huebner, W.F., and J.M. Greenberg 2002. Erice Workshop Summary on Physical and Chemical Properties of Potential Earth Impactors, Meteoritics and Planetary Science, In Press.

The Spaceguard Survey: Report of the NASA International Near-Earth-Object Detection Workshop 1992. Edited by David Morrison. Pasadena, CA: Jet Propulsion Laboratory.

USAF Scientific Advisory Board 1997. Space Surveillance, Asteroids, and Comets, and Space Debris, Vol 1, Space Surveillance, SAB-TR-9604.

NEO Related Webpages:

Inquiries and suggestions to: Nalin Samarasinha