If a comet or an asteroid was discovered to be on a collision course with Earth could we do anything to prevent the collision? According to a new report from the National Research Council, there is little that we can do. We also do not have the resources in place that can detect all of the dangerous near-Earth objects (NEOs) that could possibly cross Earth’s orbit. The report also says that the $4 million that the United States spends annually to search for NEOs is inadequate to meet the congressional mandate to detect NEOs that could threaten the Earth.
At an address to the American Geophysical Union‘s conference last month, Don Yeomans, the Manager of NASA’s Near Earth Object Program Office, said that in order to achieve what has been madated by Congress, NASA will need new technology, larger telescopes with wider fields of view. Yeomans also said that work is being done to improve the quality and quantity of the search for potentially dangerous asteroids and comets. NASA’s long term goal is to build three more 1.8 meter telescopes and the Large Synoptic Survey Telescope, which has an aperture of 8.4 meters, by 2016. In order to get all of these facilities, and others, up and running will take additional funding on top of the funding currently allocated by Congress.
Unfortunately Congress has not appropriated new funds for the survey, nor has the administration asked for more funds, despite the fact that in 2005, Congress mandated that NASA discover 90 percent of NEOs 140 meters or larger in diameter. Congress also asked the NRC to form a committee to determine the best approach to detect these objects. In 2009 the committee reported that it was not possible for NASA to meet the goal without additional funding.
Is this really an American problem? Not according to former astronaut Rusty Schweickart, speaking at the same AGU conference said “There’s the geopolitical misconception that NASA is taking care of it,” he said. “They aren’t and this is an international issue.” He also said that making decisions on how to deal with the threat after it has been discovered is too late. All of the decisions of what will be done, and how, must be made now. “The real issue here is getting international cooperation, so we can — in a coordinated way — decide what to do and act before it is too late,” he said. “If we procrastinate and argue about this, we’ll argue our way past the point of where it too late and we’ll take the hit.”
The report recommends that NASA monitor for smaller objects and that immediate action must be taken to ensure the continued operation of the Arecibo Observatory in Puerto Rico and to start a program at the Goldstone Deep Space Communications Complex, which has facilties in the Mojave Desert, near Madrid, Spain, and near Canberra, Australia. While these facilities themselves cannot detect NEOs, they can play an important role in determining orbits and characteristics of NEOs.
According the Schweikart, we have the technology right now to move an asteroid. Also time is the crucial element in the equation, not big rockets. The earlier we send a spacecraft to divert the asteroid, the less it will cost.
The NRC stresses in the report that the methods for NEO defense are new and immature. However, with sufficient warning, there are four types of mitigation that are adequate for meeting the threat from most NEOs, save the most energetic ones.
- Civil defense, whci includes evacuation, sheltering in place, and providing emergency infrastructure, is a cost-effective mitigation measure for saving lives from the smallest NEO impact events and is a necessary part of mitigation for larger events
- “Slow push” or “slow pull” methods use a spacecraft to exert force on the target object to gradually change its orbit to avoid collision with the Earth. This technique is practical only for small NEOs (tens of meters to roughly 100 meters in diameter) or possibly for medium-sized objects (hundreds of meters), but would likely require decades of warning. Of the slow push/pull techniques, the gravity tractor appears to be by far the closest to technological readiness
- Kinetic methods, which fly a spacecraft into the NEO to change its orbit, could defend against moderately sized objects (many hundreds of meters to 1 kilometer in diameter), but also may require decades of warning time
- Nuclear explosions are the only current, practical means for dealing with large NEOs (diameters greater than 1 kilometer) or as a backup for smaller ones if other methods were to fail
It should be stressed that while all of these methods are conceptually valid, none of them are ready to implement on short notice Civil defense and kinetic impactors are the closest to readiness, but even they still require additional study prior to implementation.
You can read the entire report here.