Preparing for Potentially Hazardous Asteroids

Published in Space News, July 4, 2012

By Joseph N. Pelton

In a time of serious economic recessions, high unemployment and climate change, the issue of potentially hazardous asteroids (PHAs) is not at the top of politicians’ “to do” lists.

NASA deployed the Wide-field Infrared Survey Explorer (WISE) telescope in 2009 and it has provided us an amazing amount of new information about the universe and a much better range of information about so-called killer asteroids that circle the sun close to the Earth’s orbit.

The good news is that when we combine information from ground-based observatories and space telescopes like WISE we have identified about 90 percent of near-Earth objects that are larger than 1,000 meters in diameter. But we have found only about 20 percent of those that are between 100 and 1,000 meters. For instance, we just discovered Asteroid 2011 AG5, thought to present a possible impact problem in 2040.

The survey process so far has only found three objects that have a remote chance of hitting the Earth at some point before 2200. In addition to Asteroid 2011 AG5, there are Apophis, which comes by in 2025 and again 2036 but is now expected to have a very low chance of hitting us, and asteroid 1999 RQ36, which is also considered to have a remote chance of hitting us, on Sept. 24, 2182.

The problem, however, is really about what we don’t know. At 600 meters in diameter, Apophis is still large enough to hit the Earth with the explosive force of 30,000 atomic bombs. If such an object — a “medium-sized” asteroid of the type where we consider 80 percent of the PHAs yet to be identified — were to hit in the ocean near Shanghai, New York or Rio de Janeiro, it would create a wave high enough to wipe out these cities and tens of millions of people.

Some 65 million years ago, an asteroid of over 1,000 meters slammed into Earth and created a deadly cloud that encircled the planet for years. This led to a mass extinction of not only the dinosaurs but over 30 percent of all species. We estimate that 10 percent of the PHAs yet to be identified are this size.

Arthur C. Clarke was fond of sharing a quote from his friend Larry Niven: “The dinosaurs became extinct because they didn’t have a space program.” The question is whether this will be said about humans some day by a smarter species.

If we were to start taking the threat of “killer asteroids” seriously, what should our space leaders be doing about it? I believe that there are three logical steps to take:

  • Raising public awareness. In 2004, the UNISPACE Conference in Torino, Italy, approved the concept of the 10-level “Torino Scale” that noted the level of threat represented by different size asteroids and their likelihood of occurrence. A campaign to create public awareness of this scale, as we understand the categories for hurricanes and the magnitudes for earthquakes, could help the general public have greater awareness of the problem on the basis of currently acquired scientific knowledge.
  • Completing the inventory. This suggests that we need space telescope technology that takes us beyond the WISE project. This might be a telescope with 10 times higher resolution and the ability to change its field of view from very broad to a narrow focus to see specific clusters of potentially hazardous asteroids. This would be the most expensive part of the program, but this key new tool in space also could provide dividends in terms of new research related to astrophysics.
  • Developing asteroid diversion technology. The European Union has launched an admirable multinational research project to develop better ways to divert the course of “killer asteroids.” The three prime areas of research are exploring the use of gravitational traction for course diversion, “bombing” the asteroid out of existence, or hitting it with a missile. This program is called NEOShield (NEO stands for near-Earth object). The problem is that the four-year program is funded at a very inadequate level of 4 million Euros. We spend billions on national defense and medical research against pandemics. The funding for NEOShield needs to be at least 10 times higher to produce viable results.

As we begin to approach building a sustainable space for the longer run and seek to remove space debris from low Earth orbit, such an asteroid protection program could be a part of this overall activity at relatively modest cost.

These three steps will not solve the problems associated with PHAs, but they would move us forward as we also attack the problems of orbital debris and other aspects of long-term sustainability of space.


Joseph N. Pelton is the president of the International Space Safety Foundation and the former dean of the International Space University. He is currently writing a book titled “Space Threats.”


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